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  • C++ Matrix class hierachy

    - by bpw1621
    Should a matrix software library have a root class (e.g., MatrixBase) from which more specialized (or more constrained) matrix classes (e.g., SparseMatrix, UpperTriangluarMatrix, etc.) derive? If so, should the derived classes be derived publicly/protectively/privately? If not, should they be composed with a implementation class encapsulating common functionality and be otherwise unrelated? Something else? I was having a conversation about this with a software developer colleague (I am not per se) who mentioned that it is a common programming design mistake to derive a more restricted class from a more general one (e.g., he used the example of how it was not a good idea to derive a Circle class from an Ellipse class as similar to the matrix design issue) even when it is true that a SparseMatrix "IS A" MatrixBase. The interface presented by both the base and derived classes should be the same for basic operations; for specialized operations, a derived class would have additional functionality that might not be possible to implement for an arbitrary MatrixBase object. For example, we can compute the cholesky decomposition only for a PositiveDefiniteMatrix class object; however, multiplication by a scalar should work the same way for both the base and derived classes. Also, even if the underlying data storage implementation differs the operator()(int,int) should work as expected for any type of matrix class. I have started looking at a few open-source matrix libraries and it appears like this is kind of a mixed bag (or maybe I'm looking at a mixed bag of libraries). I am planning on helping out with a refactoring of a math library where this has been a point of contention and I'd like to have opinions (that is unless there really is an objective right answer to this question) as to what design philosophy would be best and what are the pros and cons to any reasonable approach.

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  • How does object of sub-class record information about its super-class the in a Virtual Inheritance

    - by Summer_More_More_Tea
    Hi there: I encounter this problem when tackling with virtual inheritance. I remember that in a non-virtual inheritance hierarchy, object of sub-class hold an object of its direct super-class. What about virtual inheritance? In this situation, does object of sub-class hold an object of its super-class directly or just hold a pointer pointing to an object of its super-class? By the way, why the output of the following code is: sizeof(A): 8 sizeof(B): 20 sizeof(C): 32 Code: #include <iostream> using namespace std; class A{ char k[ 3 ]; public: virtual void a(){}; }; class B : public virtual A{ char j[ 3 ]; public: virtual void b(){}; }; class C : public virtual B{ char i[ 3 ]; public: virtual void c(){}; }; int main( int argc, char *argv[] ){ cout << "sizeof(A): " << sizeof( A ) << endl; cout << "sizeof(B): " << sizeof( B ) << endl; cout << "sizeof(C): " << sizeof( C ) << endl; return 0; } Thanks in advance. Kind regards.

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  • Get the parent class of a null object (C# Reflection)

    - by Nick
    How would I get the parent class of an object that has a value of null? For example... 'Class A' contains 'int? i' which is not set to any value when the class is created. Then in some other place in the code I want to pass in 'i' as a parameter to some function. Using 'i' as the only info, I want to be able to figure out that 'Class A' "owns" 'i'. The reason for this is because 'Class A' also contains some other object, and I want to call this other object's value from that same function mentioned in the above paragraph. Could also be: public class A { public class B { public int? i; public int? j; } B classBInstance = new B(); public string s; } { ... A someClassAInstance = new A(); ... doSomething(someClassAInstance.classBInstance.i); ... } public static bool doSomething(object theObject) { string s = /* SOMETHING on theObject to get to "s" from Class A */; int someValue = (int)theObject; }

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  • Printing the "source" class in a log statement with a log4j wrapper

    - by Dur4ndal
    My application has a homebrew logging class that I'm migrating to using log4j under the covers. However, since I'm using the homebrew class to pass the rest of the application's logging statements to log4j, the output statements are logged as coming from the wrapper class instead of the source class. Is there a way to ensure that the "correct" source is being shown besides creating new org.apache.log4j.Logger instances for every log statement? I've also tried using the Logger.log(String callerFQCN, Priority level, Object message, Throwable t) method, but it doesnt seem to be working, for example: public class Logger2 { public static org.apache.log4j.Logger log4JLogger = org.apache.log4j.Logger.getLogger(Logger2.class); public static void warning(Object source, String message) { log(source, message, Level.WARN, null) } private static void log(Object source, String message, Level level, Throwable t) { String className = source.getClass().getName(); System.out.println("Logging class should be " + className); log4JLogger.log(className, loggingLevel, message, t); } } When called by: public void testWarning() { Logger2.warning(new Integer(3), "This should warn"); } Prints: Logging class should be java.lang.Integer 2010-05-25 10:49:57,152 WARN test.Logger2 - This should warn

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  • Calling an Overridden Method from a Parent-Class Constructor

    - by Vaibhav Bajpai
    I tried calling an overridden method from a constructor of a parent class and noticed different behavior across languages. C++ - echoes A.foo() class A{ public: A(){foo();} virtual void foo(){cout<<"A.foo()";} }; class B : public A{ public: B(){} void foo(){cout<<"B.foo()";} }; int main(){ B *b = new B(); } Java - echoes B.foo() class A{ public A(){foo();} public void foo(){System.out.println("A.foo()");} } class B extends A{ public void foo(){System.out.println("B.foo()");} } class Demo{ public static void main(String args[]){ B b = new B(); } } C# - echoes B.foo() class A{ public A(){foo();} public virtual void foo(){Console.WriteLine("A.foo()");} } class B : A{ public override void foo(){Console.WriteLine("B.foo()");} } class MainClass { public static void Main (string[] args) { B b = new B(); } } I realize that in C++ objects are created from top-most parent going down the hierarchy, so when the constructor calls the overridden method, B does not even exist, so it calls the A' version of the method. However, I am not sure why I am getting different behavior in Java and C#.

