/**
* 創(chuàng)建Person接口
* @author ChenHao
*/
public interface Person {
//上交班費(fèi)
void giveMoney();
}

public class Student implements Person {
private String name;
public Student(String name) {
this.name = name;
}
@Override
public void giveMoney() {
System.out.println(name + "上交班費(fèi)50元");
}
}

/**
* 學(xué)生代理類(lèi)，也實(shí)現(xiàn)了Person接口，保存一個(gè)學(xué)生實(shí)體，這樣既可以代理學(xué)生產(chǎn)生行為
* @author ChenHao
*
*/
public class StudentsProxy implements Person{
//被代理的學(xué)生
Student stu;
public StudentsProxy(Student stu) {
this.stu = stu;
}
//代理上交班費(fèi)，調(diào)用被代理學(xué)生的上交班費(fèi)行為
public void giveMoney() {
stu.giveMoney();
}
}

public class StaticProxyTest {
public static void main(String[] args) {
//被代理的學(xué)生張三，他的班費(fèi)上交有代理對(duì)象monitor（班長(zhǎng)）完成
Student zhangsan = new Student("張三");
//生成代理對(duì)象，并將張三傳給代理對(duì)象
Person monitor = new StudentsProxy(zhangsan);
//班長(zhǎng)代理上交班費(fèi)
monitor.giveMoney();
}
}

/**
* 學(xué)生代理類(lèi)，也實(shí)現(xiàn)了Person接口，保存一個(gè)學(xué)生實(shí)體，這樣既可以代理學(xué)生產(chǎn)生行為
* @author ChenHao
*
*/
public class StudentsProxy implements Person{
//被代理的學(xué)生
Student stu;
public StudentsProxy(Student stu) {
this.stu = stu;
}
//代理上交班費(fèi)，調(diào)用被代理學(xué)生的上交班費(fèi)行為
public void giveMoney() {
System.out.println("張三最近學(xué)習(xí)有進(jìn)步！");
stu.giveMoney();
}
}

public class DynamicProxyTest {
interface IHello {
void sayHello();
}
static class Hello implements IHello {
@Override
public void sayHello() {
System.out.println("hello world");
}
}
static class DynamicProxy implements InvocationHandler {
Object originalObj;
Object bind(Object originalObj) {
this.originalObj = originalObj;
return Proxy.newProxyInstance(originalObj.getClass().getClassLoader(), originalObj.getClass().getInterfaces(), this);
}
/**
*Object proxy是代理的對(duì)象, Method method是真實(shí)對(duì)象中調(diào)用方法的Method類(lèi), Object[] args是真實(shí)對(duì)象中調(diào)用方法的參數(shù)
*/
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
System.out.println("welcome");
return method.invoke(originalObj, args);
}
}
public static void main(String[] args) {
IHello hello = (IHello) new DynamicProxy().bind(new Hello());
hello.sayHello();
}
}

welcome 
hello world

public static Object newProxyInstance(ClassLoader loader, Class<?>[] interfaces, InvocationHandler h) throws IllegalArgumentException {
　　// handler不能為空
if (h == null) {
throw new NullPointerException();
}
final Class<?>[] intfs = interfaces.clone();
final SecurityManager sm = System.getSecurityManager();
if (sm != null) {
checkProxyAccess(Reflection.getCallerClass(), loader, intfs);
}
/*
* Look up or generate the designated proxy class.
*/
　　// 通過(guò)loader和接口，得到代理的Class對(duì)象
Class<?> cl = getProxyClass0(loader, intfs);

/*
* Invoke its constructor with the designated invocation handler.
*/
try {
final Constructor<?> cons = cl.getConstructor(constructorParams);
final InvocationHandler ih = h;
if (sm != null && ProxyAccessHelper.needsNewInstanceCheck(cl)) {
// create proxy instance with doPrivilege as the proxy class may
// implement non-public interfaces that requires a special permission
return AccessController.doPrivileged(new PrivilegedAction<Object>() {
public Object run() {
return newInstance(cons, ih);
}
});
} else {
　　　　　　　// 創(chuàng)建代理對(duì)象的實(shí)例
return newInstance(cons, ih);
}
} catch (NoSuchMethodException e) {
throw new InternalError(e.toString());
}
}

private static Object newInstance(Constructor<?> cons, InvocationHandler h) {
try {
return cons.newInstance(new Object[] {h} );
} catch (IllegalAccessException | InstantiationException e) {
throw new InternalError(e.toString());
} catch (InvocationTargetException e) {
Throwable t = e.getCause();
if (t instanceof RuntimeException) {
throw (RuntimeException) t;
} else {
throw new InternalError(t.toString());
}
}
}

