Apache Commons BCEL 6.8.2 · org.apache.bcel.util.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."

Modifier and Type	Field and Description
private static final String	BCEL_TOKEN
private final Hashtable<String, Class<?>>	classes Hides java.lang.ClassLoader.classes.
public static final String[]	DEFAULT_IGNORED_PACKAGES
private final String[]	ignoredPackages
private Repository	repository

Access	Constructor and Description
public	ClassLoader() Ignored packages are by default ( "java.", "sun.", "javax."), i.e. loaded by system class loader
public	ClassLoader(final ClassLoader delegate class loader to use for ignored packages deferTo)
public	ClassLoader(final ClassLoader delegate class loader to use for ignored packages deferTo, final String[] classes contained in these packages will be loaded with the system class loader ignoredPackages)
public	ClassLoader(final String[] classes contained in these packages will be loaded with the system class loader ignoredPackages)

Method Summary

Modifier and Type	Method and Description
protected JavaClass	createClass(final String compressed byte code with "$$BCEL$$" in it className) Override this method to create you own classes on the fly.
protected Class<?>	loadClass(final String The binary name of the class className, final boolean If `true` then resolve the class resolve) Overrides java.lang.ClassLoader.loadClass. Loads the class with the specified binary name.
protected JavaClass	modifyClass(final JavaClass clazz) Override this method if you want to alter a class before it gets actually loaded.

Field Detail

BCEL_TOKEN	back to summary
private static final String BCEL_TOKEN

classes	back to summary
private final Hashtable<String, Class<?>> classes Hides java.lang.ClassLoader.classes.

DEFAULT_IGNORED_PACKAGES	back to summary
public static final String[] DEFAULT_IGNORED_PACKAGES

ignoredPackages	back to summary
private final String[] ignoredPackages

repository	back to summary
private Repository repository

Constructor Detail

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

ClassLoader	back to summary
public ClassLoader(final ClassLoader deferTo) Parameters deferTo:ClassLoader delegate class loader to use for ignored packages

ClassLoader	back to summary
public ClassLoader(final ClassLoader deferTo, final String[] ignoredPackages) Parameters deferTo:ClassLoader delegate class loader to use for ignored packages ignoredPackages:String[] classes contained in these packages will be loaded with the system class loader

ClassLoader	back to summary
public ClassLoader(final String[] ignoredPackages) Parameters ignoredPackages:String[] classes contained in these packages will be loaded with the system class loader

Method Detail

createClass	back to summary
protected JavaClass createClass(final String className) Override this method to create you own classes on the fly. The name contains the special token $$BCEL$$. Everything before that token is considered to be a package name. You can encode your own arguments into the subsequent string. You must ensure 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. Parameters className:String compressed byte code with "$$BCEL$$" in it

createClass

back to summary

protected JavaClass createClass(final String className)

Override this method to create you own classes on the fly. The name contains the special token $$BCEL$$. Everything before that token is considered to be a package name. You can encode your own arguments into the subsequent string. You must ensure 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.

Parameters

className:String: compressed byte code with "$$BCEL$$" in it

loadClass back to summary

loadClass	back to summary
protected Class<?> loadClass(final String className, final boolean resolve) throws ClassNotFoundException Overrides java.lang.ClassLoader.loadClass. Doc from java.lang.ClassLoader.loadClass. Loads the class with the specified binary name. The default implementation of this method searches for classes in the following order: 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 into 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. Parameters className:String The binary name of the class resolve:boolean If `true` then resolve the class Returns:Class<?> The resulting `Class` object Annotations @Override Exceptions ClassNotFoundException: If the class could not be found

protected Class<?> loadClass(final String className, final boolean resolve) throws ClassNotFoundException

Overrides java.lang.ClassLoader.loadClass.

Doc from java.lang.ClassLoader.loadClass.

Loads the class with the specified binary name. The default implementation of this method searches for classes in the following order:

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 into 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.

Parameters

className:String: The binary name of the class
resolve:boolean: If true then resolve the class

Returns:Class<?>

The resulting Class object

Annotations

@Override

Exceptions

ClassNotFoundException:: If the class could not be found

modifyClass	back to summary
protected JavaClass modifyClass(final JavaClass clazz) Override this method if you want to alter a class before it gets actually loaded. Does nothing by default.

public Class ClassLoader

Field Summary

Constructor Summary

Method Summary

Field Detail

Constructor Detail

Method Detail