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  • How to install MariaDB rpms in CentOS 6.4 using rpm (not yum cmd) + handling mysql-libs conflicts

    - by Pat C
    I need to script the install of MariaDB using the rpm command in CentOS 6.4. I can't use yum since it's going to be an offline install so there's no access to the repository. The only MySQL package installed is mysql-libs as various other packages in CentOS depend on it. When I did a test install of MariaDB with yum it correctly accounted for mysql-libs and uninstalled it at the end as MariaDB could handle the dependencies after it was installed: [root@new-host-6 ~]# yum install MariaDB-client MariaDB-common MariaDB-compat MariaDB-devel MariaDB-server MariaDB-shared Loaded plugins: downloadonly, fastestmirror, refresh-packagekit, security, verify Loading mirror speeds from cached hostfile * base: mirrors.kernel.org * extras: mirror.keystealth.org * updates: mirror.umd.edu Setting up Install Process Resolving Dependencies --> Running transaction check ---> Package MariaDB-client.x86_64 0:5.5.32-1 will be installed ---> Package MariaDB-common.x86_64 0:5.5.32-1 will be installed ---> Package MariaDB-compat.x86_64 0:5.5.32-1 will be obsoleting ---> Package MariaDB-devel.x86_64 0:5.5.32-1 will be installed ---> Package MariaDB-server.x86_64 0:5.5.32-1 will be installed ---> Package MariaDB-shared.x86_64 0:5.5.32-1 will be obsoleting ---> Package mysql-libs.x86_64 0:5.1.66-2.el6_3 will be obsoleted --> Finished Dependency Resolution Dependencies Resolved ==================================================================================================================================================================== Package Arch Version Repository Size ==================================================================================================================================================================== Installing: MariaDB-client x86_64 5.5.32-1 mariadb 10 M MariaDB-common x86_64 5.5.32-1 mariadb 23 k MariaDB-compat x86_64 5.5.32-1 mariadb 2.7 M replacing mysql-libs.x86_64 5.1.66-2.el6_3 MariaDB-devel x86_64 5.5.32-1 mariadb 5.6 M MariaDB-server x86_64 5.5.32-1 mariadb 34 M MariaDB-shared x86_64 5.5.32-1 mariadb 1.1 M replacing mysql-libs.x86_64 5.1.66-2.el6_3 Transaction Summary ==================================================================================================================================================================== Install 6 Package(s) Total download size: 53 M Is this ok [y/N]: y Downloading Packages: (1/6): MariaDB-5.5.32-centos6-x86_64-client.rpm | 10 MB 00:06 (2/6): MariaDB-5.5.32-centos6-x86_64-common.rpm | 23 kB 00:00 (3/6): MariaDB-5.5.32-centos6-x86_64-compat.rpm | 2.7 MB 00:02 (4/6): MariaDB-5.5.32-centos6-x86_64-devel.rpm | 5.6 MB 00:06 (5/6): MariaDB-5.5.32-centos6-x86_64-server.rpm | 34 MB 00:23 (6/6): MariaDB-5.5.32-centos6-x86_64-shared.rpm | 1.1 MB 00:00 -------------------------------------------------------------------------------------------------------------------------------------------------------------------- Total 1.3 MB/s | 53 MB 00:40 warning: rpmts_HdrFromFdno: Header V4 DSA/SHA1 Signature, key ID 1bb943db: NOKEY Retrieving key from https://yum.mariadb.org/RPM-GPG-KEY-MariaDB Importing GPG key 0x1BB943DB: Userid: "Daniel Bartholomew (Monty Program signing key) <[email protected]>" From : https://yum.mariadb.org/RPM-GPG-KEY-MariaDB Is this ok [y/N]: y Running rpm_check_debug Running Transaction Test Transaction Test Succeeded Running Transaction Warning: RPMDB altered outside of yum. Installing : MariaDB-compat-5.5.32-1.x86_64 1/7 Installing : MariaDB-common-5.5.32-1.x86_64 2/7 Installing : MariaDB-server-5.5.32-1.x86_64 3/7 chown: cannot access `/var/lib/mysql': No such file or directory PLEASE REMEMBER TO SET A PASSWORD FOR THE MariaDB root USER ! To do so, start the server, then issue the following commands: '/usr/bin/mysqladmin' -u root password 'new-password' '/usr/bin/mysqladmin' -u root -h new-host-6 password 'new-password' Alternatively you can run: '/usr/bin/mysql_secure_installation' which will also give you the option of removing the test databases and anonymous user created by default. This is strongly recommended for production servers. See the MariaDB Knowledgebase at http://kb.askmonty.org or the MySQL manual for more instructions. Please report any problems with the '/usr/bin/mysqlbug' script! The latest information about MariaDB is available at http://mariadb.org/. You can find additional information about the MySQL part at: http://dev.mysql.com Support MariaDB development by buying support/new features from Monty Program Ab. You can contact us about this at [email protected]. Alternatively consider joining our community based development effort: http://kb.askmonty.org/en/contributing-to-the-mariadb-project/ Installing : MariaDB-devel-5.5.32-1.x86_64 4/7 Installing : MariaDB-client-5.5.32-1.x86_64 5/7 Installing : MariaDB-shared-5.5.32-1.x86_64 6/7 Erasing : mysql-libs-5.1.66-2.el6_3.x86_64 7/7 Verifying : MariaDB-common-5.5.32-1.x86_64 1/7 Verifying : MariaDB-server-5.5.32-1.x86_64 2/7 Verifying : MariaDB-devel-5.5.32-1.x86_64 3/7 Verifying : MariaDB-client-5.5.32-1.x86_64 4/7 Verifying : MariaDB-compat-5.5.32-1.x86_64 5/7 Verifying : MariaDB-shared-5.5.32-1.x86_64 6/7 Verifying : mysql-libs-5.1.66-2.el6_3.x86_64 7/7 Installed: MariaDB-client.x86_64 0:5.5.32-1 MariaDB-common.x86_64 0:5.5.32-1 MariaDB-compat.x86_64 0:5.5.32-1 MariaDB-devel.x86_64 0:5.5.32-1 MariaDB-server.x86_64 0:5.5.32-1 MariaDB-shared.x86_64 0:5.5.32-1 Replaced: mysql-libs.x86_64 0:5.1.66-2.el6_3 Complete! My question is, what is the equivalent way to install the MariaDB packages using the rpm command only as opposed to yum? If I do rpm -ivh MariaDB*.rpm, I will get a ton of messages like the following about conflicts with mysql-libs: file /etc/my.cnf from install of MariaDB-common-5.5.32-1.x86_64 conflicts with file from package mysql-libs-5.1.66-2.el6_3.x86_64 file /usr/share/mysql/charsets/Index.xml from install of MariaDB-common-5.5.32-1.x86_64 conflicts with file from package mysql-libs-5.1.66-2.el6_3.x86_64 I then used the --force option to install the MariaDB rpms and uninstalled mysql-lib, I didn't get any weird messages but I'm not sure that is the cleanest method to handle the conflicts and do the install. So can someone confirm that installing MariaDB with the following rpm commands would be the same as using yum to install the packages and handle mysql-libs conflicts/removal: rpm -ivh --force MariaDB*.rpm rpm -e mysql-libs Thanks for any input!

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  • How do I stop postfix from handling my mail?

    - by Tatu Ulmanen
    Here's the situation: I have a domain, let's say domain.com. That domain has Google Apps for Business enabled, so all mail delivered to @domain.com will end up at Google (MX records point to Google). I have a PHP script at domain.com that I use to send mail to myself. But when the PHP script tries to send mail to [email protected], Postfix at that server decides that the recipient is a local user (because the address matches the domain Postfix itself is at), and tries to deliver the mail locally. But inevitably fails as the mailbox cannot be found. How can I instruct Postfix to not try to handle locally any emails to @domain.com and just send them forward so Google can pick them up? I have already removed $myhostname from mydestination field in Postfix's main.cf file, and I have restarted Postfix but Postfix still tries to deliver the mail locally. Here's a snip from mail.log that show the problem (addresses replaced): postfix/pickup[20643]: AF718422E5: uid=33 from=<server> postfix/cleanup[20669]: AF718422E5: message-id=<62e706bcca5a0de0bfec6baa576d88a5@server> postfix/qmgr[20642]: AF718422E5: from=<server>, size=517, nrcpt=1 (queue active) postfix/pipe[20678]: AF718422E5: to=<[email protected]>, relay=dovecot, delay=0.62, delays=0.47/0.03/0/0.13, dsn=5.1.1, status=bounced (user unknown) postfix/bounce[20680]: AF718422E5: sender non-delivery notification: 29598422E7 postfix/qmgr[20642]: AF718422E5: removed

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  • How to add exception for backup MX to tumgreyspf?

    - by Waleed Hamra
    I have an Ubuntu raring server running postfix/dovecot as an email server, with tumgreyspf doing greylisting and SPF checks. My problem is that I also have a backup MX server, that is supposed to store my emails temporarily, should my main server ever fails. It usually rejects receiving emails if it finds the main server online and functional. The problem is when it does need to do its job, tumgreyspf rejects all emails from the backup MX with an error like this: Jun 27 16:18:13 hamra postfix/smtpd[28732]: NOQUEUE: reject: RCPT from mxbackup.mydomain.com[x.x.x.x]: 550 5.7.1 <[email protected]>: Recipient address rejected: QUEUE_ID="" SPF Reports: 'SPF fail - not authorized'; from=<[email protected]> to=<[email protected]> proto=SMTP helo=<mxbackup.mydomain.com> any ideas?

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  • Handling emails on a web server - Making sure the FQDN is set correctly based on the website sending the email

    - by webnoob
    I have a Windows 2008 Web Edition server hosting multiple websites using IIS 7.5. At the moment, all the emails are sent via the IIS6 SMTP service. The FQDN of the SMTP service is set to the computer name at the moment which isn't correct as it doesn't resolve to a valid DNS entry and is not RFC compliant. Some questions: Is there any way I can change the FQDN of the SMTP service based on the site sending the email? Would it be Ok to just setup mailserver.mydomain.com and use that as the FQDN for all the sites on multiple domains. Should I be using some other mail server software to handle this better? The reason I am asking is lots of emails are hitting spam folders because the settings are incorrect. I have access to the code that is running the websites so if something needs to be done there then that shouldn't be a problem. The sites are written using ASP.NET 2.0. EDIT: I have just found an option to create an SMTP virtual service. Would this be the way forward? Create a virtual server for each site? Thanks.

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  • How are large companies handling the storing and cataloging of software installation disks?

    - by CT
    I just started working in the IT department of a small-medium sized construction company with about 200 users. One of my responsibilities is to setup and configure all new machines that come in. I would like suggestions on how to best manage the installation disks and licenses of the software that comes with them. Plus any additional licensed software such as Autocad, Photoshop, etc as well as peripheral driver disks such as printers and scanners. Right now every machine is associated and labeled with an asset id. All asset ids are kept in a spreadsheet with applicable serial numbers, current user, warranty info, and software licenses. The physical disks are then kept within a folder in a cabinet. Each folder is marked with the asset id number as well as the current user. My problems with this is that the system was not maintained very completely before I came to the company. There are plenty of software folders with no asset ids labeled on them. Plenty of missing software folders (most likely are a lot of the unlabeled folders). Folders with names but not asset ids. Machines get switched to different users without the folders and spreadsheet being updated. I am not saying this method would necessarily be bad if it was better implemented and managed, but if I am going to have to take a lot of time to fix this system currently in place. I thought I would ask the community first on how others manage this process in case there are easier, more efficient ways of doing so. Thank you.

