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• Best Practices / Patterns for Enterprise Protection/Remediation of SSNs (Social Security Numbers)

  - by Erik Neu

  I am interested in hearing about enterprise solutions for SSN handling. (I looked pretty hard for any pre-existing post on SO, including reviewing the terriffic SO automated "Related Questions" list, and did not find anything, so hopefully this is not a repeat.) First, I think it is important to enumerate the reasons systems/databases use SSNs: (note—these are reasons for de facto current state—I understand that many of them are not good reasons) Required for Interaction with External Entities. This is the most valid case—where external entities your system interfaces with require an SSN. This would typically be government, tax and financial. SSN is used to ensure system-wide uniqueness. SSN has become the default foreign key used internally within the enterprise, to perform cross-system joins. SSN is used for user authentication (e.g., log-on) The enterprise solution that seems optimum to me is to create a single SSN repository that is accessed by all applications needing to look up SSN info. This repository substitutes a globally unique, random 9-digit number (ASN) for the true SSN. I see many benefits to this approach. First of all, it is obviously highly backwards-compatible—all your systems "just" have to go through a major, synchronized, one-time data-cleansing exercise, where they replace the real SSN with the alternate ASN. Also, it is centralized, so it minimizes the scope for inspection and compliance. (Obviously, as a negative, it also creates a single point of failure.) This approach would solve issues 2 and 3, without ever requiring lookups to get the real SSN. For issue #1, authorized systems could provide an ASN, and be returned the real SSN. This would of course be done over secure connections, and the requesting systems would never persist the full SSN. Also, if the requesting system only needs the last 4 digits of the SSN, then that is all that would ever be passed. Issue #4 could be handled the same way as issue #1, though obviously the best thing would be to move away from having users supply an SSN for log-on. There are a couple of papers on this: UC Berkely: http://bit.ly/bdZPjQ Oracle Vault: bit.ly/cikbi1

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• Cannot instantiate abstract class or interface : problem while persisting

  - by sammy

  i have a class campaign that maintains a list of AdGroupInterfaces. im going to persist its implementation @Entity @Table(name = "campaigns") public class Campaign implements Serializable,Comparable<Object>,CampaignInterface { private static final long serialVersionUID = 1L; @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id; @OneToMany ( cascade = {CascadeType.ALL}, fetch = FetchType.EAGER, targetEntity=AdGroupInterface.class ) @org.hibernate.annotations.Cascade( value = org.hibernate.annotations.CascadeType.DELETE_ORPHAN ) @org.hibernate.annotations.IndexColumn(name = "CHOICE_POSITION") private List<AdGroupInterface> AdGroup; public Campaign() { super(); } public List<AdGroupInterface> getAdGroup() { return AdGroup; } public void setAdGroup(List<AdGroupInterface> adGroup) { AdGroup = adGroup; } public void set1AdGroup(AdGroupInterface adGroup) { if(AdGroup==null) AdGroup=new LinkedList<AdGroupInterface>(); AdGroup.add(adGroup); } } AdGroupInterface's implementation is AdGroups. when i add an adgroup to the list in campaign, campaign c; c.getAdGroupList().add(new AdGroups()), etc and save campaign it says"Cannot instantiate abstract class or interface :" AdGroupInterface its not recognizing the implementation just before persisting... Whereas Persisting adGroups separately works. when it is a member of another entity, it doesnt get persisted. import java.io.Serializable; import java.util.List; import javax.persistence.*; @Entity @DiscriminatorValue("1") @Table(name = "AdGroups") public class AdGroups implements Serializable,Comparable,AdGroupInterface{ /** * */ private static final long serialVersionUID = 1L; private Long Id; private String Name; private CampaignInterface Campaign; private MonetaryValue DefaultBid; public AdGroups(){ super(); } public AdGroups( String name, CampaignInterface campaign) { super(); this.Campaign=new Campaign(); Name = name; this.Campaign = campaign; DefaultBid = defaultBid; AdList=adList; } @Id @GeneratedValue(strategy = GenerationType.IDENTITY) @Column(name="AdGroup_Id") public Long getId() { return Id; } public void setId(Long id) { Id = id; } @Column(name="AdGroup_Name") public String getName() { return Name; } public void setName(String name) { Name = name; } @ManyToOne @JoinColumn (name="Cam_ID", nullable = true,insertable = false) public CampaignInterface getCampaign() { return Campaign; } public void setCampaign(CampaignInterface campaign) { this.Campaign = campaign; } } what am i missing?? please look into it ...

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• web.config 1.0 and 3.5

  - by KareemSaad

  I had aproblem I had two web site one of them with .net 3.5 and other with 1.0 and I want to run 1.0 in 3.5 but I couldnot and i tried to copy some section from 1.0 to 3.5 as I copied this section <add key="ConnectionString" value="data source=.;persist security info=True;user id=Sharp;Password=#Sharp;initial catalog=Sharp" /> <add key="ACProduct_Upload" value="SiteUploads/ACProducts/" /> <add key="ACPDF_Upload" value="SiteUploads/ACPDF/" /> <add key="ACCertifications_Upload" value="SiteUploads/ACCertifications/" /> <add key="Certifications_Upload" value="SiteUploads/Certifications/" /> <add key="flash" value="flash/" /> <add key="Product_Upload" value="SiteUploads/Products/" /> <add key="PDF_Upload" value="SiteUploads/PDF/" /> <add key="HTML_Upload" value="SiteUploads/HTML_Uploads/" /> <add key="WallPaper_Upload" value="SiteUploads/WallPapers/" /> <add key="News_Upload" value="SiteUploads/News/" /> <add key="mailserver" value="111.111.1.1" /> <add key="fromEmail" value="[email protected]" /> to 3.5 here <add key="ACProduct_Upload" value="SiteUploads/ACProducts/" /> <add key="ACPDF_Upload" value="SiteUploads/ACPDF/" /> <add key="ACCertifications_Upload" value="SiteUploads/ACCertifications/" /> <add key="Certifications_Upload" value="SiteUploads/Certifications/" /> <add key="flash" value="flash/" /> <add key="Product_Upload" value="SiteUploads/Products/" /> <add key="PDF_Upload" value="SiteUploads/PDF/" /> <add key="HTML_Upload" value="SiteUploads/HTML_Uploads/" /> <add key="WallPaper_Upload" value="SiteUploads/WallPapers/" /> <add key="News_Upload" value="SiteUploads/News/" /> <add key="mailserver" value="192.168.6.3" /> <add name="Sharp" connectionString="Data Source=.;Initial Catalog=SharpHA;User ID=SharpHA;Password=#SharpHA;" providerName="System.Data.SqlClient"/> but this problem apear Only one element allowed per config file and if present must be the first child of the root element. please any one help me

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• JSF: how to update the list after delete an item of that list

  - by Harry Pham

  It will take a moment for me to explain this, so please stay with me. I have table COMMENT that has OneToMany relationship with itself. @Entity public class Comment(){ ... @ManyToOne(optional=true, fetch=FetchType.LAZY) @JoinColumn(name="REPLYTO_ID") private Comment replyTo; @OneToMany(mappedBy="replyTo", cascade=CascadeType.ALL) private List<Comment> replies = new ArrayList<Comment>(); public void addReply(NewsFeed reply){ replies.add(reply); reply.setReplyTo(this); } public void removeReply(NewsFeed reply){ replies.remove(reply); } } So you can think like this. Each comment can have a List of replies which are also type Comment. Now it is very easy for me to delete the original comment and get the updated list back. All I need to do after delete is this. allComments = myEJB.getAllComments(); //This will query the db and return updated list But I am having problem when trying to delete replies and getting the updated list back. So here is how I delete the replies. Inside my managed bean I have //Before invoke this method, I have the value of originalFeed, and deletedFeed set. //These original comments are display inside a p:dataTable X, and the replies are //displayed inside p:dataTable Y which is inside X. So when I click the delete button //I know which comment I want to delete, and if it is the replies, I will know //which one is its original post public void deleteFeed(){ if(this.deletedFeed != null){ scholarEJB.deleteFeeds(this.deletedFeed); if(this.originalFeed != null){ //Since the originalFeed is not null, this is the `replies` //that I want to delete scholarEJB.removeReply(this.originalFeed, this.deletedFeed); } feeds = scholarEJB.findAllFeed(); } } Then inside my EJB scholarEJB, I have public void removeReply(NewsFeed comment, NewsFeed reply){ comment = em.merge(comment); comment.removeReply(reply); em.persist(comment); } public void deleteFeeds(NewsFeed e){ e = em.find(NewsFeed.class, e.getId()); em.remove(e); } When I get out, the entity (the reply) get correctly removed from the database, but inside the feeds List, reference of that reply still there. It only until I log out and log back in that the reply disappear. Please help

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• How are you using IronPython?

