Table of Contents
1. Proxy
(1) First define an interface
(2) Define the target object (target)
(3) Define the proxy object
2. Use dynamic proxy to implement a simple interceptor
1. Define an interface
2. Define a target object
3. Create an interceptor
4. Create a proxy
Home Java javaTutorial How to implement a simple interceptor operation in Java through dynamic proxy

How to implement a simple interceptor operation in Java through dynamic proxy

Apr 30, 2023 pm 08:55 PM
java

1. Proxy

Before using dynamic proxies to implement interceptors, let us first briefly understand what Java proxies are.

Agent, as the name suggests, does not directly operate the object being proxied (hereinafter referred to as the target object, which sounds more comfortable), but indirectly uses the methods in the target object through a proxy object. Agents are divided into two modes, one is static agent and the other is dynamic agent. Next, write an example of a static proxy.

Whether it is a static proxy or a dynamic proxy, the target object (target) must implement an interface (interface). Note that if you use the proxy provided by cglib, you do not have to implement the interface, but implement it through a subclass. This method will not be discussed for now.

(1) First define an interface

public interface IUserDao {
    void save();
}
Copy after login

(2) Define the target object (target)

public class UserDaoImpl implements IUserDao {
    public void save() {
        System.out.println("--------已经保存数据---------");
    }
}
Copy after login

(3) Define the proxy object

public class UserDaoProxy implements IUserDao {
 private IUserDao target;//将目标对象放到代理对象中
 public UserDaoProxy(IUserDao target){
  this.target = target;
  }
 public void save() {
     System.out.println("------开始事务------");
            target.save();
     System.out.println("-------提交事务------");
    }
}
Copy after login

Test Next:

public class Test {
public static void main(String[] args){
    IUserDao userDao = new UserDaoImpl();
    UserDaoProxy proxy = new UserDaoProxy(userDao);
    proxy.save();//通过代理对象调用save方法
    }
}
Copy after login

The output result is:

------Start transaction------
--------Data has been saved ---------

-------Commit transaction------

There is a problem with this method, that is, the proxy object must It is also necessary to implement the same interface implemented by the proxy object, which leads to serious coupling. Therefore, an improved method is used below, namely dynamic proxy (jdk proxy).

The dynamic proxy method also requires the target object (target) to implement an interface

(1) Define an interface (IUserDao)

(2) Define a target object class (UserDaoImpl )

(3) Create a dynamic proxy class

public class ProxyFactory {
    //维护一个目标对象
    private Object target; 
    public ProxyFactory(Object target) {
        this.target = target;
    }
 
    //给目标对象生成代理对象
    public Object getProxyInstance() {
        System.out.println("----target class---" + target.getClass());
        System.out.println("----target interfaces---" +
            target.getClass().getInterfaces());
 
        return Proxy.newProxyInstance(target.getClass().getClassLoader(),
            target.getClass().getInterfaces(),
            new InvocationHandler() {
                public Object invoke(Object proxy, Method method, Object[] args)
                    throws Throwable {
                    System.out.println("----开始事务2-----");
 
                    //执行目标对象方法
                    Object returnValue = method.invoke(target, args);
                    System.out.println("----提交事务2----");
 
                    return returnValue;
                }
            });
    }
}
Copy after login

Test it:

public class Test {
    public static void main(String[] args) {
        //目标对象
        IUserDao target = new UserDao();
        System.out.println(target.getClass());
 
        //给目标对象创建代理对象
        IUserDao proxy = (IUserDao) new ProxyFactory(target).getProxyInstance();
        System.out.println("----proxy----:" + proxy.getClass());
        proxy.save();
        proxy.delete();
    }
}
Copy after login

Output result:

class com.jd.pattern. proxy.dynamicProxy.UserDao
----target class---class com.jd.pattern.proxy.dynamicProxy.UserDao
----target interfaces---[Ljava.lang.Class;@1fb3ebeb
----proxy----: class com.sun.proxy.$Proxy0
----Start transaction 2-----
-----Save completed--- ---
----Submit transaction 2----
----Start transaction 2-----
----Delete completed----

----Submit transaction 2----

2. Use dynamic proxy to implement a simple interceptor

Since the dynamic proxy method is used, there will definitely be Interface, target class, proxy class, plus an interceptor

