org.apache.commons.javaflow
Class ContinuationClassLoader

java.lang.Object
  java.lang.ClassLoader
      java.security.SecureClassLoader
          java.net.URLClassLoader
              org.apache.commons.javaflow.ContinuationClassLoader

public final class ContinuationClassLoader
extends URLClassLoader

URLClassLoader with bytecode instrumentation for javaflow.

This class loader is useful where the application can set up multiple class loaders (such as in a container environment, ClassWorlds, or Forehead) and when you can isolate the continuation-enabled portion of your application into a separate jar file.

Constructor Summary

ContinuationClassLoader(URL[] urls, ClassLoader parent)

ContinuationClassLoader(URL[] urls, ClassLoader parent, ResourceTransformer transformer)
Creates a classloader by using the classpath given.

Method Summary

void	addLoaderPackageRoot(String packageRoot) Adds a package root to the list of packages which must be loaded using this loader.
void	addSystemPackageRoot(String packageRoot) Adds a package root to the list of packages which must be loaded on the parent loader.
protected Class<?>	defineClassFromData(byte[] classData, String classname) Define a class given its bytes
Class<?>	findClass(String name) Searches for and load a class on the classpath of this class loader.
Class<?>	forceLoadClass(String classname) Loads a class through this class loader even if that class is available on the parent classpath.
URL	getResource(String name) Finds the resource with the given name.
protected Class<?>	loadClass(String classname, boolean resolve) Loads a class with this class loader.
void	setIsolated(boolean isolated) Sets whether this classloader should run in isolated mode.
void	setParentFirst(boolean parentFirst) Control whether class lookup is delegated to the parent loader first or after this loader.

Methods inherited from class java.net.URLClassLoader

addURL, definePackage, findResource, findResources, getPermissions, getURLs, newInstance, newInstance

Methods inherited from class java.security.SecureClassLoader

defineClass, defineClass

Methods inherited from class java.lang.ClassLoader

clearAssertionStatus, defineClass, defineClass, defineClass, defineClass, definePackage, findLibrary, findLoadedClass, findSystemClass, getPackage, getPackages, getParent, 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

Constructor Detail

ContinuationClassLoader

public ContinuationClassLoader(URL[] urls,
                               ClassLoader parent,
                               ResourceTransformer transformer)

Creates a classloader by using the classpath given.

Parameters:

urls - The URLs from which to load classes and resources

parent - The parent classloader to which unsatisfied loading attempts are delegated. May be null, in which case the system classloader is used as the parent.

transformer - This transformer is used to perform the byte-code enhancement. May not be null.

ContinuationClassLoader

public ContinuationClassLoader(URL[] urls,
                               ClassLoader parent)

Method Detail

setParentFirst

public void setParentFirst(boolean parentFirst)

Control whether class lookup is delegated to the parent loader first or after this loader. Use with extreme caution. Setting this to false violates the class loader hierarchy and can lead to Linkage errors

Parameters:

parentFirst - if true, delegate initial class search to the parent classloader.

setIsolated

public void setIsolated(boolean isolated)

Sets whether this classloader should run in isolated mode. In isolated mode, classes not found on the given classpath will not be referred to the parent class loader but will cause a ClassNotFoundException.

Parameters:

isolated - Whether or not this classloader should run in isolated mode.

addSystemPackageRoot

public void addSystemPackageRoot(String packageRoot)

Adds a package root to the list of packages which must be loaded on the parent loader. All subpackages are also included.

Parameters:

packageRoot - The root of all packages to be included. Should not be null.

addLoaderPackageRoot

public void addLoaderPackageRoot(String packageRoot)

Adds a package root to the list of packages which must be loaded using this loader. All subpackages are also included.

Parameters:

packageRoot - The root of all packages to be included. Should not be null.

forceLoadClass

public Class<?> forceLoadClass(String classname)
                        throws ClassNotFoundException

Loads a class through this class loader even if that class is available on the parent classpath. This ensures that any classes which are loaded by the returned class will use this classloader.

Parameters:

classname - The name of the class to be loaded. Must not be null.

Returns:

the required Class object

Throws:

ClassNotFoundException - if the requested class does not exist on this loader's classpath.

loadClass

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

Loads a class with this class loader. This class attempts to load the class in an order determined by whether or not the class matches the system/loader package lists, with the loader package list taking priority. If the classloader is in isolated mode, failure to load the class in this loader will result in a ClassNotFoundException.

Overrides:

loadClass in class ClassLoader

Parameters:

classname - The name of the class to be loaded. Must not be null.

resolve - true if all classes upon which this class depends are to be loaded.

Returns:

the required Class object

Throws:

ClassNotFoundException - if the requested class does not exist on the system classpath (when not in isolated mode) or this loader's classpath.

defineClassFromData

protected Class<?> defineClassFromData(byte[] classData,
                                       String classname)

Define a class given its bytes

Parameters:

classData - the bytecode data for the class

classname - the name of the class

Returns:

the Class instance created from the given data

findClass

public Class<?> findClass(String name)
                   throws ClassNotFoundException

Searches for and load a class on the classpath of this class loader.

Overrides:

findClass in class URLClassLoader

Parameters:

name - The name of the class to be loaded. Must not be null.

Returns:

the required Class object

Throws:

ClassNotFoundException - if the requested class does not exist on this loader's classpath.

getResource

public URL getResource(String name)

Finds the resource with the given name. A resource is some data (images, audio, text, etc) that can be accessed by class code in a way that is independent of the location of the code.

Overrides:

getResource in class ClassLoader

Parameters:

name - The name of the resource for which a stream is required. Must not be null.

Returns:

a URL for reading the resource, or null if the resource could not be found or the caller doesn't have adequate privileges to get the resource.