java.net
Class URLClassLoader

java.lang.Object
  extended by java.lang.ClassLoader
      extended by java.security.SecureClassLoader
          extended by java.net.URLClassLoader

public class URLClassLoader
extends SecureClassLoader

This class loader is used to load classes and resources from a search path of URLs referring to both JAR files and directories. 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 opened as needed.

The AccessControlContext of the thread that created the instance of URLClassLoader will be used when subsequently loading classes and resources.

The classes that are loaded are by default granted permission only to access the URLs specified when the URLClassLoader was created.

Since:
1.2
Version:
1.72 10/17/00
Author:
David Connelly

Constructor Summary
URLClassLoader(URL[] urls)
          Constructs a new URLClassLoader for the specified URLs using the default delegation parent ClassLoader.
URLClassLoader(URL[] urls, ClassLoader parent)
          Constructs a new URLClassLoader for the given URLs.
URLClassLoader(URL[] urls, ClassLoader parent, URLStreamHandlerFactory factory)
          Constructs a new URLClassLoader for the specified URLs, parent class loader, and URLStreamHandlerFactory.
 
Method Summary
 URL findResource(String name)
          Finds the resource with the specified name on the URL search path.
 Enumeration findResources(String name)
          Returns an Enumeration of URLs representing all of the resources on the URL search path having the specified name.
 URL[] getURLs()
          Returns the search path of URLs for loading classes and resources.
static URLClassLoader newInstance(URL[] urls)
          Creates a new instance of URLClassLoader for the specified URLs and default parent class loader.
static URLClassLoader newInstance(URL[] urls, ClassLoader parent)
          Creates a new instance of URLClassLoader for the specified URLs and parent class loader.
 
Methods inherited from class java.lang.ClassLoader
clearAssertionStatus, getParent, getResource, getResourceAsStream, getResources, getSystemClassLoader, getSystemResource, getSystemResourceAsStream, getSystemResources, loadClass, setClassAssertionStatus, setDefaultAssertionStatus, setPackageAssertionStatus
 
Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

URLClassLoader

public URLClassLoader(URL[] urls,
                      ClassLoader parent)
Constructs a new URLClassLoader 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:
urls - the URLs from which to load classes and resources
parent - the parent class loader for delegation
Throws:
SecurityException - if a security manager exists and its checkCreateClassLoader method doesn't allow creation of a class loader.
See Also:
SecurityManager.checkCreateClassLoader()

URLClassLoader

public URLClassLoader(URL[] urls)
Constructs a new URLClassLoader for the specified URLs using the default delegation parent ClassLoader. The URLs will be searched in the order specified for classes and resources after first searching in the 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:
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()

URLClassLoader

public URLClassLoader(URL[] urls,
                      ClassLoader parent,
                      URLStreamHandlerFactory factory)
Constructs a new URLClassLoader for the specified URLs, parent class loader, and URLStreamHandlerFactory. The parent argument will be used as the parent class loader for delegation. The factory argument will be used as the stream handler factory to obtain protocol handlers when creating new URLs.

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:
urls - the URLs from which to load classes and resources
parent - the parent class loader for delegation
factory - the URLStreamHandlerFactory to use when creating URLs
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

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.

findResource

public URL findResource(String name)
Finds the resource with the specified name on the URL search path.

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 findResources(String name)
                          throws IOException
Returns an Enumeration of URLs representing all of the resources on the URL search path having the specified name.

Parameters:
name - the resource name
Returns:
an Enumeration of URLs
Throws:
IOException - if an I/O exception occurs

newInstance

public static URLClassLoader newInstance(URL[] urls,
                                         ClassLoader parent)
Creates a new instance of URLClassLoader 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:
urls - the URLs to search for classes and resources
parent - the parent class loader for delegation
Returns:
the resulting class loader

newInstance

public static URLClassLoader newInstance(URL[] urls)
Creates a new instance of URLClassLoader for the specified URLs and default parent class loader. If a security manager is installed, the loadClass method of the URLClassLoader returned by this method will invoke the SecurityManager.checkPackageAccess before loading the class.

Parameters:
urls - the URLs to search for classes and resources
Returns:
the resulting class loader