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  • @Resource annotated member not injected - bad code or bug?

    - by Brabster
    I am using an @Resource annotation in a class instantiated in a ServletContextListener's contextInitialized(...) method, but the member is always null. Here's my sample code. Listener: public void contextInitialized(ServletContextEvent sce) { System.err.println("In contextInitialised"); new ResourceListenerTargetTest().executeMe(); } ResourceListenerTargetTest: @Resource(name="MyJDBCResource") private DataSource source; public void executeMe() { /*try { InitialContext ictx = new InitialContext(); source = (DataSource)ictx.lookup("java:comp/env/MyJDBCResource"); } catch (NamingException e) { e.printStackTrace(); }*/ System.err.println("source is " + source); } If I switch the comments and run the manual resource lookup, it works fine. Should the @Resource annotation work like this, when used in a contextInitalized method? Appserver is WAS 7.0.0.5, if it should work then I guess it's a bug? Can anyone confirm?

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  • Is it bad practice to change state inside of an if statement?

    - by Benjamin
    I wrote some code that looks similar to the following: String SKIP_FIRST = "foo"; String SKIP_SECOND = "foo/bar"; int skipFooBarIndex(String[] list){ int index; if (list.length >= (index = 1) && list[0].equals(SKIP_FIRST) || list.length >= (index = 2) && (list[0] + "/" + list[1]).equals(SKIP_SECOND)){ return index; } return 0; } String[] myArray = "foo/bar/apples/peaches/cherries".split("/"); print(skipFooBarIndex(myArray); This changes state inside of the if statement by assigning index. However, my coworkers disliked this very much. Is this a harmful practice? Is there any reason to do it?

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  • Is it a bad idea to use the new Dynamic Keyword as a replacement switch statement?

    - by WeNeedAnswers
    I like the new Dynamic keyword and read that it can be used as a replacement visitor pattern. It makes the code more declarative which I prefer. Is it a good idea though to replace all instances of switch on 'Type' with a class that implements dynamic dispatch. class VistorTest { public string DynamicVisit(object obj) { return Visit((dynamic)obj); } private string Visit(string str) { return "a string was called with value " + str; } private string Visit(int value) { return "an int was called with value " + value; } }

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  • Is it Bad Practice to use C++ only for the STL containers?

    - by gmatt
    First a little background ... In what follows, I use C,C++ and Java for coding (general) algorithms, not gui's and fancy program's with interfaces, but simple command line algorithms and libraries. I started out learning about programming in Java. I got pretty good with Java and I learned to use the Java containers a lot as they tend to reduce complexity of book keeping while guaranteeing great performance. I intermittently used C++, but I was definitely not as good with it as with Java and it felt cumbersome. I did not know C++ enough to work in it without having to look up every single function and so I quickly reverted back to sticking to Java as much as possible. I then made a sudden transition into cracking and hacking in assembly language, because I felt I was concentrated too much attention on a much too high level language and I needed more experience with how a CPU interacts with memory and whats really going on with the 1's and 0's. I have to admit this was one of the most educational and fun experiences I've had with computers to date. For obviously reasons, I could not use assembly language to code on a daily basis, it was mostly reserved for fun diversions. After learning more about the computer through this experience I then realized that C++ is so much closer to the "level of 1's and 0's" than Java was, but I still felt it to be incredibly obtuse, like a swiss army knife with far too many gizmos to do any one task with elegance. I decided to give plain vanilla C a try, and I quickly fell in love. It was a happy medium between simplicity and enough "micromanagent" to not abstract what is really going on. However, I did miss one thing about Java: the containers. In particular, a simple container (like the stl vector) that expands dynamically in size is incredibly useful, but quite a pain to have to implement in C every time. Hence my code currently looks like almost entirely C with containers from C++ thrown in, the only feature I use from C++. I'd like to know if its consider okay in practice to use just one feature of C++, and ignore the rest in favor of C type code?

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  • ASP.Net: HTTP 400 Bad Request error when trying to process http://localhost:5957/http://yahoo.com

    - by mat3
    I'm trying to create something similar to the diggbar : http://digg.com/http://cnn.com I'm using Visual Studio 2010 and Asp Development server. However, I can't get the ASP dev server to handle the request because it contains "http:" in the path. I've tried to create an HTTPModule to rewrite the URL in the BeginRequest , but the event handler doesn't get called when the url is http://localhost:5957/http://yahoo.com. The event handler does get called if the url is http://localhost:5957/http/yahoo.com To summarize http://localhost:5957/http/yahoo.com works http://localhost:5957/http//yahoo.com does not work http://localhost:5957/http://yahoo.com does not work http://localhost:5957/http:/yahoo.com does not work Any ideas?

