java proxy jdk dynamic proxy application case

Author：Eve Cole Update Time：2024-11-17 14:06:01

Java proxies include jdk dynamic proxy and cglib proxy. Here we only talk about jdk dynamic proxy. JDK dynamic proxy mainly uses the java reflection mechanism (that is, the java.lang.reflect package)
The principle is (singers and managers are examples):
Establish a public interface, such as: singer public interface Singer;
Use a specific class to implement the interface, for example: Jay Chou, he is a singer, so he implements the Singer class, class MySinger implements Singer
Create an agent class, which is the broker here. He needs to implement the InvocationHandler class and rewrite the invoke method so that when something happens and you want to find Jay Chou (concrete class), you must first go to the broker (agent class) to handle it. The agent is deciding whether to meet with you (whether to execute this method)
1. Singer interface

Copy the code code as follows:

public interface Singer {

public abstract void sing();

public abstract String s();
}

2. Specific singer

Copy the code code as follows:

public class MySinger implements Singer {
public void sing() {
// TODO Auto-generated method stub
System.err.println("Singing...");
}
}

3. Agency type (broker)

Copy the code code as follows:

public class agent implements InvocationHandler{
public Object target;

//Bind
public Object bind(Object target){
this.target=target;
//Proxy must be put back
return Proxy.newProxyInstance(target.getClass().getClassLoader(), target.getClass().getInterfaces(), this);
}

//again
public Object invoke(Object proxy, Method method, Object[] args)
throws Throwable {
Object o =null;
System.out.println("Start transaction");
System.out.println("Judge permissions");

o = method.invoke(target, args);//execution method

System.out.println("End transaction");
return o;
}
}

4. Testing (why do you need an indirect interface? Below you will find that the proxy returns their interface class. This requires a proxy class, and you can proxy multiple classes, as long as the class implements the same interface)

Copy the code code as follows:

public class Test {
public static void main(String[] args) {
//
agent a =new agent();
Singer s= (Singer) a.bind(new MySinger());
s.sing();
}
}