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• JBoss classloading when 2 WARs have the same class

  - by Pacman

  I have a web applications A.war which has two servlets AServlet and BServlet. Both instantiate a helper class com.mycompany.Foo.class (this is my own class, not a third party library). Now I want to split the two servlets into two separate WARs: A.war will have only AServlet and a new B.war will have BServlet. AServlet will invoke BServlet via HTTP GET. Both WARs will have com.mycompany.Foo.class. I want to deploy both WARs on the same JBoss instance. The question is, will there be any classloading issues due to the same class being present in both WARs, and the WARs being deployed on the same JBoss instance?

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• abstract class MouseAdapter vs. interface

  - by Stefano Borini

  I noted this (it's a java.awt.event class). public abstract class MouseAdapter implements MouseListener, MouseWheelListener, MouseMotionListener { .... } Then you are clearly forced to extend from this adapter public class MouseAdapterImpl extends MouseAdapter {} the class is abstract and implements no methods. Is this a strategy to combine different interfaces into a single "basically interface" ? I assume in java it's not possible to combine different interfaces into a single one without using this approach. In other words, it's not possible to do something like this in java public interface MouseAdapterIface extends MouseListener, MouseWheelListener, MouseMotionListener { } and then eventually public class MouseAdapterImpl implements MouseAdapterIface {} Is my understanding of the point correct ? what about C# ?

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• C++: select argmax over vector of classes w.r.t. arbitrary expression

  - by karpathy

  Hello, I have trouble describing my problem so I'll give an example: I have a class description that has a couple of variables in it, for example: class A{ float a, b, c, d; } Now, I maintain a vector<A> that contains many of these classes. What I need to do very very often is to find the object inside this vector that satisfies that one of it's parameters is maximal w.r.t to the others. i.e code looks something like: int maxi=-1; float maxa=-1000; for(int i=0;i<vec.size();i++){ res= vec[i].a; if(res > maxa) { maxa= res; maxi=i; } } return vec[maxi]; However, sometimes I need to find class with maximal a, sometimes with maximal b, sometimes the class with maximal 0.8*a + 0.2*b, sometimes I want a maximal a*VAR + b, where VAR is some variable that is assigned in front, etc. In other words, I need to evaluate an expression for every class, and take the max. I find myself copy-pasting this everywhere, and only changing the single line that defines res. What makes it even more complicated is that even the name of the vector changes. Sometimes it's vec, sometimes it can be something else. I have many vectors that contain A's. This could be changed if this makes the problem too hard. Is there some nice way to avoid this insanity in C++? What's the neatest way to handle this? Thank you!

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• Ruby: Calling class method from instance

  - by Peter

  In Ruby, how do you call a class method from one of that class's instances? Say I have class Truck def self.default_make # Class method. "mac" end def initialize # Instance method. Truck.default_make # gets the default via the class's method. # But: I wish to avoid mentioning Truck. Seems I'm repeating myself. end end the line Truck.default_make retrieves the default. But is there a way of saying this without mentioning Truck? It seems like there should be.

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• C#: Abstract classes need to implement interfaces?

  - by bguiz

  My test code in C#: namespace DSnA { public abstract class Test : IComparable { } } Results in the following compiler error: error CS0535: 'DSnA.Test' does not implement interface member 'System.IComparable.CompareTo(object)' Since the class Test is an abstract class, why does the compiler require it to implement the interface? Shouldn't this requirement only be compulsory for concrete classes?

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• Class Not found exception in JApplet.

  - by Nitesh Panchal

  Hello, I created a simple Applet using JApplet and everything seems to work fine but as soon i create an object of my userdefined class named ChatUser in my applet, i get this error :- SEVERE: java.lang.ClassNotFoundException: applet.ChatUser at com.sun.enterprise.loader.ASURLClassLoader.findClassData(ASURLClassLoader.java:713) at com.sun.enterprise.loader.ASURLClassLoader.findClass(ASURLClassLoader.java:626) at java.lang.ClassLoader.loadClass(ClassLoader.java:307) at java.lang.ClassLoader.loadClass(ClassLoader.java:252) at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Class.java:247) at java.io.ObjectInputStream.resolveClass(ObjectInputStream.java:604) at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1575) at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1496) at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1732) at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1329) at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351) at misc.ChatClient.run(ChatClient.java:43) Any idea what can be wrong? It only happens when i create an object of any user defined class. Do i need to set some security settings or something? Please help :(

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• Field Members vs Method Variables?