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  • Is this a bad version of the Merge Sort algorithm?

    - by SebKom
    merge1(int low, int high, int S[], U[]) { int k = (high - low + 1)/2 for q (from low to high) U[q] = S[q] int j = low int p = low int i = low + k while (j <= low + k - 1) and (i <= high) do { if ( U[j] <= U[i] ) { S[p] := U[j] j := j+1 } else { S[p] := U[i] i := i+1 } p := p+1 } if (j <= low + k - 1) { for q from p to high do { S[q] := U[j] j := j+1 } } } merge_sort1(int low, int high, int S[], U[]) { if low < high { int k := (high - low + 1)/2 merge_sort1(low, low+k-1, S, U) merge_sort1(low+k, high, S, U) merge1(low, high, S, U) } } I am really sorry for the terrible formating, as you can tell I am not a regular visitor here. So, basically, this is on my lecture notes. I find it quite confusing in general but I understand the biggest part of it. What I don't understand is the need of the "if (j <= low + k - 1)" part. It looks like it checks if there are any elements "left" in the left part. Is that even possible when mergesorting?

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  • Best practices about creating a generic object dictionary in C#? Is this bad?

    - by JimDaniel
    For clarity I am using C# 3.5/Asp.Net MVC 2 Here is what I have done: I wanted the ability to add/remove functionality to an object at run-time. So I simply added a generic object dictionary to my class like this: public Dictionary<int, object> Components { get; set; } Then I can add/remove any kind of .Net object into this dictionary at run-time. To insert an object I do something like this: var tag = new Tag(); myObject.Components.Add((int)Types.Components.Tag, tag); Then to retrieve I just do this: if(myObject.Components.ContainsKey((int)Types.Components.Tag)) { var tag = myObject.Components[(int)Types.Components.Tag] as Tag; if(tag != null) { //do stuff } } Somehow I feel sneaky doing this. It works okay, but I am wondering what you guys think about it as a best practice. Thanks for your input, Daniel

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  • Why is it a bad idea to use ClientLogin for web apps in the Google API?

    - by Onema
    I just picked up the Google API today to allow some users of our site to upload videos to our own organization YouTube account. I Don't want our users to know our user name and password, but rather give them the option if they want to upload videos to youtube or not. If they choose to do it, they check on a check box and hit the submit button. I keep seeing over, and over in the Developers guide that ClientLogin, which to me looks like the best option to implement what I want to do, is not a good idea for user authentication in web applicaitons. The "AuthSub for web applications" doesn't seem to be the best mechanism for what I want to implement! Any ideas on what to do? Thank you

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  • Why is it bad practice to use links with the javascript: "protocol"?

    - by zneak
    Hello everyone, In the 1990s, there was a fashion to put Javascript code directly into <a> href attributes, like this: <a href="javascript:alert('Hello world!')">Press me!</a> And then suddenly I stopped to see it. They were all replaced by things like: <a href="#" onclick="alert('Hello world!')">Press me!</a> For a link whose sole purpose is to trigger Javascript code, and has no real href target, why is it encouraged to use the onclick property instead of the href property?

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  • Is locking on the requested object a bad idea?

    - by Quick Joe Smith
    Most advice on thread safety involves some variation of the following pattern: public class Thing { private static readonly object padlock = new object(); private string stuff, andNonsense; public string Stuff { get { lock (Thing.padlock) { if (this.stuff == null) this.stuff = "Threadsafe!"; } return this.stuff; } } public string AndNonsense { get { lock (Thing.padlock) { if (this.andNonsense == null) this.andNonsense = "Also threadsafe!"; } return this.andNonsense; } } // Rest of class... } In cases where the get operations are expensive and unrelated, a single locking object is unsuitable because a call to Stuff would block all calls to AndNonsense, degrading performance. And rather than create a lock object for each call, wouldn't it be better to acquire the lock on the member itself (assuming it is not something that implements SyncRoot or somesuch for that purpose? For example: public string Stuff { get { lock (this.stuff) { // Pretend that this is a very expensive operation. if (this.stuff == null) this.stuff = "Still threadsafe and good?"; } return this.stuff; } } Strangely, I have never seen this approach recommended or warned against. Am I missing something obvious?

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  • Bad idea to have the same object, have a different side effect after method call.

