//========================================================================
//Copyright 1997-2006 Mort Bay Consulting Pty. Ltd.
//------------------------------------------------------------------------
//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.mortbay.jetty;

import java.io.File;

import java.net.URL;
import java.net.URLClassLoader;

import org.mortbay.jetty.Log4JConfigLoader;
import org.mortbay.jetty.Log4JRequestLog;

/* ------------------------------------------------------------ */
/**
 * This abstract class provides static methods for configuring Log4J within a
 * separate class loader and for instantiating and providing access to Log4J
 * Loggers via interface to prevent any Log4J classes from being loaded within
 * the server's application class loader.
 * 
 * Note that setLog4JJarPath(), setLog4JImplJarPath(), and setLog4JConfigPath()
 * must be set before configure() is called. Also, these methods only need to be
 * called once during server startup. Calls to these methods are included in
 * etc/jetty-logging-log4j.xml.
 * 
 * The log4j-1.2.14.jar and jetty6-server-log4j-impl-6.1.7.jar files must be
 * specified and must not be included in the server's class path.
 * 
 * @author Chance Yeoman
 */
public abstract class JettyServerLog4JConfig {

    private static final String DEFAULT_LOG4J_JAR_PATH = "../lib/log4j/log4j-1.2.14.jar";
    private static final String DEFAULT_LOG4J_BRIDGE_JAR_PATH = "../lib/log4j/jetty6-server-log4j-impl-6.1.7.jar";
    private static final String DEFAULT_LOG4J_CONFIG_PATH = "../etc/log4j-jetty-config.xml";

    private static final String CONFIG_LOADER_IMPLEMENTATION_CLASS_NAME = "org.mortbay.jetty.Log4JConfigLoaderImpl";
    private static final String LOGGER_IMPLEMENTATION_CLASS_NAME = "org.mortbay.jetty.Log4JRequestLogImpl";

    private static String log4jJarPath = DEFAULT_LOG4J_JAR_PATH;
    private static String log4jBridgeJarPath = DEFAULT_LOG4J_BRIDGE_JAR_PATH;
    private static String log4jConfigPath = DEFAULT_LOG4J_CONFIG_PATH;

    private static URLClassLoader log4jLoader = null;

    /* ------------------------------------------------------------ */
    /**
     * Sets the path to the standard log4j-1.2.14.jar file.
     */
    public static void setLog4JJarPath(String pathToFile) {
        log4jJarPath = pathToFile;
    }

    /* ------------------------------------------------------------ */
    /**
     * Sets the path to the new jetty6-server-log4j-impl-6.1.7.jar file.
     */
    public static void setLog4JImplJarPath(String pathToFile) {
        log4jBridgeJarPath = pathToFile;
    }

    /* ------------------------------------------------------------ */
    /**
     * Sets the path to the log4j configuration file.
     */
    public static void setLog4JConfigPath(String pathToFile) {
        log4jConfigPath = pathToFile;
    }

    /* ------------------------------------------------------------ */
    /**
     * If not yet configured, this method first creates a new class loader with
     * access to the standard log4j 1.2.14 package as well as the new package
     * that contains the logger implementations and a simple configuration
     * implementation. After the new class loader is created, it is used to
     * create a configuration implementation instance, which is then used to
     * load and configure Log4J classes.
     * 
     * An Exception is thrown if this method is executed a second time.
     */
    public static void configure() throws Exception {

        if (log4jLoader == null) {
            File log4jJarFile = new File(log4jJarPath);
            File log4jBridgeJarFile = new File(log4jBridgeJarPath);

            URL[] log4jJarURL = new URL[2];
            log4jJarURL[0] = log4jJarFile.toURL();
            log4jJarURL[1] = log4jBridgeJarFile.toURL();
            log4jLoader = new URLClassLoader(log4jJarURL);

        } else {
            throw new IllegalStateException(
                    "Log4JServerLog configuration has already been set.");
        }
        ((Log4JConfigLoader) log4jLoader.loadClass(
                CONFIG_LOADER_IMPLEMENTATION_CLASS_NAME).newInstance())
                .loadLog4JConfig(log4jConfigPath);
    }

    /* ------------------------------------------------------------ */
    /**
     * If not yet configured, this method throws an Exception. Otherwise, the
     * server's Log4J class loader is used to instantiate a Log4JRequestLog
     * implementation that is then returned.
     */
    public static Log4JRequestLog getLog4JRequestLogInstance() throws Exception {
        if (log4jLoader == null) {
            throw new IllegalStateException(
                    "Log4JServerLog configuration has not been set.");
        }
        return ((Log4JRequestLog) log4jLoader.loadClass(
                LOGGER_IMPLEMENTATION_CLASS_NAME).newInstance());
    }

}