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  • The hidden cost of interrupting knowledge workers

    - by Piet
    The November issue of pragpub has an interesting article on interruptions. The article is written by Brian Tarbox, who also mentions the article on his blog. I like the subtitle: ‘Simple Strategies for Avoiding Dumping Your Mental Stack’. Brian talks about the effective cost of interrupting a ‘knowledge worker’, often with trivial questions or distractions. In the eyes of the interruptor, the interruption only costs the time the interrupted had to listen to the question and give an answer. However, depending on what the interrupted was doing at the time, getting fully immersed in their task again might take up to 15-20 minutes. Enough interruptions might even cause a knowledge worker to mentally call it a day. According to this article interruptions can consume about 28% of a knowledge worker’s time, translating in a $588 billion loss for US companies each year. Looking for a new developer to join your team? Ever thought about optimizing your team’s environment and the way they work instead? Making non knowledge workers aware You can’t. Well, I haven’t succeeded yet. And believe me: I’ve tried. When you’ve got a simple way to really increase your productivity (’give me 2 hours of uninterrupted time a day’) it wouldn’t be right not to tell your boss or team-leader about it. The problem is: only productive knowledge workers seem to understand this. People who don’t fall into this category just seem to think you’re joking, being arrogant or anti-social when you tell them the interruptions can really have an impact on your productivity. Also, knowledge workers often work in a very concentrated mental state which is described here as: It is the same mindfulness as ecstatic lovemaking, the merging of two into a fluidly harmonious one. The hallmark of flow is a feeling of spontaneous joy, even rapture, while performing a task. Yes, coding can be addictive and if you’re interrupting a programmer at the wrong moment, you’re effectively bringing down a junkie from his high in just a few seconds. This can result in seemingly arrogant, almost aggressive reactions. How to make people aware of the production-cost they’re inflicting: I’ve been often pondering that question myself. The article suggests that solutions based on that question never seem to work. To be honest: I’ve never even been able to find a half decent solution for this question. People who are not in this situations just don’t understand the issue, no matter how you try to explain it. Fun (?) thing I’ve noticed: Programmers or IT people in general who don’t get this are often the kind of people who just don’t get anything done. Interrupt handling (interruption management?) IRL Have non-urgent questions handled in a non-interruptive way It helps a bit to educate people into using non-interruptive ways to ask questions: “duh, I have no idea, but I’m a bit busy here now could you put it in an email so I don’t forget?”. Eventually, a considerable amount of people will skip interrupting you and just send an email right away. Some stubborn-headed people however will continue to just interrupt you, saying “you’re 10 meters from my desk, why can’t we just talk?”. Just remember to disable your email notifications, it can be hard to resist opening your email client when you know a new email just arrived. Use Do Not Disturb signals When working in a group of programmers, often the unofficial sign you can only be interrupted for something important is to put on headphones. And when the environment is quiet enough, often people aren’t even listening to music. Otherwise music can help to block the indirect distractions (someone else talking on the phone or tapping their feet). You might get a “they’re all just surfing and listening to music”-reaction from outsiders though. Peopleware talks about a team where the no-interruption sign was placing a shawl on the desk. If I remember correctly, I am unable to locate my copy of this really excellent must-read book. If you have all standardized on the same IM tool, maybe that tool has a ‘do not disturb’ setting. Also some phone-systems have a ‘DND’ (do not disturb) setting. Hide Brian offers a number of good suggestions, some obvious like: hide away somewhere they can’t find you. Not sure how long it’ll be till someone thinks you’re just taking a nap somewhere though. Also, this often isn’t possible or your boss might not understand this. And if you really get caught taking a nap, make sure to explain that your were powernapping. Counter-act interruptions Another suggestion he offers is when you’re being interrupted to just hold up your hand, blocking the interruption, and at least giving you time to finish your sentence or your block/line of code. The last suggestion works more as a way to make it obvious to the interruptor that they really are interrupting your work and to offload some of the cost on the interruptor. In practice, this can also helps you cool down a bit so you don’t start saying nasty things to the interruptor. Unfortunately I’ve sometimes been confronted with people who just ignore this signal and keep talking, as if they’re sure that whatever they’ve got to say is really worth listening to and without a doubt more important than anything you might be doing. This behaviour usually leaves me speechless (not good when someone just asked a question). I’ve noticed that these people are usually also the first to complain when being interrupted themselves. They’re generally not very liked as colleagues, so try not to imitate their behaviour. TDD as a way to minimize recovery time I don’t like Test Driven Development. Mainly for only one reason: It interrupts flow. At least, that’s what it does for me, but maybe I’m just not grown used to TDD yet. BUT a positive effect TDD has on me when I have to work in an interruptive environment and can’t really get into the ‘flow’ (also supposedly called ‘the zone’ by software developers, although I’ve never heard it 1st hand), TDD helps me to concentrate on the tasks at hand and helps me to get back at work after an interruption. I feel when using TDD, I can get by without the need for being totally ‘in’ the project and I can be reasonably productive without obtaining ‘flow’. Do you have a suggestion on how to make people aware of the concept of ‘flow’ and the cost of interruptions? (without looking like an arrogant ass or a weirdo)

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  • How can I set up .NET UnhandledException handling in a Windows service?

    - by Mike Pateras
    protected override void OnStart(string[] args) { AppDomain.CurrentDomain.UnhandledException += new UnhandledExceptionEventHandler(CurrentDomain_UnhandledException); Thread.Sleep(10000); throw new Exception(); } void CurrentDomain_UnhandledException(object sender, UnhandledExceptionEventArgs e) { } I attached a debugger to the above code in my windows service, setting a breakpoint in CurrentDomain_UnhandledException, but it was never hit. The exception pops up saying that it is unhandled, and then the service stops. I even tried putting some code in the event handler, in case it was getting optimized away. Is this not the proper way to set up unhandled exception handling in a windows service?

