JAVA动态加载JAR包执行程序

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入口代码

import java.io.File;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLClassLoader;
import dynamic.test.ICarFactory;public class hello {
public static void main(String args[])
{
System.out.println("Hello world");
// JAR文件地址
String jarName = "CarFactory.jar";
ICarFactory icf=null; //命名空间类名称
String className="dynamic.test.BYDFactory"; File file = new File(jarName);
URL url=null;
try {
url = file.toURL();
} catch (MalformedURLException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
} URLClassLoader loader = new URLClassLoader(new URL[]{url});
Class aClass=null;
try {
// 接口实例化
aClass = loader.loadClass(className);
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} try {
icf = (ICarFactory)aClass.newInstance();
} catch (InstantiationException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IllegalAccessException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
icf.makeCar();
}
}

接口类

package dynamic.test;
public interface ICarFactory {
public void makeCar();//等待实现的造车方法
}

实现类

//创建BMWFactory类，实现了ICarFactory
package dynamic.test;
public class BMWFactory implements ICarFactory {
//实现了ICarFactory的makeCar()方法
public void makeCar() {
System.out.println("BMWFactroy made a 宝马 for you");
}
}

//创建BYDFactory类，实现了ICarFactory
package dynamic.test;
public class BYDFactory implements ICarFactory {
//实现了ICarFactory的makeCar()方法
public void makeCar() {
System.out.println("BYDFactroy 生产一辆比亚迪 for you");
}
}