工程中使用java代码加载第三方jar文件

package com.send.start;

import java.io.File;
import java.io.FilenameFilter;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;

public class Start {

    public static String libPath = "";
    public static ClassLoader classLoader;

    /**
     * @param args
     */
    public static void main(String[] args) {
        libPath = args[0];
        createClassLoader();
        try {
            Class clazz = classLoader.loadClass("cmbcagent.tianjin.gjj.dz.MapSender");
            Method m = clazz.getDeclaredMethod("start", new Class[0]);
            m.invoke(clazz.newInstance(), new Object[0]);

        } catch (Exception e) {
            throw new RuntimeException("");
        }

    }

    public static void createClassLoader() {
        File localFile1 = new File(libPath);
        checkLibDir(localFile1);
        ArrayList localArrayList = new ArrayList(64);
        File localFile2 = new File(libPath);
        getAllJarUrl(localArrayList, localFile2);
        // File localFile3 = new File(this.libPath + "ext");
        // getAllJarUrl(localArrayList, localFile3);
        URL[] arrayOfURL = new URL[localArrayList.size()];
        localArrayList.toArray(arrayOfURL);
        System.out.println("******arrayOfURL.length: " + arrayOfURL.length);
        for (int i = 0; i < arrayOfURL.length; ++i)
            System.out.println(arrayOfURL[i]);
        AppendableURLClassloader localAppendableURLClassloader = new AppendableURLClassloader(arrayOfURL, Thread.currentThread()
                .getContextClassLoader());
        classLoader = localAppendableURLClassloader;
        Thread.currentThread().setContextClassLoader(classLoader);
    }

    public static void getAllJarUrl(List paramList, File paramFile) {
        checkLibDir(paramFile);
        String[] arrayOfString = listAllJarFile(paramFile);
        File localFile = null;
        int i = 0;
        try {
            i = 0;
            while (true) {
                if (i >= arrayOfString.length)
                    break;
                localFile = new File(paramFile, arrayOfString[i]);
                localFile = localFile.getCanonicalFile();
                paramList.add(localFile.toURL());
                ++i;
            }
        } catch (Exception localException) {
            localException.printStackTrace();
            throw new RuntimeException("Bootstrap.listJar");
        }
    }

    public static String[] listAllJarFile(File paramFile) {
        return paramFile.list(new FilenameFilter() {
            public boolean accept(File paramFile, String paramString) {
                return (paramString.endsWith(".jar"));
            }
        });
    }

    public static void checkLibDir(File paramFile) {
        if (!(paramFile.exists()))
            throw new IllegalArgumentException("libPath.notExist");
        if (!(paramFile.isDirectory()))
            throw new IllegalArgumentException("libPath.notDirectory");
        if (!(paramFile.canRead()))
            throw new IllegalArgumentException("libPath.canNotRead");
    }

}

 注意事项：
1.启动的类要单独放在一个jar包中，即含有main方法的类
2.main方法中不能引用第三方jar文件中的类(即通过import来导入的类只能是jvm自动加载的基本类，不能是第三方的jar),如果要引用只能通过反射机制来加载
3.main方法中主要是通过使用URLClassLoader来加载第三方的jar文件，并设置到当前线程下，然后通过反射机制来加载具体类，然后运行工程

含有Main的类只是负责通过反射机制调用主程序，起到一个入口的作用，其他不做任何业务操作