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  • How can I set up .Net unhanlded exception handling in a windows service?

    - by Mike Pateras
    protected override void OnStart(string[] args) { AppDomain.CurrentDomain.UnhandledException += new UnhandledExceptionEventHandler(CurrentDomain_UnhandledException); Thread.Sleep(10000); throw new Exception(); } void CurrentDomain_UnhandledException(object sender, UnhandledExceptionEventArgs e) { } I attached a debugger to the above code in my windows service, setting a breakpoint in CurrentDomain_UnhandledException, but it was never hit. The exception pops up saying that it is unhandled, and then the service stops. I even tried putting some code in the event handler, in case it was getting optimized away. Is this not the proper way to set up unhandled exception handling in a windows service?

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  • Does javascript event handling occur inside or outside the program flow?

    - by Carlo Roosen
    This question is related to Javascript event handling and flow control, but it is one step beyond. The question that remains unanswered is: when an event is fired and control is returned to the browser, could the browser decide to handle other events first (fired by other scripts or user action) (A), or will it always handle my event directly (B)? The question is important, because in case (B) you can rely on the fact that nothing has been changed between firing the event and the event handler, while (A) gives no guarantees whatsoever. My first guess is (B), how else could stopPropagation() and preventDefault() work? But giving it a second thought, it is no hard evidence.

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  • Any good idioms for error handling in straight C programs?

    - by Will Hartung
    Getting back in to some C work. Many of my functions look like this: int err = do_something(arg1, arg2, arg3, &result); With the intent the result gets populated by the function, and the return value is the status of the call. The darkside is you get something naive like this: int err = func1(...); if (!err) { err = func2(...); if (!err) { err = func3(...); } } return err; I could macro it I suppose: #define ERR(x) if (!err) { err = (x) } int err = 0; ERR(func1(...)); ERR(func2(...)); ERR(func3(...)); return err; But that only works if I'm chaining function calls, vs doing other work. Obviously Java, C#, C++ have exceptions that work very well for these kinds of things. I'm just curious what other folks do and how other folks do error handling in their C programs nowadays.

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  • ASP.NET Error Handling: Creating an extension method to send error email

    - by Jalpesh P. Vadgama
    Error handling in asp.net required to handle any kind of error occurred. We all are using that in one or another scenario. But some errors are there which will occur in some specific scenario in production environment in this case We can’t show our programming errors to the End user. So we are going to put a error page over there or whatever best suited as per our requirement. But as a programmer we should know that error so we can track the scenario and we can solve that error or can handle error. In this kind of situation an Error Email comes handy. Whenever any occurs in system it will going to send error in our email. Here I am going to write a extension method which will send errors in email. From asp.net 3.5 or higher version of .NET framework  its provides a unique way to extend your classes. Here you can fine more information about extension method. So lets create extension method via implementing a static class like following. I am going to use same code for sending email via my Gmail account from here. Following is code for that. using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Net.Mail; namespace Experiement { public static class MyExtension { public static void SendErrorEmail(this Exception ex) { MailMessage mailMessage = new MailMessage(new MailAddress("[email protected]") , new MailAddress("[email protected]")); mailMessage.Subject = "Exception Occured in your site"; mailMessage.IsBodyHtml = true; System.Text.StringBuilder errorMessage = new System.Text.StringBuilder(); errorMessage.AppendLine(string.Format("<B>{0}</B>:{1}<BR/>","Exception",ex.Message)); errorMessage.AppendLine(string.Format("<B>{0}</B>:{1}<BR/>", "Stack Trace", ex.StackTrace)); if (ex.InnerException != null) { errorMessage.AppendLine(string.Format("<B>{0}</B>:{1}<BR/>", " Inner Exception", ex.InnerException.Message)); errorMessage.AppendLine(string.Format("<B>{0}</B>:{1}<BR/>", "Inner Stack Trace", ex.InnerException.StackTrace)); } mailMessage.Body = errorMessage.ToString(); System.Net.NetworkCredential networkCredentials = new System.Net.NetworkCredential("[email protected]", "password"); SmtpClient smtpClient = new SmtpClient(); smtpClient.EnableSsl = true; smtpClient.UseDefaultCredentials = false; smtpClient.Credentials = networkCredentials; smtpClient.Host = "smtp.gmail.com"; smtpClient.Port = 587; smtpClient.Send(mailMessage); } } } After creating an extension method let us that extension method to handle error like following in page load event of page. using System; namespace Experiement { public partial class WebForm1 : System.Web.UI.Page { protected void Page_Load(object sender,System.EventArgs e) { try { throw new Exception("My custom Exception"); } catch (Exception ex) { ex.SendErrorEmail(); Response.Write(ex.Message); } } } } Now in above code I have generated custom exception for example but in production It can be any Exception. And you can see I have use ex.SendErrorEmail() function in catch block to send email. That’s it.. Now it will throw exception and you will email in your email box like below.   That’s its. It’s so simple…Stay tuned for more.. Happy programming.. Technorati Tags: Exception,Extension Mehtod,Error Handling,ASP.NET

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  • NNTP & Socket - How to interrupt?

    - by Cosmo
    Hi. I'm sending a message to a NNTP server in order to fetch an article's body. I don't want to wait for the answer to complete, cause I only need the first 3 lines from the body. How can I interrupt the transfer and move on to the next article? Now when I request another's article message body, I still get data from the previous one. The only way that worked for me, was to close the stream and reopen it. In my opinion this is a little bit hardcore, cause I have to login to the server every time I need a new file. Any help would be appreciated. Kind Regards.

