java.net
Class URLClassLoader

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

Direct Known Subclasses:

MLet

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. 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

Constructor Summary
URLClassLoader ( URL           Constructs a new URLClassLoader for the specified URLs using the default delegation parent ClassLoader.
URLClassLoader ( URL [] urls, ClassLoader           Constructs a new URLClassLoader for the given URLs.
URLClassLoader ( URL [] urls, ClassLoader  parent, URLStreamHandlerFactory           Constructs a new URLClassLoader for the specified URLs, parent class loader, and URLStreamHandlerFactory.

 

Method Summary
protected  void	addURL ( URL           Appends the specified URL to the list of URLs to search for classes and resources.
protected   Package	definePackage ( String  name, Manifest  man, URL           Defines a new package by name in this ClassLoader.
protected   Class	findClass ( String           Finds and loads the class with the specified name from the URL search path.
URL	findResource ( String           Finds the resource with the specified name on the URL search path.
Enumeration < URL	findResources ( String           Returns an Enumeration of URLs representing all of the resources on the URL search path having the specified name.
protected   PermissionCollection	getPermissions ( CodeSource           Returns the permissions for the given codesource object.
InputStream	getResourceAsStream ( String           Returns an input stream for reading the specified resource.
URL	getURLs ()           Returns the search path of URLs for loading classes and resources.
static  URLClassLoader	newInstance ( URL           Creates a new instance of URLClassLoader for the specified URLs and default parent class loader.
static  URLClassLoader	newInstance ( URL [] urls, ClassLoader           Creates a new instance of URLClassLoader for the specified URLs and parent class loader.

 

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 , 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

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 opened as needed. 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

addURL

protected 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

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

definePackage

protected PackagedefinePackage ( 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 URLfindResource ( 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

getResourceAsStream

public InputStreamgetResourceAsStream ( String name) 

Returns an input stream for reading the specified resource.

The search order is described in the documentation for ClassLoader.getResource(String) .

The AccessControlContext of the thread that created the instance of URLClassLoader will be used when subsequently loading classes and resources. Note: Overriding the super class implementation to support resource caching.

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

Overrides:

getResourceAsStream in class ClassLoader

Parameters:

name - The resource name

Returns:

An input stream for reading the resource, or null if the resource could not be found

Throws:

NullPointerException - if name is null

Since:

1.5

getPermissions

protected PermissionCollectiongetPermissions ( 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.

Since: Overrides:

1.2 getPermissions in class SecureClassLoader

Parameters:

codesource - the codesource

Returns:

the permissions granted to the codesource

newInstance

public static URLClassLoadernewInstance ( 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 URLClassLoadernewInstance ( 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

Constructor Summary
URLClassLoader ( URL           Constructs a new URLClassLoader for the specified URLs using the default delegation parent ClassLoader.
URLClassLoader ( URL [] urls, ClassLoader           Constructs a new URLClassLoader for the given URLs.
URLClassLoader ( URL [] urls, ClassLoader  parent, URLStreamHandlerFactory           Constructs a new URLClassLoader for the specified URLs, parent class loader, and URLStreamHandlerFactory.

 

Method Summary
protected  void	addURL ( URL           Appends the specified URL to the list of URLs to search for classes and resources.
protected   Package	definePackage ( String  name, Manifest  man, URL           Defines a new package by name in this ClassLoader.
protected   Class	findClass ( String           Finds and loads the class with the specified name from the URL search path.
URL	findResource ( String           Finds the resource with the specified name on the URL search path.
Enumeration < URL	findResources ( String           Returns an Enumeration of URLs representing all of the resources on the URL search path having the specified name.
protected   PermissionCollection	getPermissions ( CodeSource           Returns the permissions for the given codesource object.
URL	getURLs ()           Returns the search path of URLs for loading classes and resources.
static  URLClassLoader	newInstance ( URL           Creates a new instance of URLClassLoader for the specified URLs and default parent class loader.
static  URLClassLoader	newInstance ( URL [] urls, ClassLoader           Creates a new instance of URLClassLoader for the specified URLs and parent class loader.

 

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

 

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

addURL

 
protected 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

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

definePackage

 
protected PackagedefinePackage ( 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 URLfindResource ( 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 PermissionCollectiongetPermissions ( 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 URLClassLoadernewInstance ( 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 URLClassLoadernewInstance ( 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