org.jboss.modules
Class ConcurrentClassLoader

java.lang.Object
  java.lang.ClassLoader
      java.security.SecureClassLoader
          org.jboss.modules.ConcurrentClassLoader

Direct Known Subclasses:

ModuleClassLoader

public abstract class ConcurrentClassLoader
extends SecureClassLoader

A classloader which can delegate to multiple other classloaders without risk of deadlock. A concurrent class loader should only ever be delegated to by another concurrent class loader; however a concurrent class loader may delegate to a standard hierarchical class loader. In other words, holding a lock on another class loader while invoking a method on this class loader may cause an unexpected deadlock.

Author:

David M. Lloyd

Field Summary

protected static Enumeration<URL>

EMPTY_ENUMERATION An empty enumeration, for subclasses to use if desired.

Constructor Summary

protected	ConcurrentClassLoader() Construct a new instance.
protected	ConcurrentClassLoader(ConcurrentClassLoader parent) Construct a new instance with the given parent class loader, which must be a concurrent class loader.

Method Summary

protected Class<?>	findClass(String className) Implementation of ClassLoader.findClass(String).
protected Class<?>	findClass(String className, boolean exportsOnly, boolean resolve) Find a class, possibly delegating to other loader(s).
protected URL	findResource(String name) Never used.
protected URL	findResource(String name, boolean exportsOnly) Find the resource with the given name and exported status.
protected InputStream	findResourceAsStream(String name, boolean exportsOnly) Finds the resource with the given name and exported status, returning the resource content as a stream.
protected Enumeration<URL>	findResources(String name) Never used.
protected Enumeration<URL>	findResources(String name, boolean exportsOnly) Finds the resources with the given name and exported status.
URL	getResource(String name) Finds the resource with the given name.
InputStream	getResourceAsStream(String name) Returns an input stream for reading the specified resource.
Enumeration<URL>	getResources(String name) Finds all available resources with the given name.
Class<?>	loadClass(String className) Loads the class with the specified binary name.
Class<?>	loadClass(String className, boolean resolve) Loads the class with the specified binary name.
Class<?>	loadExportedClass(String className) Same as loadClass(String), except only exported classes will be considered.
Class<?>	loadExportedClass(String className, boolean resolve) Same as loadClass(String,boolean), except only exported classes will be considered.

Methods inherited from class java.security.SecureClassLoader

defineClass, defineClass, getPermissions

Methods inherited from class java.lang.ClassLoader

clearAssertionStatus, defineClass, defineClass, defineClass, defineClass, definePackage, findLibrary, findLoadedClass, findSystemClass, getPackage, getPackages, getParent, getSystemClassLoader, getSystemResource, getSystemResourceAsStream, getSystemResources, 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

EMPTY_ENUMERATION

protected static final Enumeration<URL> EMPTY_ENUMERATION

An empty enumeration, for subclasses to use if desired.

Constructor Detail

ConcurrentClassLoader

protected ConcurrentClassLoader(ConcurrentClassLoader parent)

Construct a new instance with the given parent class loader, which must be a concurrent class loader.

Parameters:

parent - the parent class loader

ConcurrentClassLoader

protected ConcurrentClassLoader()

Construct a new instance.

Method Detail

loadClass

public final Class<?> loadClass(String className)
                         throws ClassNotFoundException

Loads the class with the specified binary name. Equivalent to calling loadClass(className, false).

Overrides:

loadClass in class ClassLoader

Parameters:

className - The binary name of the class

Returns:

the resulting Class instance

Throws:

ClassNotFoundException - if the class was not found

loadClass

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

Loads the class with the specified binary name.

Overrides:

loadClass in class ClassLoader

Parameters:

className - The binary name of the class

resolve - true if the class should be linked after loading

Returns:

the resulting Class instance

Throws:

ClassNotFoundException

loadExportedClass

public final Class<?> loadExportedClass(String className)
                                 throws ClassNotFoundException

Same as loadClass(String), except only exported classes will be considered.