  - by Braveyard

  Recently I've been thinking about performance difference between class field members and method variables. What exactly I mean is in the example below : Lets say we have a DataContext object for Linq2SQL class DataLayer { ProductDataContext context = new ProductDataContext(); public IQueryable<Product> GetData() { return context.Where(t=>t.ProductId == 2); } } In the example above, context will be stored in heap and the GetData method variables will be removed from Stack after Method is executed. So lets examine the following example to make a distinction : class DataLayer { public IQueryable<Product> GetData() { ProductDataContext context = new ProductDataContext(); return context.Where(t=>t.ProductId == 2); } } (*1) So okay first thing we know is if we define ProductDataContext instance as a field, we can reach it everywhere in the class which means we don't have to create same object instance all the time. But lets say we are talking about Asp.NET and once the users press submit button the post data is sent to the server and the events are executed and the posted data stored in a database via the method above so it is probable that the same user can send different data after one another.If I know correctly after the page is executed, the finalizers come into play and clear things from memory (from heap) and that means we lose our instance variables from memory as well and after another post, DataContext should be created once again for the new page cycle. So it seems the only benefit of declaring it publicly to the whole class is the just number one text above. Or is there something other? Thanks in advance... (If I told something incorrect please fix me.. )

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• Get class of caller's method (via inspect) in Python (alt: super() emulator)

  - by Slava Vishnyakov

  Is it possible to get reference to class B in this example? class A(object): pass class B(A): def test(self): test2() class C(B): pass import inspect def test2(): frame = inspect.currentframe().f_back cls = frame.[?something here?] # cls here should == B (class) c = C() c.test() Basically, C is child of B, B is child of A. Then we create c of type C. Then the call to c.test() actually calls B.test() (via inheritance), which calls to test2(). test2() can get the parent frame frame; code reference to method via frame.f_code; self via frame.f_locals['self']; but type(frame.f_locals['self']) is C (of course), but not B, where method is defined. Any way to get B?

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• In PHP, is it possible to create an instance of an class without calling class's constructor ?

  - by Rachel

  By any means, is it possible to create an instance of an php class without calling its constructor ? I have Class A and while creating an instance of it am passing file and in constructor of Class A am opening the file. Now in Class A, there is function which I need to call but am not required to pass file and so there is not need to use constructor functionality of opening file as am not passing file. So my question is, Is it possible by any means to create an instance of an PHP class without calling its constructor ?

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• Ruby: Locate class definition at run time?

  - by Thor Thurn

  I'm having an odd probably with rails right now... a class is being defined somewhere, and I can't find it. Grepping for "class ClassName" hasn't managed to locate it, but it's definitely there when I load up the rails console. It's just a vanilla class inheriting from Object with nothing else defined... quite boring. So, what I'd like is a way to figure out where this class constant was originally defined from the rails console. Something to print out the value of '__ FILE __' when this class was declared, in other words. I feel like some type of metaprogramming should make this possible.

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• PHP: friend classes and ungreedy caller function/class

  - by avetis.kazarian

  Is there any way to get the caller function with something else than debug_backtrace()? I'm looking for a less greedy way to simulate scopes like friend or internal. Let's say I have a class A and a class B. Until now, I've been using debug_backtrace(), which is too greedy (IMHO). I thought of something like this: <?php class A { public function __construct(B $callerObj) {} } class B { public function someMethod() { $obj = new A($this); } } ?> It might be OK if you want to limit it to one specific class, but let's say I have 300 classes, and I want to limit it to 25 of them? One way could be using an interface to aggregate: public function __construct(CallerInterface $callerObj) But it's still an ugly code. Moreover, you can't use that trick with static classes. Have any better idea?