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  • Interrupt an Http Request blocked in read() on Android

    - by twk
    Using the Apache Http stack on Android, I'm trying to force a thread out of a call to read. This is what the stack looks like: OSNetworkSystem.receiveStreamImpl(FileDescriptor, byte[], int, int, int) line: not available [native method] OSNetworkSystem.receiveStream(FileDescriptor, byte[], int, int, int) line: 478 PlainSocketImpl.read(byte[], int, int) line: 565 SocketInputStream.read(byte[], int, int) line: 87 SocketInputBuffer(AbstractSessionInputBuffer).fillBuffer() line: 103 SocketInputBuffer(AbstractSessionInputBuffer).read(byte[], int, int) line: 134 IdentityInputStream.read(byte[], int, int) line: 86 EofSensorInputStream.read(byte[], int, int) line: 159 Fetcher.readStream() line: 89 I've tried InputStream.close(), Thread.Interrupt(), and HttpUriRequest.abort(), without any success. Any ideas? I'm also open to some kind of non-blocking IO, but I don't see any way to do that with the HttpUriRequest object. Thanks!

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  • Interrupt a thread in DatagramSocket.receive

    - by SEK
    I'm building an application that listens on both TCP and UDP, and I've run into some trouble with my shutdown mechanism. When I call Thread.interrupt() on each of the listening threads, the TCP thread is interrupted from listening, whereas the UDP listener isn't. To be specific, the TCP thread uses Socket.accept(), which simply returns (without actually connecting). Whereas the UDP thread uses DatagramSocket.receive, and doesn't exit that method. Is this an issue in my JRE, my OS, or should I just switch to (Datagram)Socket.close()?

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  • Java Application for handling records(CRUD)

    - by LivingThing
    I am new to JavaEE and am faced with a tight situation here. I have to develop a Java application for (CRUD) handling records and saving and loading an XML concerning that record. Obviously, I won't be asking you to do this for me. What I would be asking you is to give me some hints/pointer. Initially I thought JAXB would be enough for this but after putting a lot of time learning it and implementing the program I realized that it just can create the XML and read it but for update, delete I would have to do something else. Even if it wasn't for update and delete features requirement for my project I would still think that by just using JAXB is not a good implementation. I was wondering if "REST with Java (JAX-RS) using Jersey" should do the trick for me. ?

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  • Handling different screen densities in Android Devices?

    - by DevilWithin
    Well, i know there are plenty of different-sized screens in devices that run Android. The SDK I code with deploys to all major desktop platforms and android. I am aware i must have special cares to handle the different screen sizes and densities, but i just had an idea that would work in theory, and my question is exactly about that method, How could it FAIL ? So, what I do is to have an ortho camera of the same size for all devices, with possible tweaks, but anyway that would grant the proper positioning of all elements in all devices, right? We can assume everything is drawn in OpenGLES and input handling is converted to the proper camera coordinates. If you need me to improve the question, please tell me.

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  • How To Initialize Object Which May Be Used In Catch Clause?

    - by Onorio Catenacci
    I've seen this sort of pattern in code before: //pseudo C# code var exInfo = null; //Line A try { var p = SomeProperty; //Line B exInfo = new ExceptionMessage("The property was " + p); //Line C } catch(Exception ex) { exInfo.SomeOtherProperty = SomeOtherValue; //Line D } Usually the code is structured in this fashion because exInfo has to be visible outside of the try clause. The problem is that if an exception occurs on Line B, then exInfo will be null at Line D. The issue arises when something happens on Line B that must occur before exInfo is constructed. But if I set exInfo to a new Object at line A then memory may get leaked at Line C (due to "new"-ing the object there). Is there a better pattern for handling this sort of code? Is there a name for this sort of initialization pattern? By the way I know I could check for exInfo == null before line D but that seems a bit clumsy and I'm looking for a better approach.

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  • Why is nesting or piggybacking errors within errors bad in general?

    - by dietbuddha
    Why is nesting or piggybacking errors within errors bad in general? To me it seems bad intuitively, but I'm suspicious in that I cannot adequately articulate why it is bad. This may be because it is not in general bad and that it is only bad in specific instances. Why is it detrimental to design error/exception handling in such a way. The specific instance is that of a REST service. There is a desire by some to use http errors (specifically the 500 response) as a way to indicate any problem with specific instances of a resource. An example of an instance resource in this case would be: http://server/ticket/80 # instance http://server/ticket # not an instance So this is the behavior that is being proposed. If ticket 80 does not exist return a http response code of 500. Within the body of the error return the "real" error as an additional error code and description. If the ticket resource doesn't exist return a response code of 404.

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  • New ZFS Storage Appliance Objection Handling Document

    - by Cinzia Mascanzoni
    View and download the new ZFS Storage Appliance objection handling document from the Oracle HW Technical Resource Center here. If you do not already have an account to access the Oracle Hardware Technical Resource Centre you need first to register. Please click here and follow the instructions to register.  Ths document aims to address the most common objections encountered  when positioning the ZFS Storage Appliance disk systems in production environments. It will help you to be more successful in establishing the undeniable benefits of the Oracle ZFS Storage Appliance in your customers' IT environments.

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  • Arguments for or against using Try/Catch as logical operators

    - by James P. Wright
    I just discovered some lovely code in our companies app that uses Try-Catch blocks as logical operators. Meaning, "do some code, if that throws this error, do this code, but if that throws this error do this 3rd thing instead". It uses "Finally" as the "else" statement it appears. I know that this is wrong inherently, but before I go picking a fight I was hoping for some well thought out arguments. And hey, if you have arguments FOR the use of Try-Catch in this manner, please do tell. EDIT For any who are wondering, the language is C# and the code in question is about 30+ lines and is looking for specific exceptions, it is not handling ALL exceptions.