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  • Properly obsoleting old members in an XML Serializable class in C# VB .NET

    - by George
    Hi! Some time ago I defined a class that was serialized using XML. That class contained a serializable propertyA of integer type. Now I have extended and updated this class, whereby a new propertyB was added, whose type is another class that also has several serializable properties. The new propertyB is now supposed to play the role of propertyA, that is since type of propertyB is another class, one of its members would contain the value that previously propertyA contained, thus making peroptyA obsolete. What I am trying to figure out is how do I make sure that when I desireliaze the OLD version of this class (without propertyB in it), I make sure that the desreializer would take the value of propertyA from the old calss and set it as a value of one of the members of propertyB in a new class? Private WithEvents _Position As Position = New Position(Alignment.MiddleMiddle, 0, True, 0, True) Public Property Position() As Position 'NEW composite property that holds the value of the obsolted property, i.e. Alignment Get Return _Position End Get Set(ByVal value As Position) _Position = value End Set End Property Private _Alignment As Alignment = Alignment.MiddleMiddle <Xml.Serialization.XmlIgnore(), Obsolete("Use Position property instead.")> _ Public Property Alignment() As Alignment'The old, obsoleted property that I guess must be left for compliance with deserializing the old version of this class Get Return _Alignment End Get Set(ByVal value As Alignment) _Alignment = value End Set End Property Can you help me, please?

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  • PHP class extends not working why and is this how to correctly extend a class?

    - by Matthew
    Hi so I'm trying to understand how inherteince works in PHP using object oriented programming. The main class is Computer, the class that is inheriting is Mouse. I'm extedning the Computer class with the mouse class. I use __construct in each class, when I istinate the class I use the pc type first and if it has mouse after. For some reason computer returns null? why is this? class Computer { protected $type = 'null'; public function __construct($type) { $this->type = $type; } public function computertype() { $this->type = strtoupper($this->type); return $this->type; } } class Mouse extends Computer { protected $hasmouse = 'null'; public function __construct($hasmouse){ $this->hasmouse = $hasmouse; } public function computermouse() { if($this->hasmouse == 'Y') { return 'This Computer has a mouse'; } } } $pc = new Computer('PC', 'Y'); echo $pc->computertype; echo $pc->computermouse;

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  • Hiding elements based on last closed element jquery script