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• spring-nullpointerexception- cant access autowired annotated service (or dao) in a no-annotations class

  - by user286806

  I have this problem that I cannot fix. From my @Controller, i can easily access my autowired @Service class and play with it no problem. But when I do that from a separate class without annotations, it gives me a NullPointerException. My Controller (works)- @Controller public class UserController { @Autowired UserService userService;... My separate Java class (not working)- public final class UsersManagementUtil { @Autowired UserService userService; or @Autowired UserDao userDao; userService or userDao are always null! Was just trying if any one of them works. My component scan setting has the root level package set for scanning so that should be OK. my servlet context - <?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context" xmlns:tx="http://www.springframework.org/schema/tx" xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.0.xsd"> <!-- the application context definition for the springapp DispatcherServlet --> <!-- Enable annotation driven controllers, validation etc... --> <context:property-placeholder location="classpath:jdbc.properties" /> <context:component-scan base-package="x" /> <tx:annotation-driven transaction-manager="hibernateTransactionManager" /> <!-- package shortended --> <bean id="messageSource" class="o.s.c.s.ReloadableResourceBundleMessageSource"> <property name="basename" value="/WEB-INF/messages" /> </bean> <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource"> <property name="driverClassName" value="${database.driver}" /> <property name="url" value="${database.url}" /> <property name="username" value="${database.user}" /> <property name="password" value="${database.password}" /> </bean> <!-- package shortened --> <bean id="viewResolver" class="o.s.w.s.v.InternalResourceViewResolver"> <property name="prefix"> <value>/</value> </property> <property name="suffix"> <value>.jsp</value> </property> <property name="order"> <value>0</value> </property> </bean> <!-- package shortened --> <bean id="sessionFactory" class="o.s.o.h3.a.AnnotationSessionFactoryBean"> <property name="dataSource" ref="dataSource" /> <property name="annotatedClasses"> <list> <value>orion.core.models.Question</value> <value>orion.core.models.User</value> <value>orion.core.models.Space</value> <value>orion.core.models.UserSkill</value> <value>orion.core.models.Question</value> <value>orion.core.models.Rating</value> </list> </property> <property name="hibernateProperties"> <props> <prop key="hibernate.dialect">${hibernate.dialect}</prop> <prop key="hibernate.show_sql">${hibernate.show_sql}</prop> <prop key="hibernate.hbm2ddl.auto">${hibernate.hbm2ddl.auto}</prop> </props> </property> </bean> <bean id="hibernateTransactionManager" class="org.springframework.orm.hibernate3.HibernateTransactionManager"> <property name="sessionFactory" ref="sessionFactory" /> </bean> Any clue?

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• What are Class methods in Python for?

  - by Dave Webb

  I'm teaching myself Python and my most recent lesson was that Python is not Java, and so I've just spent a while turning all my Class methods into functions. I now realise that I don't need to use Class methods for what I would done with static methods in Java, but now I'm not sure when I would use them. All the advice I can find about Python Class methods is along the lines of newbies like me should steer clear of them, and the standard documentation is at its most opaque when discussing them. Does anyone have a good example of using a Class method in Python or at least can someone tell me when Class methods can be sensibly used?

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• launch android activity from non-activity class

  - by Alberto Barrera

  im New on Android. I know theres a lot of similar Questions but anyone is helping. Im using a 3rd party app that just launch a class that extends their own class. So from that class i would like to launch an activity. public class SkyTest extends VtiUserExit { @Override public VtiUserExitResult execute() throws VtiExitException { // TODO Auto-generated method stub logInfo("TEST"); return null; } } How do i launch an activity named MainActivity from here. i tryed this: Context context = null; Intent intent = new Intent(context, MainActivity.class); context.startActivity(intent); but its not working, i know i cant use the null context, but how do i create a context o how it works? Thanks

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• Pass logger instance to class

  - by mridang

  Hi Guys, I'm using a open-source Python library in my project. This library logs a lot of information using the logging class. ...but I can't see the output or log it to file. I know that i would have to create a logger instance and add a file-handler or a console-handler to it but how can i pass this logger instance to the class? Here's the init snippet of the class that I'm going to be using. class Periscope: ''' Main Periscope class''' def __init__(self): self.config = ConfigParser.SafeConfigParser({"lang": "en"}) if is_local: self.config_file = os.path.join(bd.xdg_config_home, "periscope", "config") if not os.path.exists(self.config_file): folder = os.path.dirname(self.config_file) if not os.path.exists(folder): logging.info("Creating folder %s" %folder) os.mkdir(folder) logging.info("Creating config file") configfile = open(self.config_file, "w") self.config.write(configfile) configfile.close() else: #Load it self.config.read(self.config_file) self.pluginNames = self.listExistingPlugins() self._preferedLanguages = None Any help? Thanks guys.