  - by Will Dean

  I'm keen to drink some modern dynamic language koolaid, so I've believed all the stuff on Michael Foord's blog and podcasts, I've bought his book (and read some of it), and I added an embedded IPy runtime to a large existing app a year or so ago (though that was for someone else and I didn't really use it myself). Now I need to do some fairly simple code generation stuff, where I'm going to call a few methods on a few .net objects (custom, C#-authored objects), create a few strings, write some files, etc. The experience of trying this leaves me feeling like the little boy who thinks he's the only one who can see that The Emperor has no clothes on. If you're using IronPython, I'd really appreciate knowing how you deal with the following aspects of it: Code editing - do you use the .NET framework without Intellisense? Refactoring - I know a load of 'refactoring' is about working around language-related busywork, so if Python is sufficiently lightweight then we won't need that, But things like renames seem to me to be essential to iteratively developing quality code regardless of language. Crippling startup time - One of the things which is supposed to be good about interpreted languages is the lack of compile time leading to fast interactive development. Unfortunately I can compile a C# application and launch it quicker than IPy can start up. Interactive hacking - the IPy console/repl is supposed to be good for this, but I haven't found a good way to take the code you've interactively arrived at and persist it into a file - cut and paste from the console is fairly miserable. And the console seems to hold references to .NET assemblies you've imported, so you have to quit it and restart it if you're working on the C# stuff as well. Hacking on C# in something like LinqPad seems a much faster and easier way to try things out (and has proper Intellisense). Do you use the console? Debugging - what's the story here? I know someone on the IPy team is working on a command-line hobby-project, but let's just say I'm not immediately attracted to a command line debugger. I don't really need a debugger from little Python scripts, but I would if I were to use IPy for scripting unit tests, for example. Unit testing - I can see that dynamic languages could be great for this, but is there any IDE test-runner integration (like for Resharper, etc). The Foord book has a chapter about this, which I'll admit I have not yet read properly, but it does seem to involve driving a console-mode test-runner from the command prompt, which feels to be an enormous step back from using an integrated test runner like TestDriven.net or Resharper. I really want to believe in this stuff, so I am still working on the assumption that I've missed something. I would really like to know how other people are dealing with IPy, particularly if they're doing it in a way which doesn't feel like we've just lost 15 years'-worth of tool development.

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• log4j performance

  - by Bob

  Hi, I'm developing a web app, and I'd like to log some information to help me improve and observe the app. (I'm using Tomcat6) First I thought I would use StringBuilders, append the logs to them and a task would persist them into the database like every 2 minutes. Because I was worried about the out-of-the-box logging system's performance. Then I made some test. Especially with log4j. Here is my code: Main.java public static void main(String[] args) { Thread[] threads = new Thread[LoggerThread.threadsNumber]; for(int i = 0; i < LoggerThread.threadsNumber; ++i){ threads[i] = new Thread(new LoggerThread("name - " + i)); } LoggerThread.startTimestamp = System.currentTimeMillis(); for(int i = 0; i < LoggerThread.threadsNumber; ++i){ threads[i].start(); } LoggerThread.java public class LoggerThread implements Runnable{ public static int threadsNumber = 10; public static long startTimestamp; private static int counter = 0; private String name; public LoggerThread(String name) { this.name = name; } private Logger log = Logger.getLogger(this.getClass()); @Override public void run() { for(int i=0; i<10000; ++i){ log.info(name + ": " + i); if(i == 9999){ int c = increaseCounter(); if(c == threadsNumber){ System.out.println("Elapsed time: " + (System.currentTimeMillis() - startTimestamp)); } } } } private synchronized int increaseCounter(){ return ++counter; } } } log4j.properties log4j.logger.main.LoggerThread=debug, f log4j.appender.f=org.apache.log4j.RollingFileAppender log4j.appender.f.layout=org.apache.log4j.PatternLayout log4j.appender.f.layout.ConversionPattern=%d{ABSOLUTE} %5p %c{1}:%L - %m%n log4j.appender.f.File=c:/logs/logging.log log4j.appender.f.MaxFileSize=15000KB log4j.appender.f.MaxBackupIndex=50 I think this is a very common configuration for log4j. First I used log4j 1.2.14 then I realized there was a newer version, so I switched to 1.2.16 Here are the figures (all in millisec) LoggerThread.threadsNumber = 10 1.2.14: 4235, 4267, 4328, 4282 1.2.16: 2780, 2781, 2797, 2781 LoggerThread.threadsNumber = 100 1.2.14: 41312, 41014, 42251 1.2.16: 25606, 25729, 25922 I think this is very fast. Don't forget that: in every cycle the run method not just log into the file, it has to concatenate strings (name + ": " + i), and check an if test (i == 9999). When threadsNumber is 10, there are 100.000 loggings and if tests and concatenations. When it is 100, there are 1.000.000 loggings and if tests and concatenations. (I've read somewhere JVM uses StringBuilder's append for concatenation, not simple concatenation). Did I missed something? Am I doing something wrong? Did I forget any factor that could decrease the performance? If these figures are correct I think, I don't have to worry about log4j's performance even if I heavily log, do I?

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• Accessing Content Page elements

  - by Abdel Olakara

  Hi all, I am facing a strange problem.. may be i am overlooking something and not able to find the silly issue. Need your help! I have a Master page and a Content Page: <form id="AccountForm" runat="server"> <div> <asp:ContentPlaceHolder ID="MenuHolder" runat="server"> </asp:ContentPlaceHolder> </div> <hr /> <div> <asp:ContentPlaceHolder ID="ContentHolder" runat="server"> </asp:ContentPlaceHolder> </div> And my content page has some form elements: <asp:Content ID="Content3" ContentPlaceHolderID="ContentHolder" runat="server"> First Name: <asp:TextBox ID="fName" runat="server"></asp:TextBox> <br /> Middle Name: <asp:TextBox ID="mName" runat="server"></asp:TextBox> <br /> Family Name: <asp:TextBox ID="lName" runat="server"></asp:TextBox> <br /> Birthday: <asp:TextBox ID="birthday" runat="server"></asp:TextBox> <br /> Mobile Phone: <asp:TextBox ID="mobile" runat="server"></asp:TextBox> <br /> Alternate Phone: <asp:TextBox ID="phone" runat="server"></asp:TextBox> <br /> I also have the code for submit button in the content page where i try to retrieve the values from the form elements and persist it into DB. Here is the SubmitButton_Click code: protected void SubmitButton_Click(object sender, EventArgs e) { log.Info("From Submit button: " + customerObject.first_name + " " + customerObject.family_name); if (fName != null) log.Info("First Name is not null"); log.Info("First Name:" + fName.Text); log.Info("Middle Name:" + mName.Text); log.Info("Family Name:" + fName.Text); log.Info("Mobile:" + mobile.Text); log.Info("Phone: " + phone.Text); log.Info("Address:" + bAddressL1.Text + bAddressL2.Text); Strangly.. i don't get any data that is filled into my text fields? Their objects are not null as well!! why is this behaviour happening? I am not trying to access elements in master page or other.. all the fields are in the content page.. only thing is there is no form element in the content page and the form element is in master page! Thanks in advance for your suggestions and answers. Abdel Raoof Olakara

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• NonUniqueObjectException during DAO integration test?