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  • "Errors while handling" kernel packages after dist-upgrade

    - by WOLF L?MBERT
    I did an apt-get dist-upgrade, now everytime I do something using apt-get, e.g. installing something, it gives me that there are errors while handling the following packages: linux-image-extra-3.13.0-35-generic linux-image-generic linux-generic My system still works correctly, but is this normal? And what should I do? Should I do anything? Have I done the wrong thing by doing a dist-upgrade? (Beginner-like instructions please, I'm not an expert. Using Xubuntu 14.04.)

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  • iOS NSError with global handler

    - by Sebastian Dressler
    I am in the beginning of programming an iOS app. Having read the Apple guides on how to deal with errors, I got the following most important points: Exceptions are for programmers Use NSError for the user Now, NSError is usually passed as out-argument which can then be used inside and has to be checked by the caller. However, I'm asking myself whether it is a good idea to use a global error handler, say a singleton which wraps around NSError and could be used to trigger errors and error handling from within the called function. Is there anything against that method or would it be a bad practice?

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  • Missing error handling in Streaming-AJAX-Proxy Log

    - by Michael Freidgeim
    We are using AjaxProxy(FROM http://www.codeproject.com/KB/ajax/ajaxproxy.aspx) on our web site, but started to notice errors accessing log.txt file. I found that the file is created by Log class and doesn't have ability to switch it off and error handling. I've added reading file name from configuration and try/catch block   public static class Log     {         private static StreamWriter logStream;         private static object lockObject = new object ();     public static void WriteLine(string msg)         {                       string logFileName = ConfigurationExtensions.GetAppSetting("AjaxStreamingProxy.LogFile" ,"");                       if (logFileName.IsNullOrEmpty())                             return;                       try                      {                             if (logStream == null )                            {                                    lock (lockObject)                                   {                                           if (logStream == null )                                          {                            logStream = File.AppendText(Path .Combine(AppDomain.CurrentDomain.BaseDirectory, logFileName));                                          }                                   }                            }                            logStream.WriteLine(msg);                      }                       catch (Exception exc)                      {                             string ignoredMsg = String .Format("The error occured while logging {0}, but processing will continue.\n {1} ", exc);                             LoggerHelper.LogEvent(ignoredMsg, MyCategorySource, TraceEventType .Warning, true);                      }         }

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  • Passing parameters between interrupt handlers on a Cortex-M3 ...

    - by Captain NedD
    I'm building a light kernel for a Cortex-M3. From a high priority interrupt I'd like to invoke some code to run in a lower priority interrupt and pass some parameters along. I don't want to use a queue to post work to the lower priority interrupt. I just have a buffer and size to pass to it. In the proramming manual it says that the SVC interrupt handler is synchronous which presumably means that if you invoke it from an interrupt that's a lower priority than SVC's handler it gets called immediately (the upshot of this being that you can pass parameters to it as though it were a function call (a little like the BIOS calls in MS-DOS)). I'd like to do it the other way: passing parameters from a high priority interrupt to a lower priority one (at the moment I'm doing it by leaving the parameters in a fixed location in memory). What's the best way to do this (if at all possible)? Thanks,

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  • Globally Handling Request Validation In ASP.NET MVC