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  • How do I automate the handling of a problem (no network device found) in Ubuntu 10.04 w/ preseed?

    - by user61183
    I have a preseed file that is doing some automation for an installation of Ubuntu 10.04. At the point where the network hardware is auto-detected, however, it fails to find hardware and displays a message, "No network interfaces detected". To make a long story short, I don't care if it can detect my network interface. How do I do one of the following: Skip that step alltogether. Handle the error page automagically. PS. I found somewhere where it suggested this: netcfg/no_interfaces seen true That didn't work. Thanks

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  • In terms of load handling, which is better: one server or two of equivalent power?

    - by seldary
    My goal is to figure out if i'm better off with one strong server, or multiple weaker servers with a load balancer. Does the fact of splitting the load between servers have an effect on the total load my website could take? It's hard to single that out, because there are of course a lot of parameters that affect the results, so some assumptions: Putting failover considerations aside - I know it matters, but for the sake of the question's simplicity, lets assume nothing fails. The servers in the multiple servers option have an accumulated "power" equivalent to the one server option (about the same amount of cores and RAM space). If that is too theoretical, here is a concrete question that could help: Suppose I have several instances of exactly the same server - lets call it S. Suppose that server S can serve a load of up to X calls per time unit. Will two S servers with a load balancer serve 2X calls per time unit? significantly more? significantly less?

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  • A DirectoryCatalog class for Silverlight MEF (Managed Extensibility Framework)

    - by Dixin
    In the MEF (Managed Extension Framework) for .NET, there are useful ComposablePartCatalog implementations in System.ComponentModel.Composition.dll, like: System.ComponentModel.Composition.Hosting.AggregateCatalog System.ComponentModel.Composition.Hosting.AssemblyCatalog System.ComponentModel.Composition.Hosting.DirectoryCatalog System.ComponentModel.Composition.Hosting.TypeCatalog While in Silverlight, there is a extra System.ComponentModel.Composition.Hosting.DeploymentCatalog. As a wrapper of AssemblyCatalog, it can load all assemblies in a XAP file in the web server side. Unfortunately, in silverlight there is no DirectoryCatalog to load a folder. Background There are scenarios that Silverlight application may need to load all XAP files in a folder in the web server side, for example: If the Silverlight application is extensible and supports plug-ins, there would be a /ClinetBin/Plugins/ folder in the web server, and each pluin would be an individual XAP file in the folder. In this scenario, after the application is loaded and started up, it would like to load all XAP files in /ClinetBin/Plugins/ folder. If the aplication supports themes, there would be a /ClinetBin/Themes/ folder, and each theme would be an individual XAP file too. The application would qalso need to load all XAP files in /ClinetBin/Themes/. It is useful if we have a DirectoryCatalog: DirectoryCatalog catalog = new DirectoryCatalog("/Plugins"); catalog.DownloadCompleted += (sender, e) => { }; catalog.DownloadAsync(); Obviously, the implementation of DirectoryCatalog is easy. It is just a collection of DeploymentCatalog class. Retrieve file list from a directory Of course, to retrieve file list from a web folder, the folder’s “Directory Browsing” feature must be enabled: So when the folder is requested, it responses a list of its files and folders: This is nothing but a simple HTML page: <html> <head> <title>localhost - /Folder/</title> </head> <body> <h1>localhost - /Folder/</h1> <hr> <pre> <a href="/">[To Parent Directory]</a><br> <br> 1/3/2011 7:22 PM 185 <a href="/Folder/File.txt">File.txt</a><br> 1/3/2011 7:22 PM &lt;dir&gt; <a href="/Folder/Folder/">Folder</a><br> </pre> <hr> </body> </html> For the ASP.NET Deployment Server of Visual Studio, directory browsing is enabled by default: The HTML <Body> is almost the same: <body bgcolor="white"> <h2><i>Directory Listing -- /ClientBin/</i></h2> <hr width="100%" size="1" color="silver"> <pre> <a href="/">[To Parent Directory]</a> Thursday, January 27, 2011 11:51 PM 282,538 <a href="Test.xap">Test.xap</a> Tuesday, January 04, 2011 02:06 AM &lt;dir&gt; <a href="TestFolder/">TestFolder</a> </pre> <hr width="100%" size="1" color="silver"> <b>Version Information:</b>&nbsp;ASP.NET Development Server 10.0.0.0 </body> The only difference is, IIS’s links start with slash, but here the links do not. Here one way to get the file list is read the href attributes of the links: [Pure] private IEnumerable<Uri> GetFilesFromDirectory(string html) { Contract.Requires(html != null); Contract.Ensures(Contract.Result<IEnumerable<Uri>>() != null); return new Regex( "<a href=\"(?<uriRelative>[^\"]*)\">[^<]*</a>", RegexOptions.IgnoreCase | RegexOptions.CultureInvariant) .Matches(html) .OfType<Match>() .Where(match => match.Success) .Select(match => match.Groups["uriRelative"].Value) .Where(uriRelative => uriRelative.EndsWith(".xap", StringComparison.Ordinal)) .Select(uriRelative => { Uri baseUri = this.Uri.IsAbsoluteUri ? this.Uri : new Uri(Application.Current.Host.Source, this.Uri); uriRelative = uriRelative.StartsWith("/", StringComparison.Ordinal) ? uriRelative : (baseUri.LocalPath.EndsWith("/", StringComparison.Ordinal) ? baseUri.LocalPath + uriRelative : baseUri.LocalPath + "/" + uriRelative); return new Uri(baseUri, uriRelative); }); } Please notice the folders’ links end with a slash. They are filtered by the second Where() query. The above method can find files’ URIs from the specified IIS folder, or ASP.NET Deployment Server folder while debugging. To support other formats of file list, a constructor is needed to pass into a customized method: /// <summary> /// Initializes a new instance of the <see cref="T:System.ComponentModel.Composition.Hosting.DirectoryCatalog" /> class with <see cref="T:System.ComponentModel.Composition.Primitives.ComposablePartDefinition" /> objects based on all the XAP files in the specified directory URI. /// </summary> /// <param name="uri"> /// URI to the directory to scan for XAPs to add to the catalog. /// The URI must be absolute, or relative to <see cref="P:System.Windows.Interop.SilverlightHost.Source" />. /// </param> /// <param name="getFilesFromDirectory"> /// The method to find files' URIs in the specified directory. /// </param> public DirectoryCatalog(Uri uri, Func<string, IEnumerable<Uri>> getFilesFromDirectory) { Contract.Requires(uri != null); this._uri = uri; this._getFilesFromDirectory = getFilesFromDirectory ?? this.GetFilesFromDirectory; this._webClient = new Lazy<WebClient>(() => new WebClient()); // Initializes other members. } When the getFilesFromDirectory parameter is null, the above GetFilesFromDirectory() method will be used as default. Download the directory’s XAP file list Now a public method can be created to start the downloading: /// <summary> /// Begins downloading the XAP files in the directory. /// </summary> public void DownloadAsync() { this.ThrowIfDisposed(); if (Interlocked.CompareExchange(ref this._state, State.DownloadStarted, State.Created) == 0) { this._webClient.Value.OpenReadCompleted += this.HandleOpenReadCompleted; this._webClient.Value.OpenReadAsync(this.Uri, this); } else { this.MutateStateOrThrow(State.DownloadCompleted, State.Initialized); this.OnDownloadCompleted(new AsyncCompletedEventArgs(null, false, this)); } } Here the HandleOpenReadCompleted() method is invoked when the file list HTML is downloaded. Download all XAP files After retrieving all files’ URIs, the next thing becomes even easier. HandleOpenReadCompleted() just uses built in DeploymentCatalog to download the XAPs, and aggregate them into one AggregateCatalog: private void HandleOpenReadCompleted(object sender, OpenReadCompletedEventArgs e) { Exception error = e.Error; bool cancelled = e.Cancelled; if (Interlocked.CompareExchange(ref this._state, State.DownloadCompleted, State.DownloadStarted) != State.DownloadStarted) { cancelled = true; } if (error == null && !cancelled) { try { using (StreamReader reader = new StreamReader(e.Result)) { string html = reader.ReadToEnd(); IEnumerable<Uri> uris = this._getFilesFromDirectory(html); Contract.Assume(uris != null); IEnumerable<DeploymentCatalog> deploymentCatalogs = uris.Select(uri => new DeploymentCatalog(uri)); deploymentCatalogs.ForEach( deploymentCatalog => { this._aggregateCatalog.Catalogs.Add(deploymentCatalog); deploymentCatalog.DownloadCompleted += this.HandleDownloadCompleted; }); deploymentCatalogs.ForEach(deploymentCatalog => deploymentCatalog.DownloadAsync()); } } catch (Exception exception) { error = new InvalidOperationException(Resources.InvalidOperationException_ErrorReadingDirectory, exception); } } // Exception handling. } In HandleDownloadCompleted(), if all XAPs are downloaded without exception, OnDownloadCompleted() callback method will be invoked. private void HandleDownloadCompleted(object sender, AsyncCompletedEventArgs e) { if (Interlocked.Increment(ref this._downloaded) == this._aggregateCatalog.Catalogs.Count) { this.OnDownloadCompleted(e); } } Exception handling Whether this DirectoryCatelog can work only if the directory browsing feature is enabled. It is important to inform caller when directory cannot be browsed for XAP downloading. private void HandleOpenReadCompleted(object sender, OpenReadCompletedEventArgs e) { Exception error = e.Error; bool cancelled = e.Cancelled; if (Interlocked.CompareExchange(ref this._state, State.DownloadCompleted, State.DownloadStarted) != State.DownloadStarted) { cancelled = true; } if (error == null && !cancelled) { try { // No exception thrown when browsing directory. Downloads the listed XAPs. } catch (Exception exception) { error = new InvalidOperationException(Resources.InvalidOperationException_ErrorReadingDirectory, exception); } } WebException webException = error as WebException; if (webException != null) { HttpWebResponse webResponse = webException.Response as HttpWebResponse; if (webResponse != null) { // Internally, WebClient uses WebRequest.Create() to create the WebRequest object. Here does the same thing. WebRequest request = WebRequest.Create(Application.Current.Host.Source); Contract.Assume(request != null); if (request.CreatorInstance == WebRequestCreator.ClientHttp && // Silverlight is in client HTTP handling, all HTTP status codes are supported. webResponse.StatusCode == HttpStatusCode.Forbidden) { // When directory browsing is disabled, the HTTP status code is 403 (forbidden). error = new InvalidOperationException( Resources.InvalidOperationException_ErrorListingDirectory_ClientHttp, webException); } else if (request.CreatorInstance == WebRequestCreator.BrowserHttp && // Silverlight is in browser HTTP handling, only 200 and 404 are supported. webResponse.StatusCode == HttpStatusCode.NotFound) { // When directory browsing is disabled, the HTTP status code is 404 (not found). error = new InvalidOperationException( Resources.InvalidOperationException_ErrorListingDirectory_BrowserHttp, webException); } } } this.OnDownloadCompleted(new AsyncCompletedEventArgs(error, cancelled, this)); } Please notice Silverlight 3+ application can work either in client HTTP handling, or browser HTTP handling. One difference is: In browser HTTP handling, only HTTP status code 200 (OK) and 404 (not OK, including 500, 403, etc.) are supported In client HTTP handling, all HTTP status code are supported So in above code, exceptions in 2 modes are handled differently. Conclusion Here is the whole DirectoryCatelog’s looking: Please click here to download the source code, a simple unit test is included. This is a rough implementation. And, for convenience, some design and coding are just following the built in AggregateCatalog class and Deployment class. Please feel free to modify the code, and please kindly tell me if any issue is found.

