本文實例講述了Java 動態(tài)生成類和實例, 并注入方法。分享給大家供大家參考，具體如下：

Java官方支持的, 必須要有接口才行

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<>(); // property public 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; } // 動態(tài)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 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!!');} }; IJavaGen javaGen = (IJavaGen) cons.newInstance(new JavaGenHandler(target)); javaGen.getRandomInt(); javaGen.printClassInfo(); System.out.println(target.calledMethods);} catch (Exception e) { e.printStackTrace();} }}

運行結(jié)果：

Print random int: 8143Class: class demo.$Proxy0I have to implement this method!![getRandomInt, printClassInfo]

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希望本文所述對大家java程序設(shè)計有所幫助。