    - by imran_ku07
       Introduction:           Cross Site Scripting(XSS) and Cross-Site Request Forgery (CSRF) attacks are one of dangerous attacks on web.  They are among the most famous security issues affecting web applications. OWASP regards XSS is the number one security issue on the Web. Both ASP.NET Web Forms and ASP.NET MVC paid very much attention to make applications build with ASP.NET as secure as possible. So by default they will throw an exception 'A potentially dangerous XXX value was detected from the client', when they see, < followed by an exclamation(like <!) or < followed by the letters a through z(like <s) or & followed by a pound sign(like &#123) as a part of querystring, posted form and cookie collection. This is good for lot of applications. But this is not always the case. Many applications need to allow users to enter html tags, for example applications which uses  Rich Text Editor. You can allow user to enter these tags by just setting validateRequest="false" in your Web.config application configuration file inside <pages> element if you are using Web Form. This will globally disable request validation. But in ASP.NET MVC request handling is different than ASP.NET Web Form. Therefore for disabling request validation globally in ASP.NET MVC you have to put ValidateInputAttribute in your every controller. This become pain full for you if you have hundred of controllers. Therefore in this article i will present a very simple way to handle request validation globally through web.config.   Description:           Before starting how to do this it is worth to see why validateRequest in Page directive and web.config not work in ASP.NET MVC. Actually request handling in ASP.NET Web Form and ASP.NET MVC is different. In Web Form mostly the HttpHandler is the page handler which checks the posted form, query string and cookie collection during the Page ProcessRequest method, while in MVC request validation occur when ActionInvoker calling the action. Just see the stack trace of both framework.   ASP.NET MVC Stack Trace:     System.Web.HttpRequest.ValidateString(String s, String valueName, String collectionName) +8723114   System.Web.HttpRequest.ValidateNameValueCollection(NameValueCollection nvc, String collectionName) +111   System.Web.HttpRequest.get_Form() +129   System.Web.HttpRequestWrapper.get_Form() +11   System.Web.Mvc.ValueProviderDictionary.PopulateDictionary() +145   System.Web.Mvc.ValueProviderDictionary..ctor(ControllerContext controllerContext) +74   System.Web.Mvc.ControllerBase.get_ValueProvider() +31   System.Web.Mvc.ControllerActionInvoker.GetParameterValue(ControllerContext controllerContext, ParameterDescriptor parameterDescriptor) +53   System.Web.Mvc.ControllerActionInvoker.GetParameterValues(ControllerContext controllerContext, ActionDescriptor actionDescriptor) +109   System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName) +399   System.Web.Mvc.Controller.ExecuteCore() +126   System.Web.Mvc.ControllerBase.Execute(RequestContext requestContext) +27   ASP.NET Web Form Stack Trace:    System.Web.HttpRequest.ValidateString(String s, String valueName, String collectionName) +3213202   System.Web.HttpRequest.ValidateNameValueCollection(NameValueCollection nvc, String collectionName) +108   System.Web.HttpRequest.get_QueryString() +119   System.Web.UI.Page.GetCollectionBasedOnMethod(Boolean dontReturnNull) +2022776   System.Web.UI.Page.DeterminePostBackMode() +60   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +6953   System.Web.UI.Page.ProcessRequest(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +154   System.Web.UI.Page.ProcessRequest() +86                        Since the first responder of request in ASP.NET MVC is the controller action therefore it will check the posted values during calling the action. That's why web.config's requestValidate not work in ASP.NET MVC.            So let's see how to handle this globally in ASP.NET MVC. First of all you need to add an appSettings in web.config. <appSettings>    <add key="validateRequest" value="true"/>  </appSettings>              I am using the same key used in disable request validation in Web Form. Next just create a new ControllerFactory by derving the class from DefaultControllerFactory.     public class MyAppControllerFactory : DefaultControllerFactory    {        protected override IController GetControllerInstance(Type controllerType)        {            var controller = base.GetControllerInstance(controllerType);            string validateRequest=System.Configuration.ConfigurationManager.AppSettings["validateRequest"];            bool b;            if (validateRequest != null && bool.TryParse(validateRequest,out b))                ((ControllerBase)controller).ValidateRequest = bool.Parse(validateRequest);            return controller;        }    }                         Next just register your controller factory in global.asax.        protected void Application_Start()        {            //............................................................................................            ControllerBuilder.Current.SetControllerFactory(new MyAppControllerFactory());        }              This will prevent the above exception to occur in the context of ASP.NET MVC. But if you are using the Default WebFormViewEngine then you need also to set validateRequest="false" in your web.config file inside <pages> element            Now when you run your application you see the effect of validateRequest appsetting. One thing also note that the ValidateInputAttribute placed inside action or controller will always override this setting.    Summary:          Request validation is great security feature in ASP.NET but some times there is a need to disable this entirely. So in this article i just showed you how to disable this globally in ASP.NET MVC. I also explained the difference between request validation in Web Form and ASP.NET MVC. Hopefully you will enjoy this.

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  • Handling HumanTask attachments in Oracle BPM 11g PS4FP+ (I)