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  • Migrating BizTalk 2006 R2 to BizTalk 2010 XLANGs Issue

    - by SURESH GIRIRAJAN
    When we migrate some BizTalk apps from BizTalk 2006 R2 to BizTalk 2010, and we ran into issue when a .net component called inside the orchestration. In the .net component we are trying to retrieve some promoted property and we also checked in the BizTalk group hub to validate it was promoted, no issues there.  Only when we try to access the data into the .net component we had issue. We just moved all the assembly what we had in BizTalk 2006 R2 to BizTalk 2010, didn’t recompile anything in BizTalk 2010 environment. But looking further there is couple of new namespace added to the Microsoft.XLANGs… in BizTalk 2010 compared to BizTalk 2006 R2 caused the issue. So all we did to fix the issue is recompile the project in 2010 environment and it worked fine. So it looks like some backward compatibility issue.  public static void Load(XLANGMessage msg) {  try  {      // get the process id from context.       object ctxVal = msg.GetPropertyValue(typeof(ProcessID)); … } BizTalk 2010: Error Message in the event viewer:  The service instance will remain suspended until administratively resumed or terminated. If resumed the instance will continue from its last persisted state and may re-throw the same unexpected exception. InstanceId: 441d73d3-2e84-49d2-b6bd-7218065b5e1d Shape name: Bulk Load ShapeId: bb959e56-9221-48be-a80f-24051196617d Exception thrown from: segment 1, progress 65 Inner exception: A property cannot be associated with the type 'Tellago.Common.Schemas.ProcessId'.   Exception type: InvalidPropertyTypeException Source: Microsoft.XLANGs.Engine Target Site: Microsoft.XLANGs.RuntimeTypes.MessagePropertyDefinition _getMessagePropertyDefinition(System.Type) The following is a stack trace that identifies the location where the exception occured   at Microsoft.XLANGs.Core.XMessage._getMessagePropertyDefinition(Type propType) at Microsoft.XLANGs.Core.XMessage.GetContentProperty(Type propType) at Microsoft.XLANGs.Core.XMessage.GetPropertyValue(Type propType) at Microsoft.BizTalk.XLANGs.BTXEngine.BTXMessage.GetPropertyValue(Type propType) at Microsoft.XLANGs.Core.MessageWrapperForUserCode.GetPropertyValue(Type propType) at Tellago.Common.Components.Load(XLANGMessage msg) at Tellago.SuspensionProcess.segment1(StopConditions stopOn) at Microsoft.XLANGs.Core.SegmentScheduler.RunASegment(Segment s, StopConditions stopCond, Exception& exp)

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  • Why do I get "Sequence contains no elements"?

    - by Gary McGill
    NOTE: see edits at bottom. I am an idiot. I had the following code to process set of tag names and identify/process new ones: IEnumberable<string> tagNames = GetTagNames(); List<Tag> allTags = GetAllTags(); var newTagNames = tagNames.Where(n => !allTags.Any(t => t.Name == n)); foreach (var tagName in newTagNames) { // ... } ...and this worked fine, except that it failed to deal with cases where there's a tag called "Foo" and the list contains "foo". In other words, it wasn't doing a case-insensitive comparison. I changed the test to use a case-insensitive comparison, as follows: var newTagNames = tagNames.Where(n => !allTags.Any(t => t.Name.Equals(n, StringComparison.InvariantCultureIgnoreCase))); ... and suddenly I get an exception thrown when the foreach runs (and calls MoveNext on) newTagNames. The exception says: Sequence has no elements I'm confused by this. Why would foreach insist on the sequence being non-empty? I'd expect to see that error if I was calling First(), but not when using foreach? EDIT: more info. This is getting weirder by the minute. Because my code is in an async method, and I'm superstitious, I decided that there was too much "distance" between the point at which the exception is raised, and the point at which it's caught and reported. So, I put a try/catch around the offending code, in the hope of verifying that the exception being thrown really was what I thought it was. So now I can step through in the debugger to the foreach line, I can verify that the sequence is empty, and I can step right up to the bit where the debugger highlights the word "in". One more step, and I'm in my exception handler. But, not the exception handler I just added, no! It lands in my outermost exception handler, without visiting my recently-added one! It doesn't match catch (Exception ex) and nor does it match a plain catch. (I did also put in a finally, and verified that it does visit that on the way out). I've always taken it on faith that an Exception handler such as those would catch any exception. I'm scared now. I need an adult. EDIT 2: OK, so um, false alarm... The exception was not being caught by my local try/catch simply because it was not being raised by the code I thought. As I said above, I watched the execution in the debugger jump from the "in" of the foreach straight to the outer exception handler, hence my (wrong) assumption that that was where the error lay. However, with the empty enumeration, that was simply the last statement executed within the function, and for some reason the debugger did not show me the step out of the function or the execution of the next statement at the point of call - which was in fact the one causing the error. Apologies to all those who responded, and if you would like to create an answer saying that I am an idoit, I will gladly accept it. That is, if I ever show my face on SO again...

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  • BinaryWrite exception "OutputStream is not available when a custom TextWriter is used" in MVC 2 ASP.

    - by Grant
    Hi, I have a view rendering a stream using the response BinaryWrite method. This all worked fine under ASP.NET 4 using the Beta 2 but throws this exception in the RC release: "HttpException" , "OutputStream is not available when a custom TextWriter is used." <%@ Page Title="" Language="C#" Inherits="System.Web.Mvc.ViewPage" %> <%@ Import Namespace="System.IO" %> <script runat="server"> protected void Page_Load(object sender, EventArgs e) { if (ViewData["Error"] == null) { Response.Buffer = true; Response.Clear(); Response.ContentType = ViewData["DocType"] as string; Response.AddHeader("content-disposition", ViewData["Disposition"] as string); Response.CacheControl = "No-cache"; MemoryStream stream = ViewData["DocAsStream"] as MemoryStream; Response.BinaryWrite(stream.ToArray()); Response.Flush(); Response.Close(); } } </script> </script> The view is generated from a client side redirect (jquery replace location call in the previous page using Url.Action helper to render the link of course). This is all in an iframe. Anyone have an idea why this occurs?

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  • System.Net.WebException: The remote server returned an error: (405) Method Not Allowed .exception occurred during the execution of the web request

    - by user88
    When I ran my web application code I got this error on this line. using (HttpWebResponse response = (HttpWebResponse)request.GetResponse()){} Actually when I ran my url directly on browser.It will give proper o/p but when I ran my url in code. It will give exception. Here MyCode is :- string service = "http://api.ean.com/ean-services/rs/hotel/"; string version = "v3/"; string method = "info/"; string hotelId1 = "188603"; int hotelId = Convert.ToInt32(hotelId1); string otherElemntsStr = "&cid=411931&minorRev=[12]&customerUserAgent=[hotel]&locale=en_US&currencyCode=INR"; string apiKey = "tzyw4x2zspckjayrbjekb397"; string sig = "a6f828b696ae6a9f7c742b34538259b0"; string url = service + version + method + "?&type=xml" + "&apiKey=" + apiKey + "&sig=" + sig + otherElemntsStr + "&hotelId=" + hotelId; HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url) as HttpWebRequest; request.Method = "POST"; request.ContentType = "text/xml"; request.ContentLength = 0; XmlDocument xmldoc = new XmlDocument(); using (HttpWebResponse response = (HttpWebResponse)request.GetResponse()) { StreamReader responsereader = new StreamReader(response.GetResponseStream()); var responsedata = responsereader.ReadToEnd(); xmldoc = (XmlDocument)JsonConvert.DeserializeXmlNode(responsedata); xmldoc.Save(@"D:\FlightSearch\myfile.xml"); xmldoc.Load(@"D:\FlightSearch\myfile.xml"); DataSet ds = new DataSet(); ds.ReadXml(Request.PhysicalApplicationPath + "myfile.xml"); GridView1.DataSource = ds.Tables["HotelSummary"]; GridView1.DataBind(); }

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  • How to solve this nullPointer Exception in jasper report?

    - by Kumar
    Hi, I am new to jasper report, I need to create pdf document with BeanDatasource and subreport. I refer the following blog " http://knol.google.com/k/jasper-reports-working-with-beans-and-sub-report# " . I followed all the steps perfectly. While i am running the report using IReport i can get the pdf document with the content. But when we try to create from java program i m getting exception in the following line Line number 110: " JasperFillManager.fillReportToFile("C:/JasperReports/contacts.jasper", parameters, new JRBeanCollectionDataSource(TestPerson.getBeanCollection())); " and this is the following error i am getting in my Eclipse Console window . java.lang.NullPointerException at net.sf.jasperreports.engine.JRPropertiesMap.readObject(JRPropertiesMap.java:185) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at java.io.ObjectStreamClass.invokeReadObject(Unknown Source) at java.io.ObjectInputStream.readSerialData(Unknown Source) at java.io.ObjectInputStream.readOrdinaryObject(Unknown Source) at java.io.ObjectInputStream.readObject0(Unknown Source) at java.io.ObjectInputStream.defaultReadFields(Unknown Source) at java.io.ObjectInputStream.readSerialData(Unknown Source) at java.io.ObjectInputStream.readOrdinaryObject(Unknown Source) at java.io.ObjectInputStream.readObject0(Unknown Source) at java.io.ObjectInputStream.readArray(Unknown Source) at java.io.ObjectInputStream.readObject0(Unknown Source) at java.io.ObjectInputStream.defaultReadFields(Unknown Source) at java.io.ObjectInputStream.readSerialData(Unknown Source) at java.io.ObjectInputStream.readOrdinaryObject(Unknown Source) at java.io.ObjectInputStream.readObject0(Unknown Source) at java.io.ObjectInputStream.defaultReadFields(Unknown Source) at java.io.ObjectInputStream.readSerialData(Unknown Source) at java.io.ObjectInputStream.readOrdinaryObject(Unknown Source) at java.io.ObjectInputStream.readObject0(Unknown Source) at java.io.ObjectInputStream.readObject(Unknown Source) at net.sf.jasperreports.engine.util.JRLoader.loadObject(JRLoader.java:88) at net.sf.jasperreports.engine.util.JRLoader.loadObjectFromLocation(JRLoader.java:257) at net.sf.jasperreports.engine.fill.JRFillSubreport.evaluateSubreport(JRFillSubreport.java:308) at net.sf.jasperreports.engine.fill.JRFillSubreport.evaluate(JRFillSubreport.java:257) at net.sf.jasperreports.engine.fill.JRFillElementContainer.evaluate(JRFillElementContainer.java:275) at net.sf.jasperreports.engine.fill.JRFillBand.evaluate(JRFillBand.java:426) at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillColumnBand(JRVerticalFiller.java:1380) at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillDetail(JRVerticalFiller.java:692) at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillReportStart(JRVerticalFiller.java:255) at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillReport(JRVerticalFiller.java:113) at net.sf.jasperreports.engine.fill.JRBaseFiller.fill(JRBaseFiller.java:891) at net.sf.jasperreports.engine.fill.JRBaseFiller.fill(JRBaseFiller.java:814) at net.sf.jasperreports.engine.fill.JRFiller.fillReport(JRFiller.java:89) at net.sf.jasperreports.engine.JasperFillManager.fillReport(JasperFillManager.java:601) at test.TestJasperReport.main(TestJasperReport.java:110)

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  • JACOB (Java/COM/ActiveX) - How to troubleshoot event handling?