    - by Jared
    Hi my question is, how can I make this jquery script close all previously opened children when entering a new parent? At the moment it traverses thru all the tree structure fine, but switching from one parent to another does not close the previous children, but rather only the each individual parents elements as a user browses. Here is the jquery I'm using: <script type="text/javascript"> $(document).ready($(function(){ $('#nav>li>ul').hide(); $('.children').hide(); $('#nav>li').mousedown(function(){ // check that the menu is not currently animated if ($('#nav ul:animated').size() == 0) { // create a reference to the active element (this) // so we don't have to keep creating a jQuery object $heading = $(this); // create a reference to visible sibling elements // so we don't have to keep creating a jQuery object $expandedSiblings = $heading.siblings().find('ul:visible'); if ($expandedSiblings.size() > 0) { $expandedSiblings.slideUp(0, function(){ $heading.find('ul').slideDown(0); }); } else { $heading.find('ul').slideDown(0); } } }); $('#nav>li>ul>li').mousedown(function(){ // check that the menu is not currently animated if ($('#nav ul:animated').size() == 0) { // create a reference to the active element (this) // so we don't have to keep creating a jQuery object $heading2 = $(this); // create a reference to visible sibling elements // so we don't have to keep creating a jQuery object $expandedSiblings2 = $heading2.siblings().find('.children:visible'); if ($expandedSiblings2.size() > 0) { $expandedSiblings2.slideUp(0, function(){ $heading2.find('.children').slideDown(0); }); } else { $heading2.find('.children').slideDown(0); } } }); })); </script> and here is my html output <ul id="nav"> <li><a href="#">folder 4</a> <ul><li><a href="#">2001</a> <ul><li class="children"><a href="./directory//folder 4/2001/doc1.txt">doc1.txt</a></li> <li class="children"><a href="./directory//folder 4/2001/doc2.txt">doc2.txt</a></li> <li class="children"><a href="./directory//folder 4/2001/doc3.txt">doc3.txt</a></li> </ul> </li> <li><a href="#">2002</a> <ul><li class="children"><a href="./directory//folder 4/2002/doc1.txt">doc1.txt</a></li> <li class="children"><a href="./directory//folder 4/2002/doc2.txt">doc2.txt</a></li> <li class="children"><a href="./directory//folder 4/2002/doc3.txt">doc3.txt</a></li> <li class="children"><a href="./directory//folder 4/2002/doc4.txt">doc4.txt</a></li> </ul> </li> <li><a href="#">2003</a> <ul><li class="children"><a href="./directory//folder 4/2003/Copy of doc1.txt">Copy of doc1.txt</a></li> <li class="children"><a href="./directory//folder 4/2003/doc1.txt">doc1.txt</a></li> <li class="children"><a href="./directory//folder 4/2003/doc2.txt">doc2.txt</a></li> </ul> </li> <li><a href="#">2004</a> <ul><li class="children"><a href="./directory//folder 4/2004/doc1.txt">doc1.txt</a></li> <li class="children"><a href="./directory//folder 4/2004/doc2.txt">doc2.txt</a></li> <li class="children"><a href="./directory//folder 4/2004/doc3.txt">doc3.txt</a></li> <li class="children"><a href="./directory//folder 4/2004/doc4.txt">doc4.txt</a></li> </ul> </li> </ul> </li> <li><a href="#">folder1</a> <ul><li><a href="#">2001</a> <ul><li class="children"><a href="./directory//folder1/2001/doc1.txt">doc1.txt</a></li> <li class="children"><a href="./directory//folder1/2001/doc2.txt">doc2.txt</a></li> <li class="children"><a href="./directory//folder1/2001/doc3.txt">doc3.txt</a></li> </ul> </li> <li><a href="#">2002</a> <ul><li class="children"><a href="./directory//folder1/2002/doc1.txt">doc1.txt</a></li> <li class="children"><a href="./directory//folder1/2002/doc2.txt">doc2.txt</a></li> <li class="children"><a href="./directory//folder1/2002/doc3.txt">doc3.txt</a></li> <li class="children"><a href="./directory//folder1/2002/doc4.txt">doc4.txt</a></li> </ul> </li> <li><a href="#">2003</a> <ul><li class="children"><a href="./directory//folder1/2003/Copy of doc1.txt">Copy of doc1.txt</a></li> <li class="children"><a href="./directory//folder1/2003/doc1.txt">doc1.txt</a></li> <li class="children"><a href="./directory//folder1/2003/doc2.txt">doc2.txt</a></li> </ul> </li> <li><a href="#">2004</a> <ul><li class="children"><a href="./directory//folder1/2004/doc1.txt">doc1.txt</a></li> <li class="children"><a href="./directory//folder1/2004/doc2.txt">doc2.txt</a></li> <li class="children"><a href="./directory//folder1/2004/doc3.txt">doc3.txt</a></li> <li class="children"><a href="./directory//folder1/2004/doc4.txt">doc4.txt</a></li> </ul> </li> </ul> </li> <li><a href="#">folder2</a> <ul><li><a href="#">2001</a> <ul><li class="children"><a href="./directory//folder2/2001/doc1.txt">doc1.txt</a></li> <li class="children"><a href="./directory//folder2/2001/doc2.txt">doc2.txt</a></li> <li class="children"><a href="./directory//folder2/2001/doc3.txt">doc3.txt</a></li> </ul> </li> <li><a href="#">2002</a> <ul><li class="children"><a href="./directory//folder2/2002/doc1.txt">doc1.txt</a></li> <li class="children"><a href="./directory//folder2/2002/doc2.txt">doc2.txt</a></li> <li class="children"><a href="./directory//folder2/2002/doc3.txt">doc3.txt</a></li> <li class="children"><a href="./directory//folder2/2002/doc4.txt">doc4.txt</a></li> </ul> </li> <li><a href="#">2003</a> <ul><li class="children"><a href="./directory//folder2/2003/Copy of doc1.txt">Copy of doc1.txt</a></li> <li class="children"><a href="./directory//folder2/2003/doc1.txt">doc1.txt</a></li> <li class="children"><a href="./directory//folder2/2003/doc2.txt">doc2.txt</a></li> </ul> </li> <li><a href="#">2004</a> <ul><li class="children"><a href="./directory//folder2/2004/doc1.txt">doc1.txt</a></li> <li class="children"><a href="./directory//folder2/2004/doc2.txt">doc2.txt</a></li> <li class="children"><a href="./directory//folder2/2004/doc3.txt">doc3.txt</a></li> <li class="children"><a href="./directory//folder2/2004/doc4.txt">doc4.txt</a></li> </ul> </li> </ul> </li> <li><a href="#">folder3</a> <ul><li><a href="#">2001</a> <ul><li class="children"><a href="./directory//folder3/2001/doc1.txt">doc1.txt</a></li> <li class="children"><a href="./directory//folder3/2001/doc2.txt">doc2.txt</a></li> <li class="children"><a href="./directory//folder3/2001/doc3.txt">doc3.txt</a></li> </ul> </li> <li><a href="#">2002</a> <ul><li class="children"><a href="./directory//folder3/2002/doc1.txt">doc1.txt</a></li> <li class="children"><a href="./directory//folder3/2002/doc2.txt">doc2.txt</a></li> <li class="children"><a href="./directory//folder3/2002/doc3.txt">doc3.txt</a></li> <li class="children"><a href="./directory//folder3/2002/doc4.txt">doc4.txt</a></li> </ul> </li> <li><a href="#">2003</a> <ul><li class="children"><a href="./directory//folder3/2003/Copy of doc1.txt">Copy of doc1.txt</a></li> <li class="children"><a href="./directory//folder3/2003/doc1.txt">doc1.txt</a></li> <li class="children"><a href="./directory//folder3/2003/doc2.txt">doc2.txt</a></li> </ul> </li> <li><a href="#">2004</a> <ul><li class="children"><a href="./directory//folder3/2004/doc1.txt">doc1.txt</a></li> <li class="children"><a href="./directory//folder3/2004/doc2.txt">doc2.txt</a></li> <li class="children"><a href="./directory//folder3/2004/doc3.txt">doc3.txt</a></li> <li class="children"><a href="./directory//folder3/2004/doc4.txt">doc4.txt</a></li> </ul> </li> </ul> </li> </ul> I assume my problem is, jquery isn't closing the children between each new parent so I need to make a call, but I'm a bit lost on how to do that. I know the code is pretty messy, this project was done in a huge rush and a very tight timeframe. Appreciate your answers and any other constructive comments, cheers :)