  - by HDave

  I have a JPA/Hibernate application and am trying to get it to run against H2 and MySQL. Currently I am using Atomikos for transactions and C3P0 for connection pooling. Despite my best efforts my DAO integration tests are failing with org.hibernate.NonUniqueObjectException. I do tend to re-use the same object (same ID even) over and over for all the different tests and I am sure that is the cause, but I can see in the logs that Spring Test and Atomikos are clearly rolling back the transaction associated with each test method. I would have thought the rollback would have also cleared the persistence context too. On a hunch, I added an a call to dao.clear() at the beginning of the faulty test methods and the problem went away!! Rollback doesn't clear the persistence context...hmmm.... Not sure if this is relevant, but I see a possible autocommit setting problem in the log file: [20100613 23:06:34] DEBUG [main] SessionFactoryImpl.(242) | instantiating session factory with properties: .....edited for brevity.... hibernate.connection.autocommit=true, ....more stuff follows Because I am using connection pooling, I figure that Hibernate is where I'll have to indicate I want autocommit off. I found the autocommit property documented here and I put it in my EntityManagerFactory config as follows: <bean id="myappTestLocalEmf" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean"> <property name="persistenceUnitName" value="myapp-core" /> <property name="persistenceUnitPostProcessors"> <bean class="com.myapp.core.persist.util.JtaPersistenceUnitPostProcessor"> <property name="jtaDataSource" ref="myappPersistTestJdbcDataSource" /> </bean> </property> <property name="jpaVendorAdapter"> <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter"> <property name="showSql" value="true" /> <property name="database" value="$DS{hibernate.database}" /> <property name="databasePlatform" value="$DS{hibernate.dialect}" /> </bean> </property> <property name="jpaProperties"> <props> <prop key="hibernate.transaction.factory_class">com.atomikos.icatch.jta.hibernate3.AtomikosJTATransactionFactory</prop> <prop key="hibernate.transaction.manager_lookup_class">com.atomikos.icatch.jta.hibernate3.TransactionManagerLookup</prop> <prop key="hibernate.connection.autocommit">false</prop> <prop key="hibernate.format_sql">true"</prop> <prop key="hibernate.use_sql_comments">true</prop> </property> </bean>

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• how to create a system-wide independent universal counter object primarily for Database keys?

  - by andora

  I would like to create/use a system-wide independent universal 'counter object' that can be called via COM in a thread-safe manner. The counter object will be passed an ID to identify which counter to return, handle the counting, 'persist' the count (occasionally), have reasonable performance (as fast as possible) perhaps capable of 1000 counts per second or better (1mS) and be accessible cross-process/out-of-process. The current count status must be persisted between object restarts/shutdowns. The counter object is liklely to be a 'singleton' type object implemented in some form of free-threaded dictionary, containing maybe 10 counters (perhaps 50 max). The count needs to be monotonic and consistent, (ie: guaranteed unique sequential values). Each counter should have a few methods, like reset, inc, dec, set, clear, remove. As a luxury, I would like to have a variable-increment (ie: 'step by' value). To support thread-safefty, perhaps some sorm of critical-section or mutex call. It just needs to return a long/4byte signed integer. I really want something that can be called from anywhere, including VBScript, so I figure COM is my preferred solution. The primary use of this is for database keys. I am unable to use autoinc or guid type keys and have ruled out database-generated counting systems at this point. I've spent days researching this and I have really struggled to find a solution. The best I can find is a free-threaded dictionary object that can be instantiated using COM+ from Motobit - it seems to offer all the 'basics' and I guess I could create some form of wrapper for this. So, here are my questions: Does such a 'general purpose counter-object already exist? Can you direct me to it? (MS did do an IIS/ASP object called 'MSWC.Counter' but this isn't 'cross-process'/ out-of-process component and isn't thread-safe. (but if it was, it would do!) What is the best way of creating such a Component? (I'd prefer VB6 right-now, [don't ask!] but can do in VB.NET2005 if I had to). I don't have the skills/knowledge/tools to use anything else. I am desparate for a workable solution. I need specific guidance! If anybody can code something up for me I am prepared to pay for it.

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• Different behaviour using unidirectional or bidirectional relation

  - by sinuhepop

  I want to persist a mail entity which has some resources (inline or attachment). First I related them as a bidirectional relation: @Entity public class Mail extends BaseEntity { @OneToMany(mappedBy = "mail", cascade = CascadeType.ALL, orphanRemoval = true) private List<MailResource> resource; private String receiver; private String subject; private String body; @Temporal(TemporalType.TIMESTAMP) private Date queued; @Temporal(TemporalType.TIMESTAMP) private Date sent; public Mail(String receiver, String subject, String body) { this.receiver = receiver; this.subject = subject; this.body = body; this.queued = new Date(); this.resource = new ArrayList<>(); } public void addResource(String name, MailResourceType type, byte[] content) { resource.add(new MailResource(this, name, type, content)); } } @Entity public class MailResource extends BaseEntity { @ManyToOne(optional = false) private Mail mail; private String name; private MailResourceType type; private byte[] content; } And when I saved them: Mail mail = new Mail("[email protected]", "Hi!", "..."); mail.addResource("image", MailResourceType.INLINE, someBytes); mail.addResource("documentation.pdf", MailResourceType.ATTACHMENT, someOtherBytes); mailRepository.save(mail); Three inserts were executed: INSERT INTO MAIL (ID, BODY, QUEUED, RECEIVER, SENT, SUBJECT) VALUES (?, ?, ?, ?, ?, ?) INSERT INTO MAILRESOURCE (ID, CONTENT, NAME, TYPE, MAIL_ID) VALUES (?, ?, ?, ?, ?) INSERT INTO MAILRESOURCE (ID, CONTENT, NAME, TYPE, MAIL_ID) VALUES (?, ?, ?, ?, ?) Then I thought it would be better using only a OneToMany relation. No need to save which Mail is in every MailResource: @Entity public class Mail extends BaseEntity { @OneToMany(cascade = CascadeType.ALL, orphanRemoval = true) @JoinColumn(name = "mail_id") private List<MailResource> resource; ... public void addResource(String name, MailResourceType type, byte[] content) { resource.add(new MailResource(name, type, content)); } } @Entity public class MailResource extends BaseEntity { private String name; private MailResourceType type; private byte[] content; } Generated tables are exactly the same (MailResource has a FK to Mail). The problem is the executed SQL: INSERT INTO MAIL (ID, BODY, QUEUED, RECEIVER, SENT, SUBJECT) VALUES (?, ?, ?, ?, ?, ?) INSERT INTO MAILRESOURCE (ID, CONTENT, NAME, TYPE) VALUES (?, ?, ?, ?) INSERT INTO MAILRESOURCE (ID, CONTENT, NAME, TYPE) VALUES (?, ?, ?, ?) UPDATE MAILRESOURCE SET mail_id = ? WHERE (ID = ?) UPDATE MAILRESOURCE SET mail_id = ? WHERE (ID = ?) Why this two updates? I'm using EclipseLink, will this behaviour be the same using another JPA provider as Hibernate? Which solution is better?

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• Is this a legitimate implementation of a 'remember me' function for my web app?

  - by user246114

  Hi, I'm trying to add a "remember me" feature to my web app to let a user stay logged in between browser restarts. I think I got the bulk of it. I'm using google app engine for the backend which lets me use java servlets. Here is some pseudo-code to demo: public class MyServlet { public void handleRequest() { if (getThreadLocalRequest().getSession().getAttribute("user") != null) { // User already has session running for them. } else { // No session, but check if they chose 'remember me' during // their initial login, if so we can have them 'auto log in' // now. Cookie[] cookies = getThreadLocalRequest().getCookies(); if (cookies.find("rememberMePlz").exists()) { // The value of this cookie is the cookie id, which is a // unique string that is in no way based upon the user's // name/email/id, and is hard to randomly generate. String cookieid = cookies.find("rememberMePlz").value(); // Get the user object associated with this cookie id from // the data store, would probably be a two-step process like: // // select * from cookies where cookieid = 'cookieid'; // select * from users where userid = 'userid fetched from above select'; User user = DataStore.getUserByCookieId(cookieid); if (user != null) { // Start session for them. getThreadLocalRequest().getSession() .setAttribute("user", user); } else { // Either couldn't find a matching cookie with the // supplied id, or maybe we expired the cookie on // our side or blocked it. } } } } } // On first login, if user wanted us to remember them, we'd generate // an instance of this object for them in the data store. We send the // cookieid value down to the client and they persist it on their side // in the "rememberMePlz" cookie. public class CookieLong { private String mCookieId; private String mUserId; private long mExpirationDate; } Alright, this all makes sense. The only frightening thing is what happens if someone finds out the value of the cookie? A malicious individual could set that cookie in their browser and access my site, and essentially be logged in as the user associated with it! On the same note, I guess this is why the cookie ids must be difficult to randomly generate, because a malicious user doesn't have to steal someone's cookie - they could just randomly assign cookie values and start logging in as whichever user happens to be associated with that cookie, if any, right? Scary stuff, I feel like I should at least include the username in the client cookie such that when it presents itself to the server, I won't auto-login unless the username+cookieid match in the DataStore. Any comments would be great, I'm new to this and trying to figure out a best practice. I'm not writing a site which contains any sensitive personal information, but I'd like to minimize any potential for abuse all the same, Thanks

