JDK动态代理Demo代码，进一步学习分析

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;public class ProxyHandler<T> implements InvocationHandler { private T target; public ProxyHandler(T target) {
this.target = target;
} @Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { System.out.println("before invoke .");
Object ret = method.invoke(target, args);
System.out.println("after invoke .");
return ret;
} public T getProxy() {
return (T) Proxy.newProxyInstance(Thread.currentThread().getContextClassLoader(), target.getClass().getInterfaces(), this);
}
}

public interface UserService { String echo(String content);
}

import sun.misc.ProxyGenerator;import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;public class UserServiceImpl implements UserService { @Override
public String echo(String content) {
return content + "_impl";
} public static void main(String[] args) throws IOException { UserService us = new UserServiceImpl();
ProxyHandler<UserService> proxyHandler = new ProxyHandler<>(us);
UserService userService = proxyHandler.getProxy(); System.out.println(userService.echo("hello java "));
System.out.println(userService.getClass());
generateProxyClassToFile(); } public static void generateProxyClassToFile() throws IOException {
byte[] bts = ProxyGenerator.generateProxyClass("$Proxy0", new Class[]{UserService.class});
File file = new File("./", "$Proxy0.class");
if (!file.exists()) {
file.createNewFile();
}
FileOutputStream fos = new FileOutputStream(file);
fos.write(bts);
fos.flush();
fos.close();
}
}

//生成的代理类字节码：import com.javartisan.springboot.javartisanspringboot.aop.UserService;
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 UserService {
private static Method m1;
private static Method m3;
private static Method m2;
private static Method m0; public $Proxy0(InvocationHandler var1) throws {
super(var1);
} public final boolean equals(Object var1) throws {
try {
return (Boolean)super.h.invoke(this, m1, new Object[]{var1});
} catch (RuntimeException | Error var3) {
throw var3;
} catch (Throwable var4) {
throw new UndeclaredThrowableException(var4);
}
} public final String echo(String var1) throws {
try { // 代理实现的关键地方，h是继承至Proxy
return (String)super.h.invoke(this, m3, new Object[]{var1});
} catch (RuntimeException | Error var3) {
throw var3;
} catch (Throwable var4) {
throw new UndeclaredThrowableException(var4);
}
} public final String toString() throws {
try {
return (String)super.h.invoke(this, m2, (Object[])null);
} catch (RuntimeException | Error var2) {
throw var2;
} catch (Throwable var3) {
throw new UndeclaredThrowableException(var3);
}
} public final int hashCode() throws {
try {
return (Integer)super.h.invoke(this, m0, (Object[])null);
} catch (RuntimeException | Error var2) {
throw var2;
} catch (Throwable var3) {
throw new UndeclaredThrowableException(var3);
}
} static {
try {
m1 = Class.forName("java.lang.Object").getMethod("equals", Class.forName("java.lang.Object"));
m3 = Class.forName("com.javartisan.springboot.javartisanspringboot.aop.UserService").getMethod("echo", Class.forName("java.lang.String"));
m2 = Class.forName("java.lang.Object").getMethod("toString");
m0 = Class.forName("java.lang.Object").getMethod("hashCode");
} catch (NoSuchMethodException var2) {
throw new NoSuchMethodError(var2.getMessage());
} catch (ClassNotFoundException var3) {
throw new NoClassDefFoundError(var3.getMessage());
}
}
}