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  • Extending the IndexController with a BaseController in Zend

    - by BillA
    I'm trying to extend my controllers with a global base controller as such: class BaseController extends Zend_Controller_Action { // common controller actions public function listAction() { // do stuff } } class IndexController extends BaseController { // index controller specific actions } class LoginController extends BaseController { // login controller specific actions } But I get this error: PHP Fatal error: Class 'BaseController' not found in /var/www/Zend/project/application/controllers/IndexController.php on line 3 Any ideas on how to get Zend to "see" this controller?

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  • Combining multiple classes gives me errors

    - by Martti Laine
    Hello I'm creating a website with structure like this: class main { } class mysql extends main { } class user extends main { } class etc extends main { } The idea is for these classes to use functions from each other. This doesn't work. How can I call a function from mysql in user? Martti Laine

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  • IS classOf[] in scala 2.8 different from 2.7?

    - by redtank
    I have an interface from java public class IJava { ... public java.lang.Class getType(); ... } It is inherited in Scala class CScala { def getType() = classOf[Foo] } it worked in scala 2.7.7. But in 2.8.0.RC1, i get type mismatch; found : java.lang.ClassFoo required: java.lang.Class How do i get java.langClass in Scala 2.8

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  • What is the best way to declare sorted association in grails domain classes ?

    - by fabien7474
    It seems that there are two different ways of declaring sorted associations in Grails : Method 1 (see here) using default sort order class Book { String title } class Author { static hasMany = [books : Book] static mapping = { books sort: "title"} } Method 2 (see here) using SortedSet class Book implements Comparable { String title int compareTo(obj) { title <=> obj.title } } class Author { SortedSet books static hasMany = [books : Book] } I am not sure which one to use and what is the difference (if any), pros and cons between using one against the other. I would appreciate any clarification. Thank you

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  • How do I write object classes effectively when dealing with table joins?

    - by Chris
    I should start by saying I'm not now, nor do I have any delusions I'll ever be a professional programmer so most of my skills have been learned from experience very much as a hobby. I learned PHP as it seemed a good simple introduction in certain areas and it allowed me to design simple web applications. When I learned about objects, classes etc the tutor's basic examnples covered the idea that as a rule of thumb each database table should have its own class. While that worked well for the photo gallery project we wrote, as it had very simple mysql queries, it's not working so well now my projects are getting more complex. If I require data from two separate tables which require a table join I've instead been ignoring the class altogether and handling it on a case by case basis, OR, even worse been combining some of the data into the class and the rest as a separate entity and doing two queries, which to me seems inefficient. As an example, when viewing content on a forum I wrote, if you view a thread, I retrieve data from the threads table, the posts table and the user table. The queries from the user and posts table are retrieved via a join and not instantiated as an object, whereas the thread data is called using my Threads class. So how do I get from my current state of affairs to something a little less 'stupid', for want of a better word. Right now I have a DB class that deals with connection and escaping values etc, a parent db query class that deals with the common queries and methods, and all of the other classes (Thread, Upload, Session, Photo and ones thats aren't used Post, User etc ) are children of that. Do I make a big posts class that has the relevant extra attributes that I retrieve from the users (and potentially threads) table? Do I have separate classes that populate each of their relevant attributes with a single query? If so how do I do that? Because of the way my classes are written, based on what I was taught, my db update row method, or insert method both just take the attributes as an array and update all of that, if I have extra attributes from other db tables in each class then how do I rewrite those methods as obbiously updating automatically like that would result in errors? In short I think my understanding is limited right now and I'd like some pointers when it comes to the fundamentals of how to write more complex classes.

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  • Using nested classes for constants?

    - by antirysm
    What's wrong with using nested classes to group constants? Like so: public static class Constants { public static class CategoryA { public const string ValueX = "CatA_X"; public const string ValueY = "CatA_Y"; } public static class CategoryB { public const string ValueX = "CatB_X"; public const string ValueY = "CatB_Y"; } } Used like so: Console.WriteLine(Constants.CategoryA.ValueY); Console.WriteLine(Constants.CategoryB.ValueX); You could also make the "Constants"-class partial...

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  • Java: Using Dynamically loaded classes

    - by Snigger
    Hi I'm new to java. I'm trying to use some dynamically loaded classes in my application. The application doesn't know classes , Just it try to load a class by name that its name came from input. It doesn't know class (So I can't use casting) but just needs to call some methods of that class (every class should have that methods). I thought about interfaces but I don't know how. How can I call those methods? Thanks

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  • Using enums in Java across multiple classes

    - by Richard Mar.
    I have the following class: public class Card { public enum Suit { SPACES, HEARTS, DIAMONDS, CLUBS }; public Card(Suit nsuit, int nrank) { suit = nsuit; rank = nrank; } private Suit suit; private int rank; } I want to instantiate it in another class, but that class doesn't understand the Suit enum. Where should I put the enum to make it publicly visible?

