java.net.URLClassLoader

public class java.net

URLClassLoader

Java SE 6

Extends: ClassLoader > SecureClassLoader

Extended by: MLet

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.

version 1.89, 08/03/06

since 1.2

Constructors

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.

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 checkCreateClassLoader

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.

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 checkCreateClassLoader

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 jar 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.

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 checkCreateClassLoader

Methods

protected void

addURL(URL url)
Appends the specified URL to the list of URLs to search for classes and resources.

url

the URL to be added to the search path of URLs

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.

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
Throws	IllegalArgumentException: if the package name duplicates an existing package either in this class loader or one of its ancestors
return	the newly defined Package object

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.

name	the name of the class
return	the resulting class
Throws	ClassNotFoundException: if the class could not be found

public URL

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

name	the name of the resource
return	a `URL` for the resource, or `null` if the resource could not be found.

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.

name	the resource name
Throws	IOException: if an I/O exception occurs
return	an `Enumeration` of `URL`s

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.

urls	the URLs to search for classes and resources
parent	the parent class loader for delegation
return	the resulting class loader

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.

urls	the URLs to search for classes and resources
return	the resulting class loader

Properties

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 of this URL is "jar", then the permission granted is based on the permission that is required by the URL of the Jar file.

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.

codesource the codesource

return the permissions granted to the codesource

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.

return

the search path of URLs for loading classes and resources.

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Java SE 6