pluginfactory.java

《JSP网站开发典型模块与实例精讲》一书光盘源码

package org.appfuse.util.security.plugin;

/**
 *
 * <p>Title: </p>
 * <p>Description: </p>
 * <p>Copyright: Copyright (c) 2005</p>
 * <p>Company: www.aspire-tech.com</p>
 * @author chentao
 * @version 1.0
 */
import java.io.File;
import java.util.ArrayList;
import java.util.Hashtable;
import java.util.Iterator;
import java.util.List;
import org.jdom.Element;
import org.jdom.input.SAXBuilder;
import org.appfuse.util.security.*;
import org.apache.commons.logging.LogFactory;
import org.apache.commons.logging.Log;
import org.appfuse.util.exception.AppException;
import org.appfuse.util.exception.ExceptionConstants;
import org.appfuse.util.exception.AppSystemException;
import org.appfuse.util.exception.AppBusinessException;
import org.appfuse.util.security.PlugIn;
import org.appfuse.util.*;

public class PluginFactory {
    private static final Log log = LogFactory.getLog(PluginFactory.class);
    private static Element rootElement = null;

    //保存interceptors实现类的名称
    private static Hashtable interceptorQueue;

    /**
     * 载入配置文件
     * @param cfg 配置文件名称
     */
    public static void load(String cfg) {
        try {
            rootElement = new SAXBuilder().build(new File(cfg)).getRootElement();
        } catch(Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * 获得配置文件中指定名称的Element
     * @param elementName String
     * @return Element
     */
    public static Element getElement(String elementName) {
        return rootElement.getChild(elementName);
    }

    /**
     * 初始化interceptorQueue
     */
    public static void initInterceptorQueue() {
        if(interceptorQueue==null)
            interceptorQueue = new Hashtable();
        List intercptList = new ArrayList();
        Element interceptors = getElement("plugins");
        intercptList = interceptors.getChildren("plugin");
        Iterator it = intercptList.iterator();
        Element tmpElement = null;
        while(it.hasNext()) {
            tmpElement = (Element)it.next();
            PluginItem plugin = new PluginItem();
            //解析singleton
            String singleton = tmpElement.getAttributeValue("singleton");
            boolean isSingleton = false;
            if(singleton != null) {
                if(singleton.equalsIgnoreCase("yes")) {
                    isSingleton = true;
                }
            }
            plugin.setName(tmpElement.getAttributeValue("name"));
            plugin.setClassName(tmpElement.getAttributeValue("classname"));
            plugin.setSpringID(tmpElement.getAttributeValue("springID"));
            plugin.setSingleton(isSingleton);
            interceptorQueue.put(plugin.getName(), plugin);
        }
    }

    /**
     * 获得配置文件中指定的interceptor等实现类名称
     * @param InterceptorName String
     * @return PluginItem
     */
    public static PluginItem getPluginItem(String InterceptorName) {
        PluginItem plugin = null;
        if(interceptorQueue == null) {
            initInterceptorQueue();
        }
        plugin = (PluginItem)interceptorQueue.get(InterceptorName);
        return plugin;
    }

    public static String getClassName(String name) {
        String className = "";
        PluginItem plugin = getPluginItem(name);
        if(plugin != null) {
            className = plugin.getClassName();
        }

        return className;
    }

    public static void main(String[] args) {

        PluginFactory factory = new PluginFactory();
        //需要在系统加载的时候执行load()
        factory.load("config/plugin.xml");
        factory.initInterceptorQueue();

        PluginItem plugin = factory.getPluginItem("AuthenticateInterceptor");
        System.out.println("---className:  " + plugin.getClassName() +
                           "  name:  " + plugin.getName() + "   isSingleton:  " +
                           plugin.isSingleton() + "---");
        plugin = factory.getPluginItem("LogoutInterceptor");
        System.out.println("---className:  " + plugin.getClassName() +
                           "  name:  " + plugin.getName() + "   isSingleton:  " +
                           plugin.isSingleton() + "---");
        plugin = factory.getPluginItem("LoginInterceptor");
        System.out.println("---className:  " + plugin.getClassName() +
                           "  name:  " + plugin.getName() + "   isSingleton:  " +
                           plugin.isSingleton() + "---");

    }

    public PluginFactory() {
    }

    /**
     * 生成plugin对象
     * @param pluginName String
     * @throws AppException
     * @return PlugIn
     */

    public static PlugIn getPlugin(String pluginName) throws AppException {
        if(interceptorQueue==null){
            initInterceptorQueue();
        }
        PluginItem plugin = (PluginItem)interceptorQueue.get(pluginName);
        int size = interceptorQueue.size();
        //interceptorQueue.get
        Class pluginClass = null;
        try {
            if(plugin == null) {
                log.error("plugin object can not be  null .");
                return null;
            }
            String springID = plugin.getSpringID();
            String name = plugin.getName();
            if(springID != null && !"".equals(springID.trim())) {
                return(PlugIn)ServiceFactory.getService(name);
            }

            String className = parseName(pluginName);
            pluginClass = Class.forName(className);
            return(PlugIn)pluginClass.newInstance();

        } catch(Exception e) {
            log.error("getPlugin error", e);
            throw new AppSystemException("CreatePluginObject Failed", e,
                                         ExceptionConstants.SYS_GENERAL_ERR);
        }

    }

    /**
     * Locate the implement class by service name
     * @param serviceName the service name
     * @return service implement class name
     */
    private static String parseName(String serviceName) {
        return getClassName(serviceName);
    }

    public static PlugIn getPluginServ(String pluginName) throws AppException {
        return(PlugIn)ServiceFactory.getService(pluginName);
    }

}