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• Precise explanation of JavaScript <-> DOM circular reference issue

  - by Joey Adams

  One of the touted advantages of jQuery.data versus raw expando properties (arbitrary attributes you can assign to DOM nodes) is that jQuery.data is "safe from circular references and therefore free from memory leaks". An article from Google titled "Optimizing JavaScript code" goes into more detail: The most common memory leaks for web applications involve circular references between the JavaScript script engine and the browsers' C++ objects' implementing the DOM (e.g. between the JavaScript script engine and Internet Explorer's COM infrastructure, or between the JavaScript engine and Firefox XPCOM infrastructure). It lists two examples of circular reference patterns: DOM element → event handler → closure scope → DOM DOM element → via expando → intermediary object → DOM element However, if a reference cycle between a DOM node and a JavaScript object produces a memory leak, doesn't this mean that any non-trivial event handler (e.g. onclick) will produce such a leak? I don't see how it's even possible for an event handler to avoid a reference cycle, because the way I see it: The DOM element references the event handler. The event handler references the DOM (either directly or indirectly). In any case, it's almost impossible to avoid referencing window in any interesting event handler, short of writing a setInterval loop that reads actions from a global queue. Can someone provide a precise explanation of the JavaScript ↔ DOM circular reference problem? Things I'd like clarified: What browsers are effected? A comment in the jQuery source specifically mentions IE6-7, but the Google article suggests Firefox is also affected. Are expando properties and event handlers somehow different concerning memory leaks? Or are both of these code snippets susceptible to the same kind of memory leak? // Create an expando that references to its own element. var elem = document.getElementById('foo'); elem.myself = elem; // Create an event handler that references its own element. var elem = document.getElementById('foo'); elem.onclick = function() { elem.style.display = 'none'; }; If a page leaks memory due to a circular reference, does the leak persist until the entire browser application is closed, or is the memory freed when the window/tab is closed?

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• Sessions not persisting between requests

  - by klonq

  My session objects are only stored within the request scope on google app engine and I can't figure out how to persist objects between requests. The docs are next to useless on this matter and I can't find anyone who's experienced a similar problem. Please help. When I store session objects in the servlet and forward the request to a JSP using: getServletContext().getRequestDispatcher("/example.jsp").forward(request,response); Everything works like it should. But when I store objects to the session and redirect the request using: response.sendRedirect("/example/url"); The session objects are lost to the ether. In fact when I dump session key/value pairs on new requests there is absolutely nothing, session objects only appear within the request scope of servlets which create session objects. It appears to me that the objects are not being written to Memcache or Datastore. In terms of configuring sessions for my application I have set <sessions-enabled>true</sessions-enabled> In appengine-web.xml. Is there anything else I am missing? The single paragraph of documentation on sessions also notes that only objects which implement Serializable can be stored in the session between requests. I have included an example of the code which is not working below. The obvious solution is to not use redirects, and this might be ok for the example given below but some application data does need to be stored in the session between requests so I need to find a solution to this problem. EXAMPLE: The class FlashMessage gives feedback to the user from server-side operations. if (email.send()) { FlashMessage flash = new FlashMessage(FlashMessage.SUCCESS, "Your message has been sent."); session.setAttribute(FlashMessage.SESSION_KEY, flash); // The flash message will not be available in the session object in the next request response.sendRedirect(URL.HOME); } else { FlashMessage flash = new FlashMessage(FlashMessage.ERROR, FlashMessage.INVALID_FORM_DATA); session.setAttribute(FlashMessage.SESSION_KEY, flash); // The flash message is displayed without problem getServletContext().getRequestDispatcher(Templates.CONTACT_FORM).forward(request,response); } FlashMessage.java import java.io.Serializable; public class FlashMessage implements Serializable { private static final long serialVersionUID = 8109520737272565760L; // I have tried using different, default and no serialVersionUID public static final String SESSION_KEY = "flashMessage"; public static final String ERROR = "error"; public static final String SUCCESS = "success"; public static final String INVALID_FORM_DATA = "Your request failed to validate."; private String message; private String type; public FlashMessage (String type, String message) { this.type = type; this.message = message; } public String display(){ return "<div id='flash' class='" + type + "'>" + message + "</div>"; } }

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• SVG via dynamic XML+XSL

  - by Daniel

  This is a bit of a vague notion which I have been running over in my head, and which I am very curious if there is an elegant method of solving. Perhaps it should be taken as a thought experiment. Imagine you have an XML schema with a corresponding XSL transform, which renders the XML as SVG in the browser. The XSL generates SVG with appropriate Javascript handlers that, ultimately, implement editing-like functionality such that properties of the objects or their locations on the SVG canvas can be edited by the user. For instance, an element can be dragged from one location to another. Now, this isn't particularly difficult - the drag/drop example is simply a matter of changing the (x,y) coordinates of the SVG object, or a resize operation would be a simple matter of changing its width or height. But is there an elegant way to have Javascript work on the DOM of the source XML document instead of the rendered SVG? Why, you ask? Well, imagine you have very complex XSL transforms, where the modification of one property results in complex changes to the SVG. You want to maintain simplicity in your Javascript code, but also a simple way to persist the modified XML back to the server. Some possibilities of how this may function: After modification of the source DOM, simply re-run the XSL transform and replace the original. Downside: brute force, potentially expensive operation. Create id/class naming conventions in the source and target XML/SVG so elements can be related back to each other, and do an XSL transform on only a subset of the new DOM. In other words, modify temporary DOM, apply XSL to it, remove changed elements from SVG, and insert the new one. Downside: May not be possible to apply XSL to temporary in-browser DOMs(?). Also, perhaps a bit convoluted or ugly to maintain. I think that it may be possible to come up with a framework that handles the second scenario, but the challenge would be making it lightweight and not heavily tied to the actual XML schema. Any ideas or other possibilities? Or is there maybe an existing method of doing this which I'm not aware of? UPDATE: To clarify, as I mentioned in a comment below, this aids in separating the draw code from the edit code. For a more concrete example of how this is useful, imagine an element which determines how it is drawn dependent on the value of a property of an adjacent element. It's better to condense that logic directly in the draw code instead of also duplicating it in the edit code.

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• Strategies for "Always-Connected" Windows Client Data Architecture

  - by magz2010

  Hi. Let me start by saying: this is my 1st post here, this is a bit lenghty, and I havent done Windows Forms development in years....with that in mind please excuse me if this isn't directly a programming question and please bear with me as I really need the help!! I have been asked to develop a Windows Forms app for our company that talks to a central (local area network) Linux Server hosting a PostgreSQL database. The app is to allow users to authenticate themselves into the system and thereafter conduct the usual transactions with the PG database. Ordinarily, I would propose writing a webforms app against Mono, but the clients need to utilise local resources such as USB peripheral devices, so that is out of the question. While it might not seem clear, my questions are italised below: Dilemma #1: The application is meant to be always connected. How should I structure my DAL/BLL - Should this reside on the server or with the client? Dilemma #2: I have been reading up on Client Application Services (CAS), and it seems like a great fit for authentication, as everything is exposed via URIs. I know that a .NET Data Provider exists for PostgreSQL, but not too sure if CAS will all work on a Linux (Debian) server? Believe me, I would get my hands dirty and try myself, but I need to come up with a logical design first before resources are allocated to me for "trial purposes"! Dilemma #3: If the DAL/BLL is to reside on the server, is there any way I can create data services, and expose only these services to authenticated clients. There is a (security) requirement whereby a connection string with username and password to the database cannot be present on any client machines...even if security on the database side is quite rigid. I'm guessing that the only way for this to work would be to create the various CRUD data service methods that are exposed by an ASP.NET app, and have the WindowsForms make a request for data or persist data to the ASP.NET app (thru a URI) and have that return a resultset or value. Would I be correct in assuming this? Should I be looking into WCF Data Services? and will WCF work with a non-SQL Server database? Thank you for taking the time out to read this, but know that I am desperately seeking any advice on this! THANKS A MILLION!!!!

