The principle of the interceptor about Struts2

There are two interceptors set up here, firstInterception, SecondInterception

 1 package struts2_inteception;
 2 
 3 public class firstInterception implements Interception{
 4     public void interceptor(ActionInvocaton invocation){
 5         System.out.println("-1");
 6         invocation.invoke();
 7         System.out.println("1");
 8         
 9     }
10 }

 1 package struts2_inteception;
 2 
 3 public class SecondInterception2 implements Interception{
 4     public void interceptor(ActionInvocaton invocation){
 5         System.out.println("-2");
 6         invocation.invoke();
 7         System.out.println("2");
 8         
 9     }
10 }

 

Main function Main class

1 package struts2_inteception;
2 
3 public class Main {
4     public static void main(String []args){
5         new ActionInvocaton().invoke();
6     }
7 
8 }

 

Interceptor interface Interceptor

1 package struts2_inteception;
2 
3 public interface Interception {
4     public void interceptor(ActionInvocaton actionInvocaton);
5 }

 

An Action class that simulates struts2

 

package struts2_inteception;

public class Action {
    public void execute(){
        System.out.println( "execute() method execution" );
    }

}

 

 

an ActionInvocation class,

 

package struts2_inteception;

import java.util.List;
import java.util.ArrayList;


public class ActionInvocaton {
    int index=-1;
    Action action=new Action();
    List <Interception> interceptions= new ArrayList<Interception> ();
     public ActionInvocaton(){
         // Call a series of interceptors here 
        this .interceptions.add( new firstInterception());
         this .interceptions.add( new SecondInterception2 ( ));
    }
    public void invoke(){
        index ++ ;
         if (index>= interceptions.size()){
             // Call the action method 
            action.execute();
        } else {
             // Call the things added in the interceptor 
            this .interceptions.get(index).interceptor( this );
        }
        
    }
    
    

}

 The execution process of the real struts2 interceptor is as follows:

 

The result of execution is as follows:

-1
-2
Execution of the execute() method
2
1