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  • Access specifier's and classes and objects?

    - by TimothyTech
    Alright, im trying to understand this, so a class is simply creating a template for an object. class Bow { int arrows; }; and an object is simply creating a specific item using the class template. Bow::Bow(arrows) { arrows = 20; } also another question, public specifiers are used to make data members avaible in objects and private specifiers are used to make data memebers only avaialble inside the class?

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  • How to reference or connect a variable to another class without stack overflow?

    - by SystemNetworks
    I really need to re-arrange all my functions. I created a class. All my var, booleans, int, doubles and other things. I created every new variable so they can reference it and so they don't have an error. If your asking why I never just reference my main class vars to my sub-class becuase it will give me stack overflow! When in my main class i link my sub-class. subClass s = new subClass(); Then I reference my fake variable to my real variable for example: This is my sub-class variable(I call it fake) public int x = 0; In my main class, I put it like this: s.x = x; The problem is, it does not work! Maybe this is not the right place but I cant ask any questions on stack overflow because they banned me. If I connect my main class and connect my sub-class it will give me stack overflow. How do I stop it?

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  • How to generate a Program template by generating an abstract class

    - by Byron-Lim Timothy Steffan
    i have the following problem. The 1st step is to implement a program, which follows a specific protocol on startup. Therefore, functions as onInit, onConfigRequest, etc. will be necessary. (These are triggered e.g. by incoming message on a TCP Port) My goal is to generate a class for example abstract one, which has abstract functions as onInit(), etc. A programmer should just inherit from this base class and should merely override these abstract functions of the base class. The rest as of the protocol e.g. should be simply handled in the background (using the code of the base class) and should not need to appear in the programmers code. What is the correct design strategy for such tasks? and how do I deal with, that the static main method is not inheritable? What are the key-tags for this problem? (I have problem searching for a solution since I lack clear statements on this problem) Goal is to create some sort of library/class, which - included in ones code - results in executables following the protocol. EDIT (new explanation): Okay let me try to explain more detailled: In this case programs should be clients within a client server architecture. We have a client server connection via TCP/IP. Each program needs to follow a specific protocol upon program start: As soon as my program starts and gets connected to the server it will receive an Init Message (TcpClient), when this happens it should trigger the function onInit(). (Should this be implemented by an event system?) After onInit() a acknowledgement message should be sent to the server. Afterwards there are some other steps as e.g. a config message from the server which triggers an onConfig and so on. Let's concentrate on the onInit function. The idea is, that onInit (and onConfig and so on) should be the only functions the programmer should edit while the overall protocol messaging is hidden for him. Therefore, I thought using an abstract class with the abstract methods onInit(), onConfig() in it should be the right thing. The static Main class I would like to hide, since within it e.g. there will be some part which connects to the tcp port, which reacts on the Init Message and which will call the onInit function. 2 problems here: 1. the static main class cant be inherited, isn it? 2. I cannot call abstract functions from the main class in the abstract master class. Let me give an Pseudo-example for my ideas: public abstract class MasterClass { static void Main(string[] args){ 1. open TCP connection 2. waiting for Init Message from server 3. onInit(); 4. Send Acknowledgement, that Init Routine has ended successfully 5. waiting for Config message from server 6..... } public abstract void onInit(); public abstract void onConfig(); } I hope you get the idea now! The programmer should afterwards inherit from this masterclass and merely need to edit the functions onInit and so on. Is this way possible? How? What else do you recommend for solving this? EDIT: The strategy ideo provided below is a good one! Check out my comment on that.

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  • Injection of an EJB into a web java class under JBoss 7.1.1

    - by Dobbo
    I am trying to build a website using JBoss 7.1.1 and RESTeasy. I have managed to constructed and deploy and EAR with a both a WAR and an EJB-JAR contained within: voyager-app.ear META-INF/MANIFEST.MF META-INF/application.xml META-INF/jboss-app.xml lib/voyager-lib.jar voyager-adm.war voyager-ejb.jar voyager-web.war So far things are very simple. voyager-adm.war & voyager-lib.jar are empty (just the manifest file) but I know that I'm going to have code for them shortly. There is just one Stateful EJB - HarbourMasterBean (with just a local interface) and a few Database Entity Beans in the EJB jar file: voyager-ejb.jar META-INF/MANIFEST.MF META-INF/persistence.xml com/nutrastat/voyager/db/HarbourMasterBean.class com/nutrastat/voyager/db/HarbourMasterLocal.class com/nutrastat/voyager/db/PortEntity.class com/nutrastat/voyager/db/ShipEntity.class As far as I can tell the EJBs deploy correctly because the database units are created and the log shows that the publication of some HarbourMaster references: java:global/voyager-app/voyager-ejb/harbour-master!com.nutrastat.voyager.db.HarbourMasterLocal java:app/voyager-ejb/harbour-master!com.nutrastat.voyager.db.HarbourMasterLocal java:module/harbour-master!com.nutrastat.voyager.db.HarbourMasterLocal java:global/voyager-app/voyager-ejb/harbour-master java:app/voyager-ejb/harbour-master java:module/harbour-master The problem lies in getting the HarbourMaster EJB injected into my web bean. The reference to it is alway NULL no matter what I try. voyager-web.war META-INF/MANIFEST.MF WEB-INF/web.xml WEB-INF/classes/com/nutrastat/voyager/web/ WEB-INF/classes/com/nutrastat/voyager/web/Ships.class WEB-INF/classes/com/nutrastat/voyager/web/VoyagerApplication.class Ships.java: @Path("fleet") public class Ships { protected transient final Logger log; @EJB private HarbourMasterLocal harbourMaster; public Ships() { log = LoggerFactory.getLogger(getClass()); } @GET @Path("ships") @Produces({"text/plain"}) public String listShips() { if (log.isDebugEnabled()) log.debug("Harbour master value: " + harbourMaster); return "Harbour Master: " + harbourMaster; } } &lt;web-app xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" version="3.0" &gt; <display-name>Voyager Web Application</display-name> <listener> <listener-class> org.jboss.resteasy.plugins.server.servlet.ResteasyBootstrap </listener-class> </listener> <servlet> <servlet-name>Resteasy</servlet-name> <servlet-class> org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher </servlet-class> <init-param> <param-name> javax.ws.rs.Application </param-name> <param-value> com.nutrastat.voyager.web.VoyagerApplication </param-value> </init-param> </servlet> <servlet-mapping> <servlet-name>Resteasy</servlet-name> <url-pattern>/*</url-pattern> </servlet-mapping> &lt;/web-app&gt; I have been searching the web for an answer and read a number of places, both on StackOverflow and elsewhere that suggests is can be done, and that the problems lies with configuration. But they post only snippets and I'm never sure if I'm doing things correctly. Many thanks for any help you can provide. Dobbo