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• Symfony2 Forms: is it possible to bind a form in an "unconventional way"?

  - by DonCallisto

  Imagine this scenario: in our company there is an employee that "play" around graphic,css,html and so on. Our new project will born under symfony2 so we're trying some silly - but "real" - stuff (like authentication from db, submit data from a form and persist it to db and so on..) The problem As far i know, learnt from symfony2 "book" that i found on the site (you can find it here), there is an "automated" way for creating and rendering forms: 1) Build the form up into a controller in this way $form = $this->createFormBuilder($task) ->add('task','text'), ->add('dueDate','date'), ->getForm(); return $this->render('pathToBundle:Controller:templateTwig', array('form'=>$form->createview()); 2) Into templateTwig render the template {{ form_widget(form) }} // or single rows method 3) Into a controller (the same that have a route where you can submit data), take back submitted information if($rquest->getMethod()=='POST'){ $form->bindRequest($request); /* and so on */ } Return to scenario Our graphic employee don't want to access controllers, write php and other stuff like those. So he'll write a twig template with a "unconventional" (from symfony2 point of view, but conventional from HTML point of view) method: /* into twig template */ <form action="{{ path('SestanteUserBundle_homepage') }}" method="post" name="userForm"> <div> USERNAME: <input type="text" name="user_name" value="{{ user.username}}"/> </div> <div> EMAIL: <input type="text" name="user_mail" value="{{ user.email }}"/> </div> <input type="hidden" name="user_id" value="{{ id }}" /> <input type="submit" value="modifica i dati"> </form> Now, if into the controller that handle the submission of data we do something like that public function indexAction(Request $request) { if($request->getMethod() == 'POST'){ // sono arrivato per via di un submit, quindi devo modificare i dati prima di farli vedere a video $defaultData = array('message'=>'ho visto questa cosa in esempio, ma non capisco se posso farne a meno'); $form = $this->createFormBuilder($defaultData) ->add('user_name','text') ->add('user_mail','email') ->add('user_id','integer') ->getForm(); $form->bindRequest($request); //bindo la form ad una request $data = $form->getData(); //mi aspetto un'array chiave=>valore /* .... */ We expected that $data will contain an array with key,value from the submitted form. We found that it isn't true. After googling for a while and try with other "bad" ideas, we're frozen into that. So, if you have a "graphic office" that can't handle directly php code, how can we interface from form(s) to controller(s) ? UPDATE It seems that Symfony2 use a different convention for form's field name and lookup once you've submitted that. In particular, if my form's name is addUser and a field is named userName, the field's name will be AddUser[username] so maybe it have a "dynamic" lookup method that will extract form's name, field's name, concat them and lookup for values. Is it possible?

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• How to page multiple data sets in ASP.NET MVC

  - by REA_ANDREW

  On a single view I will have three sets of paged data. Which means for each model I will have The Objects The Page Index The Page Size My initial thought was for example: public class PagedModel<T> where T:class { public IList<T> Objects { get; set; } public int ModelPageIndex { get; set; } public int ModelPageSize { get; set; } } Then having a model which is to be supplied to the action as for example: public class TypesViewModel { public PagedModel<ObjectA> Types1 { get; set; } public PagedModel<ObjectB> Typed2 { get; set; } public PagedModel<ObjectC> Types3 { get; set; } } So if I then for example have the Index view inherit from the type: System.Web.Mvc.ViewPage<uk.co.andrewrea.forum.Web.Models.TypesViewModel> Now my initial aciton method for the index is simply: public ActionResult Index() { var forDisplayPurposes = new TypesViewModel(); return View(forDisplayPurposes); } If I then want to page, it is here where I am struggling to decide which action to take. Lets say that I select the next page of the Types2 PageModel. What should the action look like for this in order to return the new view showing the second page of the Types2 PageModel I was thinking possibly to duplicate the action but use it with POST [AcceptVerbs(HttpVerbs.Post)] public ActionResult Index(TypesViewModel model) { return View(model); } Is this a good way to approach it. I understand there is always Session, but I was just wondering how such a thing is achieved currently out there. If any best methods have been mutually accepted and things. So simply, one page with multiple paged models. How to persist the data for each using a wrapper model. Which way should you pass in the model and which way should you page the data, i.e. Form Post Lastly, I have seen the routes take this into account i.e. {controller}/{action}/{id}/{pageindex}/{pagesize} but this only accounts for one model and I do not really wwant to repeat the pagesize and pageindex values for the number of models I have inside the wrapper model. Thanks for your time!! Andrew

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• Techniques for querying a set of object in-memory in a Java application

  - by Edd Grant

  Hi All, We have a system which performs a 'coarse search' by invoking an interface on another system which returns a set of Java objects. Once we have received the search results I need to be able to further filter the resulting Java objects based on certain criteria describing the state of the attributes (e.g. from the initial objects return all objects where x.y z && a.b == c). The criteria used to filter the set of objects each time is partially user configurable, by this I mean that users will be able to select the values and ranges to match on but the attributes they can pick from will be a fixed set. The data sets are likely to contain <= 10,000 objects for each search. The search will be executed manually by the application user base probably no more than 2000 times a day (approx). It's probably worth mentioning that all the objects in the result set are known domain object classes which have Hibernate and JPA annotations describing their structure and relationship. Off the top of my head I can think of 3 ways of doing this: For each search persist the initial result set objects in our database, then use Hibernate to re-query them using the finer grained criteria. Use an in-memory Database (such as hsqldb?) to query and refine the initial result set. Write some custom code which iterates the initial result set and pulls out the desired records. Option 1 seems to involve a lot of toing and froing across a network to a physical Database (Oracle 10g) which might result in a lot of network and disk activity. It would also require the results from each search to be isolated from other result sets to ensure that different searches don't interfere with each other. Option 2 seems like a good idea in principle as it would allow me to do the finer query in memory and would not require the persistence of result data which would only be discarded after the search was complete. Gut feeling is that this could be pretty performant too but might result in larger memory overheads (which is fine as we can be pretty flexible on the amount of memory our JVM gets). Option 3 could be very performant but is something I would like to avoid as any code we write would require such careful testing that the time taken to acheive something flexible and robust enough would probably be prohibitive. I don't have time to prototype all 3 ideas so I am looking for comments people may have on the 3 options above, plus any further ideas I have not considered, to help me decide which idea might be most suitable. I'm currently leaning toward option 2 (in memory database) so would be keen to hear from people with experience of querying POJOs in memory too. Hopefully I have described the situation in enough detail but don't hesitate to ask if any further information is required to better understand the scenario. Cheers, Edd

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• EJB / JSF java.lang.ClassNotFoundException: com.ericsantanna.jobFC.dao.DAOFactoryRemote from [Module "com.sun.jsf-impl:main" from local module loader