1. Define an interface

public interface BusinessFacade {
    void doSomething();
}
Copy after login

2. Define a target object

public class BusinessClass implements BusinessFacade {
    public void doSomething() {
        System.out.println("在业务组件BusinessClass中调用doSomething方法");
    }
}
Copy after login

3. Create an interceptor

public class InterceptorClass {
    public void before() {
        System.out.println("在InterceptorClass中调用方法:before()");
    }
 
    public void after() {
        System.out.println("在InterceptorClass中调用方法:after()");
    }
}
Copy after login

4. Create a proxy

public class DynamicProxyHandler {
    //声明被代理对象
    private Object target;
    //创建拦截器
    InterceptorClass interceptor = new InterceptorClass();
    //动态生成一个代理对象,并绑定被代理类和代理处理器
    public Object getProxyInstance(final Object target) {
        this.target = target;
        return Proxy.newProxyInstance(target.getClass().getClassLoader(),
            target.getClass().getInterfaces(),
            new InvocationHandler() {
                public Object invoke(Object proxy, Method method, Object[] args)
                    throws Throwable {
                    interceptor.before();
                    Object result = method.invoke(target, args);
                    interceptor.after();
                    return result;
                }
            });
    }
}
Copy after login

Test it:

public class Test {
    public static void main(String[] args) {
        //创建动态代理工具
        DynamicProxyHandler proxyHandler = new DynamicProxyHandler();
        //创建业务组件
        BusinessFacade target = new BusinessClass();
        //获取代理对象
        BusinessFacade proxy = (BusinessFacade) proxyHandler.getProxyInstance(target);
        //通过代理对象调用目标对象方法
        proxy.doSomething();
    }
}
Copy after login

Output result:

Call the method in InterceptorClass: before()
Call the doSomething method in the business component BusinessClass
Call the method in InterceptorClass: after()

The above is the detailed content of How to implement a simple interceptor operation in Java through dynamic proxy. For more information, please follow other related articles on the PHP Chinese website!

Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

AI Hentai Generator

AI Hentai Generator

Generate AI Hentai for free.

Hot Article

R.E.P.O. Energy Crystals Explained and What They Do (Yellow Crystal)
2 weeks ago By 尊渡假赌尊渡假赌尊渡假赌
Repo: How To Revive Teammates
1 months ago By 尊渡假赌尊渡假赌尊渡假赌
Hello Kitty Island Adventure: How To Get Giant Seeds
4 weeks ago By 尊渡假赌尊渡假赌尊渡假赌

Hot Tools

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

Square Root in Java Square Root in Java Aug 30, 2024 pm 04:26 PM

Guide to Square Root in Java. Here we discuss how Square Root works in Java with example and its code implementation respectively.

Perfect Number in Java Perfect Number in Java Aug 30, 2024 pm 04:28 PM

Guide to Perfect Number in Java. Here we discuss the Definition, How to check Perfect number in Java?, examples with code implementation.

Random Number Generator in Java Random Number Generator in Java Aug 30, 2024 pm 04:27 PM

Guide to Random Number Generator in Java. Here we discuss Functions in Java with examples and two different Generators with ther examples.

Weka in Java Weka in Java Aug 30, 2024 pm 04:28 PM

Guide to Weka in Java. Here we discuss the Introduction, how to use weka java, the type of platform, and advantages with examples.

Armstrong Number in Java Armstrong Number in Java Aug 30, 2024 pm 04:26 PM

Guide to the Armstrong Number in Java. Here we discuss an introduction to Armstrong's number in java along with some of the code.

Smith Number in Java Smith Number in Java Aug 30, 2024 pm 04:28 PM

Guide to Smith Number in Java. Here we discuss the Definition, How to check smith number in Java? example with code implementation.

Java Spring Interview Questions Java Spring Interview Questions Aug 30, 2024 pm 04:29 PM

In this article, we have kept the most asked Java Spring Interview Questions with their detailed answers. So that you can crack the interview.

Break or return from Java 8 stream forEach? Break or return from Java 8 stream forEach? Feb 07, 2025 pm 12:09 PM

Java 8 introduces the Stream API, providing a powerful and expressive way to process data collections. However, a common question when using Stream is: How to break or return from a forEach operation? Traditional loops allow for early interruption or return, but Stream's forEach method does not directly support this method. This article will explain the reasons and explore alternative methods for implementing premature termination in Stream processing systems. Further reading: Java Stream API improvements Understand Stream forEach The forEach method is a terminal operation that performs one operation on each element in the Stream. Its design intention is

See all articles