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  • Doxygen for C++ template class member specialization

    - by Ziv
    When I write class templates, and need to fully-specialize members of those classes, Doxygen doesn't recognize the specialization - it documents only the generic definition, or (if there are only specializations) the last definition. Here's a simple example: ===MyClass.hpp=== #ifndef MYCLASS_HPP #define MYCLASS_HPP template<class T> class MyClass{ public: static void foo(); static const int INT_CONST; static const T TTYPE_CONST; }; /* generic definitions */ template<class T> void MyClass<T>::foo(){ printf("Generic foo\n"); } template<class T> const int MyClass<T>::INT_CONST = 5; /* specialization declarations */ template<> void MyClass<double>::foo(); template<> const int MyClass<double>::INT_CONST; template<> const double MyClass<double>::TTYPE_CONST; template<> const char MyClass<char>::TTYPE_CONST; #endif === MyClass.cpp === #include "MyClass.hpp" /* specialization definitions */ template<> void MyClass<double>::foo(){ printf("Specialized double foo\n"); } template<> const int MyClass<double>::INT_CONST = 10; template<> const double MyClass<double>::TTYPE_CONST = 3.141; template<> const char MyClass<char>::TTYPE_CONST = 'a'; So in this case, foo() will be documented as printing "Generic foo," INT_CONST will be documented as set to 5, with no mention of the specializations, and TTYPE_CONST will be documented as set to 'a', with no mention of 3.141 and no indication that 'a' is a specialized case. I need to be able to document the specializations - either within the documentation for MyClass<T>, or on new pages for MyClass<double>, MyClass<char>. How do I do this? Can Doxygen even handle this? Am I possibly doing something wrong in the declarations/code structure that's keeping Doxygen from understanding what I want? I should note two related cases: A) For templated functions, specialization works fine, e.g.: /* functions that are global/in a namespace */ template<class T> void foo(){ printf("Generic foo\n"); } template<> void foo<double>(){ printf("Specialized double foo\n"); } This will document both foo() and foo(). B) If I redeclare the entire template, i.e. template<> class MyClass<double>{...};, then MyClass<double> will get its own documentation page, as a seperate class. But this means actually declaring an entirely new class - there is no relation between MyClass<T> and MyClass<double> if MyClass<double> itself is declared. So I'd have to redeclare the class and all its members, and repeat all the definitions of class members, specialized for MyClass<double>, all to make it appear as though they're using the same template. Very awkward, feels like a kludge solution. Suggestions? Thanks much :) --Ziv

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  • A Communication System for XAML Applications