    - by ccasares
    Adding attachments to a HumanTask is a feature that exists in Oracle HWF (Human Workflow) since 10g. However, in 11g there have been many improvements on this feature and this entry will try to summarize them. Oracle BPM 11g 11.1.1.5.1 (aka PS4 Feature Pack or PS4FP) introduced two great features: Ability to link attachments at a Task scope or at a Process scope: "Task" attachments are only visible within the scope (lifetime) of a task. This means that, initially, any member of the assignment pattern of the Human Task will be able to handle (add, review or remove) attachments. However, once the task is completed, subsequent human tasks will not have access to them. This does not mean those attachments got lost. Once the human task is completed, attachments can be retrieved in order to, i.e., check them in to a Content Server or to inject them to a new and different human task. Aside note: a "re-initiated" human task will inherit comments and attachments, along with history and -optionally- payload. See here for more info. "Process" attachments are visible within the scope of the process. This means that subsequent human tasks in the same process instance will have access to them. Ability to use Oracle WebCenter Content (previously known as "Oracle UCM") as the backend for the attachments instead of using HWF database backend. This feature adds all content server document lifecycle capabilities to HWF attachments (versioning, RBAC, metadata management, etc). As of today, only Oracle WCC is supported. However, Oracle BPM Suite does include a license of Oracle WCC for the solely usage of document management within BPM scope. Here are some code samples that leverage the above features. Retrieving uploaded attachments -Non UCM- Non UCM attachments (default ones or those that have existed from 10g, and are stored "as-is" in HWK database backend) can be retrieved after the completion of the Human Task. Firstly, we need to know whether any attachment has been effectively uploaded to the human task. There are two ways to find it out: Through an XPath function: Checking the execData/attachment[] structure. For example: Once we are sure one ore more attachments were uploaded to the Human Task, we want to get them. In this example, by "get" I mean to get the attachment name and the payload of the file. Aside note: Oracle HWF lets you to upload two kind of [non-UCM] attachments: a desktop document and a Web URL. This example focuses just on the desktop document one. In order to "retrieve" an uploaded Web URL, you can get it directly from the execData/attachment[] structure. Attachment content (payload) is retrieved through the getTaskAttachmentContents() XPath function: This example shows how to retrieve as many attachments as those had been uploaded to the Human Task and write them to the server using the File Adapter service. The sample process excerpt is as follows:  A dummy UserTask using "HumanTask1" Human Task followed by a Embedded Subprocess that will retrieve the attachments (we're assuming at least one attachment is uploaded): and once retrieved, we will write each of them back to a file in the server using a File Adapter service: In detail: We've defined an XSD structure that will hold the attachments (both name and payload): Then, we can create a BusinessObject based on such element (attachmentCollection) and create a variable (named attachmentBPM) of such BusinessObject type. We will also need to keep a copy of the HumanTask output's execData structure. Therefore we need to create a variable of type TaskExecutionData... ...and copy the HumanTask output execData to it: Now we get into the embedded subprocess that will retrieve the attachments' payload. First, and using an XSLT transformation, we feed the attachmentBPM variable with the name of each attachment and setting an empty value to the payload: Please note that we're using the XSLT for-each node to create as many target structures as necessary. Also note that we're setting an Empty text to the payload variable. The reason for this is to make sure the <payload></payload> tag gets created. This is needed when we map the payload to the XML variable later. Aside note: We are assuming that we're retrieving non-UCM attachments. However in real life you might want to check the type of attachment you're handling. The execData/attachment[]/storageType contains the values "UCM" for UCM type attachments, "TASK" for non-UCM ones or "URL" for Web URL ones. Those values are part of the "Ext.Com.Oracle.Xmlns.Bpel.Workflow.Task.StorageTypeEnum" enumeration. Once we have fed the attachmentsBPM structure and so it now contains the name of each of the attachments, it is time to iterate through it and get the payload. Therefore we will use a new embedded subprocess of type MultiInstance, that will iterate over the attachmentsBPM/attachment[] element: In every iteration we will use a Script activity to map the corresponding payload element with the result of the XPath function getTaskAttachmentContents(). Please, note how the target array element is indexed with the loopCounter predefined variable, so that we make sure we're feeding the right element during the array iteration:  The XPath function used looks as follows: hwf:getTaskAttachmentContents(bpmn:getDataObject('UserTask1LocalExecData')/ns1:systemAttributes/ns1:taskId, bpmn:getDataObject('attachmentsBPM')/ns:attachment[bpmn:getActivityInstanceAttribute('SUBPROCESS3067107484296', 'loopCounter')]/ns:fileName)  where the input parameters are: taskId of the just completed Human Task attachment name we're retrieving the payload from array index (loopCounter predefined variable)  Aside note: The reason whereby we're iterating the execData/attachment[] structure through embedded subprocess and not, i.e., using XSLT and for-each nodes, is mostly because the getTaskAttachmentContents() XPath function is currently not available in XSLT mappings. So all this example might be considered as a workaround until this gets fixed/enhanced in future releases. Once this embedded subprocess ends, we will have all attachments (name + payload) in the attachmentsBPM variable, which is the main goal of this sample. But in order to test everything runs fine, we finish the sample writing each attachment to a file. To that end we include a final embedded subprocess to concurrently iterate through each attachmentsBPM/attachment[] element: On each iteration we will use a Service activity that invokes a File Adapter write service. In here we have two important parameters to set. First, the payload itself. The file adapter awaits binary data in base64 format (string). We have to map it using XPath (Simple mapping doesn't recognize a String as a base64-binary valid target):  Second, we must set the target filename using the Service Properties dialog box:  Again, note how we're making use of the loopCounter index variable to get the right element within the embedded subprocess iteration. Handling UCM attachments will be part of a different and upcoming blog entry. Once I finish will all posts on this matter, I will upload the whole sample project to java.net.

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  • Abstract exception super type

    - by marcof
    If throwing System.Exception is considered so bad, why wasn't Exception made abstract in the first place? That way, it would not be possible to call: throw new Exception("Error occurred."); This would enforce using derived exceptions to provide more details about the error that occurred. For example, when I want to provide a custom exception hierarchy for a library, I usually declare an abstract base class for my exceptions: public abstract class CustomExceptionBase : Exception { /* some stuff here */ } And then some derived exception with a more specific purpose: public class DerivedCustomException : CustomExceptionBase { /* some more specific stuff here */ } Then when calling any library method, one could have this generic try/catch block to directly catch any error coming from the library: try { /* library calls here */ } catch (CustomExceptionBase ex) { /* exception handling */ } Is this a good practice? Would it be good if Exception was made abstract? EDIT : My point here is that even if an exception class is abstract, you can still catch it in a catch-all block. Making it abstract is only a way to forbid programmers to throw a "super-wide" exception. Usually, when you voluntarily throw an exception, you should know what type it is and why it happened. Thus enforcing to throw a more specific exception type.

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  • Keyboard input system handling

    - by The Communist Duck
    Note: I have to poll, rather than do callbacks because of API limitations (SFML). I also apologize for the lack of a 'decent' title. I think I have two questions here; how to register the input I'm receiving, and what to do with it. Handling Input I'm talking about after the fact you've registered that the 'A' key has been pressed, for example, and how to do it from there. I've seen an array of the whole keyboard, something like: bool keyboard[256]; //And each input loop check the state of every key on the keyboard But this seems inefficient. Not only are you coupling the key 'A' to 'player moving left', for example, but it checks every key, 30-60 times a second. I then tried another system which just looked for keys it wanted. std::map< unsigned char, Key keyMap; //Key stores the keycode, and whether it's been pressed. Then, I declare a load of const unsigned char called 'Quit' or 'PlayerLeft'. input-BindKey(Keys::PlayerLeft, KeyCode::A); //so now you can check if PlayerLeft, rather than if A. However, the problem with this is I cannot now type a name, for example, without having to bind every single key. Then, I have the second problem, which I cannot really think of a good solution for: Sending Input I now know that the A key has been pressed or that playerLeft is true. But how do I go from here? I thought about just checking if(input-IsKeyDown(Key::PlayerLeft) { player.MoveLeft(); } This couples the input greatly to the entities, and I find it rather messy. I'd prefer the player to handle its own movement when it gets updated. I thought some kind of event system could work, but I do not know how to go with it. (I heard signals and slots was good for this kind of work, but it's apparently very slow and I cannot see how it'd fit). Thanks.