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• Get class of caller's method (via inspect) in Python; or: super(Class,self).method() replacement wit

  - by Slava Vishnyakov

  Is it possible to get reference to class B in this example? class A(object): pass class B(A): def test(self): test2() class C(B): pass import inspect def test2(): frame = inspect.currentframe().f_back cls = frame.[?something here?] # cls here should == B (class) c = C() c.test() Basically, C is child of B, B is child of A. Then we create c of type C. Then the call to c.test() actually calls B.test() (via inheritance), which calls to test2(). test2() can get the parent frame frame; code reference to method via frame.f_code; self via frame.f_locals['self']; but type(frame.f_locals['self']) is C (of course), but not B, where method is defined. Any way to get B?

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• Template class implicit copy constructor issues

  - by Nate

  Stepping through my program in gdb, line 108 returns right back to the calling function, and doesn't call the copy constructor in class A, like (I thought) it should: template <class S> class A{ //etc... A( const A & old ){ //do stuff... } //etc... }; template <class T> class B{ //etc... A<T> ReturnsAnA(){ A<T> result; // do some stuff with result return result; //line 108 } //etc... }; Any hints? I've banged my head against the wall about this for 4 hours now, and can't seem to come up with what's happening here.

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• Silencing GCC warnings when using an "Uncopyable" class

  - by Kazade

  I have several classes that I don't want to be copyable, some of these classes have pointer data members. To make these classes uncopyable I privately inherit the following class template: template <class T> class Uncopyable { protected: Uncopyable() {} virtual ~Uncopyable() {} private: Uncopyable(const Uncopyable &); T & operator=(const T&); }; Which I used like so: class Entity : private Uncopyable<Entity> { } This works fine, however when I compile with -Weffc++ I still get the following warning: class Entity has pointer data members but does not override Entity(const Entity&) or operator=(const Entity&) Why is it still giving me this warning?

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• Prevent mapping all public members of a class in Fluent NHibernate

  - by alimbada

  I have a class generated from a WSDL that has a bunch of public properties and a public event. I'm extending this class with my own and adding some properties to it. All of my own properties are declared virtual, but the base class properties are not virtual. I'm using Fluent NHibernate's ClassMap to map only the properties from my extended class. How do I prevent (Fluent)NHibernate from trying to persist all the base class's public members? At the moment, I get the following exception when creating the ISessionFactory: NHibernate.InvalidProxyTypeException: The following types may not be used as proxies: Type: method get_<BaseClassProperty should be 'public/protected virtual' or 'protected internal virtual' Type: method set_<BaseClassProperty should be 'public/protected virtual' or 'protected internal virtual' ... Type: method add_<BaseClassEvent should be 'public/protected virtual' or 'protected internal virtual' Type: method remove_<BaseClassEvent should be 'public/protected virtual' or 'protected internal virtual'

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• Check if CSS Class exists in StyleSheet using javascript/jQuery

  - by Akhil Sekharan

  Is there a way to check if there is a class named 'some-class-name' in css? For example, I have: <style type="text/css"> .box { position: absolute; left: 150%; } </style> My intention is to randomly assign a class to a div on certain event: var classList = []; //Need to populate this array $('#updateClass').on('click', function() { $('#resultDiv').attr('class',classList[Math.floor((Math.random()*classList.length)+1)]); }); Is it possible to check by JS/jQuery whether a class named 'box' exists in the stylesheet? Thanks.

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• How to generalize a method call in Java (to avoid code duplication)