    - by Youval Bronicki
    I'm trying to use JACOB to interact with a COM object. I was able to invoke an initialization method on the object (and to get its properties), but am not getting any events back. The code is quoted below. I have a sample HTML+Javascript page (running in IE) that successfully receives events from the same object. I'm considering the following options, but would appreciate any concrete troubleshooting ideas ... Send my Java program to the team who developed the COM object, and have them look for anything suspicious on their side (does the object have a way on knowing whether there's a client listening to its events, and whether they were successfully delivered?) Get into the native parts of JACOB and try to debug on that side. That's a little scary given that my C++ is rusty and that I've never programmed for Windows. public static void main(String[] args) { try { ActiveXComponent c = new ActiveXComponent( "CLSID:{********-****-****-****-************}"); // My object's clsid if (c != null) { System.out.println("Version:"+c.getProperty("Version")); InvocationProxy proxy = new InvocationProxy() { @Override public Variant invoke(String methodName, Variant[] targetParameters) { System.out.println("*** Event ***: " + methodName); return null; } }; DispatchEvents de = new DispatchEvents((Dispatch) c.getObject(), proxy); c.invoke("Init", new Variant[] { new Variant(10), //param1 new Variant(2), //param2 }); System.out.println("Wating for events ..."); Thread.sleep(60000); // 60 seconds is long enough System.out.println("Cleaning up ..."); c.safeRelease(); } } catch (Exception e) { e.printStackTrace(); } finally { ComThread.Release(); } }

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  • Why does ObservableCollection throws an exception when being modified?

    - by Oliver Hanappi
    Hi! My application uses a WPF DataGrid. One of the columns is a template column that containts a combobox bound to an ObservableCollection of the entity which feeds the row. When I add a value to the ObservableCollection, a NullReferenceException is thrown. Has anybody an idea why this happens? Here is the stacktrace of the exception: at MS.Internal.Data.PropertyPathWorker.DetermineWhetherDBNullIsValid() at MS.Internal.Data.PropertyPathWorker.get_IsDBNullValidForUpdate() at MS.Internal.Data.ClrBindingWorker.get_IsDBNullValidForUpdate() at System.Windows.Data.BindingExpression.ConvertProposedValue(Object value) at System.Windows.Data.BindingExpressionBase.UpdateValue() at System.Windows.Data.BindingExpression.Update(Boolean synchronous) at System.Windows.Data.BindingExpressionBase.Dirty() at System.Windows.Data.BindingExpression.SetValue(DependencyObject d, DependencyProperty dp, Object value) at System.Windows.DependencyObject.SetValueCommon(DependencyProperty dp, Object value, PropertyMetadata metadata, Boolean coerceWithDeferredReference, OperationType operationType, Boolean isInternal) at System.Windows.DependencyObject.SetValue(DependencyProperty dp, Object value) at System.Windows.Controls.Primitives.Selector.UpdatePublicSelectionProperties() at System.Windows.Controls.Primitives.Selector.SelectionChanger.End() at System.Windows.Controls.Primitives.Selector.OnItemsChanged(NotifyCollectionChangedEventArgs e) at System.Windows.Controls.ItemsControl.OnItemCollectionChanged(Object sender, NotifyCollectionChangedEventArgs e) at System.Collections.Specialized.NotifyCollectionChangedEventHandler.Invoke(Object sender, NotifyCollectionChangedEventArgs e) at System.Windows.Data.CollectionView.OnCollectionChanged(NotifyCollectionChangedEventArgs args) at System.Windows.Controls.ItemCollection.System.Windows.IWeakEventListener.ReceiveWeakEvent(Type managerType, Object sender, EventArgs e) at System.Windows.WeakEventManager.DeliverEventToList(Object sender, EventArgs args, ListenerList list) at System.Windows.WeakEventManager.DeliverEvent(Object sender, EventArgs args) at System.Collections.Specialized.CollectionChangedEventManager.OnCollectionChanged(Object sender, NotifyCollectionChangedEventArgs args) at System.Windows.Data.CollectionView.OnCollectionChanged(NotifyCollectionChangedEventArgs args) at System.Windows.Data.ListCollectionView.ProcessCollectionChangedWithAdjustedIndex(NotifyCollectionChangedEventArgs args, Int32 adjustedOldIndex, Int32 adjustedNewIndex) at System.Windows.Data.ListCollectionView.ProcessCollectionChanged(NotifyCollectionChangedEventArgs args) at System.Windows.Data.CollectionView.OnCollectionChanged(Object sender, NotifyCollectionChangedEventArgs args) at System.Collections.ObjectModel.ObservableCollection`1.OnCollectionChanged(NotifyCollectionChangedEventArgs e) at System.Collections.ObjectModel.ObservableCollection`1.InsertItem(Int32 index, T item) at System.Collections.ObjectModel.Collection`1.Add(T item) at ORF.PersonBook.IdentityModule.Model.SubsidiaryModel.AddRoom(RoomModel room) in C:\Project\Phoenix\Development\src\ORF.PersonBook.IdentityModule\Model\SubsidiaryModel.cs:line 127

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  • object reference not set to an instance of object exception coming at runtime.

    - by amby
    Hi, I am getting this error at runtime: object reference not set to an instance of object my question is that am i using stringbuilder array correctly here. Because I am new in C#. and i think its the problem with my stringbuilder array. Below is the code: using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.Services; using System.Web.UI; using System.Web.UI.WebControls; using System.Data; using System.Text; using System.Web.Script.Serialization; using System.Web.Script.Services; using System.Collections; public partial class Testing : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { } [WebMethod] public static string SendMessage() { try { al2c00.ldap ws = new al2c00.ldap(); Hashtable htPeople = new Hashtable(); //DataTable dt = ws.GetEmployeeDetailsBy_NTID("650FA25C-9561-430B-B757-835D043EA5E5", "john"); StringBuilder[] empDetails = new StringBuilder[100]; string num = "ambreen"; empDetails[0].Append("amby"); num = empDetails[0].ToString(); htPeople.Add("bellempposreport", num); JavaScriptSerializer jss = new JavaScriptSerializer(); string output = jss.Serialize(htPeople); return output; } catch(Exception ex) { return ex.Message + "-" + ex.StackTrace; } } } please reply me what i am doing wrong here.

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  • Why is Swing Parser's handleText not handling nested tags?

    - by Jim P
    I need to transform some HTML text that has nested tags to decorate 'matches' with a css attribute to highlight it (like firefox search). I can't just do a simple replace (think if user searched for "img" for example), so I'm trying to just do the replace within the body text (not on tag attributes). I have a pretty straightforward HTML parser that I think should do this: final Pattern pat = Pattern.compile(srch, Pattern.CASE_INSENSITIVE); Matcher m = pat.matcher(output); if (m.find()) { final StringBuffer ret = new StringBuffer(output.length()+100); lastPos=0; try { new ParserDelegator().parse(new StringReader(output.toString()), new HTMLEditorKit.ParserCallback () { public void handleText(char[] data, int pos) { ret.append(output.subSequence(lastPos, pos)); Matcher m = pat.matcher(new String(data)); ret.append(m.replaceAll("<span class=\"search\">$0</span>")); lastPos=pos+data.length; } }, false); ret.append(output.subSequence(lastPos, output.length())); return ret; } catch (Exception e) { return output; } } return output; My problem is, when I debug this, the handleText is getting called with text that includes tags! It's like it's only going one level deep. Anyone know why? Is there some simple thing I need to do to HTMLParser (haven't used it much) to enable 'proper' behavior of nested tags? PS - I figured it out myself - see answer below. Short answer is, it works fine if you pass it HTML, not pre-escaped HTML. Doh! Hope this helps someone else. <span>example with <a href="#">nested</a> <p>more nesting</p> </span> <!-- all this gets thrown together -->

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  • .NET Speech recognition plugin Runtime Error: Unhandled Exception. What could possibly cause it?

    - by manuel
    I'm writing a plugin (dll file) for speech recognition, and I'm creating a WinForm as its interface/dialog. When I run the plugin and click the 'Speak' to start the initialization, I get an unhandled exception. Here is a piece of the code: public ref class Dialog : public System::Windows::Forms::Form { public: SpeechRecognitionEngine^ sre; private: System::Void btnSpeak_Click(System::Object^ sender, System::EventArgs^ e) { Initialize(); } protected: void Initialize() { if (System::Threading::Thread::CurrentThread->GetApartmentState() != System::Threading::ApartmentState::STA) { throw gcnew InvalidOperationException("UI thread required"); } //create the recognition engine sre = gcnew SpeechRecognitionEngine(); //set our recognition engine to use the default audio device sre->SetInputToDefaultAudioDevice(); //create a new GrammarBuilder to specify which commands we want to use GrammarBuilder^ grammarBuilder = gcnew GrammarBuilder(); //append all the choices we want for commands. //we want to be able to move, stop, quit the game, and check for the cake. grammarBuilder->Append(gcnew Choices("play", "stop")); //create the Grammar from th GrammarBuilder Grammar^ customGrammar = gcnew Grammar(grammarBuilder); //unload any grammars from the recognition engine sre->UnloadAllGrammars(); //load our new Grammar sre->LoadGrammar(customGrammar); //add an event handler so we get events whenever the engine recognizes spoken commands sre->SpeechRecognized += gcnew EventHandler<SpeechRecognizedEventArgs^> (this, &Dialog::sre_SpeechRecognized); //set the recognition engine to keep running after recognizing a command. //if we had used RecognizeMode.Single, the engine would quite listening after //the first recognized command. sre->RecognizeAsync(RecognizeMode::Multiple); //this->init(); } void sre_SpeechRecognized(Object^ sender, SpeechRecognizedEventArgs^ e) { //simple check to see what the result of the recognition was if (e->Result->Text == "play") { MessageBox(plugin.hwndParent, L"play", 0, 0); } if (e->Result->Text == "stop") { MessageBox(plugin.hwndParent, L"stop", 0, 0); } } };

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  • Exception while hosting a WCF Service in a DependencyInjection Module ?

