org.fabric3.spi.classloader

Class MultiParentClassLoader

java.lang.Object

java.lang.ClassLoader

java.security.SecureClassLoader

java.net.URLClassLoader

org.fabric3.api.host.classloader.DelegatingResourceClassLoader

org.fabric3.spi.classloader.MultiParentClassLoader

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable

Direct Known Subclasses:

BytecodeClassLoader

public class MultiParentClassLoader
extends org.fabric3.api.host.classloader.DelegatingResourceClassLoader

A classloader implementation that supports a multi-parent hierarchy and extension resolution mechanism. Class resolution is performed in the following order: - Parents are searched. Parents will delegate to their classloader hierarchy. - If a resource is not found, the current classloader is searched. - If a resource is not found, extension classloaders are searched. Extension classloaders will not delegate to their classloader hierarchy. The extension mechanism allows classes to be dynamically loaded via Class.forName() and ClassLoader.loadClass(). This is used to accommodate contributions and libraries that rely on Java reflection to add additional capabilities provided by another contribution. Since resolution is performed dynamically, cycles between classloaders are supported where one classloader is a parent of the other and the former is an extension of the latter. Each classloader has a name that can be used to reference it in the runtime.

Constructor Summary

Constructors

Constructor and Description
MultiParentClassLoader(java.net.URI name, java.lang.ClassLoader parent) Constructs a classloader with a name and a single parent.
MultiParentClassLoader(java.net.URI name, java.net.URL[] urls, java.lang.ClassLoader parent) Constructs a classloader with a name, a set of resources and a single parent.

Method Summary

Modifier and Type	Method and Description
void	addExtensionClassLoader(MultiParentClassLoader classloader) Adds a classloader as an extension of this classloader.
void	addParent(java.lang.ClassLoader parent) Add a parent to this classloader.
void	addURL(java.net.URL url) Add a resource URL to this classloader's classpath.
protected java.lang.Class<?>	findClass(java.lang.String string)
java.net.URL	findExtensionResource(java.lang.String name) Resolves a resource only in this classloader.
java.util.Enumeration<java.net.URL>	findExtensionResources(java.lang.String name)
java.net.URL	findResource(java.lang.String name)
java.util.Enumeration<java.net.URL>	findResources(java.lang.String name)
java.net.URI	getName() Returns the name of this classloader.
java.util.List<java.lang.ClassLoader>	getParents() Returns the parent classLoaders.
protected java.lang.Class<?>	loadClass(java.lang.String name, boolean resolve)
void	removeExtensionClassLoader(MultiParentClassLoader classloader) Removes a classloader as an extension of this classloader.
java.lang.String	toString()

Methods inherited from class org.fabric3.api.host.classloader.DelegatingResourceClassLoader

getResource, getResources

Methods inherited from class java.net.URLClassLoader

close, definePackage, getPermissions, getResourceAsStream, 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, getClassLoadingLock, getPackage, getPackages, getParent, getSystemClassLoader, getSystemResource, getSystemResourceAsStream, getSystemResources, loadClass, registerAsParallelCapable, resolveClass, setClassAssertionStatus, setDefaultAssertionStatus, setPackageAssertionStatus, setSigners

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

MultiParentClassLoader

public MultiParentClassLoader(java.net.URI name,
                              java.lang.ClassLoader parent)

Constructs a classloader with a name and a single parent.

Parameters:

name - a name used to identify this classloader

parent - the initial parent

MultiParentClassLoader

public MultiParentClassLoader(java.net.URI name,
                              java.net.URL[] urls,
                              java.lang.ClassLoader parent)

Constructs a classloader with a name, a set of resources and a single parent.

Parameters:

name - a name used to identify this classloader

urls - the URLs from which to load classes and resources

parent - the initial parent

Method Detail

addURL

public void addURL(java.net.URL url)

Add a resource URL to this classloader's classpath. The "createClassLoader" RuntimePermission is required.

Overrides:

addURL in class java.net.URLClassLoader

Parameters:

url - an additional URL from which to load classes and resources

addParent

public void addParent(java.lang.ClassLoader parent)

Add a parent to this classloader. The "createClassLoader" RuntimePermission is required.

Parameters:

parent - an additional parent classloader

getName

public java.net.URI getName()

Returns the name of this classloader.

Returns:

the name of this classloader

getParents

public java.util.List<java.lang.ClassLoader> getParents()

Returns the parent classLoaders. The "getClassLoader" RuntimePermission is required.

Returns:

the parent classLoaders

addExtensionClassLoader

public void addExtensionClassLoader(MultiParentClassLoader classloader)

Adds a classloader as an extension of this classloader.

Parameters:

classloader - the extension classloader.

removeExtensionClassLoader

public void removeExtensionClassLoader(MultiParentClassLoader classloader)

Removes a classloader as an extension of this classloader.

Parameters:

classloader - the extension classloader.

findExtensionResource

public java.net.URL findExtensionResource(java.lang.String name)

Resolves a resource only in this classloader. Note this method does not delegate to parent classloaders.

Parameters:

name - the resource name

Returns:

the resource URL or null if not found

findExtensionResources

public java.util.Enumeration<java.net.URL> findExtensionResources(java.lang.String name)
                                                           throws java.io.IOException

Throws:

java.io.IOException

loadClass

protected java.lang.Class<?> loadClass(java.lang.String name,
                                       boolean resolve)
                                throws java.lang.ClassNotFoundException

Overrides:

loadClass in class java.lang.ClassLoader

Throws:

java.lang.ClassNotFoundException

findClass

protected java.lang.Class<?> findClass(java.lang.String string)
                                throws java.lang.ClassNotFoundException

Overrides:

findClass in class java.net.URLClassLoader

Throws:

java.lang.ClassNotFoundException

findResource

public java.net.URL findResource(java.lang.String name)

Overrides:

findResource in class java.net.URLClassLoader

findResources

public java.util.Enumeration<java.net.URL> findResources(java.lang.String name)
                                                  throws java.io.IOException

Overrides:

findResources in class java.net.URLClassLoader

Throws:

java.io.IOException

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object