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  • data handling with javascript

    - by Vincent Warmerdam
    Python has a very neat package called pandas which allows for quick data transformation; tables, aggregation, that sort of thing. A lot of these types of functionality can also be found in the python itertools module. The plyR package in R is also very similar. Usually one woud use this functionality to produce a table which is later visualized with a plot. I am personally very fond of d3, and I would like to allow the user to first indicate what type of data aggregation he wants on the dataset before it is visualized. The visualisation in question involves making a heatmap where the user gets to select the size of the bins of the heatmap beforehand (I want d3 to project this through leaflet). I want to visually select the ideal size of the bins for the heatmap. The way I work now is that I take the dataset, aggregate it with python and then manually load it in d3. This is a process that takes a lot of human effort and I was wondering if the data aggregation can be done through the javascript of the browser. I couldn't find a package for javascript specifically built for data, suggesting (to me) that this is a bad idea and that one should not use javascript for the data handling. Is there a good module/package for javascript to handle data aggregation? Is it a good/bad idea to do the data aggregation in javascript (performance wise)?

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  • C#: Handling Notifications: inheritance, events, or delegates?

    - by James Michael Hare
    Often times as developers we have to design a class where we get notification when certain things happen. In older object-oriented code this would often be implemented by overriding methods -- with events, delegates, and interfaces, however, we have far more elegant options. So, when should you use each of these methods and what are their strengths and weaknesses? Now, for the purposes of this article when I say notification, I'm just talking about ways for a class to let a user know that something has occurred. This can be through any programmatic means such as inheritance, events, delegates, etc. So let's build some context. I'm sitting here thinking about a provider neutral messaging layer for the place I work, and I got to the point where I needed to design the message subscriber which will receive messages from the message bus. Basically, what we want is to be able to create a message listener and have it be called whenever a new message arrives. Now, back before the flood we would have done this via inheritance and an abstract class: 1:  2: // using inheritance - omitting argument null checks and halt logic 3: public abstract class MessageListener 4: { 5: private ISubscriber _subscriber; 6: private bool _isHalted = false; 7: private Thread _messageThread; 8:  9: // assign the subscriber and start the messaging loop 10: public MessageListener(ISubscriber subscriber) 11: { 12: _subscriber = subscriber; 13: _messageThread = new Thread(MessageLoop); 14: _messageThread.Start(); 15: } 16:  17: // user will override this to process their messages 18: protected abstract void OnMessageReceived(Message msg); 19:  20: // handle the looping in the thread 21: private void MessageLoop() 22: { 23: while(!_isHalted) 24: { 25: // as long as processing, wait 1 second for message 26: Message msg = _subscriber.Receive(TimeSpan.FromSeconds(1)); 27: if(msg != null) 28: { 29: OnMessageReceived(msg); 30: } 31: } 32: } 33: ... 34: } It seems so odd to write this kind of code now. Does it feel odd to you? Maybe it's just because I've gotten so used to delegation that I really don't like the feel of this. To me it is akin to saying that if I want to drive my car I need to derive a new instance of it just to put myself in the driver's seat. And yet, unquestionably, five years ago I would have probably written the code as you see above. To me, inheritance is a flawed approach for notifications due to several reasons: Inheritance is one of the HIGHEST forms of coupling. You can't seal the listener class because it depends on sub-classing to work. Because C# does not allow multiple-inheritance, I've spent my one inheritance implementing this class. Every time you need to listen to a bus, you have to derive a class which leads to lots of trivial sub-classes. The act of consuming a message should be a separate responsibility than the act of listening for a message (SRP). Inheritance is such a strong statement (this IS-A that) that it should only be used in building type hierarchies and not for overriding use-specific behaviors and notifications. Chances are, if a class needs to be inherited to be used, it most likely is not designed as well as it could be in today's modern programming languages. So lets look at the other tools available to us for getting notified instead. Here's a few other choices to consider. Have the listener expose a MessageReceived event. Have the listener accept a new IMessageHandler interface instance. Have the listener accept an Action<Message> delegate. Really, all of these are different forms of delegation. Now, .NET events are a bit heavier than the other types of delegates in terms of run-time execution, but they are a great way to allow others using your class to subscribe to your events: 1: // using event - ommiting argument null checks and halt logic 2: public sealed class MessageListener 3: { 4: private ISubscriber _subscriber; 5: private bool _isHalted = false; 6: private Thread _messageThread; 7:  8: // assign the subscriber and start the messaging loop 9: public MessageListener(ISubscriber subscriber) 10: { 11: _subscriber = subscriber; 12: _messageThread = new Thread(MessageLoop); 13: _messageThread.Start(); 14: } 15:  16: // user will override this to process their messages 17: public event Action<Message> MessageReceived; 18:  19: // handle the looping in the thread 20: private void MessageLoop() 21: { 22: while(!