Java 动态生成类和实例, 并注入方法

Java官方支持的, 必须要有接口才行

import java.lang.reflect.Constructor;import java.lang.reflect.InvocationHandler;import java.lang.reflect.Method;import java.lang.reflect.Proxy;import java.util.LinkedList;import java.util.List;import java.util.Random;/** * @author David Ding * */interface IJavaGen {int getRandomInt();void printClassInfo();}abstract class JavaGen implements IJavaGen {protected List<String> calledMethods = new LinkedList<>(); // propertypublic int getRandomInt() { // Get a random integerreturn new Random().nextInt(10000);}public abstract void printClassInfo();}class JavaGenHandler implements InvocationHandler {private JavaGen mTarget;public JavaGenHandler(JavaGen javaGen) {mTarget = javaGen;}// 动态注入@Overridepublic Object invoke(Object obj, Method method, Object[] params) throws Throwable {Object ret = null;String name = method.getName();if (name.equals("getRandomInt")) { // intercept the getRandomIntret = method.invoke(mTarget, params); // call the base methodSystem.out.println("Print random int: " + ret);} else if (name.equals("printClassInfo")) { // print class infoSystem.out.println("Class: " + obj.getClass());method.invoke(mTarget, params);}mTarget.calledMethods.add(name); // change the propertyreturn ret;}}public class JavaCodeGen {public static void main(String[] args) {try {Class<?> genClass = Proxy.getProxyClass(IJavaGen.class.getClassLoader(), IJavaGen.class);Constructor<?> cons = genClass.getConstructor(InvocationHandler.class);JavaGen target = new JavaGen() {@Overridepublic void printClassInfo() {System.out.println("I have to implement this method! fuck!");}};IJavaGen javaGen = (IJavaGen) cons.newInstance(new JavaGenHandler(target));javaGen.getRandomInt();javaGen.printClassInfo();System.out.println(target.calledMethods);} catch (Exception e) {e.printStackTrace();}}}