java-rmi.zip_RMI java_rmi

/* * @(#)RMIClassLoader.java 1.34 01/12/03 * * Copyright 2002 Sun Microsystems, Inc. All rights reserved. * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */ package java.rmi.server; import java.net.MalformedURLException; import java.net.URL; import java.util.Iterator; import sun.misc.Service; /** * <code>RMIClassLoader</code> comprises static methods to support * dynamic class loading with RMI. Included are methods for loading * classes from a network location (one or more URLs) and obtaining * the location from which an existing class should be loaded by * remote parties. These methods are used by the RMI runtime when * marshalling and unmarshalling classes contained in the arguments * and return values of remote method calls, and they also may be * invoked directly by applications in order to mimic RMI's dynamic * class loading behavior. * * <p>The implementation of the following static methods * * <ul> * * <li>{@link #loadClass(URL,String)} * <li>{@link #loadClass(String,String)} * <li>{@link #loadClass(String,String,ClassLoader)} * <li>{@link #loadProxyClass(String,String[],ClassLoader)} * <li>{@link #getClassLoader(String)} * <li>{@link #getClassAnnotation(Class)} * * </ul> * * is provided by an instance of {@link RMIClassLoaderSpi}, the * service provider interface for those methods. When one of the * methods is invoked, its behavior is to delegate to a corresponding * method on the service provider instance. The details of how each * method delegates to the provider instance is described in the * documentation for each particular method. * * <p>The service provider instance is chosen as follows: * * <ul> * * <li>If the system property * <code>java.rmi.server.RMIClassLoaderSpi</code> is defined, then if * its value equals the string <code>"default"</code>, the provider * instance will be the value returned by an invocation of the {@link * #getDefaultProviderInstance()} method, and for any other value, if * a class named with the value of the property can be loaded by the * system class loader (see {@link ClassLoader#getSystemClassLoader}) * and that class is assignable to {@link RMIClassLoaderSpi} and has a * public no-argument constructor, then that constructor will be * invoked to create the provider instance. If the property is * defined but any other of those conditions are not true, then an * unspecified <code>Error</code> will be thrown to code that attempts * to use <code>RMIClassLoader</code>, indicating the failure to * obtain a provider instance. * * <li>If a resource named * <code>META-INF/services/java.rmi.server.RMIClassLoaderSpi</code> is * visible to the system class loader, then the contents of that * resource are interpreted as a provider-configuration file, and the * first class name specified in that file is used as the provider * class name. If a class with that name can be loaded by the system * class loader and that class is assignable to {@link * RMIClassLoaderSpi} and has a public no-argument constructor, then * that constructor will be invoked to create the provider instance. * If the resource is found but a provider cannot be instantiated as * described, then an unspecified <code>Error</code> will be thrown to * code that attempts to use <code>RMIClassLoader</code>, indicating * the failure to obtain a provider instance. * * <li>Otherwise, the provider instance will be the value returned by * an invocation of the {@link #getDefaultProviderInstance()} method. * * </ul> * * @version 1.34, 01/12/03 * @author Ann Wollrath * @author Peter Jones * @author Laird Dornin * @see RMIClassLoaderSpi * @since JDK1.1 */ public class RMIClassLoader { /** "default" provider instance */ private static final RMIClassLoaderSpi defaultProvider = newDefaultProviderInstance(); /** provider instance */ private static final RMIClassLoaderSpi provider = (RMIClassLoaderSpi) java.security.AccessController.doPrivileged( new java.security.PrivilegedAction() { public Object run() { return initializeProvider(); } }); /* * Disallow anyone from creating one of these. */ private RMIClassLoader() {} /** * Loads a class from the codebase URL path specified by the * <code>java.rmi.server.codebase</code> property. * * <p>This method delegates to {@link #loadClass(String,String)}, * passing <code>null</code> as the first argument and * <code>name</code> as the second argument. * * @param name the name of the class to load * * @return the <code>Class</code> object representing the loaded class * * @throws MalformedURLException if the system property * <code>java.rmi.server.codebase</code> contains an invalid URL * * @throws ClassNotFoundException if a definition for the class * could not be found at the codebase location * * @deprecated replaced by <code>loadClass(String,String)</code> method * @see #loadClass(String,String) */ public static Class loadClass(String name) throws MalformedURLException, ClassNotFoundException { return loadClass((String) null, name); } /** * Loads a class from a codebase URL. * * If <code>codebase</code> is <code>null</code>, then this method * will behave the same as {@link #loadClass(String,String)} with a * <code>null</code> <code>codebase</code> and the given class name. * * <p>This method delegates to the * {@link RMIClassLoaderSpi#loadClass(String,String,ClassLoader)} * method of the provider instance, passing the result of invoking * {@link URL#toString} on the given URL (or <code>null</code> if * <code>codebase</code> is null) as the first argument, * <code>name</code> as the second argument, * and <code>null</code> as the third argument. * * @param codebase the URL to load the class from, or <code>null</code> * * @param name the name of the class to load * * @return the <code>Class</code> object representing the loaded class * * @throws MalformedURLException if <code>codebase</code> is * <code>null</code> and the system property * <code>java.rmi.server.codebase</code> contains an invalid URL * * @throws ClassNotFoundException if a definition for the class * could not be found at the specified URL */ public static Class loadClass(URL codebase, String name) throws MalformedURLException, ClassNotFoundException { return provider.loadClass( codebase != null ? codebase.toString() : null, name, null); } /** * Loads a class from a codebase URL path. * * If <code>codebase</code> is <code>null</code>, then the value of * the system property <code>java.rmi.server.codebase</code> is used * as the URL path. * * <p>This method delegates to the * {@link RMIClassLoaderSpi#loadClass(String,String,ClassLoader)} * method of the provider instance, passing <code>codebase</code> * as the first argument, <code>name</code> as the second argument, * and <code>null</code> as the third argument. * * @param codebase the list of URLs (separated by spaces) to load * the class from, or <code>null</code> * * @param name the name of the class to load * * @return the <code>Class</code> object representing the loaded class * * @throws MalformedURLException if <code>codebase</code> is * non-<code>null</code> and contains an invalid URL, or * if <code>codebase</code> is <code>null</code> and the system * property <code>java.rmi.server.codebase</code> contains an * invalid URL * * @throws ClassNotFoundException if a definition for the class * could not be found at the specified location * * @since 1.2 */ public static Class loadClass(String codebase, String name) throws Malfor