java之注解（一）

1.注解的定义

package com.eshore.sweetop.annotations;

import java.lang.annotation.ElementType;

import java.lang.annotation.Retention;

import java.lang.annotation.RetentionPolicy;

import java.lang.annotation.Target;

@Target(ElementType.METHOD)

@Retention(RetentionPolicy.RUNTIME)

public @interface UseCase {

public int id();

public String description() default "no description";

}

2.注解的引用

package com.eshore.sweetop.annotations;

import java.util.List;

public class PasswordUtils {

@UseCase(id=47,description="Passwords must contain at least one numeric")

public boolean validatePassword(String password){

return password.matches("//w*//d//w*");

}

@UseCase(id=48)

public String encryptPassword(String password){

return new StringBuilder(password).reverse().toString();

}

@UseCase(id=49,description="New password can't equal previously used ones")

public boolean checkForNewPassword(List<String> prevPassword,String password){

return !prevPassword.contains(password);

}

}

3.注解的处理器

package com.eshore.sweetop.annotations;

import java.lang.reflect.Method;

import java.util.ArrayList;

import java.util.Collections;

import java.util.List;

public class UseCaseTracker {

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

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

UseCase uc = m.getAnnotation(UseCase.class);

if (uc != null) {

System.out.println("Found Use Case:" + uc.id() + " "

+ uc.description());

useCases.remove(new Integer(uc.id()));

}

}

for (int i : useCases) {

System.out.println("Warning: Missing use case-" + i);

}

}

public static void main(String[] args) {

List<Integer> useCases = new ArrayList<Integer>();

Collections.addAll(useCases, 47, 48, 49, 50);

trackUseCases(useCases, PasswordUtils.class);

}

}