    - by Maciek
    Hello, I've written a small just-for-fun console project using Ninject, I'm pasting some of the code below just so that you get the idea : Program.cs using System; using Ninject; using Ninjectionn.Modules; // My namespace for my modules namespace Ninjections { class Program { static void Main(string[] args) { IKernel kernel = new StandardKernel(); kernel.Load<ServicesHostModule>(); Console.ReadKey(); } } } ServicesHostModule.cs using System; using System.ServiceModel; using Ninject; using Ninject.Modules; namespace Ninjections.Modules { public class ServicesHostModule : INinjectModule { #region INinjectModule Members public string Name { get { return "ServicesHost"; }} public void OnLoad(IKernel kernel) { if(m_host != null) m_host.Close(); else m_host = new ServiceHost(typeof(WCFTestService)); m_host.Open(); // (!) EXCEPTION HERE } public void OnUnLoad(IKernel kernel) { m_host.Close(); } #endregion } } ITestWCFService.cs using System.ServiceModel; namespace Ninjections.Modules { [ServiceContract] public interface ITestWCFService { [OperationContract] string GetString1(); [OperationContract] string GetString2(); } } An auto-generated App.config is in the ServicesHostModule project. I've "added" an existing item (the app config) as link in the main project. Q: at the m_host.Open(); line, an InvalidOperationException occurs. The message says : "Service "Ninjections.Modules.TestWCFService" has zero application endopints. What's wrong?

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  • Messages not forwarded to error queue when exception is thrown in handler (it works on my machine)

    - by darthjit
    e are using NServicebus 4.0.5 with sql server(sql server 2012) as transport. When the handler throws an exception, NSB does not retry or move the message to the error queue. Successful messages make it to the audit queue but the failed/errored ones don't! . Interestingly, all this works on our local machines(windows 7 ,sql server localdb) but not on windows server 2012 (sql server 2012). Here is the config info on the subscriber: <add name="NServiceBus/Transport" connectionString="Data Source=xxx;Initial Catalog=NServiceBus;Integrated Security=SSPI;Enlist=false;" /> <add name="NServiceBus/Persistence" connectionString="Data Source=xxx;Initial Catalog=NServiceBus;Integrated Security=SSPI;Enlist=false;" /> <MessageForwardingInCaseOfFaultConfig ErrorQueue="error" /> <UnicastBusConfig ForwardReceivedMessagesTo="audit"> <MessageEndpointMappings> <add Assembly="Services.Section.Messages" Endpoint= "Services.ACL.Worker" /> </MessageEndpointMappings> </UnicastBusConfig> And in code it is configured as follows: public class EndpointConfig : IConfigureThisEndpoint, AsA_Server, IWantCustomInitialization { public void Init() { IContainer container = ContainerInstanceProvider. GetContainerInstance(); Configure .Transactions.Enable(); Configure.With() .AutofacBuilder(container) .UseTransport<SqlServer>() .Log4Net() //.Serialization.Json() .UseNHibernateSubscriptionPersister() .UseNHibernateTimeoutPersister() .MessageForwardingInCaseOfFault() .RijndaelEncryptionService() .DefiningCommandsAs(type => type.Namespace != null &&type .Namespace.EndsWith("Commands")) .DefiningEventsAs(type => type.Namespace != null &&type .Namespace.EndsWith("Events")) .UnicastBus(); } } Any ideas on how to fix this? here is the log info (there is a lot there, search for error to see the relevant parts) https://gist.github.com/ranji/7378249

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  • Understanding C# async / await (1) Compilation

    - by Dixin
    Now the async / await keywords are in C#. Just like the async and ! in F#, this new C# feature provides great convenience. There are many nice documents talking about how to use async / await in specific scenarios, like using async methods in ASP.NET 4.5 and in ASP.NET MVC 4, etc. In this article we will look at the real code working behind the syntax sugar. According to MSDN: The async modifier indicates that the method, lambda expression, or anonymous method that it modifies is asynchronous. Since lambda expression / anonymous method will be compiled to normal method, we will focus on normal async method. Preparation First of all, Some helper methods need to make up. internal class HelperMethods { internal static int Method(int arg0, int arg1) { // Do some IO. WebClient client = new WebClient(); Enumerable.Repeat("http://weblogs.asp.net/dixin", 10) .Select(client.DownloadString).ToArray(); int result = arg0 + arg1; return result; } internal static Task<int> MethodTask(int arg0, int arg1) { Task<int> task = new Task<int>(() => Method(arg0, arg1)); task.Start(); // Hot task (started task) should always be returned. return task; } internal static void Before() { } internal static void Continuation1(int arg) { } internal static void Continuation2(int arg) { } } Here Method() is a long running method doing some IO. Then MethodTask() wraps it into a Task and return that Task. Nothing special here. Await something in async method Since MethodTask() returns Task, let’s try to await it: internal class AsyncMethods { internal static async Task<int> MethodAsync(int arg0, int arg1) { int result = await HelperMethods.MethodTask(arg0, arg1); return result; } } Because we used await in the method, async must be put on the method. Now we get the first async method. According to the naming convenience, it is called MethodAsync. Of course a async method can be awaited. So we have a CallMethodAsync() to call MethodAsync(): internal class AsyncMethods { internal static async Task<int> CallMethodAsync(int arg0, int arg1) { int result = await MethodAsync(arg0, arg1); return result; } } After compilation, MethodAsync() and CallMethodAsync() becomes the same logic. This is the code of MethodAsyc(): internal class CompiledAsyncMethods { [DebuggerStepThrough] [AsyncStateMachine(typeof(MethodAsyncStateMachine))] // async internal static /*async*/ Task<int> MethodAsync(int arg0, int arg1) { MethodAsyncStateMachine methodAsyncStateMachine = new MethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Builder = AsyncTaskMethodBuilder<int>.Create(), State = -1 }; methodAsyncStateMachine.Builder.Start(ref methodAsyncStateMachine); return methodAsyncStateMachine.Builder.Task; } } It just creates and starts a state machine MethodAsyncStateMachine: [CompilerGenerated] [StructLayout(LayoutKind.Auto)] internal struct MethodAsyncStateMachine : IAsyncStateMachine { public int State; public AsyncTaskMethodBuilder<int> Builder; public int Arg0; public int Arg1; public int Result; private TaskAwaiter<int> awaitor; void IAsyncStateMachine.MoveNext() { try { if (this.State != 0) { this.awaitor = HelperMethods.MethodTask(this.Arg0, this.Arg1).GetAwaiter(); if (!this.awaitor.IsCompleted) { this.State = 0; this.Builder.AwaitUnsafeOnCompleted(ref this.awaitor, ref this); return; } } else { this.State = -1; } this.Result = this.awaitor.GetResult(); } catch (Exception exception) { this.State = -2; this.Builder.SetException(exception); return; } this.State = -2; this.Builder.SetResult(this.Result); } [DebuggerHidden] void IAsyncStateMachine.SetStateMachine(IAsyncStateMachine param0) { this.Builder.SetStateMachine(param0); } } The generated code has been cleaned up so it is readable and can be compiled. Several things can be observed here: The async modifier is gone, which shows, unlike other modifiers (e.g. static), there is no such IL/CLR level “async” stuff. It becomes a AsyncStateMachineAttribute. This is similar to the compilation of extension method. The generated state machine is very similar to the state machine of C# yield syntax sugar. The local variables (arg0, arg1, result) are compiled to fields of the state machine. The real code (await HelperMethods.MethodTask(arg0, arg1)) is compiled into MoveNext(): HelperMethods.MethodTask(this.Arg0, this.Arg1).GetAwaiter(). CallMethodAsync() will create and start its own state machine CallMethodAsyncStateMachine: internal class CompiledAsyncMethods { [DebuggerStepThrough] [AsyncStateMachine(typeof(CallMethodAsyncStateMachine))] // async internal static /*async*/ Task<int> CallMethodAsync(int arg0, int arg1) { CallMethodAsyncStateMachine callMethodAsyncStateMachine = new CallMethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Builder = AsyncTaskMethodBuilder<int>.Create(), State = -1 }; callMethodAsyncStateMachine.Builder.Start(ref callMethodAsyncStateMachine); return callMethodAsyncStateMachine.Builder.Task; } } CallMethodAsyncStateMachine has the same logic as MethodAsyncStateMachine above. The detail of the state machine will be discussed soon. Now it is clear that: async /await is a C# level syntax sugar. There is no difference to await a async method or a normal method. A method returning Task will be awaitable. State machine and continuation To demonstrate more details in the state machine, a more complex method is created: internal class