    - by psheriff
    In any application, you want to keep the coupling between any two or more objects as loose as possible. Coupling happens when one class contains a property that is used in another class, or uses another class in one of its methods. If you have this situation, then this is called strong or tight coupling. One popular design pattern to help with keeping objects loosely coupled is called the Mediator design pattern. The basics of this pattern are very simple; avoid one object directly talking to another object, and instead use another class to mediate between the two. As with most of my blog posts, the purpose is to introduce you to a simple approach to using a message broker, not all of the fine details. IPDSAMessageBroker Interface As with most implementations of a design pattern, you typically start with an interface or an abstract base class. In this particular instance, an Interface will work just fine. The interface for our Message Broker class just contains a single method “SendMessage” and one event “MessageReceived”. public delegate void MessageReceivedEventHandler( object sender, PDSAMessageBrokerEventArgs e); public interface IPDSAMessageBroker{  void SendMessage(PDSAMessageBrokerMessage msg);   event MessageReceivedEventHandler MessageReceived;} PDSAMessageBrokerMessage Class As you can see in the interface, the SendMessage method requires a type of PDSAMessageBrokerMessage to be passed to it. This class simply has a MessageName which is a ‘string’ type and a MessageBody property which is of the type ‘object’ so you can pass whatever you want in the body. You might pass a string in the body, or a complete Customer object. The MessageName property will help the receiver of the message know what is in the MessageBody property. public class PDSAMessageBrokerMessage{  public PDSAMessageBrokerMessage()  {  }   public PDSAMessageBrokerMessage(string name, object body)  {    MessageName = name;    MessageBody = body;  }   public string MessageName { get; set; }   public object MessageBody { get; set; }} PDSAMessageBrokerEventArgs Class As our message broker class will be raising an event that others can respond to, it is a good idea to create your own event argument class. This class will inherit from the System.EventArgs class and add a couple of additional properties. The properties are the MessageName and Message. The MessageName property is simply a string value. The Message property is a type of a PDSAMessageBrokerMessage class. public class PDSAMessageBrokerEventArgs : EventArgs{  public PDSAMessageBrokerEventArgs()  {  }   public PDSAMessageBrokerEventArgs(string name,     PDSAMessageBrokerMessage msg)  {    MessageName = name;    Message = msg;  }   public string MessageName { get; set; }   public PDSAMessageBrokerMessage Message { get; set; }} PDSAMessageBroker Class Now that you have an interface class and a class to pass a message through an event, it is time to create your actual PDSAMessageBroker class. This class implements the SendMessage method and will also create the event handler for the delegate created in your Interface. public class PDSAMessageBroker : IPDSAMessageBroker{  public void SendMessage(PDSAMessageBrokerMessage msg)  {    PDSAMessageBrokerEventArgs args;     args = new PDSAMessageBrokerEventArgs(      msg.MessageName, msg);     RaiseMessageReceived(args);  }   public event MessageReceivedEventHandler MessageReceived;   protected void RaiseMessageReceived(    PDSAMessageBrokerEventArgs e)  {    if (null != MessageReceived)      MessageReceived(this, e);  }} The SendMessage method will take a PDSAMessageBrokerMessage object as an argument. It then creates an instance of a PDSAMessageBrokerEventArgs class, passing to the constructor two items: the MessageName from the PDSAMessageBrokerMessage object and also the object itself. It may seem a little redundant to pass in the message name when that same message name is part of the message, but it does make consuming the event and checking for the message name a little cleaner – as you will see in the next section. Create a Global Message Broker In your WPF application, create an instance of this message broker class in the App class located in the App.xaml file. Create a public property in the App class and create a new instance of that class in the OnStartUp event procedure as shown in the following code: public partial class App : Application{  public PDSAMessageBroker MessageBroker { get; set; }   protected override void OnStartup(StartupEventArgs e)  {    base.OnStartup(e);     MessageBroker = new PDSAMessageBroker();  }} Sending and Receiving Messages Let’s assume you have a user control that you load into a control on your main window and you want to send a message from that user control to the main window. You might have the main window display a message box, or put a string into a status bar as shown in Figure 1. Figure 1: The main window can receive and send messages The first thing you do in the main window is to hook up an event procedure to the MessageReceived event of the global message broker. This is done in the constructor of the main window: public MainWindow(){  InitializeComponent();   (Application.Current as App).MessageBroker.     MessageReceived += new MessageReceivedEventHandler(       MessageBroker_MessageReceived);} One piece of code you might not be familiar with is accessing a property defined in the App class of your XAML application. Within the App.Xaml file is a class named App that inherits from the Application object. You access the global instance of this App class by using Application.Current. You cast Application.Current to ‘App’ prior to accessing any of the public properties or methods you defined in the App class. Thus, the code (Application.Current as App).MessageBroker, allows you to get at the MessageBroker property defined in the App class. In the MessageReceived event procedure in the main window (shown below) you can now check to see if the MessageName property of the PDSAMessageBrokerEventArgs is equal to “StatusBar” and if it is, then display the message body into the status bar text block control. void MessageBroker_MessageReceived(object sender,   PDSAMessageBrokerEventArgs e){  switch (e.MessageName)  {    case "StatusBar":      tbStatus.Text = e.Message.MessageBody.ToString();      break;  }} In the Page 1 user control’s Loaded event procedure you will send the message “StatusBar” through the global message broker to any listener using the following code: private void UserControl_Loaded(object sender,  RoutedEventArgs e){  // Send Status Message  (Application.Current as App).MessageBroker.    SendMessage(new PDSAMessageBrokerMessage("StatusBar",      "This is Page 1"));} Since the main window is listening for the message ‘StatusBar’, it will display the value “This is Page 1” in the status bar at the bottom of the main window. Sending a Message to a User Control The previous example sent a message from the user control to the main window. You can also send messages from the main window to any listener as well. Remember that the global message broker is really just a broadcaster to anyone who has hooked into the MessageReceived event. In the constructor of the user control named ucPage1 you can hook into the global message broker’s MessageReceived event. You can then listen for any messages that are sent to this control by using a similar switch-case structure like that in the main window. public ucPage1(){  InitializeComponent();   // Hook to the Global Message Broker  (Application.Current as App).MessageBroker.    MessageReceived += new MessageReceivedEventHandler(      MessageBroker_MessageReceived);} void MessageBroker_MessageReceived(object sender,  PDSAMessageBrokerEventArgs e){  // Look for messages intended for Page 1  switch (e.MessageName)  {    case "ForPage1":      MessageBox.Show(e.Message.MessageBody.ToString());      break;  }} Once the ucPage1 user control has been loaded into the main window you can then send a message using the following code: private void btnSendToPage1_Click(object sender,  RoutedEventArgs e){  PDSAMessageBrokerMessage arg =     new PDSAMessageBrokerMessage();   arg.MessageName = "ForPage1";  arg.MessageBody = "Message For Page 1";   // Send a message to Page 1  (Application.Current as App).MessageBroker.SendMessage(arg);} Since the MessageName matches what is in the ucPage1 MessageReceived event procedure, ucPage1 can do anything in response to that event. It is important to note that when the message gets sent it is sent to all MessageReceived event procedures, not just the one that is looking for a message called “ForPage1”. If the user control ucPage1 is not loaded and this message is broadcast, but no other code is listening for it, then it is simply ignored. Remove Event Handler In each class where you add an event handler to the MessageReceived event you need to make sure to remove those event handlers when you are done. Failure to do so can cause a strong reference to the class and thus not allow that object to be garbage collected. In each of your user control’s make sure in the Unloaded event to remove the event handler. private void UserControl_Unloaded(object sender, RoutedEventArgs e){  if (_MessageBroker != null)    _MessageBroker.MessageReceived -=         _MessageBroker_MessageReceived;} Problems with Message Brokering As with most “global” classes or classes that hook up events to other classes, garbage collection is something you need to consider. Just the simple act of hooking up an event procedure to a global event handler creates a reference between your user control and the message broker in the App class. This means that even when your user control is removed from your UI, the class will still be in memory because of the reference to the message broker. This can cause messages to still being handled even though the UI is not being displayed. It is up to you to make sure you remove those event handlers as discussed in the previous section. If you don’t, then the garbage collector cannot release those objects. Instead of using events to send messages from one object to another you might consider registering your objects with a central message broker. This message broker now becomes a collection class into which you pass an object and what messages that object wishes to receive. You do end up with the same problem however. You have to un-register your objects; otherwise they still stay in memory. To alleviate this problem you can look into using the WeakReference class as a method to store your objects so they can be garbage collected if need be. Discussing Weak References is beyond the scope of this post, but you can look this up on the web. Summary In this blog post you learned how to create a simple message broker system that will allow you to send messages from one object to another without having to reference objects directly. This does reduce the coupling between objects in your application. You do need to remember to get rid of any event handlers prior to your objects going out of scope or you run the risk of having memory leaks and events being called even though you can no longer access the object that is responding to that event. NOTE: You can download the sample code for this article by visiting my website at http://www.pdsa.com/downloads. Select “Tips & Tricks”, then select “A Communication System for XAML Applications” from the drop down list.