  - by Eric Sant'Anna

  I'm in my first time using EJB and JSF, and I can't resolve this: 20:23:12,457 Grave [javax.enterprise.resource.webcontainer.jsf.application] (http-localhost-127.0.0.1-8081-2) com.ericsantanna.jobFC.dao.DAOFactoryRemote from [Module "com.sun.jsf-impl:main" from local module loader @439db2b2 (roots: C:\jboss-as-7.1.1.Final\modules)]: java.lang.ClassNotFoundException: com.ericsantanna.jobFC.dao.DAOFactoryRemote from [Module "com.sun.jsf-impl:main" from local module loader @439db2b2 (roots: C:\jboss-as-7.1.1.Final\modules)] I'm getting this when I do an action like a selectOneMenu or a commandButton click. DAOFactory.class @Singleton @Remote(DAOFactoryRemote.class) public class DAOFactory implements DAOFactoryRemote { private static final long serialVersionUID = 6030538139815885895L; @PersistenceContext private EntityManager entityManager; @EJB private JobDAORemote jobDAORemote; /** * Default constructor. */ public DAOFactory() { // TODO Auto-generated constructor stub } @Override public JobDAORemote getJobDAO() { JobDAO jobDAO = (JobDAO) jobDAORemote; jobDAO.setEntityManager(entityManager); return jobDAO; } JobDAO.class @Stateless @Remote(JobDAORemote.class) public class JobDAO implements JobDAORemote { private static final long serialVersionUID = -5483992924812255349L; private EntityManager entityManager; /** * Default constructor. */ public JobDAO() { // TODO Auto-generated constructor stub } @Override public void insert(Job t) { entityManager.persist(t); } @Override public Job findById(Class<Job> classe, Long id) { return entityManager.getReference(classe, id); } @Override public Job findByName(Class<Job> clazz, String name) { return entityManager .createQuery("SELECT job FROM " + clazz.getName() + " job WHERE job.nome = :nome" , Job.class) .setParameter("name", name) .getSingleResult(); } ... TriggerFormBean.class @ManagedBean @ViewScoped @Stateless public class TriggerFormBean implements Serializable { private static final long serialVersionUID = -3293560384606586480L; @EJB private DAOFactoryRemote daoFactory; @EJB private TriggerManagerRemote triggerManagerRemote; ... triggerForm.xhtml (a portion with problem) </p:layoutUnit> <p:layoutUnit id="eastConditionPanel" position="center" size="50%"> <p:panel header="Conditions to Release" style="width:97%;height:97%;"> <h:panelGrid columns="2" cellpadding="3"> <h:outputLabel value="Condition Name:" for="conditionName" /> <p:inputText id="conditionName" value="#{triggerFormBean.newCondition.name}" /> </h:panelGrid> <p:commandButton value="Add Condition" update="conditionsToReleaseList" id="addConditionToRelease" actionListener="#{triggerFormBean.addNewCondition}" /> <p:orderList id="conditionsToReleaseList" value="#{triggerFormBean.trigger.conditionsToRelease}" var="condition" controlsLocation="none" itemLabel="#{condition.name}" itemValue="#{condition}" iconOnly="true" style="width:97%;heigth:97%;"/> </p:panel> </p:layoutUnit> In TriggerFormBean.class if comments daoFactory we get the same exception with triggerManagerRemote, both annotated with @EJB. I'm don't understand the relationship between my DAOFactory and the "Module com.sun.jsf-impl:main"... Thanks.

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• I am unsure of how to access a persistence entity from a JSP page?

  - by pharma_joe

  Hi, I am just learning Java EE, I have created a Persistence entity for a User object, which is stored in the database. I am now trying to create a JSP page that will allow a client to enter a new User object into the System. I am unsure of how the JSP page interacts with the User facade, the tutorials are confusing me a little. This is the code for the facade: <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Add User to System</title> </head> <body> <h2>Add User</h2> <h3>Please fill out the details to add a user to the system</h3> <form action=""> <label>Email:</label> <input type="text" name="email"><br /> <label>Password:</label> <input type="password" name="name"><br /> <label>Name:</label> <input type="text" name="name"><br /> <label>Address:</label> <input type="text" name="address"><br /> <label>Type:</label> <select name="type"> <option>Administrator</option> <option>Member</option> </select><br /> <input type="submit" value="Add" name="add"/> <input type="reset" value="clear" /> </form> </body> This is the code I have to add a new User object within the User facade class: @Stateless public class CinemaUserFacade { @PersistenceContext(unitName = "MonashCinema-warPU") private EntityManager em; public void create(CinemaUser cinemaUser) { em.persist(cinemaUser); } I am finding it a little difficult to get my head around the whole MVC thing, getting there but would appreciate it if someone could turn the light on for me!

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• When to use new layouts and when to use new activities?

  - by cmdfrg

  I'm making a game in Android and I'm trying to add a set of menu screens. Each screen takes up the whole display and has various transitions available to other screens. As a rough summary, the menu screens are: Start screen Difficult select screen Game screen. Pause screen. Game over screen. And there are several different ways you can transition between screen: 1 - 2 2 - 3 3 - 4 (pause game) 4 - 1 (exit game) 4 - 3 (resume game) 3 - 5 (game ends) Obviously, I need some stored state when moving between screens, such as the difficulty level select when starting a game and what the player's score is when the game over screen is shown. Can anyone give me some advice for the easiest way to implement the above screens and transitions in Android? All the create/destroy/pause/resume methods make me nervous about writing brittle code if I'm not careful. I'm not fond of using an Activity for each screen. It seems too heavy weight, having to pass data around using intents seems like a real pain and each screen isn't a useful module by itself. As the "back" button doesn't always go back to the previous screen either, my menu layout doesn't seem to fit the activity model well. At the moment, I'm representing each screen as an XML layout file and I have one activity. I set the different buttons on each layout to call setContentView to update the screen the main activity is showing (e.g. the pause button changes the layout to the pause screen). The activity holds onto all the state needed (e.g. the current difficulty level and the game high score), which makes it easy to share data between screens. This seems roughly similar to the LunarLander sample, except I'm using multiple screens. Does what I have at the moment sound OK or am I not doing things the typical Android way? Is there a class I can use (e.g. something like ViewFlipper) that could make my life easier? By the way, my game screen is implemented as a SurfaceView that stores the game state. I need the state in this view to persist between calls to setContentView (e.g. to resume from paused). Is the right idea to create the game view when the activity starts, keep a reference to it and then use this reference with setContentView whenever I want the game screen to appear?

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• Parallelism in .NET – Part 15, Making Tasks Run: The TaskScheduler

  - by Reed

  In my introduction to the Task class, I specifically made mention that the Task class does not directly provide it’s own execution.  In addition, I made a strong point that the Task class itself is not directly related to threads or multithreading.  Rather, the Task class is used to implement our decomposition of tasks.  Once we’ve implemented our tasks, we need to execute them.  In the Task Parallel Library, the execution of Tasks is handled via an instance of the TaskScheduler class. The TaskScheduler class is an abstract class which provides a single function: it schedules the tasks and executes them within an appropriate context.  This class is the class which actually runs individual Task instances.  The .NET Framework provides two (internal) implementations of the TaskScheduler class. Since a Task, based on our decomposition, should be a self-contained piece of code, parallel execution makes sense when executing tasks.  The default implementation of the TaskScheduler class, and the one most often used, is based on the ThreadPool.  This can be retrieved via the TaskScheduler.Default property, and is, by default, what is used when we just start a Task instance with Task.Start(). Normally, when a Task is started by the default TaskScheduler, the task will be treated as a single work item, and run on a ThreadPool thread.  This pools tasks, and provides Task instances all of the advantages of the ThreadPool, including thread pooling for reduced resource usage, and an upper cap on the number of work items.  In addition, .NET 4 brings us a much improved thread pool, providing work stealing and reduced locking within the thread pool queues.  By using the default TaskScheduler, our Tasks are run asynchronously on the ThreadPool. There is one notable exception to my above statements when using the default TaskScheduler.  If a Task is created with the TaskCreationOptions set to TaskCreationOptions.LongRunning, the default TaskScheduler will generate a new thread for that Task, at least in the current implementation.  This is useful for Tasks which will persist for most of the lifetime of your application, since it prevents your Task from starving the ThreadPool of one of it’s work threads. The Task Parallel Library provides one other implementation of the TaskScheduler class.  In addition to providing a way to schedule tasks on the ThreadPool, the framework allows you to create a TaskScheduler which works within a specified SynchronizationContext.  This scheduler can be retrieved within a thread that provides a valid SynchronizationContext by calling the TaskScheduler.FromCurrentSynchronizationContext() method. This implementation of TaskScheduler is intended for use with user interface development.  Windows Forms and Windows Presentation Foundation both require any access to user interface controls to occur on the same thread that created the control.  For example, if you want to set the text within a Windows Forms TextBox, and you’re working on a background thread, that UI call must be marshaled back onto the UI thread.  The most common way this is handled depends on the framework being used.  In Windows Forms, Control.Invoke or Control.BeginInvoke is most often used.  In WPF, the equivelent calls are Dispatcher.Invoke or Dispatcher.BeginInvoke. As an example, say we’re working on a background thread, and we want to update a TextBlock in our user interface with a status label.  The code would typically look something like: // Within background thread work... string status = GetUpdatedStatus(); Dispatcher.BeginInvoke(DispatcherPriority.Normal, new Action( () => { statusLabel.Text = status; })); // Continue on in background method .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } This works fine, but forces your method to take a dependency on WPF or Windows Forms.  There is an alternative option, however.  Both Windows Forms and WPF, when initialized, setup a SynchronizationContext in their thread, which is available on the UI thread via the SynchronizationContext.Current property.  This context is used by classes such as BackgroundWorker to marshal calls back onto the UI thread in a framework-agnostic manner. The Task Parallel Library provides the same functionality via the TaskScheduler.FromCurrentSynchronizationContext() method.  When setting up our Tasks, as long as we’re working on the UI thread, we can construct a TaskScheduler via: TaskScheduler uiScheduler = TaskScheduler.FromCurrentSynchronizationContext(); We then can use this scheduler on any thread to marshal data back onto the UI thread.  For example, our code above can then be rewritten as: string status = GetUpdatedStatus(); (new Task(() => { statusLabel.Text = status; })) .Start(uiScheduler); // Continue on in background method This is nice since it allows us to write code that isn’t tied to Windows Forms or WPF, but is still fully functional with those technologies.  I’ll discuss even more uses for the SynchronizationContext based TaskScheduler when I demonstrate task continuations, but even without continuations, this is a very useful construct. In addition to the two implementations provided by the Task Parallel Library, it is possible to implement your own TaskScheduler.  The ParallelExtensionsExtras project within the Samples for Parallel Programming provides nine sample TaskScheduler implementations.  These include schedulers which restrict the maximum number of concurrent tasks, run tasks on a single threaded apartment thread, use a new thread per task, and more.

