Write your own annotation processor, little chestnut

1、代码

import java.lang.annotation.ElementType;

import java.lang.annotation.Retention;

import java.lang.annotation.RetentionPolicy;

import java.lang.annotation.Target;

import java.lang.reflect.Method;

import java.util.ArrayList;

import java.util.Collections;

import java.util.List;

/**

  
  
  


   
   
   
Created by cxh on 17/3/18.

   
   
   
自己写注解处理器

*/

  
  
  
//编写自定义注解

@Target(ElementType.METHOD)

@Retention(RetentionPolicy.RUNTIME)

@interface Test{

public int id();

public String description() default "no descrition >>>";

}

//应用自定义注解

class PasswordUtils{

@Test(id=23,description = "pass1")

public boolean pass11(){

System.out.println("this is pass1");

return true;

}

@Test(id=22,description = "pass2")

public String pass2(){

System.out.println("this is pass2");

return "pass2";

}

@Test(id=21)

public int pass3(){

System.out.println("this is pass3");

return 1;

}

}

//如果没有一个可以读取注解的工具,那么注解就不会比注释更有用.使用注解的过程中,很重要的一个部分就是:创建与使用注解处理器.

//注解处理器

public class UseCaseTracker {

public static void trackUseCases(List
    
    
     useCases,Class<?> cl){
    
    
    

for(Method m:cl.getDeclaredMethods()){//反射
    
    
    

Test t=m.getAnnotation(Test.class);//反射
    
    
    

if(t!=null){
    
    
    

Sy
    stem.out.println("found use case:"+t.id()+" "+t.description());
    
    
    

useCases.remove(new Integer(t.id()));//?????
    
    
    

}
    
    
    

}
    
    
    

for(int i:useCases){
    
    
    

Sy
    stem.out.println("warning :missing use case:"+i);
    
    
    

}
    
    
    

}
   
   
   
public static void main(String[] args) {
    List<Integer> list=new ArrayList<Integer>();
    Collections.addAll(list,24,23,22,21);
    trackUseCases(list,PasswordUtils.class);
}



    }


2、运行结果：
found use case:23 pass1
found use case:22 pass2
found use case:21 no descrition >>>
warning :missing use case:24