使用反射技术和字节码的技术,在运行期创建指定接口或类的子类(动态代理)以及其实例对象的技术,通过这个技术可以无侵入性的为代码进行增强;
先来回忆一下 class源文件的实例过程
根据上面的定义来看整个过程就是跳过了原class文件
公共类:
/**
* @Author: jimmy
* @Date: 2021/9/2 11:40
* @Description:
*/
public class User {
private String name;
private int age;
private String sex;
private String password;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
@Override
public String toString() {
return "User{" +
"name='" + name + ''' +
", age=" + age +
", sex='" + sex + ''' +
", password='" + password + ''' +
'}';
}
}
public interface UserService {
void printUser(User user);
}
public class UserServiceImpl implements UserService {
@Override
public void printUser(User user) {
System.out.println(user);
}
}
jdk代理:
public class JDKUserInvocationHandler implements InvocationHandler {
// 原始对象
private Object obj;
public Object getObj() {
return obj;
}
public void setObj(Object obj) {
this.obj = obj;
}
public JDKUserInvocationHandler(Object obj) {
this.obj = obj;
}
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
if(args !=null && args[0] instanceof User){
User u = (User)args[0];
if(u.getAge() > 80){
System.out.println("jdk: 你这个人有点长寿啊");
}
}
Object res = method.invoke(obj, args);
System.out.println("---------- jdk调用方法后 ----------");
return res;
}
}
cglib:
public class CglibMethodIntercepter implements MethodInterceptor {
@Override
public Object intercept(Object o, Method method, Object[] args, MethodProxy methodProxy) throws Throwable {
if(args !=null && args[0] instanceof User){
User u = (User)args[0];
if(u.getAge() > 80){
System.out.println("cglib: 疯狂暗示");
}
}
Object res = methodProxy.invokeSuper(o, args);
System.out.println("---------- cglib调用方法后 ----------");
return res;
}
}
测试类
public class ProxyTest {
public static void main(String[] args) {
User user = new User();
user.setAge(180);
user.setName("非鸽传书");
user.setSex("跪星人");
user.setPassword("点赞、关注、评论,求求你啦");
// ------ JDK 代理
UserService userService = new UserServiceImpl();
UserService proxy =
(UserService)Proxy.newProxyInstance(
userService.getClass().getClassLoader(),
userService.getClass().getInterfaces(),
new JDKUserInvocationHandler(userService)
);
proxy.printUser(user);
System.out.println("---------------------------------");
// ----- cglib 代理
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass(UserServiceImpl.class);
enhancer.setCallback(new CglibMethodIntercepter());
UserService us = (UserServiceImpl) enhancer.create();
us.printUser(user);
}
}
// 输出结果
jdk: 你这个人有点长寿啊
User{name='非鸽传书', age=180, sex='外星人', password='点赞、关注、评论,求求你啦'}
---------- jdk调用方法后 ----------
---------------------------------
cglib: 疯狂暗示
User{name='非鸽传书', age=180, sex='外星人', password='点赞、关注、评论,求求你啦'}
---------- cglib调用方法后 ----------
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