AsyncMethods { internal static async Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { HelperMethods.Before(); int resultOfAwait1 = await MethodAsync(arg0, arg1); HelperMethods.Continuation1(resultOfAwait1); int resultOfAwait2 = await MethodAsync(arg2, arg3); HelperMethods.Continuation2(resultOfAwait2); int resultToReturn = resultOfAwait1 + resultOfAwait2; return resultToReturn; } } In this method: There are multiple awaits. There are code before the awaits, and continuation code after each await After compilation, this multi-await method becomes the same as above single-await methods: internal class CompiledAsyncMethods { [DebuggerStepThrough] [AsyncStateMachine(typeof(MultiCallMethodAsyncStateMachine))] // async internal static /*async*/ Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { MultiCallMethodAsyncStateMachine multiCallMethodAsyncStateMachine = new MultiCallMethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Arg2 = arg2, Arg3 = arg3, Builder = AsyncTaskMethodBuilder<int>.Create(), State = -1 }; multiCallMethodAsyncStateMachine.Builder.Start(ref multiCallMethodAsyncStateMachine); return multiCallMethodAsyncStateMachine.Builder.Task; } } It creates and starts one single state machine, MultiCallMethodAsyncStateMachine: [CompilerGenerated] [StructLayout(LayoutKind.Auto)] internal struct MultiCallMethodAsyncStateMachine : IAsyncStateMachine { public int State; public AsyncTaskMethodBuilder<int> Builder; public int Arg0; public int Arg1; public int Arg2; public int Arg3; public int ResultOfAwait1; public int ResultOfAwait2; public int ResultToReturn; private TaskAwaiter<int> awaiter; void IAsyncStateMachine.MoveNext() { try { switch (this.State) { case -1: HelperMethods.Before(); this.awaiter = AsyncMethods.MethodAsync(this.Arg0, this.Arg1).GetAwaiter(); if (!this.awaiter.IsCompleted) { this.State = 0; this.Builder.AwaitUnsafeOnCompleted(ref this.awaiter, ref this); } break; case 0: this.ResultOfAwait1 = this.awaiter.GetResult(); HelperMethods.Continuation1(this.ResultOfAwait1); this.awaiter = AsyncMethods.MethodAsync(this.Arg2, this.Arg3).GetAwaiter(); if (!this.awaiter.IsCompleted) { this.State = 1; this.Builder.AwaitUnsafeOnCompleted(ref this.awaiter, ref this); } break; case 1: this.ResultOfAwait2 = this.awaiter.GetResult(); HelperMethods.Continuation2(this.ResultOfAwait2); this.ResultToReturn = this.ResultOfAwait1 + this.ResultOfAwait2; this.State = -2; this.Builder.SetResult(this.ResultToReturn); break; } } catch (Exception exception) { this.State = -2; this.Builder.SetException(exception); } } [DebuggerHidden] void IAsyncStateMachine.SetStateMachine(IAsyncStateMachine stateMachine) { this.Builder.SetStateMachine(stateMachine); } } The above code is already cleaned up, but there are still a lot of things. More clean up can be done, and the state machine can be very simple: [CompilerGenerated] [StructLayout(LayoutKind.Auto)] internal struct MultiCallMethodAsyncStateMachine : IAsyncStateMachine { // State: // -1: Begin // 0: 1st await is done // 1: 2nd await is done // ... // -2: End public int State; public TaskCompletionSource<int> ResultToReturn; // int resultToReturn ... public int Arg0; // int Arg0 public int Arg1; // int arg1 public int Arg2; // int arg2 public int Arg3; // int arg3 public int ResultOfAwait1; // int resultOfAwait1 ... public int ResultOfAwait2; // int resultOfAwait2 ... private Task<int> currentTaskToAwait; /// <summary> /// Moves the state machine to its next state. /// </summary> void IAsyncStateMachine.MoveNext() { try { switch (this.State) { // Orginal code is splitted by "case"s: // case -1: // HelperMethods.Before(); // MethodAsync(Arg0, arg1); // case 0: // int resultOfAwait1 = await ... // HelperMethods.Continuation1(resultOfAwait1); // MethodAsync(arg2, arg3); // case 1: // int resultOfAwait2 = await ... // HelperMethods.Continuation2(resultOfAwait2); // int resultToReturn = resultOfAwait1 + resultOfAwait2; // return resultToReturn; case -1: // -1 is begin. HelperMethods.Before(); // Code before 1st await. this.currentTaskToAwait = AsyncMethods.MethodAsync(this.Arg0, this.Arg1); // 1st task to await // When this.currentTaskToAwait is done, run this.MoveNext() and go to case 0. this.State = 0; IAsyncStateMachine this1 = this; // Cannot use "this" in lambda so create a local variable. this.currentTaskToAwait.ContinueWith(_ => this1.MoveNext()); // Callback break; case 0: // Now 1st await is done. this.ResultOfAwait1 = this.currentTaskToAwait.Result; // Get 1st await's result. HelperMethods.Continuation1(this.ResultOfAwait1); // Code after 1st await and before 2nd await. this.currentTaskToAwait = AsyncMethods.MethodAsync(this.Arg2, this.Arg3); // 2nd task to await // When this.currentTaskToAwait is done, run this.MoveNext() and go to case 1. this.State = 1; IAsyncStateMachine this2 = this; // Cannot use "this" in lambda so create a local variable. this.currentTaskToAwait.ContinueWith(_ => this2.MoveNext()); // Callback break; case 1: // Now 2nd await is done. this.ResultOfAwait2 = this.currentTaskToAwait.Result; // Get 2nd await's result. HelperMethods.Continuation2(this.ResultOfAwait2); // Code after 2nd await. int resultToReturn = this.ResultOfAwait1 + this.ResultOfAwait2; // Code after 2nd await. // End with resultToReturn. this.State = -2; // -2 is end. this.ResultToReturn.SetResult(resultToReturn); break; } } catch (Exception exception) { // End with exception. this.State = -2; // -2 is end. this.ResultToReturn.SetException(exception); } } /// <summary> /// Configures the state machine with a heap-allocated replica. /// </summary> /// <param name="stateMachine">The heap-allocated replica.</param> [DebuggerHidden] void IAsyncStateMachine.SetStateMachine(IAsyncStateMachine stateMachine) { // No core logic. } } Only Task and TaskCompletionSource are involved in this version. And MultiCallMethodAsync() can be simplified to: [DebuggerStepThrough] [AsyncStateMachine(typeof(MultiCallMethodAsyncStateMachine))] // async internal static /*async*/ Task<int> MultiCallMethodAsync_(int arg0, int arg1, int arg2, int arg3) { MultiCallMethodAsyncStateMachine multiCallMethodAsyncStateMachine = new MultiCallMethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Arg2 = arg2, Arg3 = arg3, ResultToReturn = new TaskCompletionSource<int>(), // -1: Begin // 0: 1st await is done // 1: 2nd await is done // ... // -2: End State = -1 }; (multiCallMethodAsyncStateMachine as IAsyncStateMachine).MoveNext(); // Original code are in this method. return multiCallMethodAsyncStateMachine.ResultToReturn.Task; } Now the whole state machine becomes very clear - it is about callback: Original code are split into pieces by “await”s, and each piece is put into each “case” in the state machine. Here the 2 awaits split the code into 3 pieces, so there are 3 “case”s. The “piece”s are chained by callback, that is done by Builder.AwaitUnsafeOnCompleted(callback), or currentTaskToAwait.ContinueWith(callback) in the simplified code. A previous “piece” will end with a Task (which is to be awaited), when the task is done, it will callback the next “piece”. The state machine’s state works with the “case”s to ensure the code “piece”s executes one after another. Callback Since it is about callback, the simplification  can go even further – the entire state machine can be completely purged. Now MultiCallMethodAsync() becomes: internal static Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { TaskCompletionSource<int> taskCompletionSource = new TaskCompletionSource<int>(); try { // Oringinal code begins. HelperMethods.Before(); MethodAsync(arg0, arg1).ContinueWith(await1 => { int resultOfAwait1 = await1.Result; HelperMethods.Continuation1(resultOfAwait1); MethodAsync(arg2, arg3).ContinueWith(await2 => { int resultOfAwait2 = await2.Result; HelperMethods.Continuation2(resultOfAwait2); int resultToReturn = resultOfAwait1 + resultOfAwait2; // Oringinal code ends. taskCompletionSource.SetResult(resultToReturn); }); }); } catch (Exception exception) { taskCompletionSource.SetException(exception); } return taskCompletionSource.Task; } Please compare with the original async / await code: HelperMethods.Before(); int resultOfAwait1 = await MethodAsync(arg0, arg1); HelperMethods.Continuation1(resultOfAwait1); int resultOfAwait2 = await MethodAsync(arg2, arg3); HelperMethods.Continuation2(resultOfAwait2); int resultToReturn = resultOfAwait1 + resultOfAwait2; return resultToReturn; Yeah that is the magic of C# async / await: Await is literally pretending to wait. In a await expression, a Task object will be return immediately so that caller is not blocked. The continuation code is compiled as that Task’s callback code. When that task is done, continuation code will execute. Please notice that many details inside the state machine are omitted for simplicity, like context caring, etc. If you want to have a detailed picture, please do check out the source code of AsyncTaskMethodBuilder and TaskAwaiter.

