Which classloader

But it isn't. It is the com. I've made sure that Thread. But this as you know has no effect. I even set it as the first thing i do in main due to some stuff I read and still, MyClass. How can I control which ClassLoader is used to load the class via their static Class. I believe if I can force MyClass. This reminds me of an article I read 10 years ago about the classloading arrangements in Java. It's still there on JavaWorld. The article won't answer your question directly, but it may help understand your problem.

You need to cause MyClass to be loaded through your custom class loader and trump the default class loading behavior, which is to first delegate class loading to the parent classloader and only attempt to load a class if that fails. Allowing MyClass to get loaded by a classloader other than yours will store a relationship from the instantiated class to that classloader via getClassLoader and cause Java to use that other classloader to try to discover any referenced classes found at compile time , effectively bypassing your custom class loader by virtue of the class loader hierarchy and the delegation model.

If MyClass is instead defined by your class loader, you get a second chance. You'll probably want to use a bootstrap approach as suggested by Thomas in a comment above to force a single entrypoint class to be loaded through your custom class loader, dragging all the others with it.

Also informative is this other JavaWorld article by the same guy, which warns you about the caveats of Class. That too may trip your classloading arrangements. I hope this helps and proves informative.

In any case, it sounds like a difficult solution that is easy to break as your code evolves. I think everyone gave good solid attempts at answering the problem. However, it turns out that I misdiagnosed the problem. We were confused why it was still using the ancient. Well, it turns out that on client machines, Java caches the. Even if your application changes and it redownloads your application, it still won't re-download the new.

If you run: javaws -uninstall On the client machine then that will clear the. Really sad that this was the problem. Hopefully, this saves someone else endless hours of frustration like it caused us.

Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. It is required to avoid loading the class multiple times. If the class is already loaded, it delegates the request to parent ClassLoader to load the class.

If the ClassLoader is not finding the class, it invokes the findClass method to look for the classes in the file system. The following diagram shows how ClassLoader loads class in Java using delegation. Suppose that we have an application specific class Demo. The request for loading of this class files transfers to Application ClassLoader.

It delegates to its parent Extension ClassLoader. Further, it delegates to Bootstrap ClassLoader. Bootstrap search that class in rt. If the class is found there, Extension ClassLoader loads that class. Application ClassLoader never loads that class.

Visibility principle states that child ClassLoader can see the class loaded by the parent ClassLoader, but vice versa is not true. It means if Application ClassLoader loads Demo. According to the uniqueness principle, a class loaded by the parent should not be loaded by Child ClassLoader again.

So, it is possible to write class loader which violates delegation and uniqueness principles and loads class by itself. It is useful when using class loader for loading classes dynamically. The following figure shows the output. Classes are statically loaded with "new" operator. Dynamic class loading invokes the functions of a class loader at run time by using Class.

The loadClass method loads only the class but does not initialize the object. While Class. For example, if you are using ClassLoader. The java. It throws ClassNotFoundException if the class is not found. In this example, java. String class is loaded. It prints the class name, package name, and the names of all available methods of String class.

We are using Class. The Class type contains meta-information about a class. For example, type of String. JavaTpoint offers too many high quality services. Mail us on [email protected] , to get more information about given services.

Please mail your requirement at [email protected] Duration: 1 week to 2 week. Java Main Method System. JavaScript Java vs. Kotlin Java vs. String" ; System. Instances of this newly defined class can be created using Class. The methods and constructors of objects created by a class loader may reference other classes. To determine the class es referred to, the Java virtual machine invokes the loadClass method of the class loader that originally created the class.

For example, an application could create a network class loader to download class files from a server. The network class loader subclass must define the methods findClass and loadClassData to load a class from the network. Once it has downloaded the bytes that make up the class, it should use the method defineClass to create a class instance. Examples of valid class names include: "java. String" "javax. Method Summary Methods Modifier and Type Method and Description void clearAssertionStatus Sets the default assertion status for this class loader to false and discards any package defaults or class assertion status settings associated with the class loader.

ClassLoader getParent Returns the parent class loader for delegation. Methods inherited from class java. Object clone , equals , finalize , getClass , hashCode , notify , notifyAll , toString , wait , wait , wait Constructor Detail ClassLoader protected ClassLoader ClassLoader parent Creates a new class loader using the specified parent class loader for delegation. If there is a security manager, its checkCreateClassLoader method is invoked. This may result in a security exception.

Invoke findLoadedClass String to check if the class has already been loaded. Invoke the loadClass method on the parent class loader. If the parent is null the class loader built-in to the virtual machine is used, instead. Invoke the findClass String method to find the class. If the class was found using the above steps, and the resolve flag is true, this method will then invoke the resolveClass Class method on the resulting Class object.

Subclasses of ClassLoader are encouraged to override findClass String , rather than this method. Unless overridden, this method synchronizes on the result of getClassLoadingLock method during the entire class loading process.

For backward compatibility, the default implementation of this method behaves as follows. If this ClassLoader object is registered as parallel capable, the method returns a dedicated object associated with the specified class name. Otherwise, the method returns this ClassLoader object.

This method assigns a default ProtectionDomain to the newly defined class. The ProtectionDomain is effectively granted the same set of permissions returned when Policy. The default domain is created on the first invocation of defineClass , and re-used on subsequent invocations. To assign a specific ProtectionDomain to the class, use the defineClass method that takes a ProtectionDomain as one of its arguments. The first class defined in a package determines the exact set of certificates that all subsequent classes defined in that package must contain.

The set of certificates for a class is obtained from the CodeSource within the ProtectionDomain of the class. Any classes added to that package must contain the same set of certificates or a SecurityException will be thrown. Note that if name is null , this check is not performed.

You should always pass in the binary name of the class you are defining as well as the bytes. This ensures that the class you are defining is indeed the class you think it is. The specified name cannot begin with " java. If name is not null , it must be equal to the binary name of the class specified by the byte array " b ", otherwise a NoClassDefFoundError will be thrown.

The rules about the first class defined in a package determining the set of certificates for the package, and the restrictions on class names are identical to those specified in the documentation for defineClass String, byte[], int, int, ProtectionDomain. An invocation of this method of the form cl. The bytes from positions b. Returns: The Class object created from the data, and optional ProtectionDomain. Throws: ClassFormatError - If the data did not contain a valid class.

NoClassDefFoundError - If name is not equal to the binary name of the class specified by b SecurityException - If an attempt is made to add this class to a package that contains classes that were signed by a different set of certificates than this class, or if name begins with " java. Since: 1. This misleadingly named method may be used by a class loader to link a class.

If the class c has already been linked, then this method simply returns. This method loads the class through the system class loader see getSystemClassLoader. The Class object returned might have more than one ClassLoader associated with it. Subclasses of ClassLoader need not usually invoke this method, because most class loaders need to override just findClass String. This method will first search the parent class loader for the resource; if the parent is null the path of the class loader built-in to the virtual machine is searched.

That failing, this method will invoke findResource String to find the resource. The search order is described in the documentation for getResource String.