    - by Nathan W
    Hi all, I'm having a bit of a gesign issue(again). Say I have this Buttonpad object: now this object is a wrapper object over one in a com object. At the moment it has a method on it called CreateInto(IComObject). Now to make a new button pad in the Com Object. You do: ButtonPad pad = new ButtonPad(); pad.Title = "Hello"; // Set some more properties. pad.CreateInto(Cominstance); The createinfo method will excute the right commands to buid the button pad in the com object. After it has been created it any calls against it are foward to the underlying object for change so: pad.Title = "New title"; will call the com object to set the title and also set the internal title variable. Basically any calls before the CreateInfo method only affect the .NET object anything after has the side effect of calling the com object also. I'm not very good at sequence diagrams but here is my attempt to explain whats going on: This doesn't feel good to me, it feels like I'm lying to the user about what the button pad does. I was going to have a object called WrappedButtonPad, which is returned from CreateInto and the user could make calls against that to make changes to the Com Object, but I feel having two objects that almost do the same thing but only differ by names might be even worse. Are these valid designs, or am I right to be worried? How else would you handle a object the can create and query a com object?

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  • Is concatenating with an empty string to do a string conversion really that bad?

    - by polygenelubricants
    Let's say I have two char variables, and later on I want to concatenate them into a string. This is how I would do it: char c1, c2; // ... String s = "" + c1 + c2; I've seen people who say that the "" + "trick" is "ugly", etc, and that you should use String.valueOf or Character.toString instead. I prefer this construct because: I prefer using language feature instead of API call if possible In general, isn't the language usually more stable than the API? If language feature only hides API call, then even stronger reason to prefer it! More abstract! Hiding is good! I like that the c1 and c2 are visually on the same level String.valueOf(c1) + c2 suggests something is special about c1 It's shorter. Is there really a good argument why String.valueOf or Character.toString is preferrable to "" +? Trivia: in java.lang.AssertionError, the following line appears 7 times, each with a different type: this("" + detailMessage);

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  • Is it so bad to have heaps of elements in your DOM?

    - by alex
    I am making a real estate non interactive display for their shop window. I have kicked jCarousel into doing what I want: Add panels per AJAX Towards the end of the current set, go and AJAX some new panels and insert them This works fine, but it appears calling jQuery's remove() on the prior elements cause an ugly bump. I'm not sure if calling hide() will free up any resources, as the element will still exist (and the element will be off screen anyway). I've seen this, and tried carousel.reset() from within a callback. It just clears out all the elements. This will be running on Google Chrome on Windows XP, and will solely by displaying on LCD televisions. I am wondering, if I can't find a reasonable solution to remove the extra DOM elements, will it bring my application to a crawl, or will Chrome do some clever garbage collecting? Or, how would you solve this problem? Thanks

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  • Are indexes good or bad for a large database?

    - by gmemon
    Hello All, I read on MySQL Performance Blog that when tables are large, it is better to scan full tables, instead of using indexes. I have a table with tens of millions of rows. When conducting queries, if I use no indexes, then queries are 24 times slower than with indexes. I know lot of things may cause this (e.g., are rows stored sequentially), but can you please give me some hints what might be happening? Or how I should start examining this issue? I want to understand when use of indexes is preferred and when it's not Thanks

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  • Is it bad practice to 'mix class and interfaces in the same package'?

    - by DerMike
    Hello, I just found something that I never heard of before and I do not agree with (by now). In an (upvoted and not further commented) answer I read "why to mix class and interfaces in the same package" So I wonder, if there are reasons to separate Interfaces and implementations in Java. I know that we are not obliged to have all implementations in the package of the interface, but is it (sometimes) wise to have none there? Regards Mike [;-)

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  • Is it bad practice to declare an array mid-function...

    - by Maximus
    In C, which would be more proper... void MyFunction() { int* array; int size; //do a bunch of stuff size = 10; array = (int*)(sizeof(int)*size); //do more stuff... //no longer need array... free(array); } Or is something like this okay? void MyFunction() { int size; //do a bunch of stuff size = 10; array[size]; //do more stuff... } The malloc uses the heap instead of the stack, so I suppose if you know size is going to be very large you'd want to malloc... but if you're quite certain size will be small enough, would the second method be reasonable?

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  • Using low level api for datastore in google app engine ? is it bad ?

    - by Chez
    There is little documentation on how to use the low level api for datastore and quite a lot on JPA and JDO and how it translates to it. My question is: is there any advantage in coding against the JPA or JDO specs instead of accessing directly the low level api for datastore ? From an initial look, it seems simple and straight forward but I am not sure if there are good reasons why not to do it. Thanks Cx

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