Java Doc for MultiClassLoader.java in  » J2EE » Enhydra-Application-Framework » com » lutris » classloader » Java Source Code / Java DocumentationJava Source Code and Java Documentation

Summary:

A class loader that can load classes from class files and zip files residing in a specified class path.

This class loader can also load resources that reside on the class path and return them as is, as input streams, or as byte arrays.

Features:

• Loads classes from class files and zip files.
• Finds resources and can return them as is, as input streams and as byte arrays.
• Loads classes and resources using the specified class path. Class path entries can be URLs, directories, zip files or jar files.

  A secondary classloader can be specified which is used to locate the class if its not found by this classloader.

• A filter object can be supplied to determine if the current class loader should load the class or it should be passed to the parent or secondary class loader.

Class Path

If classes are to be loaded from a class path, it must be set by the setClassPath or addClassPath methods or by the constructor prior to calling loadClass. If the class path is not set, the class will be loaded with the system class loader.

The class path can consist of directories, files, and/or URLs.

Example valid class path entries are:

 Files and directories on the local file system
 ../../java/classes
 /users/kristen/java/classes
 /users/kristen/java/classes/
 /users/kristen/java/zipfiles/MyClasses.zip
 /users/kristen/java/jarfiles/MyClasses.jar
 file:///users/kristen/java/classes
 file://localhost/users/kristen/java/classes
 

 Files and directories on a remote file system
 (must be in URL format)
 ftp://www.foo.com/pub/java/classes
 file://www.foo.com/pub/java/classes/
 http://www.foo.com/web/java/classes/
 file://www.foo.com:8080/pub/java/zipfiles/MyClasses.zip
 http://www.foo.com:8080/web/java/jarfiles/MyClasses.jar
 

Note that the location of the entry includes the protocol, the host name, and the port while the file name is everything else. For example,

 http://www.foo.com:8080/web/java/jarfiles/MyClasses.jar
 

 [http://www.foo.com:8080/][/web/java/jarfiles/MyClasses.jar]
 

Note that the two references

 /users/kristen/java/classes/
 file:///users/kristen/java/classes/
 

 C|/windows/java/classes/
 file:///C|/windows/java/classes/
 

But the two references

 /users/kristen/java/classes/
 file://monet.lutris.com/users/kristen/java/classes/
 

 /users/ftp/pub/classes/
 file://picasso.lutris.com/pub/classes/
 

System Class Path

The system class path is the system-dependent path of directories and files (e.g. CLASSPATH on Unix and Windows) used by the system class loader to load classes. This class path is usually configured prior to executing a Java program but can be dynamically configured during runtime if desired. If you want to use the system class path for this class loader, the convenience method getSystemClassPath has been provided.

Valid system class path entries are directories and zip files, specified by absolute path or relative path on the system. Any valid system class path entry is also valid for this class loader.

Example

Here is an example of how to use this class loader:

 MultiClassLoader loader = new MultiClassLoader();
 loader.setClassPath("/web/java/lutris.jar");
 loader.addClassPath("/users/kristen/java/");
 loader.addClassPath("/usr/local/lib/graphics.zip");
 try {
 Class c = loader.loadClass("com.lutris.util.MyClass");
 System.out.println("My loader is " + c.getClassLoader());
 Object o = (Object) c.newInstance();
 System.out.println("My class is " + o.getClass());
 } catch (ClassNotFoundException e) {
 Throwable t = new Throwable();
 t.printStackTrace();
 }
 

Warning: This class loader is not yet fully compliant with Java 1.2. It maybe used on 1.2, but not all features are available. The parent loader, secondary loader, and filter may change in a future release without maintaining compatibility.
author:
   Kristen Pol, Lutris Technologies
version:
   $Revision : 1.0 $
See Also:   java.lang.ClassLoader
See Also:   com.lutris.classloader.Resource
See Also:   java.net.URL