org.xwiki.classloader
Class URIClassLoader

java.lang.Object
  java.lang.ClassLoader
      java.security.SecureClassLoader
          java.net.URLClassLoader
              org.xwiki.classloader.ExtendedURLClassLoader
                  org.xwiki.classloader.URIClassLoader

Direct Known Subclasses:

NamespaceURLClassLoader

public class URIClassLoader
extends ExtendedURLClassLoader

Equivalent of java.net.URLClassloader but without bugs related to ill-formed URLs and with customizable JAR caching policy. The standard URLClassLoader accepts URLs containing spaces and other characters which are forbidden in the URI syntax, according to the RFC 2396. As a workaround to this problem, Java escapes and un-escapes URLs in various arbitrary places; however, this is inconsistent and leads to numerous problems with URLs referring to local files with spaces in the path. SUN acknowledges the problem, but refuses to modify the behavior for compatibility reasons; see Java Bug Parade 4273532, 4466485.

Additionally, the JAR caching policy used by URLClassLoader is system-wide and inflexible: once downloaded JAR files are never re-downloaded, even if one creates a fresh instance of the class loader that happens to have the same URL in its search path. In fact, that policy is a security vulnerability: it is possible to crash any URL class loader, thus affecting potentially separate part of the system, by creating URL connection to one of the URLs of that class loader search path and closing the associated JAR file. See Java Bug Parade 4405789, 4388666, 4639900.

This class avoids these problems by 1) using URIs instead of URLs for the search path (thus enforcing strict syntax conformance and defining precise escaping semantics), and 2) using custom URLStreamHandler which ensures per-classloader JAR caching policy.

Originally written by Dawid Kurzyniec and released to the public domain, as explained at http://creativecommons.org/licenses/publicdomain

Source: http://dcl.mathcs.emory.edu/php/loadPage.php?content=util/features.html#classloading

Since:

2.0.1

Version:

$Id: 2688ff01039a9dfef53380d1f7efbdcb4415884b $d

See Also:

File.toURL(), File.toURI()

Constructor Summary

URIClassLoader(URI[] uris)
Creates URIClassLoader with the specified search path.

URIClassLoader(URI[] uris, ClassLoader parent)
Creates URIClassLoader with the specified search path and parent class loader.

URIClassLoader(URI[] uris, ClassLoader parent, URLStreamHandlerFactory handlerFactory)
Creates URIClassLoader with the specified search path and parent class loader.

URIClassLoader(URI[] uris, URLStreamHandlerFactory handlerFactory)
Creates URIClassLoader with the specified search path.

Method Summary

protected void	addURI(URI uri) Add specified URI at the end of the search path.
void	addURL(URL url) Add specified URL at the end of the search path.
void	addURLs(List<URL> urls) Add specified URLs at the end of the search path.
protected Class<?>	defineClass(String name, edu.emory.mathcs.util.classloader.ResourceHandle h)
protected Class<?>	findClass(String name) Finds and loads the class with the specified name.
protected String	findLibrary(String libname) Returns the absolute path name of a native library.
URL	findResource(String name) Finds the resource with the specified name.
Enumeration<URL>	findResources(String name) Returns an Enumeration of URLs representing all of the resources having the specified name.
protected edu.emory.mathcs.util.classloader.ResourceHandle	getClassHandle(String name) Finds the ResourceHandle object for the class with the specified name.
protected edu.emory.mathcs.util.classloader.ResourceHandle	getLibraryHandle(String name) Finds the ResourceHandle object for the native library with the specified name.
protected edu.emory.mathcs.util.classloader.ResourceHandle	getResourceHandle(String name) Finds the ResourceHandle object for the resource with the specified name.
protected Enumeration<edu.emory.mathcs.util.classloader.ResourceHandle>	getResourceHandles(String name) Returns an Enumeration of ResourceHandle objects representing all of the resources having the specified name.
URL[]	getURLs()

Methods inherited from class java.net.URLClassLoader

definePackage, getPermissions, newInstance, newInstance

Methods inherited from class java.security.SecureClassLoader

defineClass, defineClass

Methods inherited from class java.lang.ClassLoader

clearAssertionStatus, defineClass, defineClass, defineClass, defineClass, definePackage, findLoadedClass, findSystemClass, getPackage, getPackages, getParent, getResource, getResourceAsStream, getResources, getSystemClassLoader, getSystemResource, getSystemResourceAsStream, getSystemResources, loadClass, 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

URIClassLoader

public URIClassLoader(URI[] uris)

Creates URIClassLoader with the specified search path.