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• Class-Level Model Validation with EF Code First and ASP.NET MVC 3

  - by ScottGu

  Earlier this week the data team released the CTP5 build of the new Entity Framework Code-First library.  In my blog post a few days ago I talked about a few of the improvements introduced with the new CTP5 build.  Automatic support for enforcing DataAnnotation validation attributes on models was one of the improvements I discussed.  It provides a pretty easy way to enable property-level validation logic within your model layer. You can apply validation attributes like [Required], [Range], and [RegularExpression] – all of which are built-into .NET 4 – to your model classes in order to enforce that the model properties are valid before they are persisted to a database.  You can also create your own custom validation attributes (like this cool [CreditCard] validator) and have them be automatically enforced by EF Code First as well.  This provides a really easy way to validate property values on your models.  I showed some code samples of this in action in my previous post. Class-Level Model Validation using IValidatableObject DataAnnotation attributes provides an easy way to validate individual property values on your model classes.  Several people have asked - “Does EF Code First also support a way to implement class-level validation methods on model objects, for validation rules than need to span multiple property values?”  It does – and one easy way you can enable this is by implementing the IValidatableObject interface on your model classes. IValidatableObject.Validate() Method Below is an example of using the IValidatableObject interface (which is built-into .NET 4 within the System.ComponentModel.DataAnnotations namespace) to implement two custom validation rules on a Product model class.  The two rules ensure that: New units can’t be ordered if the Product is in a discontinued state New units can’t be ordered if there are already more than 100 units in stock We will enforce these business rules by implementing the IValidatableObject interface on our Product class, and by implementing its Validate() method like so: The IValidatableObject.Validate() method can apply validation rules that span across multiple properties, and can yield back multiple validation errors. Each ValidationResult returned can supply both an error message as well as an optional list of property names that caused the violation (which is useful when displaying error messages within UI). Automatic Validation Enforcement EF Code-First (starting with CTP5) now automatically invokes the Validate() method when a model object that implements the IValidatableObject interface is saved.  You do not need to write any code to cause this to happen – this support is now enabled by default. This new support means that the below code – which violates one of our above business rules – will automatically throw an exception (and abort the transaction) when we call the “SaveChanges()” method on our Northwind DbContext: In addition to reactively handling validation exceptions, EF Code First also allows you to proactively check for validation errors.  Starting with CTP5, you can call the “GetValidationErrors()” method on the DbContext base class to retrieve a list of validation errors within the model objects you are working with.  GetValidationErrors() will return a list of all validation errors – regardless of whether they are generated via DataAnnotation attributes or by an IValidatableObject.Validate() implementation.  Below is an example of proactively using the GetValidationErrors() method to check (and handle) errors before trying to call SaveChanges(): ASP.NET MVC 3 and IValidatableObject ASP.NET MVC 2 included support for automatically honoring and enforcing DataAnnotation attributes on model objects that are used with ASP.NET MVC’s model binding infrastructure.  ASP.NET MVC 3 goes further and also honors the IValidatableObject interface.  This combined support for model validation makes it easy to display appropriate error messages within forms when validation errors occur.  To see this in action, let’s consider a simple Create form that allows users to create a new Product: We can implement the above Create functionality using a ProductsController class that has two “Create” action methods like below: The first Create() method implements a version of the /Products/Create URL that handles HTTP-GET requests - and displays the HTML form to fill-out.  The second Create() method implements a version of the /Products/Create URL that handles HTTP-POST requests - and which takes the posted form data, ensures that is is valid, and if it is valid saves it in the database.  If there are validation issues it redisplays the form with the posted values.  The razor view template of our “Create” view (which renders the form) looks like below: One of the nice things about the above Controller + View implementation is that we did not write any validation logic within it.  The validation logic and business rules are instead implemented entirely within our model layer, and the ProductsController simply checks whether it is valid (by calling the ModelState.IsValid helper method) to determine whether to try and save the changes or redisplay the form with errors. The Html.ValidationMessageFor() helper method calls within our view simply display the error messages our Product model’s DataAnnotations and IValidatableObject.Validate() method returned.  We can see the above scenario in action by filling out invalid data within the form and attempting to submit it: Notice above how when we hit the “Create” button we got an error message.  This was because we ticked the “Discontinued” checkbox while also entering a value for the UnitsOnOrder (and so violated one of our business rules).  You might ask – how did ASP.NET MVC know to highlight and display the error message next to the UnitsOnOrder textbox?  It did this because ASP.NET MVC 3 now honors the IValidatableObject interface when performing model binding, and will retrieve the error messages from validation failures with it. The business rule within our Product model class indicated that the “UnitsOnOrder” property should be highlighted when the business rule we hit was violated: Our Html.ValidationMessageFor() helper method knew to display the business rule error message (next to the UnitsOnOrder edit box) because of the above property name hint we supplied: Keeping things DRY ASP.NET MVC and EF Code First enables you to keep your validation and business rules in one place (within your model layer), and avoid having it creep into your Controllers and Views.  Keeping the validation logic in the model layer helps ensure that you do not duplicate validation/business logic as you add more Controllers and Views to your application.  It allows you to quickly change your business rules/validation logic in one single place (within your model layer) – and have all controllers/views across your application immediately reflect it.  This help keep your application code clean and easily maintainable, and makes it much easier to evolve and update your application in the future. Summary EF Code First (starting with CTP5) now has built-in support for both DataAnnotations and the IValidatableObject interface.  This allows you to easily add validation and business rules to your models, and have EF automatically ensure that they are enforced anytime someone tries to persist changes of them to a database.  ASP.NET MVC 3 also now supports both DataAnnotations and IValidatableObject as well, which makes it even easier to use them with your EF Code First model layer – and then have the controllers/views within your web layer automatically honor and support them as well.  This makes it easy to build clean and highly maintainable applications. You don’t have to use DataAnnotations or IValidatableObject to perform your validation/business logic.  You can always roll your own custom validation architecture and/or use other more advanced validation frameworks/patterns if you want.  But for a lot of applications this built-in support will probably be sufficient – and provide a highly productive way to build solutions. Hope this helps, Scott P.S. In addition to blogging, I am also now using Twitter for quick updates and to share links. Follow me at: twitter.com/scottgu

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• Persistent static routes fail on MacOS 10.6.5 startup!

