Struts example source code file (ClassReloadingXMLWebApplicationContext.java)

This example Struts source code file (ClassReloadingXMLWebApplicationContext.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 - Struts tags/keywords

arraylist, change, classreloadingbeanfactory, classreloadingbeanfactory, file, file, filesystemalterationmonitor, illegalstateexception, io, list, regex, reloadingclassloader, reloadingclassloader, servlet, string, string, util, watching

The Struts ClassReloadingXMLWebApplicationContext.java source code

/*
 * $Id: ClassReloadingXMLWebApplicationContext.java 1076544 2011-03-03 07:19:37Z lukaszlenart $
 *
 * 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.struts2.spring;

import com.opensymphony.xwork2.util.classloader.FileResourceStore;
import com.opensymphony.xwork2.util.classloader.JarResourceStore;
import com.opensymphony.xwork2.util.classloader.ReloadingClassLoader;
import com.opensymphony.xwork2.util.logging.Logger;
import com.opensymphony.xwork2.util.logging.LoggerFactory;
import org.apache.commons.jci.monitor.FilesystemAlterationListener;
import org.apache.commons.jci.monitor.FilesystemAlterationMonitor;
import org.apache.commons.jci.monitor.FilesystemAlterationObserver;
import org.apache.commons.lang.StringUtils;
import org.apache.struts2.dispatcher.Dispatcher;
import org.springframework.web.context.support.XmlWebApplicationContext;
import org.springframework.beans.factory.support.DefaultListableBeanFactory;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.beans.BeansException;

import javax.servlet.ServletContext;
import java.io.File;
import java.util.List;
import java.util.ArrayList;
import java.util.Set;
import java.util.HashSet;
import java.util.regex.Pattern;

/**
 * This class can be used instead of XmlWebApplicationContext, and it will watch jar files and directories for changes
 * and reload then changed classes.
 * <br />
 * To use this class:
 * <ul>
 * <li>Set "struts.devMode" to "true" 
 * <li>Set "struts.class.reloading.watchList" to a comma separated list of directories, or jar files (absolute paths)

 * <li>Add this to web.xml:
 * <pre>
 *  <context-param>
 *       <param-name>contextClass</param-name>
 *       <param-value>org.apache.struts2.spring.ClassReloadingXMLWebApplicationContext</param-value>
 *   </context-param>
 *  </li>
 * <li>Add Apache Commons JCI FAM to the classpath. If you are using maven, add this to pom.xml:
 *  <pre>
 *  <dependency>
 *       <groupId>org.apache.commons</groupId>
 *       <artifactId>commons-jci-fam</artifactId>
 *       <version>1.0</version>
 *       <optional>true</optional>
 *  </dependency>
 *  </pre>
 * </li>
 * </ul>
 */
public class ClassReloadingXMLWebApplicationContext extends XmlWebApplicationContext implements FilesystemAlterationListener {
    private static final Logger LOG = LoggerFactory.getLogger(ClassReloadingXMLWebApplicationContext.class);

    protected ReloadingClassLoader classLoader;
    protected FilesystemAlterationMonitor fam;

    protected ClassReloadingBeanFactory beanFactory;
    //reload the runtime configuration when a change is detected
    private boolean reloadConfig;

    public void setupReloading(String[] watchList, String acceptClasses, ServletContext servletContext, boolean reloadConfig) {
        this.reloadConfig = reloadConfig;

        classLoader = new ReloadingClassLoader(ClassReloadingXMLWebApplicationContext.class.getClassLoader());

        //make a list of accepted classes
        if (StringUtils.isNotBlank(acceptClasses)) {
            String[] splitted = acceptClasses.split(",");
            Set<Pattern> patterns = new HashSet(splitted.length);
            for (String pattern : splitted)
                patterns.add(Pattern.compile(pattern));

            classLoader.setAccepClasses(patterns);
        }

        fam = new FilesystemAlterationMonitor();

        //setup stores
        for (String watch : watchList) {
            File file = new File(watch);

            //make it absolute, if it is a relative path
            if (!file.isAbsolute())
                file = new File(servletContext.getRealPath(watch));

            if (watch.endsWith(".jar")) {
                classLoader.addResourceStore(new JarResourceStore(file));
                //register with the fam
                fam.addListener(file, this);
                LOG.debug("Watching [#0] for changes", file.getAbsolutePath());
            } else {
                //get all subdirs
                List<File> dirs = new ArrayList();
                getAllPaths(file, dirs);

                classLoader.addResourceStore(new FileResourceStore(file));

                for (File dir : dirs) {
                    //register with the fam
                    fam.addListener(dir, this);
                    LOG.debug("Watching [#0] for changes", dir.getAbsolutePath());
                }
            }
        }
        //setup the bean factory
        beanFactory = new ClassReloadingBeanFactory();
        beanFactory.setInstantiationStrategy(new ClassReloadingInstantiationStrategy());
        beanFactory.setBeanClassLoader(classLoader);

        //start watch thread
        fam.start();
    }

    /**
     * If root is a dir, find al the subdir paths
     */
    private void getAllPaths(File root, List<File> dirs) {
        dirs.add(root);

        if (root.isDirectory()) {
            File[] files = root.listFiles();
            if (files != null) {
                for (File file : files) {
                    if (file.isDirectory()) {
                        getAllPaths(file, dirs);
                    }
                }
            }
        }
    }

    public void close() {
        super.close();

        if (fam != null) {
            fam.removeListener(this);
            fam.stop();
        }
    }

    public void refresh() throws BeansException, IllegalStateException {
        if (classLoader != null) {
            classLoader.reload();
        }

        super.refresh();
    }

    protected DefaultListableBeanFactory createBeanFactory() {
        return beanFactory != null ? beanFactory : super.createBeanFactory();
    }

    protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
        super.prepareBeanFactory(beanFactory);

        //overwrite the class loader in the bean factory
        if (classLoader != null)
            beanFactory.setBeanClassLoader(classLoader);
    }

    public void onDirectoryChange(File file) {
        reload(file);
    }

    public void onDirectoryCreate(File file) {
        reload(file);
    }

    public void onDirectoryDelete(File file) {
    }

    public void onFileChange(File file) {
        reload(file);
    }

    public void onFileCreate(File file) {
        reload(file);
    }

    private void reload(File file) {
        if (classLoader != null) {
            final boolean debugEnabled = LOG.isDebugEnabled();
            if (debugEnabled)
                LOG.debug("Change detected in file [#0], reloading class loader", file.getAbsolutePath());
            classLoader.reload();
            if (reloadConfig && Dispatcher.getInstance() != null) {
                if (debugEnabled)
                    LOG.debug("Change detected in file [#0], reloading configuration", file.getAbsolutePath());
                Dispatcher.getInstance().getConfigurationManager().reload();
            }
        }
    }

    public void onFileDelete(File file) {
    }

    public void onStart(FilesystemAlterationObserver filesystemAlterationObserver) {
    }

    public void onStop(FilesystemAlterationObserver filesystemAlterationObserver) {
    }

    public ReloadingClassLoader getReloadingClassLoader() {
        return classLoader;
    }
}