/**
* 代理類(lèi)的生成工具 
* @author ChenHao
* @since 2019-4-2 
*/
public class ProxyGeneratorUtils {
/**
* 把代理類(lèi)的字節(jié)碼寫(xiě)到硬盤(pán)上 
* @param path 保存路徑 
*/
public static void writeProxyClassToHardDisk(String path) {
// 第一種方法
// System.getProperties().put("sun.misc.ProxyGenerator.saveGeneratedFiles", true); 
// 第二種方法 
// 獲取代理類(lèi)的字節(jié)碼 
byte[] classFile = ProxyGenerator.generateProxyClass("$Proxy11", UserServiceImpl.class.getInterfaces());
FileOutputStream out = null;
try {
out = new FileOutputStream(path);
out.write(classFile);
out.flush();
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
out.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
public static void main(String[] args) {
ProxyGeneratorUtils.writeProxyClassToHardDisk("C:/x/$Proxy11.class");
}
} 

package org.fenixsoft.bytecode;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.lang.reflect.UndeclaredThrowableException;
public final class $Proxy0 extends Proxy
implements DynamicProxyTest.IHello
{
private static Method m3;
private static Method m1;
private static Method m0;
private static Method m2;
/**
*注意這里是生成代理類(lèi)的構(gòu)造方法，方法參數(shù)為InvocationHandler類(lèi)型，看到這，是不是就有點(diǎn)明白
*super(paramInvocationHandler)，是調(diào)用父類(lèi)Proxy的構(gòu)造方法。
*父類(lèi)持有：protected InvocationHandler h;
*Proxy構(gòu)造方法：
* protected Proxy(InvocationHandler h) {
* Objects.requireNonNull(h);
* this.h = h;
* }
*
*/
public $Proxy0(InvocationHandler paramInvocationHandler)
throws 
{
super(paramInvocationHandler);
}
/**
* 
*這里調(diào)用代理對(duì)象的sayHello方法，直接就調(diào)用了InvocationHandler中的invoke方法，并把m3傳了進(jìn)去。
*this.h.invoke(this, m3, null); this.h就是父類(lèi)Proxy中保存的InvocationHandler實(shí)例變量
*來(lái)，再想想，代理對(duì)象持有一個(gè)InvocationHandler對(duì)象，InvocationHandler對(duì)象持有一個(gè)被代理的對(duì)象，
*再聯(lián)系到InvacationHandler中的invoke方法。嗯，就是這樣。
*/
public final void sayHello()
throws 
{
try
{
this.h.invoke(this, m3, null);
return;
}
catch (RuntimeException localRuntimeException)
{
throw localRuntimeException;
}
catch (Throwable localThrowable)
{
throw new UndeclaredThrowableException(localThrowable);
}
}
// 此處由于版面原因，省略equals()、hashCode()、toString()三個(gè)方法的代碼
// 這3個(gè)方法的內(nèi)容與sayHello()非常相似。
static
{
try
{
m3 = Class.forName("org.fenixsoft.bytecode.DynamicProxyTest$IHello").getMethod("sayHello", new Class[0]);
m1 = Class.forName("java.lang.Object").getMethod("equals", new Class[] { Class.forName("java.lang.Object") });
m0 = Class.forName("java.lang.Object").getMethod("hashCode", new Class[0]);
m2 = Class.forName("java.lang.Object").getMethod("toString", new Class[0]);
return;
}
catch (NoSuchMethodException localNoSuchMethodException)
{
throw new NoSuchMethodError(localNoSuchMethodException.getMessage());
}
catch (ClassNotFoundException localClassNotFoundException)
{
throw new NoClassDefFoundError(localClassNotFoundException.getMessage());
}
}
}