Java in a Nutshell, 5th Edition [Electronic resources]

This ClassLoader provides a useful way to load untrusted Java code from a search path of arbitrary URLs, where each URL represents a directory or JAR file to search. Use the inherited loadClass( ) method to load a named class with a URLClassLoader. Classes loaded by a URLClassLoader have whatever permissions are granted to their java.security.CodeSource by the system java.security.Policy, plus they have one additional permission that allows the class loader to read any resource files associated with the class. If the class is loaded from a local file: URL that represents a directory, the class is given permission to read all files and directories below that directory. If the class is loaded from a local file: URL that represents a JAR file, the class is given permission to read that JAR file. If the class is loaded from a URL that represents a resource on another host, that class is given permission to connect to and accept network connections from that host. Note, however, that loaded classes are not granted this additional permission if the code that created the URLClassLoader in the first place would not have had that permission.

You can obtain a URLClassLoader by calling one of the URLClassLoader( ) constructors or one of the static newInstance( ) methods. If you call newInstance( ), the loadClass( ) method of the returned URLClassLoader performs an additional check to ensure that the caller has permission to access the specified package.

public class

URLClassLoader extends java.security.SecureClassLoader { // Public Constructors public

URLClassLoader (URL[ ]

urls ); public

URLClassLoader (URL[ ]

urls , ClassLoader

parent ); public

URLClassLoader (URL[ ]

urls , ClassLoader

parent , URLStreamHandlerFactory

factory ); // Public Class Methods public static URLClassLoader

newInstance (URL[ ]

urls ); public static URLClassLoader

newInstance (URL[ ]

urls , ClassLoader

parent ); // Public Instance Methods public URL[ ]

getURLs ( ); // Protected Methods Overriding SecureClassLoader protected java.security.PermissionCollection

getPermissions (java.security. CodeSource

codesource ); // Public Methods Overriding ClassLoader public URL

findResource (String

name ); public java.util.Enumeration<URL>

findResources (String

name ) throws java.io.IOException; // Protected Methods Overriding ClassLoader protected Class<?>

findClass (String

name ) throws ClassNotFoundException; // Protected Instance Methods protected void

addURL (URL

url ); protected Package

definePackage (String

name , java.util.jar.Manifest

man , URL

url ) throws IllegalArgumentException; }