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  • Explicit method tables in C# instead of OO - good? bad?

    - by FunctorSalad
    Hi! I hope the title doesn't sound too subjective; I absolutely do not mean to start a debate on OO in general. I'd merely like to discuss the basic pros and cons for different ways of solving the following sort of problem. Let's take this minimal example: you want to express an abstract datatype T with functions that may take T as input, output, or both: f1 : Takes a T, returns an int f2 : Takes a string, returns a T f3 : Takes a T and a double, returns another T I'd like to avoid downcasting and any other dynamic typing. I'd also like to avoid mutation whenever possible. 1: Abstract-class-based attempt abstract class T { abstract int f1(); // We can't have abstract constructors, so the best we can do, as I see it, is: abstract void f2(string s); // The convention would be that you'd replace calls to the original f2 by invocation of the nullary constructor of the implementing type, followed by invocation of f2. f2 would need to have side-effects to be of any use. // f3 is a problem too: abstract T f3(double d); // This doesn't express that the return value is of the *same* type as the object whose method is invoked; it just expresses that the return value is *some* T. } 2: Parametric polymorphism and an auxilliary class (all implementing classes of TImpl will be singleton classes): abstract class TImpl<T> { abstract int f1(T t); abstract T f2(string s); abstract T f3(T t, double d); } We no longer express that some concrete type actually implements our original spec -- an implementation is simply a type Foo for which we happen to have an instance of TImpl. This doesn't seem to be a problem: If you want a function that works on arbitrary implementations, you just do something like: // Say we want to return a Bar given an arbitrary implementation of our abstract type Bar bar<T>(TImpl<T> ti, T t); At this point, one might as well skip inheritance and singletons altogether and use a 3 First-class function table class /* or struct, even */ TDictT<T> { readonly Func<T,int> f1; readonly Func<string,T> f2; readonly Func<T,double,T> f3; TDict( ... ) { this.f1 = f1; this.f2 = f2; this.f3 = f3; } } Bar bar<T>(TDict<T> td; T t); Though I don't see much practical difference between #2 and #3. Example Implementation class MyT { /* raw data structure goes here; this class needn't have any methods */ } // It doesn't matter where we put the following; could be a static method of MyT, or some static class collecting dictionaries static readonly TDict<MyT> MyTDict = new TDict<MyT>( (t) => /* body of f1 goes here */ , // f2 (s) => /* body of f2 goes here */, // f3 (t,d) => /* body of f3 goes here */ ); Thoughts? #3 is unidiomatic, but it seems rather safe and clean. One question is whether there are any performance concerns with it. I don't usually need dynamic dispatch, and I'd prefer if these function bodies get statically inlined in places where the concrete implementing type is known statically. Is #2 better in that regard?

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