Parameters:

className - the class name

Returns:

the class

Throws:

ClassNotFoundException - if the class isn't found

loadExportedClass

public final Class<?> loadExportedClass(String className,
                                        boolean resolve)
                                 throws ClassNotFoundException

Same as loadClass(String,boolean), except only exported classes will be considered.

Parameters:

className - the class name

resolve - true if the class should be linked after loading

Returns:

the class

Throws:

ClassNotFoundException - if the class isn't found

findClass

protected Class<?> findClass(String className,
                             boolean exportsOnly,
                             boolean resolve)
                      throws ClassNotFoundException

Find a class, possibly delegating to other loader(s). This method should never synchronize across a delegation method call of any sort. The default implementation always throws ClassNotFoundException.

Parameters:

className - the class name

exportsOnly - true if only exported classes should be considered

resolve - true if the class should be linked after loading

Returns:

the class

Throws:

ClassNotFoundException - if the class is not found

findClass

protected final Class<?> findClass(String className)
                            throws ClassNotFoundException

Implementation of ClassLoader.findClass(String).

Overrides:

findClass in class ClassLoader

Parameters:

className - the class name

Returns:

the result of findClass(className, false, false)

Throws:

ClassNotFoundException

getResource

public final URL getResource(String name)

Finds the resource with the given name. The name of a resource is a '/'-separated path name that identifies the resource. If the resource name starts with "java/" then the parent class loader is used. Otherwise, this method delegates to findResource(String, boolean).

Overrides:

getResource in class ClassLoader

Parameters:

name - the name of the resource

Returns:

the resource URL, or null if no such resource exists or the invoker does not have adequate permission to access it

getResources

public final Enumeration<URL> getResources(String name)
                                    throws IOException

Finds all available resources with the given name.

Overrides:

getResources in class ClassLoader

Parameters:

name - the resource name

Returns:

an enumeration over all the resource URLs; if no resources could be found, the enumeration will be empty

Throws:

IOException - if an I/O error occurs

See Also:

getResource(String)

findResource

protected URL findResource(String name,
                           boolean exportsOnly)

Find the resource with the given name and exported status.

Parameters:

name - the resource name

exportsOnly - true to consider only exported resources or false to consider all resources

Returns:

the resource URL

See Also:

getResource(String)

findResource

protected final URL findResource(String name)

Never used. ClassLoader.getResource(String) and related methods can cause a loop condition when this method is implemented; use findResource(String, boolean) instead.

Overrides:

findResource in class ClassLoader

Parameters:

name - ignored

Returns:

null always

findResources

protected Enumeration<URL> findResources(String name,
                                         boolean exportsOnly)
                                  throws IOException

Finds the resources with the given name and exported status.

Parameters:

name - the resource name

exportsOnly - true to consider only exported resources or false to consider all resources

Returns:

the resource enumeration

Throws:

IOException - if an I/O error occurs

See Also:

getResources(String)

findResources

protected final Enumeration<URL> findResources(String name)

Never used. ClassLoader.getResources(String) and related methods can cause a loop condition when this method is implemented; use findResources(String, boolean) instead. By default, returns an empty enumeration.

Overrides:

findResources in class ClassLoader

Parameters:

name - ignored

Returns:

an empty enumeration

findResourceAsStream

protected InputStream findResourceAsStream(String name,
                                           boolean exportsOnly)

Finds the resource with the given name and exported status, returning the resource content as a stream.

Parameters:

name - the resource name

exportsOnly - true to consider only exported resources or false to consider all resources

Returns:

the resource stream, or null if the resource is not found

getResourceAsStream

public final InputStream getResourceAsStream(String name)

Returns an input stream for reading the specified resource. If the resource starts with "java/", then this method delegates to the parent class loader. Otherwise, this method delegates to findResourceAsStream(String, boolean).

Overrides:

getResourceAsStream in class ClassLoader

Parameters:

name - the resource name

Returns:

the resource stream, or null if the resource is not found