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  • Understanding C# async / await (1) Compilation

    - by Dixin
    Now the async / await keywords are in C#. Just like the async and ! in F#, this new C# feature provides great convenience. There are many nice documents talking about how to use async / await in specific scenarios, like using async methods in ASP.NET 4.5 and in ASP.NET MVC 4, etc. In this article we will look at the real code working behind the syntax sugar. According to MSDN: The async modifier indicates that the method, lambda expression, or anonymous method that it modifies is asynchronous. Since lambda expression / anonymous method will be compiled to normal method, we will focus on normal async method. Preparation First of all, Some helper methods need to make up. internal class HelperMethods { internal static int Method(int arg0, int arg1) { // Do some IO. WebClient client = new WebClient(); Enumerable.Repeat("http://weblogs.asp.net/dixin", 10) .Select(client.DownloadString).ToArray(); int result = arg0 + arg1; return result; } internal static Task<int> MethodTask(int arg0, int arg1) { Task<int> task = new Task<int>(() => Method(arg0, arg1)); task.Start(); // Hot task (started task) should always be returned. return task; } internal static void Before() { } internal static void Continuation1(int arg) { } internal static void Continuation2(int arg) { } } Here Method() is a long running method doing some IO. Then MethodTask() wraps it into a Task and return that Task. Nothing special here. Await something in async method Since MethodTask() returns Task, let’s try to await it: internal class AsyncMethods { internal static async Task<int> MethodAsync(int arg0, int arg1) { int result = await HelperMethods.MethodTask(arg0, arg1); return result; } } Because we used await in the method, async must be put on the method. Now we get the first async method. According to the naming convenience, it is named MethodAsync. Of course a async method can be awaited. So we have a CallMethodAsync() to call MethodAsync(): internal class AsyncMethods { internal static async Task<int> CallMethodAsync(int arg0, int arg1) { int result = await MethodAsync(arg0, arg1); return result; } } After compilation, MethodAsync() and CallMethodAsync() becomes the same logic. This is the code of MethodAsyc(): internal class CompiledAsyncMethods { [DebuggerStepThrough] [AsyncStateMachine(typeof(MethodAsyncStateMachine))] // async internal static /*async*/ Task<int> MethodAsync(int arg0, int arg1) { MethodAsyncStateMachine methodAsyncStateMachine = new MethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Builder = AsyncTaskMethodBuilder<int>.Create(), State = -1 }; methodAsyncStateMachine.Builder.Start(ref methodAsyncStateMachine); return methodAsyncStateMachine.Builder.Task; } } It just creates and starts a state machine, MethodAsyncStateMachine: [CompilerGenerated] [StructLayout(LayoutKind.Auto)] internal struct MethodAsyncStateMachine : IAsyncStateMachine { public int State; public AsyncTaskMethodBuilder<int> Builder; public int Arg0; public int Arg1; public int Result; private TaskAwaiter<int> awaitor; void IAsyncStateMachine.MoveNext() { try { if (this.State != 0) { this.awaitor = HelperMethods.MethodTask(this.Arg0, this.Arg1).GetAwaiter(); if (!this.awaitor.IsCompleted) { this.State = 0; this.Builder.AwaitUnsafeOnCompleted(ref this.awaitor, ref this); return; } } else { this.State = -1; } this.Result = this.awaitor.GetResult(); } catch (Exception exception) { this.State = -2; this.Builder.SetException(exception); return; } this.State = -2; this.Builder.SetResult(this.Result); } [DebuggerHidden] void IAsyncStateMachine.SetStateMachine(IAsyncStateMachine param0) { this.Builder.SetStateMachine(param0); } } The generated code has been refactored, so it is readable and can be compiled. Several things can be observed here: The async modifier is gone, which shows, unlike other modifiers (e.g. static), there is no such IL/CLR level “async” stuff. It becomes a AsyncStateMachineAttribute. This is similar to the compilation of extension method. The generated state machine is very similar to the state machine of C# yield syntax sugar. The local variables (arg0, arg1, result) are compiled to fields of the state machine. The real code (await HelperMethods.MethodTask(arg0, arg1)) is compiled into MoveNext(): HelperMethods.MethodTask(this.Arg0, this.Arg1).GetAwaiter(). CallMethodAsync() will create and start its own state machine CallMethodAsyncStateMachine: internal class CompiledAsyncMethods { [DebuggerStepThrough] [AsyncStateMachine(typeof(CallMethodAsyncStateMachine))] // async internal static /*async*/ Task<int> CallMethodAsync(int arg0, int arg1) { CallMethodAsyncStateMachine callMethodAsyncStateMachine = new CallMethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Builder = AsyncTaskMethodBuilder<int>.Create(), State = -1 }; callMethodAsyncStateMachine.Builder.Start(ref callMethodAsyncStateMachine); return callMethodAsyncStateMachine.Builder.Task; } } CallMethodAsyncStateMachine has the same logic as MethodAsyncStateMachine above. The detail of the state machine will be discussed soon. Now it is clear that: async /await is a C# language level syntax sugar. There is no difference to await a async method or a normal method. As long as a method returns Task, it is awaitable. State machine and continuation To demonstrate more details in the state machine, a more complex method is created: internal class AsyncMethods { internal static async Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { HelperMethods.Before(); int resultOfAwait1 = await MethodAsync(arg0, arg1); HelperMethods.Continuation1(resultOfAwait1); int resultOfAwait2 = await MethodAsync(arg2, arg3); HelperMethods.Continuation2(resultOfAwait2); int resultToReturn = resultOfAwait1 + resultOfAwait2; return resultToReturn; } } In this method: There are multiple awaits. There are code before the awaits, and continuation code after each await After compilation, this multi-await method becomes the same as above single-await methods: internal class CompiledAsyncMethods { [DebuggerStepThrough] [AsyncStateMachine(typeof(MultiCallMethodAsyncStateMachine))] // async internal static /*async*/ Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { MultiCallMethodAsyncStateMachine multiCallMethodAsyncStateMachine = new MultiCallMethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Arg2 = arg2, Arg3 = arg3, Builder = AsyncTaskMethodBuilder<int>.Create(), State = -1 }; multiCallMethodAsyncStateMachine.Builder.Start(ref multiCallMethodAsyncStateMachine); return multiCallMethodAsyncStateMachine.Builder.Task; } } It creates and starts one single state machine, MultiCallMethodAsyncStateMachine: [CompilerGenerated] [StructLayout(LayoutKind.Auto)] internal struct MultiCallMethodAsyncStateMachine : IAsyncStateMachine { public int State; public AsyncTaskMethodBuilder<int> Builder; public int Arg0; public int Arg1; public int Arg2; public int Arg3; public int ResultOfAwait1; public int ResultOfAwait2; public int ResultToReturn; private TaskAwaiter<int> awaiter; void IAsyncStateMachine.MoveNext() { try { switch (this.State) { case -1: HelperMethods.Before(); this.awaiter = AsyncMethods.MethodAsync(this.Arg0, this.Arg1).GetAwaiter(); if (!this.awaiter.IsCompleted) { this.State = 0; this.Builder.AwaitUnsafeOnCompleted(ref this.awaiter, ref this); } break; case 0: this.ResultOfAwait1 = this.awaiter.GetResult(); HelperMethods.Continuation1(this.ResultOfAwait1); this.awaiter = AsyncMethods.MethodAsync(this.Arg2, this.Arg3).GetAwaiter(); if (!this.awaiter.IsCompleted) { this.State = 1; this.Builder.AwaitUnsafeOnCompleted(ref this.awaiter, ref this); } break; case 1: this.ResultOfAwait2 = this.awaiter.GetResult(); HelperMethods.Continuation2(this.ResultOfAwait2); this.ResultToReturn = this.ResultOfAwait1 + this.ResultOfAwait2; this.State = -2; this.Builder.SetResult(this.ResultToReturn); break; } } catch (Exception exception) { this.State = -2; this.Builder.SetException(exception); } } [DebuggerHidden] void IAsyncStateMachine.SetStateMachine(IAsyncStateMachine stateMachine) { this.Builder.SetStateMachine(stateMachine); } } Once again, the above state machine code is already refactored, but it still has a lot of things. More clean up can be done if we only keep the core logic, and the state machine can become very simple: [CompilerGenerated] [StructLayout(LayoutKind.Auto)] internal struct MultiCallMethodAsyncStateMachine : IAsyncStateMachine { // State: // -1: Begin // 0: 1st await is done // 1: 2nd await is done // ... // -2: End public int State; public TaskCompletionSource<int> ResultToReturn; // int resultToReturn ... public int Arg0; // int Arg0 public int Arg1; // int arg1 public int Arg2; // int arg2 public int Arg3; // int arg3 public int ResultOfAwait1; // int resultOfAwait1 ... public int ResultOfAwait2; // int resultOfAwait2 ... private Task<int> currentTaskToAwait; /// <summary> /// Moves the state machine to its next state. /// </summary> public void MoveNext() // IAsyncStateMachine member. { try { switch (this.State) { // Original code is split by "await"s into "case"s: // case -1: // HelperMethods.Before(); // MethodAsync(Arg0, arg1); // case 0: // int resultOfAwait1 = await ... // HelperMethods.Continuation1(resultOfAwait1); // MethodAsync(arg2, arg3); // case 1: // int resultOfAwait2 = await ... // HelperMethods.Continuation2(resultOfAwait2); // int resultToReturn = resultOfAwait1 + resultOfAwait2; // return resultToReturn; case -1: // -1 is begin. HelperMethods.Before(); // Code before 1st await. this.currentTaskToAwait = AsyncMethods.MethodAsync(this.Arg0, this.Arg1); // 1st task to await // When this.currentTaskToAwait is done, run this.MoveNext() and go to case 0. this.State = 0; MultiCallMethodAsyncStateMachine that1 = this; // Cannot use "this" in lambda so create a local variable. this.currentTaskToAwait.ContinueWith(_ => that1.MoveNext()); break; case 0: // Now 1st await is done. this.ResultOfAwait1 = this.currentTaskToAwait.Result; // Get 1st await's result. HelperMethods.Continuation1(this.ResultOfAwait1); // Code after 1st await and before 2nd await. this.currentTaskToAwait = AsyncMethods.MethodAsync(this.Arg2, this.Arg3); // 2nd task to await // When this.currentTaskToAwait is done, run this.MoveNext() and go to case 1. this.State = 1; MultiCallMethodAsyncStateMachine that2 = this; this.currentTaskToAwait.ContinueWith(_ => that2.MoveNext()); break; case 1: // Now 2nd await is done. this.ResultOfAwait2 = this.currentTaskToAwait.Result; // Get 2nd await's result. HelperMethods.Continuation2(this.ResultOfAwait2); // Code after 2nd await. int resultToReturn = this.ResultOfAwait1 + this.ResultOfAwait2; // Code after 2nd await. // End with resultToReturn. this.State = -2; // -2 is end. this.ResultToReturn.SetResult(resultToReturn); break; } } catch (Exception exception) { // End with exception. this.State = -2; // -2 is end. this.ResultToReturn.SetException(exception); } } /// <summary> /// Configures the state machine with a heap-allocated replica. /// </summary> /// <param name="stateMachine">The heap-allocated replica.</param> [DebuggerHidden] public void SetStateMachine(IAsyncStateMachine stateMachine) // IAsyncStateMachine member. { // No core logic. } } Only Task and TaskCompletionSource are involved in this version. And MultiCallMethodAsync() can be simplified to: [DebuggerStepThrough] [AsyncStateMachine(typeof(MultiCallMethodAsyncStateMachine))] // async internal static /*async*/ Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { MultiCallMethodAsyncStateMachine multiCallMethodAsyncStateMachine = new MultiCallMethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Arg2 = arg2, Arg3 = arg3, ResultToReturn = new TaskCompletionSource<int>(), // -1: Begin // 0: 1st await is done // 1: 2nd await is done // ... // -2: End State = -1 }; multiCallMethodAsyncStateMachine.MoveNext(); // Original code are moved into this method. return multiCallMethodAsyncStateMachine.ResultToReturn.Task; } Now the whole state machine becomes very clean - it is about callback: Original code are split into pieces by “await”s, and each piece is put into each “case” in the state machine. Here the 2 awaits split the code into 3 pieces, so there are 3 “case”s. The “piece”s are chained by callback, that is done by Builder.AwaitUnsafeOnCompleted(callback), or currentTaskToAwait.ContinueWith(callback) in the simplified code. A previous “piece” will end with a Task (which is to be awaited), when the task is done, it will callback the next “piece”. The state machine’s state works with the “case”s to ensure the code “piece”s executes one after another. Callback If we focus on the point of callback, the simplification  can go even further – the entire state machine can be completely purged, and we can just keep the code inside MoveNext(). Now MultiCallMethodAsync() becomes: internal static Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { TaskCompletionSource<int> taskCompletionSource = new TaskCompletionSource<int>(); try { // Oringinal code begins. HelperMethods.Before(); MethodAsync(arg0, arg1).ContinueWith(await1 => { int resultOfAwait1 = await1.Result; HelperMethods.Continuation1(resultOfAwait1); MethodAsync(arg2, arg3).ContinueWith(await2 => { int resultOfAwait2 = await2.Result; HelperMethods.Continuation2(resultOfAwait2); int resultToReturn = resultOfAwait1 + resultOfAwait2; // Oringinal code ends. taskCompletionSource.SetResult(resultToReturn); }); }); } catch (Exception exception) { taskCompletionSource.SetException(exception); } return taskCompletionSource.Task; } Please compare with the original async / await code: HelperMethods.Before(); int resultOfAwait1 = await MethodAsync(arg0, arg1); HelperMethods.Continuation1(resultOfAwait1); int resultOfAwait2 = await MethodAsync(arg2, arg3); HelperMethods.Continuation2(resultOfAwait2); int resultToReturn = resultOfAwait1 + resultOfAwait2; return resultToReturn; Yeah that is the magic of C# async / await: Await is not to wait. In a await expression, a Task object will be return immediately so that execution is not blocked. The continuation code is compiled as that Task’s callback code. When that task is done, continuation code will execute. Please notice that many details inside the state machine are omitted for simplicity, like context caring, etc. If you want to have a detailed picture, please do check out the source code of AsyncTaskMethodBuilder and TaskAwaiter.

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  • Developing Spring Portlet for use inside Weblogic Portal / Webcenter Portal