Parameters:

uris - the search path

URIClassLoader

public URIClassLoader(URI[] uris,
                      URLStreamHandlerFactory handlerFactory)

Creates URIClassLoader with the specified search path.

Parameters:

uris - the search path

handlerFactory - the URLStreamHandlerFactory to use when creating URLs

URIClassLoader

public URIClassLoader(URI[] uris,
                      ClassLoader parent)

Creates URIClassLoader with the specified search path and parent class loader.

Parameters:

uris - the search path

parent - the parent class loader

URIClassLoader

public URIClassLoader(URI[] uris,
                      ClassLoader parent,
                      URLStreamHandlerFactory handlerFactory)

Creates URIClassLoader with the specified search path and parent class loader.

Parameters:

uris - the search path

parent - the parent class loader.

handlerFactory - the URLStreamHandlerFactory to use when creating URLs

Method Detail

addURI

protected void addURI(URI uri)

Add specified URI at the end of the search path.

Parameters:

uri - the URI to add

addURL

public void addURL(URL url)

Add specified URL at the end of the search path.

Overrides:

addURL in class ExtendedURLClassLoader

Parameters:

url - the URL to add

addURLs

public void addURLs(List<URL> urls)

Add specified URLs at the end of the search path.

Overrides:

addURLs in class ExtendedURLClassLoader

Parameters:

urls - the URLs to add

getURLs

public URL[] getURLs()

Overrides:

getURLs in class URLClassLoader

findClass

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

Finds and loads the class with the specified name.

Overrides:

findClass in class URLClassLoader

Parameters:

name - the name of the class

Returns:

the resulting class

Throws:

ClassNotFoundException - if the class could not be found

defineClass

protected Class<?> defineClass(String name,
                               edu.emory.mathcs.util.classloader.ResourceHandle h)
                        throws IOException

Throws:

IOException

findResource

public URL findResource(String name)

Finds the resource with the specified name.

Overrides:

findResource in class URLClassLoader

Parameters:

name - the name of the resource

Returns:

a URL for the resource, or null if the resource could not be found.

findResources

public Enumeration<URL> findResources(String name)
                               throws IOException

Returns an Enumeration of URLs representing all of the resources having the specified name.

Overrides:

findResources in class URLClassLoader

Parameters:

name - the resource name

Returns:

an Enumeration of URLs

Throws:

IOException - if an I/O exception occurs

findLibrary

protected String findLibrary(String libname)

Returns the absolute path name of a native library. The VM invokes this method to locate the native libraries that belong to classes loaded with this class loader. If this method returns null, the VM searches the library along the path specified as the java.library.path property. This method invoke getLibraryHandle(java.lang.String) method to find handle of this library. If the handle is found and its URL protocol is "file", the system-dependent absolute library file path is returned. Otherwise this method returns null.

Subclasses can override this method to provide specific approaches in library searching.

Overrides:

findLibrary in class ClassLoader

Parameters:

libname - the library name

Returns:

the absolute path of the native library

See Also:

System.loadLibrary(java.lang.String), System.mapLibraryName(java.lang.String)

getClassHandle

protected edu.emory.mathcs.util.classloader.ResourceHandle getClassHandle(String name)

Finds the ResourceHandle object for the class with the specified name. Unlike findClass(), this method does not load the class.

Parameters:

name - the name of the class

Returns:

the ResourceHandle of the class

getResourceHandle

protected edu.emory.mathcs.util.classloader.ResourceHandle getResourceHandle(String name)

Finds the ResourceHandle object for the resource with the specified name.

Parameters:

name - the name of the resource

Returns:

the ResourceHandle of the resource

getLibraryHandle

protected edu.emory.mathcs.util.classloader.ResourceHandle getLibraryHandle(String name)

Finds the ResourceHandle object for the native library with the specified name. The library name must be '/'-separated path. The last part of this path is substituted by its system-dependent mapping (using System.mapLibraryName(String) method). Next, the ResourceFinder is used to look for the library as it was ordinary resource.

Subclasses can override this method to provide specific approaches in library searching.

Parameters:

name - the name of the library

Returns:

the ResourceHandle of the library

getResourceHandles

protected Enumeration<edu.emory.mathcs.util.classloader.ResourceHandle> getResourceHandles(String name)

Returns an Enumeration of ResourceHandle objects representing all of the resources having the specified name.

Parameters:

name - the name of the resource

Returns:

the ResourceHandle of the resource