org.mdiutil.net

Class JarClassLoader

java.lang.Object

java.lang.ClassLoader

java.security.SecureClassLoader

java.net.URLClassLoader

org.mdiutil.net.JarClassLoader

All Implemented Interfaces:

Closeable, AutoCloseable

public class JarClassLoader
extends URLClassLoader

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.

Constructor Summary

Constructors

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

Method Summary

Modifier and Type	Method and Description
protected void	addURL(URL url) Appends the specified URL to the list of URLs to search for classes and resources.
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.
URL[]	getURLs() Returns the search path of URLs for loading classes and resources.
static JarClassLoader	newInstance(URL[] urls) Creates a new instance of URLClassLoader for the specified URLs and default parent class loader.
static JarClassLoader	newInstance(URL[] urls, ClassLoader parent) Creates a new instance of URLClassLoader for the specified URLs and parent class loader.

Methods inherited from class java.net.URLClassLoader

close, getPermissions, getResourceAsStream

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, getClassLoadingLock, getPackage, getPackages, getParent, getResource, getResources, getSystemClassLoader, getSystemResource, getSystemResourceAsStream, getSystemResources, loadClass, loadClass, registerAsParallelCapable, 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

JarClassLoader

public JarClassLoader(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()

JarClassLoader

public JarClassLoader(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()

JarClassLoader

public JarClassLoader(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.

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.

Overrides:

addURL in class URLClassLoader

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.

Overrides:

getURLs in class URLClassLoader

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 URLClassLoader

Parameters:

name - the name of the class

Returns:

the resulting class

Throws:

ClassNotFoundException - if the class could not be found

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.

Overrides:

definePackage in class URLClassLoader

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 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 on the URL search path 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

newInstance

public static JarClassLoader 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 JarClassLoader 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