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org.apache.bcel.util
Class ClassLoader  view ClassLoader download ClassLoader.java

java.lang.Object
  extended byjava.lang.ClassLoader
      extended byorg.apache.bcel.util.ClassLoader

public class ClassLoader
extends java.lang.ClassLoader

Drop in replacement for the standard class loader of the JVM. You can use it in conjunction with the JavaWrapper to dynamically modify/create classes as they're requested.

This class loader recognizes special requests in a distinct format, i.e., when the name of the requested class contains with "$$BCEL$$" it calls the createClass() method with that name (everything bevor the $$BCEL$$ is considered to be the package name. You can subclass the class loader and override that method. "Normal" classes class can be modified by overriding the modifyClass() method which is called just before defineClass().

There may be a number of packages where you have to use the default class loader (which may also be faster). You can define the set of packages where to use the system class loader in the constructor. The default value contains "java.", "sun.", "javax."

Version:
$Id: ClassLoader.java 386056 2006-03-15 11:31:56Z tcurdt $

Nested Class Summary
 
Nested classes inherited from class java.lang.ClassLoader
 
Field Summary
private  java.util.Hashtable classes
           
static java.lang.String[] DEFAULT_IGNORED_PACKAGES
           
private  java.lang.String[] ignored_packages
           
private  Repository repository
           
 
Fields inherited from class java.lang.ClassLoader
 
Constructor Summary
ClassLoader()
          Ignored packages are by default ( "java.", "sun.", "javax."), i.e.
ClassLoader(java.lang.ClassLoader deferTo)
           
ClassLoader(java.lang.ClassLoader deferTo, java.lang.String[] ignored_packages)
           
ClassLoader(java.lang.String[] ignored_packages)
           
 
Method Summary
protected  org.apache.bcel.classfile.JavaClass createClass(java.lang.String class_name)
          Override this method to create you own classes on the fly.
protected  java.lang.Class loadClass(java.lang.String class_name, boolean resolve)
          Load a class using this ClassLoader or its parent, possibly resolving it as well using resolveClass().
protected  org.apache.bcel.classfile.JavaClass modifyClass(org.apache.bcel.classfile.JavaClass clazz)
          Override this method if you want to alter a class before it gets actually loaded.
 
Methods inherited from class java.lang.ClassLoader
clearAssertionStatus, defineClass, defineClass, defineClass, defineClass, definePackage, findClass, findLibrary, findLoadedClass, findResource, findResources, findSystemClass, getPackage, getPackages, getParent, getResource, getResourceAsStream, getResources, getSystemClassLoader, getSystemResource, getSystemResourceAsStream, getSystemResources, loadClass, resolveClass, setClassAssertionStatus, setDefaultAssertionStatus, setPackageAssertionStatus, setSigners
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

DEFAULT_IGNORED_PACKAGES

public static final java.lang.String[] DEFAULT_IGNORED_PACKAGES

classes

private java.util.Hashtable classes

ignored_packages

private java.lang.String[] ignored_packages

repository

private Repository repository
Constructor Detail

ClassLoader

public ClassLoader()
Ignored packages are by default ( "java.", "sun.", "javax."), i.e. loaded by system class loader


ClassLoader

public ClassLoader(java.lang.ClassLoader deferTo)

ClassLoader

public ClassLoader(java.lang.String[] ignored_packages)

ClassLoader

public ClassLoader(java.lang.ClassLoader deferTo,
                   java.lang.String[] ignored_packages)
Method Detail

loadClass

protected java.lang.Class loadClass(java.lang.String class_name,
                                    boolean resolve)
                             throws java.lang.ClassNotFoundException
Description copied from class: java.lang.ClassLoader
Load a class using this ClassLoader or its parent, possibly resolving it as well using resolveClass(). It first tries to find out if the class has already been loaded through this classloader by calling findLoadedClass(). Then it calls loadClass() on the parent classloader (or when there is no parent it uses the VM bootclassloader). If the class is still not loaded it tries to create a new class by calling findClass(). Finally when resolve is true it also calls resolveClass() on the newly loaded class.

Subclasses should not override this method but should override findClass() which is called by this method.


modifyClass

protected org.apache.bcel.classfile.JavaClass modifyClass(org.apache.bcel.classfile.JavaClass clazz)
Override this method if you want to alter a class before it gets actually loaded. Does nothing by default.


createClass

protected org.apache.bcel.classfile.JavaClass createClass(java.lang.String class_name)
Override this method to create you own classes on the fly. The name contains the special token $$BCEL$$. Everything before that token is consddered to be a package name. You can encode you own arguments into the subsequent string. You must regard however not to use any "illegal" characters, i.e., characters that may not appear in a Java class name too
The default implementation interprets the string as a encoded compressed Java class, unpacks and decodes it with the Utility.decode() method, and parses the resulting byte array and returns the resulting JavaClass object.