    - by Murali Veligeti
    We need to understand the main difference between portlet workflow and servlet workflow.The main difference between portlet workflow and servlet workflow is that, the request to the portlet can have two distinct phases: 1) Action phase 2) Render phase. The Action phase is executed only once and is where any 'backend' changes or actions occur, such as making changes in a database. The Render phase then produces what is displayed to the user each time the display is refreshed. The critical point here is that for a single overall request, the action phase is executed only once, but the render phase may be executed multiple times. This provides a clean separation between the activities that modify the persistent state of your system and the activities that generate what is displayed to the user.The dual phases of portlet requests are one of the real strengths of the JSR-168 specification. For example, dynamic search results can be updated routinely on the display without the user explicitly re-running the search. Most other portlet MVC frameworks attempt to completely hide the two phases from the developer and make it look as much like traditional servlet development as possible - we think this approach removes one of the main benefits of using portlets. So, the separation of the two phases is preserved throughout the Spring Portlet MVC framework. The primary manifestation of this approach is that where the servlet version of the MVC classes will have one method that deals with the request, the portlet version of the MVC classes will have two methods that deal with the request: one for the action phase and one for the render phase. For example, where the servlet version of AbstractController has the handleRequestInternal(..) method, the portlet version of AbstractController has handleActionRequestInternal(..) and handleRenderRequestInternal(..) methods.The Spring Portlet Framework is designed around a DispatcherPortlet that dispatches requests to handlers, with configurable handler mappings and view resolution, just as the DispatcherServlet in the Spring Web Framework does.  Developing portlet.xml Let's start the sample development by creating the portlet.xml file in the /WebContent/WEB-INF/ folder as shown below: <?xml version="1.0" encoding="UTF-8"?> <portlet-app version="2.0" xmlns="http://java.sun.com/xml/ns/portlet/portlet-app_2_0.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> <portlet> <portlet-name>SpringPortletName</portlet-name> <portlet-class>org.springframework.web.portlet.DispatcherPortlet</portlet-class> <supports> <mime-type>text/html</mime-type> <portlet-mode>view</portlet-mode> </supports> <portlet-info> <title>SpringPortlet</title> </portlet-info> </portlet> </portlet-app> DispatcherPortlet is responsible for handling every client request. When it receives a request, it finds out which Controller class should be used for handling this request, and then it calls its handleActionRequest() or handleRenderRequest() method based on the request processing phase. The Controller class executes business logic and returns a View name that should be used for rendering markup to the user. The DispatcherPortlet then forwards control to that View for actual markup generation. As you can see, DispatcherPortlet is the central dispatcher for use within Spring Portlet MVC Framework. Note that your portlet application can define more than one DispatcherPortlet. If it does so, then each of these portlets operates its own namespace, loading its application context and handler mapping. The DispatcherPortlet is also responsible for loading application context (Spring configuration file) for this portlet. First, it tries to check the value of the configLocation portlet initialization parameter. If that parameter is not specified, it takes the portlet name (that is, the value of the <portlet-name> element), appends "-portlet.xml" to it, and tries to load that file from the /WEB-INF folder. In the portlet.xml file, we did not specify the configLocation initialization parameter, so let's create SpringPortletName-portlet.xml file in the next section. Developing SpringPortletName-portlet.xml Create the SpringPortletName-portlet.xml file in the /WebContent/WEB-INF folder of your application as shown below: <?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd"> <bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver"> <property name="viewClass" value="org.springframework.web.servlet.view.JstlView"/> <property name="prefix" value="/jsp/"/> <property name="suffix" value=".jsp"/> </bean> <bean id="pointManager" class="com.wlp.spring.bo.internal.PointManagerImpl"> <property name="users"> <list> <ref bean="point1"/> <ref bean="point2"/> <ref bean="point3"/> <ref bean="point4"/> </list> </property> </bean> <bean id="point1" class="com.wlp.spring.bean.User"> <property name="name" value="Murali"/> <property name="points" value="6"/> </bean> <bean id="point2" class="com.wlp.spring.bean.User"> <property name="name" value="Sai"/> <property name="points" value="13"/> </bean> <bean id="point3" class="com.wlp.spring.bean.User"> <property name="name" value="Rama"/> <property name="points" value="43"/> </bean> <bean id="point4" class="com.wlp.spring.bean.User"> <property name="name" value="Krishna"/> <property name="points" value="23"/> </bean> <bean id="messageSource" class="org.springframework.context.support.ResourceBundleMessageSource"> <property name="basename" value="messages"/> </bean> <bean name="/users.htm" id="userController" class="com.wlp.spring.controller.UserController"> <property name="pointManager" ref="pointManager"/> </bean> <bean name="/pointincrease.htm" id="pointIncreaseController" class="com.wlp.spring.controller.IncreasePointsFormController"> <property name="sessionForm" value="true"/> <property name="pointManager" ref="pointManager"/> <property name="commandName" value="pointIncrease"/> <property name="commandClass" value="com.wlp.spring.bean.PointIncrease"/> <property name="formView" value="pointincrease"/> <property name="successView" value="users"/> </bean> <bean id="parameterMappingInterceptor" class="org.springframework.web.portlet.handler.ParameterMappingInterceptor" /> <bean id="portletModeParameterHandlerMapping" class="org.springframework.web.portlet.handler.PortletModeParameterHandlerMapping"> <property name="order" value="1" /> <property name="interceptors"> <list> <ref bean="parameterMappingInterceptor" /> </list> </property> <property name="portletModeParameterMap"> <map> <entry key="view"> <map> <entry key="pointincrease"> <ref bean="pointIncreaseController" /> </entry> <entry key="users"> <ref bean="userController" /> </entry> </map> </entry> </map> </property> </bean> <bean id="portletModeHandlerMapping" class="org.springframework.web.portlet.handler.PortletModeHandlerMapping"> <property name="order" value="2" /> <property name="portletModeMap"> <map> <entry key="view"> <ref bean="userController" /> </entry> </map> </property> </bean> </beans> The SpringPortletName-portlet.xml file is an application context file for your MVC portlet. It has a couple of bean definitions: viewController. At this point, remember that the viewController bean definition points to the com.ibm.developerworks.springmvc.ViewController.java class. portletModeHandlerMapping. As we discussed in the last section, whenever DispatcherPortlet gets a client request, it tries to find a suitable Controller class for handling that request. That is where PortletModeHandlerMapping comes into the picture. The PortletModeHandlerMapping class is a simple implementation of the HandlerMapping interface and is used by DispatcherPortlet to find a suitable Controller for every request. The PortletModeHandlerMapping class uses Portlet mode for the current request to find a suitable Controller class to use for handling the request. The portletModeMap property of portletModeHandlerMapping bean is the place where we map the Portlet mode name against the Controller class. In the sample code, we show that viewController is responsible for handling View mode requests. Developing UserController.java In the preceding section, you learned that the viewController bean is responsible for handling all the View mode requests. Your next step is to create the UserController.java class as shown below: public class UserController extends AbstractController { private PointManager pointManager; public void handleActionRequest(ActionRequest request, ActionResponse response) throws Exception { } public ModelAndView handleRenderRequest(RenderRequest request, RenderResponse response) throws ServletException, IOException { String now = (new java.util.Date()).toString(); Map<String, Object> myModel = new HashMap<String, Object>(); myModel.put("now", now); myModel.put("users", this.pointManager.getUsers()); return new ModelAndView("users", "model", myModel); } public void setPointManager(PointManager pointManager) { this.pointManager = pointManager; } } Every controller class in Spring Portlet MVC Framework must implement the org.springframework.web. portlet.mvc.Controller interface directly or indirectly. To make things easier, Spring Framework provides AbstractController class, which is the default implementation of the Controller interface. As a developer, you should always extend your controller from either AbstractController or one of its more specific subclasses. Any implementation of the Controller class should be reusable, thread-safe, and capable of handling multiple requests throughout the lifecycle of the portlet. In the sample code, we create the ViewController class by extending it from AbstractController. Because we don't want to do any action processing in the HelloSpringPortletMVC portlet, we override only the handleRenderRequest() method of AbstractController. Now, the only thing that HelloWorldPortletMVC should do is render the markup of View.jsp to the user when it receives a user request to do so. To do that, return the object of ModelAndView with a value of view equal to View. Developing web.xml According to Portlet Specification 1.0, every portlet application is also a Servlet Specification 2.3-compliant Web application, and it needs a Web application deployment descriptor (that is, web.xml). Let’s create the web.xml file in the /WEB-INF/ folder as shown in listing 4. Follow these steps: Open the existing web.xml file located at /WebContent/WEB-INF/web.xml. Replace the contents of this file with the code as shown below: <servlet> <servlet-name>ViewRendererServlet</servlet-name> <servlet-class>org.springframework.web.servlet.ViewRendererServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>ViewRendererServlet</servlet-name> <url-pattern>/WEB-INF/servlet/view</url-pattern> </servlet-mapping> <context-param> <param-name>contextConfigLocation</param-name> <param-value>/WEB-INF/applicationContext.xml</param-value> </context-param> <listener> <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class> </listener> The web.xml file for the sample portlet declares two things: ViewRendererServlet. The ViewRendererServlet is the bridge servlet for portlet support. During the render phase, DispatcherPortlet wraps PortletRequest into ServletRequest and forwards control to ViewRendererServlet for actual rendering. This process allows Spring Portlet MVC Framework to use the same View infrastructure as that of its servlet version, that is, Spring Web MVC Framework. ContextLoaderListener. The ContextLoaderListener class takes care of loading Web application context at the time of the Web application startup. The Web application context is shared by all the portlets in the portlet application. In case of duplicate bean definition, the bean definition in the portlet application context takes precedence over the Web application context. The ContextLoader class tries to read the value of the contextConfigLocation Web context parameter to find out the location of the context file. If the contextConfigLocation parameter is not set, then it uses the default value, which is /WEB-INF/applicationContext.xml, to load the context file. The Portlet Controller interface requires two methods that handle the two phases of a portlet request: the action request and the render request. The action phase should be capable of handling an action request and the render phase should be capable of handling a render request and returning an appropriate model and view. While the Controller interface is quite abstract, Spring Portlet MVC offers a lot of controllers that already contain a lot of the functionality you might need – most of these are very similar to controllers from Spring Web MVC. The Controller interface just defines the most common functionality required of every controller - handling an action request, handling a render request, and returning a model and a view. How rendering works As you know, when the user tries to access a page with PointSystemPortletMVC portlet on it or when the user performs some action on any other portlet on that page or tries to refresh that page, a render request is sent to the PointSystemPortletMVC portlet. In the sample code, because DispatcherPortlet is the main portlet class, Weblogic Portal / Webcenter Portal calls its render() method and then the following sequence of events occurs: The render() method of DispatcherPortlet calls the doDispatch() method, which in turn calls the doRender() method. After the doRenderService() method gets control, first it tries to find out the locale of the request by calling the PortletRequest.getLocale() method. This locale is used while making all the locale-related decisions for choices such as which resource bundle should be loaded or which JSP should be displayed to the user based on the locale. After that, the doRenderService() method starts iterating through all the HandlerMapping classes configured for this portlet, calling their getHandler() method to identify the appropriate Controller for handling this request. In the sample code, we have configured only PortletModeHandlerMapping as a HandlerMapping class. The PortletModeHandlerMapping class reads the value of the current portlet mode, and based on that, it finds out, the Controller class that should be used to handle this request. In the sample code, ViewController is configured to handle the View mode request so that the PortletModeHandlerMapping class returns the object of ViewController. After the object of ViewController is returned, the doRenderService() method calls its handleRenderRequestInternal() method. Implementation of the handleRenderRequestInternal() method in ViewController.java is very simple. It logs a message saying that it got control, and then it creates an instance of ModelAndView with a value equal to View and returns it to DispatcherPortlet. After control returns to doRenderService(), the next task is to figure out how to render View. For that, DispatcherPortlet starts iterating through all the ViewResolvers configured in your portlet application, calling their resolveViewName() method. In the sample code we have configured only one ViewResolver, InternalResourceViewResolver. When its resolveViewName() method is called with viewName, it tries to add /WEB-INF/jsp as a prefix to the view name and to add JSP as a suffix. And it checks if /WEB-INF/jsp/View.jsp exists. If it does exist, it returns the object of JstlView wrapping View.jsp. After control is returned to the doRenderService() method, it creates the object PortletRequestDispatcher, which points to /WEB-INF/servlet/view – that is, ViewRendererServlet. Then it sets the object of JstlView in the request and dispatches the request to ViewRendererServlet. After ViewRendererServlet gets control, it reads the JstlView object from the request attribute and creates another RequestDispatcher pointing to the /WEB-INF/jsp/View.jsp URL and passes control to it for actual markup generation. The markup generated by View.jsp is returned to user. At this point, you may question the need for ViewRendererServlet. Why can't DispatcherPortlet directly forward control to View.jsp? Adding ViewRendererServlet in between allows Spring Portlet MVC Framework to reuse the existing View infrastructure. You may appreciate this more when we discuss how easy it is to integrate Apache Tiles Framework with your Spring Portlet MVC Framework. The attached project SpringPortlet.zip should be used to import the project in to your OEPE Workspace. SpringPortlet_Jars.zip contains jar files required for the application. Project is written on Spring 2.5.  The same JSR 168 portlet should work on Webcenter Portal as well.  Downloads: Download WeblogicPotal Project which consists of Spring Portlet. Download Spring Jars In-addition to above you need to download Spring.jar (Spring2.5)

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