_isHalted) 23: { 24: // as long as processing, wait 1 second for message 25: Message msg = _subscriber.Receive(TimeSpan.FromSeconds(1)); 26: if(msg != null && MessageReceived != null) 27: { 28: MessageReceived(msg); 29: } 30: } 31: } 32: } Note, now we can seal the class to avoid changes and the user just needs to provide a message handling method: 1: theListener.MessageReceived += CustomReceiveMethod; However, personally I don't think events hold up as well in this case because events are largely optional. To me, what is the point of a listener if you create one with no event listeners? So in my mind, use events when handling the notification is optional. So how about the delegation via interface? I personally like this method quite a bit. Basically what it does is similar to inheritance method mentioned first, but better because it makes it easy to split the part of the class that doesn't change (the base listener behavior) from the part that does change (the user-specified action after receiving a message). So assuming we had an interface like: 1: public interface IMessageHandler 2: { 3: void OnMessageReceived(Message receivedMessage); 4: } Our listener would look like this: 1: // using delegation via interface - omitting argument null checks and halt logic 2: public sealed class MessageListener 3: { 4: private ISubscriber _subscriber; 5: private IMessageHandler _handler; 6: private bool _isHalted = false; 7: private Thread _messageThread; 8:  9: // assign the subscriber and start the messaging loop 10: public MessageListener(ISubscriber subscriber, IMessageHandler handler) 11: { 12: _subscriber = subscriber; 13: _handler = handler; 14: _messageThread = new Thread(MessageLoop); 15: _messageThread.Start(); 16: } 17:  18: // handle the looping in the thread 19: private void MessageLoop() 20: { 21: while(!_isHalted) 22: { 23: // as long as processing, wait 1 second for message 24: Message msg = _subscriber.Receive(TimeSpan.FromSeconds(1)); 25: if(msg != null) 26: { 27: _handler.OnMessageReceived(msg); 28: } 29: } 30: } 31: } And they would call it by creating a class that implements IMessageHandler and pass that instance into the constructor of the listener. I like that this alleviates the issues of inheritance and essentially forces you to provide a handler (as opposed to events) on construction. Well, this is good, but personally I think we could go one step further. While I like this better than events or inheritance, it still forces you to implement a specific method name. What if that name collides? Furthermore if you have lots of these you end up either with large classes inheriting multiple interfaces to implement one method, or lots of small classes. Also, if you had one class that wanted to manage messages from two different subscribers differently, it wouldn't be able to because the interface can't be overloaded. This brings me to using delegates directly. In general, every time I think about creating an interface for something, and if that interface contains only one method, I start thinking a delegate is a better approach. Now, that said delegates don't accomplish everything an interface can. Obviously having the interface allows you to refer to the classes that implement the interface which can be very handy. In this case, though, really all you want is a method to handle the messages. So let's look at a method delegate: 1: // using delegation via delegate - omitting argument null checks and halt logic 2: public sealed class MessageListener 3: { 4: private ISubscriber _subscriber; 5: private Action<Message> _handler; 6: private bool _isHalted = false; 7: private Thread _messageThread; 8:  9: // assign the subscriber and start the messaging loop 10: public MessageListener(ISubscriber subscriber, Action<Message> handler) 11: { 12: _subscriber = subscriber; 13: _handler = handler; 14: _messageThread = new Thread(MessageLoop); 15: _messageThread.Start(); 16: } 17:  18: // handle the looping in the thread 19: private void MessageLoop() 20: { 21: while(!_isHalted) 22: { 23: // as long as processing, wait 1 second for message 24: Message msg = _subscriber.Receive(TimeSpan.FromSeconds(1)); 25: if(msg != null) 26: { 27: _handler(msg); 28: } 29: } 30: } 31: } Here the MessageListener now takes an Action<Message>.  For those of you unfamiliar with the pre-defined delegate types in .NET, that is a method with the signature: void SomeMethodName(Message). The great thing about delegates is it gives you a lot of power. You could create an anonymous delegate, a lambda, or specify any other method as long as it satisfies the Action<Message> signature. This way, you don't need to define an arbitrary helper class or name the method a specific thing. Incidentally, we could combine both the interface and delegate approach to allow maximum flexibility. Doing this, the user could either pass in a delegate, or specify a delegate interface: 1: // using delegation - give users choice of interface or delegate 2: public sealed class MessageListener 3: { 4: private ISubscriber _subscriber; 5: private Action<Message> _handler; 6: private bool _isHalted = false; 7: private Thread _messageThread; 8:  9: // assign the subscriber and start the messaging loop 10: public MessageListener(ISubscriber subscriber, Action<Message> handler) 11: { 12: _subscriber = subscriber; 13: _handler = handler; 14: _messageThread = new Thread(MessageLoop); 15: _messageThread.Start(); 16: } 17:  18: // passes the interface method as a delegate using method group 19: public MessageListener(ISubscriber subscriber, IMessageHandler handler) 20: : this(subscriber, handler.OnMessageReceived) 21: { 22: } 23:  24: // handle the looping in the thread 25: private void MessageLoop() 26: { 27: while(!_isHalted) 28: { 29: // as long as processing, wait 1 second for message 30: Message msg = _subscriber.Receive(TimeSpan.FromSeconds(1)); 31: if(msg != null) 32: { 33: _handler(msg); 34: } 35: } 36: } 37: } } This is the method I tend to prefer because it allows the user of the class to choose which method works best for them. You may be curious about the actual performance of these different methods. 1: Enter iterations: 2: 1000000 3:  4: Inheritance took 4 ms. 5: Events took 7 ms. 6: Interface delegation took 4 ms. 7: Lambda delegate took 5 ms. Before you get too caught up in the numbers, however, keep in mind that this is performance over over 1,000,000 iterations. Since they are all < 10 ms which boils down to fractions of a micro-second per iteration so really any of them are a fine choice performance wise. As such, I think the choice of what to do really boils down to what you're trying to do. Here's my guidelines: Inheritance should be used only when defining a collection of related types with implementation specific behaviors, it should not be used as a hook for users to add their own functionality. Events should be used when subscription is optional or multi-cast is desired. Interface delegation should be used when you wish to refer to implementing classes by the interface type or if the type requires several methods to be implemented. Delegate method delegation should be used when you only need to provide one method and do not need to refer to implementers by the interface name.

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