  - by dln385

  I have a process that needs to call a method and return its value. However, there are several different methods that this process may need to call, depending on the situation. If I could pass the method and its arguments to the process (like in Python), then this would be no problem. However, I don't know of any way to do this in Java. Here's a concrete example. (This example uses Apache ZooKeeper, but you don't need to know anything about ZooKeeper to understand the example.) The ZooKeeper object has several methods that will fail if the network goes down. In this case, I always want to retry the method. To make this easy, I made a "BetterZooKeeper" class that inherits the ZooKeeper class, and all of its methods automatically retry on failure. This is what the code looked like: public class BetterZooKeeper extends ZooKeeper { private void waitForReconnect() { // logic } @Override public Stat exists(String path, Watcher watcher) { while (true) { try { return super.exists(path, watcher); } catch (KeeperException e) { // We will retry. } waitForReconnect(); } } @Override public byte[] getData(String path, boolean watch, Stat stat) { while (true) { try { return super.getData(path, watch, stat); } catch (KeeperException e) { // We will retry. } waitForReconnect(); } } @Override public void delete(String path, int version) { while (true) { try { super.delete(path, version); return; } catch (KeeperException e) { // We will retry. } waitForReconnect(); } } } (In the actual program there is much more logic and many more methods that I took out of the example for simplicity.) We can see that I'm using the same retry logic, but the arguments, method call, and return type are all different for each of the methods. Here's what I did to eliminate the duplication of code: public class BetterZooKeeper extends ZooKeeper { private void waitForReconnect() { // logic } @Override public Stat exists(final String path, final Watcher watcher) { return new RetryableZooKeeperAction<Stat>() { @Override public Stat action() { return BetterZooKeeper.super.exists(path, watcher); } }.run(); } @Override public byte[] getData(final String path, final boolean watch, final Stat stat) { return new RetryableZooKeeperAction<byte[]>() { @Override public byte[] action() { return BetterZooKeeper.super.getData(path, watch, stat); } }.run(); } @Override public void delete(final String path, final int version) { new RetryableZooKeeperAction<Object>() { @Override public Object action() { BetterZooKeeper.super.delete(path, version); return null; } }.run(); return; } private abstract class RetryableZooKeeperAction<T> { public abstract T action(); public final T run() { while (true) { try { return action(); } catch (KeeperException e) { // We will retry. } waitForReconnect(); } } } } The RetryableZooKeeperAction is parameterized with the return type of the function. The run() method holds the retry logic, and the action() method is a placeholder for whichever ZooKeeper method needs to be run. Each of the public methods of BetterZooKeeper instantiates an anonymous inner class that is a subclass of the RetryableZooKeeperAction inner class, and it overrides the action() method. The local variables are (strangely enough) implicitly passed to the action() method, which is possible because they are final. In the end, this approach does work and it does eliminate the duplication of the retry logic. However, it has two major drawbacks: (1) it creates a new object every time a method is called, and (2) it's ugly and hardly readable. Also I had to workaround the 'delete' method which has a void return value. So, here is my question: is there a better way to do this in Java? This can't be a totally uncommon task, and other languages (like Python) make it easier by allowing methods to be passed. I suspect there might be a way to do this through reflection, but I haven't been able to wrap my head around it.

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• NHibernate: discriminator without common base class?

  - by joniba

  Is it possible to map two classes to the same property without them sharing a common base class? For example, a situation like this: class Rule { public virtual int SequenceNumber { get; set; } public virtual ICondition Condition { get; set; } } interface ICondition { } class ExpressionCondition : ICondition { public virtual string Expression { get; set; } } class ThresholdCondition : ICondition { public virtual int Threshold { get; set; } } I also cannot add some empty abstract class that both conditions inherit from because the two ICondition implementations exist in different domains that are not allowed to reference each other. (Please no responses telling me that this situation should not occur in the first place - I'm aware of it and it doesn't help me.)

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• How do I trigger a single event defined for a class of objects

  - by mrbinky3000

  I have a question. I have 8 buttons that have unique incrementing id's and a shared class. <button class="btnChapter" id="btnChapter_1" value="1">1</button> <button class="btnChapter" id="btnChapter_2" value="2">2</button> <button class="btnChapter" id="btnChapter_3" value="3">3</button> ... In order to prevent me from duplicating code, I bound a click event to the btnChapter class instead of binding an event individually to each button's ID. $('.btnChapter').click(function(){ .. do stuff .. }); How do I trigger() the click() event only for #btnChapter_2? The following doesn't seem to work. $('#btnChapter_2').click()

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• How to implement callback methods inside classes (PHP)

  - by sombe

  I need to use a class callback method on an array inside another method (the callback function belongs to the class). class Database { public function escape_string_for_db($string){ return mysql_real_escape_string($string); } public function escape_all_array($array){ return array_filter($array,"$this->escape_string_for_db"); } } Is this the right way to go about that? (I mean, in terms of the second parameter passed to array_filter)

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• XNA how to organize code with game components (managers)

  - by Johannes

  XNA If I have a button class, and I have a buttonManager class that manages what buttons to be drawn to the screen depending on what the current game state is (main menu, in game, etc), how do I organize my code so that when I click on a button, it takes the user to a different screen. (ex. options menu, ingame). To be more specific, if I were to put the check to see if the user clicks on the button within the buttonManager how would I have the game switch and run the actual game (which is in an entire different class)? Main gameclass buttonManager game component (adds buttons) Button class

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