  - by verbalicious

  I'm unable to get static routes to persist a reboot on Mac OS 10.6.5. I've tried all of the methods prescribed in Google search results, and previous posts on this site. I've tried manually creating a launchd daemon, and used RouteSplit's launchd daemon to no avail. It's clear that the interface is not ready when these methods attempt to apply the route. This workstation in question is getting its IP from DHCP and probably hasn't gotten its DHCP lease when the command runs. We're able to apply the route by hand when logged in, but not through startup methods. Is there another way to apply this route by sneaking the command into something later, but before the login window appears to the user? Here is some relevant log info from system.log. You can see the "route: writing to routing socket: Network is unreachable" errors where my launchd script fires off. I've tried adding extra "sleep" and "ipconfig waitall" statements later in the script but this doesn't fly. Dec 15 19:30:41 localhost com.apple.launchd[1]: *** launchd[1] has started up. *** Dec 15 19:30:45 localhost mDNSResponder[18]: mDNSResponder mDNSResponder-258.13 (Oct 8 2010 17:10:30) starting Dec 15 19:30:47 localhost configd[15]: bootp_session_transmit: bpf_write(en1) failed: Network is down (50) Dec 15 19:30:47 localhost configd[15]: DHCP en1: INIT transmit failed Dec 15 19:30:47 localhost configd[15]: network configuration changed. Dec 15 19:30:47 Administrators-MacBook-Pro configd[15]: setting hostname to "Administrators-MacBook-Pro.local" Dec 15 19:30:47 Administrators-MacBook-Pro blued[16]: Apple Bluetooth daemon started Dec 15 19:30:52 Administrators-MacBook-Pro syslog[67]: routes.sh: Starting RouteSplit Dec 15 19:30:53 Administrators-MacBook-Pro com.apple.usbmuxd[41]: usbmuxd-207 built for iTunesTenOne on Oct 19 2010 at 13:50:35, running 64 bit Dec 15 19:30:54 Administrators-MacBook-Pro /System/Library/CoreServices/loginwindow.app/Contents/MacOS/loginwindow[50]: Login Window Application Started Dec 15 19:30:55 Administrators-MacBook-Pro bootlog[61]: BOOT_TIME: 1292459441 0 Dec 15 19:30:55 Administrators-MacBook-Pro syslog[86]: routes.sh: static route 192.168.0.0/23 192.168.2.2 Dec 15 19:30:55 Administrators-MacBook-Pro net.routes.static[65]: route: writing to routing socket: Network is unreachable Dec 15 19:30:55 Administrators-MacBook-Pro net.routes.static[65]: add net 192.168.0.0: gateway 192.168.2.2: Network is unreachable Dec 15 19:30:57 Administrators-MacBook-Pro org.apache.httpd[38]: httpd: Could not reliably determine the server's fully qualified domain name, using Administrators-MacBook-Pro.local for ServerName Dec 15 19:30:58 Administrators-MacBook-Pro loginwindow[50]: Login Window Started Security Agent Dec 15 19:30:58 Administrators-MacBook-Pro WindowServer[89]: kCGErrorFailure: Set a breakpoint @ CGErrorBreakpoint() to catch errors as they are logged. Dec 15 19:30:58 Administrators-MacBook-Pro com.apple.WindowServer[89]: Wed Dec 15 19:30:58 Administrators-MacBook-Pro.local WindowServer[89] <Error>: kCGErrorFailure: Set a breakpoint @ CGErrorBreakpoint() to catch errors as they are logged. Dec 15 19:31:18 Administrators-MacBook-Pro configd[15]: network configuration changed. Dec 15 19:31:19 administrators-macbook-pro configd[15]: setting hostname to "administrators-macbook-pro.local" Dec 15 19:31:25 administrators-macbook-pro _mdnsresponder[121]: /usr/libexec/ntpd-wrapper: scutil key State:/Network/Global/DNS not present after 30 seconds Dec 15 19:31:25 administrators-macbook-pro _mdnsresponder[124]: sntp options: a=2 v=1 e=0.100 E=5.000 P=2147483647.000 Dec 15 19:31:25 administrators-macbook-pro _mdnsresponder[124]: d=15 c=5 x=0 op=1 l=/var/run/sntp.pid f= time.apple.com Dec 15 19:31:25 administrators-macbook-pro _mdnsresponder[124]: sntp: getaddrinfo(hostname, ntp) failed with nodename nor servname provided, or not known Dec 15 19:31:27 administrators-macbook-pro configd[15]: network configuration changed. Dec 15 19:31:27 Administrators-MacBook-Pro configd[15]: setting hostname to "Administrators-MacBook-Pro.local" Dec 15 19:31:27 Administrators-MacBook-Pro ntpd[37]: Cannot find existing interface for address 17.151.16.20 Dec 15 19:31:27 Administrators-MacBook-Pro ntpd_initres[125]: ntpd indicates no data available! Dec 15 19:31:31 Administrators-MacBook-Pro sshd[128]: USER_PROCESS: 133 ttys000 Dec 15 19:31:37 Administrators-MacBook-Pro sudo[138]: administrator : TTY=ttys000 ; PWD=/Users/administrator ; USER=root ; COMMAND=/usr/bin/less /var/log/system.log ``You can see the following line in /var/log/kernel.log that shows the en0 interface coming up: Dec 15 19:30:51 Administrators-MacBook-Pro kernel[0]: Ethernet [AppleBCM5701Ethernet]: Link up on en0, 1-Gigabit, Full-duplex, No flow-control, Debug [796d,0f01,0de1,0300,c1e1,3800]

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• Linux pptp client stops working after several hours

  - by Aron Rotteveel

  Here's the situation: Setup: 1 Windows Server 2008 machine acting as a Domain Controller and RRAS server 1 CentOS machine in a datacentre located elsewhere PPTP client running on CentOS machine, connected to the DC via When I connect to the DC, everything is working fine. I have set up a static IP for the dialup connection in my RRAS server so that the CentOS machine is automatically assigned the IP 192.168.1.240. Inside the VPN, it is not possible to access this machine on the local IP-address. Perfect. However, after several hours, it simply seems to stop working (IE: I cannot ping to or from this machine on the local network). The strange thing is, however: The DC shows the VPN client as still being connected The CentOS machine shows the network interface as being up There are no entries in my /var/log/messages that indicate a problem Output from ifconfig: ppp0 Link encap:Point-to-Point Protocol inet addr:192.168.1.240 P-t-P:192.168.1.160 Mask:255.255.255.255 UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1396 Metric:1 RX packets:43 errors:0 dropped:0 overruns:0 frame:0 TX packets:58 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:3 RX bytes:4511 (4.4 KiB) TX bytes:15071 (14.7 KiB) Output from route -n: 192.168.1.160 0.0.0.0 255.255.255.255 UH 0 0 0 ppp0 192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 ppp0 I have the following in my ip-up.local: route add -net 192.168.1.0 netmask 255.255.255.0 dev ppp0 The situation can be easily fixed by issueing a killall pppd and re-connecting. However, I obviously do not want to do this every X-hours or so. I have tried running pppd with both the debug as the kdebug flag but cannot find the cause of this problem. Currently, my ppp0 network interface seems to be running and the last log lines mentioning it are: Feb 19 14:10:40 graviton pppd[10934]: local IP address 192.168.1.240 Feb 19 14:10:40 graviton pppd[10934]: remote IP address 192.168.1.160 Feb 19 14:10:40 graviton pppd[10934]: Script /etc/ppp/ip-up started (pid 10952) Feb 19 14:10:40 graviton pppd[10934]: Script /etc/ppp/ip-up finished (pid 10952), status = 0x0 Feb 19 14:11:27 graviton pptp[10935]: anon log[decaps_gre:pptp_gre.c:414]: buffering packet 190 (expecting 189, lost or reordered) Feb 19 14:11:37 graviton pptp[10942]: anon log[logecho:pptp_ctrl.c:677]: Echo Request received. Feb 19 14:11:37 graviton pptp[10942]: anon log[ctrlp_rep:pptp_ctrl.c:251]: Sent control packet type is 6 'Echo-Reply' Feb 19 14:12:37 graviton pptp[10942]: anon log[logecho:pptp_ctrl.c:677]: Echo Request received. Feb 19 14:12:37 graviton pptp[10942]: anon log[ctrlp_rep:pptp_ctrl.c:251]: Sent control packet type is 6 'Echo-Reply' Feb 19 14:12:37 graviton pptp[10942]: anon log[logecho:pptp_ctrl.c:677]: Echo Reply received. Feb 19 14:13:37 graviton pptp[10942]: anon log[logecho:pptp_ctrl.c:677]: Echo Reply received. Feb 19 14:14:37 graviton pptp[10942]: anon log[logecho:pptp_ctrl.c:677]: Echo Reply received. Feb 19 14:15:37 graviton pptp[10942]: anon log[logecho:pptp_ctrl.c:677]: Echo Reply received. Feb 19 14:16:37 graviton pptp[10942]: anon log[logecho:pptp_ctrl.c:677]: Echo Reply received. Feb 19 14:19:37 graviton pptp[10942]: anon log[logecho:pptp_ctrl.c:677]: Echo Reply received. Feb 19 14:19:37 graviton pptp[10942]: anon log[logecho:pptp_ctrl.c:679]: no more Echo Reply/Request packets will be reported. I have enabled the persist option. The network interface is still running, but it is still impossible to send data through the VPN. Any help is appreciated.

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