org.arakhne.vmutil
Class DynamicURLClassLoader

java.lang.Object
  java.lang.ClassLoader
      java.security.SecureClassLoader
          org.arakhne.vmutil.DynamicURLClassLoader

Direct Known Subclasses:

DynamicURLClassLoader.FactoryDynamicURLClassLoader

public class DynamicURLClassLoader
extends SecureClassLoader

This class loader permits to load classes from a set of classpaths.

Version:

6.3 (rev:285) 2011-10-14 12:02:41

Author:

Stéphane GALLAND

Maven Group Id:

org.arakhne.afc

Maven Artifact Id:

arakhneVmutils

Nested Class Summary

protected static class

DynamicURLClassLoader.FactoryDynamicURLClassLoader

Field Summary

protected AccessControlContext	_acc The context to be used when loading classes and resources
protected sun.misc.URLClassPath	_ucp The search path for classes and resources.

Constructor Summary

protected

DynamicURLClassLoader(ClassLoader parent, AccessControlContext acc, URL... urls) Constructs a new ClassPathClassLoader for the given URLs.

Method Summary

void	addURL(URL url) Appends the specified URL to the list of URLs to search for classes and resources.
void	addURLs(URL... urls) Appends the specified URL to the list of URLs to search for classes and resources.
protected Class<?>	defineClass(String name, sun.misc.Resource res) Defines a Class using the class bytes obtained from the specified Resource.
protected Package	definePackage(String name, Manifest man, URL url) Defines a new package by name in this ClassLoader.
protected Class<?>	findClass(String name) Finds and loads the class with the specified name from the URL search path.
URL	findResource(String name) Finds the resource with the specified name on the URL search path.
Enumeration<URL>	findResources(String name) Returns an Enumeration of URLs representing all of the resources on the URL search path having the specified name.
protected PermissionCollection	getPermissions(CodeSource codesource) Returns the permissions for the given codesource object.
URL[]	getURLs() Returns the search path of URLs for loading classes and resources.
static DynamicURLClassLoader	newInstance(ClassLoader parent, URL... urls) Creates a new instance of DynamicURLClassLoader for the specified URLs and parent class loader.
void	removeURL(URL url) Appends the specified URL to the list of URLs to search for classes and resources.
void	removeURLs(URL... urls) Appends the specified URL to the list of URLs to search for classes and resources.

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, 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

Field Detail

_ucp

protected sun.misc.URLClassPath _ucp

The search path for classes and resources.

_acc

protected AccessControlContext _acc

The context to be used when loading classes and resources

Constructor Detail

DynamicURLClassLoader

protected DynamicURLClassLoader(ClassLoader parent,
                                AccessControlContext acc,
                                URL... urls)

Constructs a new ClassPathClassLoader for the given URLs. The URLs will be searched in the order specified for classes and resources after first searching in the specified parent class loader. Any URL that ends with a '/' is assumed to refer to a directory. Otherwise, the URL is assumed to refer to a JAR file which will be downloaded and opened as needed.

If there is a security manager, this method first calls the security manager's checkCreateClassLoader method to ensure creation of a class loader is allowed.

Parameters:

parent - the parent class loader for delegation

acc - is the current access context

urls - the URLs from which to load classes and resources

Throws:

SecurityException - if a security manager exists and its checkCreateClassLoader method doesn't allow creation of a class loader.

See Also:

SecurityManager.checkCreateClassLoader()

Method Detail

addURL

public void addURL(URL url)

Appends the specified URL to the list of URLs to search for classes and resources.

Parameters:

url - the URL to be added to the search path of URLs

addURLs

public void addURLs(URL... urls)

Appends the specified URL to the list of URLs to search for classes and resources.

Parameters:

urls - the URLs to be added to the search path of URLs

removeURLs

public void removeURLs(URL... urls)

Appends the specified URL to the list of URLs to search for classes and resources.

Parameters:

urls - the URL to be added to the search path of URLs

removeURL

public void removeURL(URL url)

Appends the specified URL to the list of URLs to search for classes and resources.

Parameters:

url - the URL to be added to the search path of URLs

getURLs

public URL[] getURLs()

Returns the search path of URLs for loading classes and resources. This includes the original list of URLs specified to the constructor, along with any URLs subsequently appended by the addURL() method.

Returns:

the search path of URLs for loading classes and resources.

findClass

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

Finds and loads the class with the specified name from the URL search path. Any URLs referring to JAR files are loaded and opened as needed until the class is found.

Overrides:

findClass in class ClassLoader

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,
                               sun.misc.Resource res)
                        throws IOException

Defines a Class using the class bytes obtained from the specified Resource. The resulting Class must be resolved before it can be used.

Parameters:

name - is the name of the class to define

res - is the resource from which the class byte-code could be obtained

Returns:

the loaded class.

Throws:

IOException - in case the byte-code was unavailable.

definePackage

protected Package definePackage(String name,
                                Manifest man,
                                URL url)
                         throws IllegalArgumentException

Defines a new package by name in this ClassLoader. The attributes contained in the specified Manifest will be used to obtain package version and sealing information. For sealed packages, the additional URL specifies the code source URL from which the package was loaded.

Parameters:

name - the package name

man - the Manifest containing package version and sealing information

url - the code source url for the package, or null if none

Returns:

the newly defined Package object

Throws:

IllegalArgumentException - if the package name duplicates an existing package either in this class loader or one of its ancestors

findResource

public URL findResource(String name)

Finds the resource with the specified name on the URL search path.

Overrides:

findResource in class ClassLoader

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 on the URL search path having the specified name.

Overrides:

findResources in class ClassLoader

Parameters:

name - the resource name

Returns:

an Enumeration of URLs

Throws:

IOException - if an I/O exception occurs

getPermissions

protected PermissionCollection getPermissions(CodeSource codesource)

Returns the permissions for the given codesource object. The implementation of this method first calls super.getPermissions and then adds permissions based on the URL of the codesource.

If the protocol is "file" and the path specifies a file, then permission to read that file is granted. If protocol is "file" and the path is a directory, permission is granted to read all files and (recursively) all files and subdirectories contained in that directory.

If the protocol is not "file", then to connect to and accept connections from the URL's host is granted.

Overrides:

getPermissions in class SecureClassLoader

Parameters:

codesource - the codesource

Returns:

the permissions granted to the codesource

newInstance

public static DynamicURLClassLoader newInstance(ClassLoader parent,
                                                URL... urls)

Creates a new instance of DynamicURLClassLoader for the specified URLs and parent class loader. If a security manager is installed, the loadClass method of the URLClassLoader returned by this method will invoke the SecurityManager.checkPackageAccess method before loading the class.

Parameters:

parent - the parent class loader for delegation

urls - the URLs to search for classes and resources

Returns:

the resulting class loader