Tomcat example source code file (JasperLoader.java)

This example Tomcat source code file (JasperLoader.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Tomcat tags/keywords

class, class, classloader, classnotfoundexception, classnotfoundexception, codesource, inputstream, io, ioexception, jasperloader, net, network, permissioncollection, permissioncollection, security, security, string, string

The Tomcat JasperLoader.java source code

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.jasper.servlet;

import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.net.URLClassLoader;
import java.security.CodeSource;
import java.security.PermissionCollection;

import org.apache.jasper.Constants;

/**
 * Class loader for loading servlet class files (corresponding to JSP files) 
 * and tag handler class files (corresponding to tag files).
 *
 * @author Anil K. Vijendran
 * @author Harish Prabandham
 * @author Jean-Francois Arcand
 */
public class JasperLoader extends URLClassLoader {

    private PermissionCollection permissionCollection;
    private CodeSource codeSource;
    private String className;
    private ClassLoader parent;
    private SecurityManager securityManager;

    public JasperLoader(URL[] urls, ClassLoader parent,
			PermissionCollection permissionCollection,
			CodeSource codeSource) {
	super(urls, parent);
	this.permissionCollection = permissionCollection;
	this.codeSource = codeSource;
	this.parent = parent;
	this.securityManager = System.getSecurityManager();
    }

    /**
     * Load the class with the specified name.  This method searches for
     * classes in the same manner as <code>loadClass(String, boolean)
     * with <code>false as the second argument.
     *
     * @param name Name of the class to be loaded
     *
     * @exception ClassNotFoundException if the class was not found
     */
    public Class loadClass(String name) throws ClassNotFoundException {

        return (loadClass(name, false));
    }

    /**
     * Load the class with the specified name, searching using the following
     * algorithm until it finds and returns the class.  If the class cannot
     * be found, returns <code>ClassNotFoundException.
     * <ul>
     * <li>Call findLoadedClass(String) to check if the
     *     class has already been loaded.  If it has, the same
     *     <code>Class object is returned.
     * <li>If the delegate property is set to true,
     *     call the <code>loadClass() method of the parent class
     *     loader, if any.</li>            
     * <li>Call findClass() to find this class in our locally
     *     defined repositories.</li>      
     * <li>Call the loadClass() method of our parent
     *     class loader, if any.</li>      
     * </ul>
     * If the class was found using the above steps, and the
     * <code>resolve flag is true, this method will then
     * call <code>resolveClass(Class) on the resulting Class object.
     *                                     
     * @param name Name of the class to be loaded
     * @param resolve If <code>true then resolve the class
     *                                     
     * @exception ClassNotFoundException if the class was not found
     */                                    
    public Class loadClass(final String name, boolean resolve)
        throws ClassNotFoundException {

        Class clazz = null;                
                                           
        // (0) Check our previously loaded class cache
        clazz = findLoadedClass(name);     
        if (clazz != null) {               
            if (resolve)                   
                resolveClass(clazz);       
            return (clazz);        
        }                          
                          
        // (.5) Permission to access this class when using a SecurityManager
        if (securityManager != null) {     
            int dot = name.lastIndexOf('.');
            if (dot >= 0) {                
                try {        
                    // Do not call the security manager since by default, we grant that package.
                    if (!"org.apache.jasper.runtime".equalsIgnoreCase(name.substring(0,dot))){
                        securityManager.checkPackageAccess(name.substring(0,dot));
                    }
                } catch (SecurityException se) {
                    String error = "Security Violation, attempt to use " +
                        "Restricted Class: " + name;
                    se.printStackTrace();
                    throw new ClassNotFoundException(error);
                }                          
            }                              
        }

	if( !name.startsWith(Constants.JSP_PACKAGE_NAME) ) {
            // Class is not in org.apache.jsp, therefore, have our
            // parent load it
            clazz = parent.loadClass(name);            
	    if( resolve )
		resolveClass(clazz);
	    return clazz;
	}

	return findClass(name);
    }

    
    /**
     * Delegate to parent
     * 
     * @see java.lang.ClassLoader#getResourceAsStream(java.lang.String)
     */
    public InputStream getResourceAsStream(String name) {
        InputStream is = parent.getResourceAsStream(name);
        if (is == null) {
            URL url = findResource(name);
            if (url != null) {
                try {
                    is = url.openStream();
                } catch (IOException e) {
                    is = null;
                }
            }
        }
        return is;
    }
    
    
    /**
     * Get the Permissions for a CodeSource.
     *
     * Since this ClassLoader is only used for a JSP page in
     * a web application context, we just return our preset
     * PermissionCollection for the web app context.
     *
     * @param codeSource Code source where the code was loaded from
     * @return PermissionCollection for CodeSource
     */
    public final PermissionCollection getPermissions(CodeSource codeSource) {
        return permissionCollection;
    }
}