1、插件接口定义（提供插件开发者实现）

    package com.zhong;
     
    public interface PluginService {
     
        public void service();
    }

2、插件实体定义

package com.zhong;
 
/**
 * 插件封装
 * @author admin
 *
 */
public class Plugin {
 
    private String name;
    private String jar;
    private String className;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getJar() {
        return jar;
    }
    public void setJar(String jar) {
        this.jar = jar;
    }
    public String getClassName() {
        return className;
    }
    public void setClassName(String className) {
        this.className = className;
    }
    
}

3、插件管理类

package com.zhong;
 
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.List;
/**
 * 使用URLClassLoader动态加载jar文件，实例化插件中的对象
 * @author zhong
 *
 */
public class PluginManager {
    
    private URLClassLoader urlClassLoader;
 
    public PluginManager(List plugins) throws MalformedURLException {
        init(plugins);
    }
    
    private void init(List plugins) throws MalformedURLException {
        
        int size = plugins.size();
        URL[] urls = new URL[size];
        
        for(int i = 0; i < size; i++) {
            
            Plugin plugin = plugins.get(i);
            String filePath = plugin.getJar();
 
            urls[i] = new URL("file:" + filePath);
        }
        
        // 将jar文件组成数组，来创建一个URLClassLoader
        urlClassLoader = new URLClassLoader(urls);
    }
    
    /**
     * 获得插件
     * @param className
     * @return
     * @throws ClassNotFoundException
     * @throws InstantiationException
     * @throws IllegalAccessException
     */
    public PluginService getInstance(String className) throws ClassNotFoundException, InstantiationException, IllegalAccessException {
       
        // 插件实例化对象，插件都是实现PluginService接口
        Class clazz = urlClassLoader.loadClass(className);
        Object instance = clazz.newInstance();
 
        return (PluginService)instance;
    }
}

4、读取插件配置工具类（使用dom4j实现）

package com.zhong;
 
import java.io.File;
import java.util.ArrayList;
import java.util.List;
 
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;
 
/**
 * 解析XML获取所有插件信息（这里用到dom4j）
 * @author admin
 *
 */
public class XMLParser {
    
    public static List getPluginList() throws DocumentException {
        
        List list = new ArrayList();
        
        SAXReader saxReader =new SAXReader();
        Document document = saxReader.read(new File("plugin.xml"));
        
        Element root = document.getRootElement();
        List plugins = root.elements("plugin");
        for(Object pluginObj : plugins) {
            Element pluginEle = (Element)pluginObj;
            Plugin plugin = new Plugin();
            plugin.setName(pluginEle.elementText("name"));
            plugin.setJar(pluginEle.elementText("jar"));
            plugin.setClassName(pluginEle.elementText("class"));
            list.add(plugin);
        }
        return list;
    }
}

5、main类客户端

package com.zhong;
 
import java.util.List;
 
public class Main {
    
    public static void main(String[] args) {
        try {
            
            List pluginList = XMLParser.getPluginList();
            
            PluginManager pluginManager = new PluginManager(pluginList);
            
            for(Plugin plugin : pluginList) {
                
                PluginService pluginService = pluginManager.getInstance(plugin.getClassName());
                System.out.println("开始执行[" + plugin.getName() + "]插件...");
                // 调用插件
                pluginService.service();
                
                System.out.println("[" + plugin.getName() + "]插件执行完成");
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

6、插件配置文件格式

<?xml version="1.0" encoding="UTF-8"?>
<plugins>
    <plugin>
        <name>A插件</name>
        <jar>D:/plugins/a-plugin.jar</jar>
        <class>com.zhong.aplugin.APlugin</class>
    </plugin>
   <plugin>
        <name>B插件</name>
        <jar>D:/plugins/b-plugin.jar</jar>
        <class>com.zhong.bplugin.BPlugin</class>
    </plugin>
   <plugin>
        <name>C插件</name>
        <jar>D:/plugins/c-plugin.jar</jar>
        <class>com.zhong.cplugin.CPlugin</class>
    </plugin>
</plugins>