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);
}
}

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