Java 动态生成类和实例, 并注入方法操作示例

 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 calledMethods = new LinkedList<>(); // property public int getRandomInt() { // Get a random integer return 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 @Override public Object invoke(Object obj, Method method, Object[] params) throws Throwable { Object ret = null; String name = method.getName(); if (name.equals("getRandomInt")) { // intercept the getRandomInt ret = method.invoke(mTarget, params); // call the base method System.out.println("Print random int: " + ret); } else if (name.equals("printClassInfo")) { // print class info System.out.println("Class: " + obj.getClass()); method.invoke(mTarget, params); } mTarget.calledMethods.add(name); // change the property return 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() { @Override public void printClassInfo() { System.out.println("I have to implement this method!!"); } }; IJavaGen javaGen = (IJavaGen) cons.newInstance(new JavaGenHandler(target)); javaGen.getRandomInt(); javaGen.printClassInfo(); System.out.println(target.calledMethods); } catch (Exception e) { e.printStackTrace(); } } }