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/*
 * Copyright 1999,2004 The Apache Software Foundation.
 * 
 * Licensed 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.ByteArrayOutputStream;
import java.io.InputStream;
import java.net.URL;
import java.net.URLClassLoader;
import java.security.AccessController;
import java.security.CodeSource;
import java.security.PermissionCollection;
import java.security.PrivilegedAction;
import java.security.ProtectionDomain;

import org.apache.jasper.Constants;

/**
 * This is a class loader that loads JSP files as though they were
 * Java classes. It calls the compiler to compile the JSP file into a
 * servlet and then loads the generated class. 
 *
 * @author Anil K. Vijendran
 * @author Harish Prabandham
 */
public class JasperLoader extends URLClassLoader {

    protected class PrivilegedLoadClass
        implements PrivilegedAction {

        PrivilegedLoadClass() {
        }
         
        public Object run() {
            return Thread.currentThread().getContextClassLoader();
        }

    }

    private PermissionCollection permissionCollection = null;
    private CodeSource codeSource = null;
    private String className = null;
    private ClassLoader parent = null;
    private SecurityManager securityManager = null;
    private PrivilegedLoadClass privLoadClass = null;

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

    /**
     * Load the class with the specified name.  This method searches for
     * classes in the same manner as loadClass(String, boolean)
     * with 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 ClassNotFoundException.
     * 
     * Call findLoadedClass(String) to check if the
     *     class has already been loaded.  If it has, the same
     *     Class object is returned.
     * If the delegate property is set to true,
     *     call the loadClass() method of the parent class
     *     loader, if any.            
     * Call findClass() to find this class in our locally
     *     defined repositories.      
     * Call the loadClass() method of our parent
     *     class loader, if any.      
     * 
     * If the class was found using the above steps, and the
     * resolve flag is true, this method will then
     * call resolveClass(Class) on the resulting Class object.
     *                                     
     * @param name Name of the class to be loaded
     * @param resolve If true then resolve the class
     *                                     
     * @exception ClassNotFoundException if the class was not found
     */                                    
    public Class loadClass(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
        int dot = name.lastIndexOf('.');
        if (securityManager != null) {     
            if (dot >= 0) {                
                try {                    
                    securityManager.checkPackageAccess(name.substring(0,dot));
                } catch (SecurityException se) {
                    String error = "Security Violation, attempt to use " +
                        "Restricted Class: " + name;
                    System.out.println(error);
                    throw new ClassNotFoundException(error);
                }                          
            }                              
        }

        // Class is in a package, delegate to thread context class loader
        if( !name.startsWith(Constants.JSP_PACKAGE_NAME) ) {
            ClassLoader classLoader = null;
            if (securityManager != null) {
                 classLoader = (ClassLoader)AccessController.doPrivileged(privLoadClass);
            } else {
                classLoader = Thread.currentThread().getContextClassLoader();
            }
            clazz = classLoader.loadClass(name);
            if( resolve )
                resolveClass(clazz);
            return clazz;
        }

        // Only load classes for this JSP page
        if( name.startsWith(className) ) {
            String classFile = name.substring(Constants.JSP_PACKAGE_NAME.length()+1) +
                ".class";
            byte [] cdata = loadClassDataFromFile(classFile);
            if( cdata == null )
                throw new ClassNotFoundException(name);
            if( securityManager != null ) {
                ProtectionDomain pd = new ProtectionDomain(
                        codeSource,permissionCollection);
                clazz = defineClass(name,cdata,0,cdata.length,pd);
            } else {
                clazz = defineClass(name,cdata,0,cdata.length);
            }
            if( clazz != null ) {
                if( resolve )                
                    resolveClass(clazz);
                return clazz;
            }
        }

        throw new ClassNotFoundException(name);
    }

    /**
     * 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 where the code was loaded from
     * @return PermissionCollection for CodeSource
     */
    protected final PermissionCollection getPermissions(CodeSource codeSource) {
        return permissionCollection;
    }


    /**
     * Load JSP class data from file.
     */
    protected byte[] loadClassDataFromFile(String fileName) {
        byte[] classBytes = null;
        try {
            InputStream in = getResourceAsStream(fileName);
            if (in == null) {
                return null;
            }
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            byte buf[] = new byte[1024];
            for(int i = 0; (i = in.read(buf)) != -1; )
                baos.write(buf, 0, i);
            in.close();     
            baos.close();    
            classBytes = baos.toByteArray();
        } catch(Exception ex) {
            ex.printStackTrace();
            return null;     
        }                    
        return classBytes;
    }

}