自定义注解

佚名 6年前 (2019-05-06) 随笔 1850人围观抢沙发百度已收录

示例出自《java编程思想》

自定义注解：

package demo;

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";

}

注解处理器：

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package demo;

import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

//注解处理器 使用反射机制查找@UseCase标记
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<>();
        Collections.addAll(useCases, 47,48,49,50);
        trackUseCases(useCases, PasswordUtils.class);
    }
}

// 输出结果：
// Found Use Case:49 password muset contain at least one numeric
// Found Use Case:47 password muset contain at least one numeric
// Found Use Case:48 password muset contain at least one numeric
// Warning: Missing use case-50

注解示例：

package demo;

public class PasswordUtils {

    @UseCase(id=47, description="password muset contain at least one numeric")
    public boolean validatePassword(String password){
        return (password.matches("\\w*\\d\\w*"));
    }

    @UseCase(id=48, description="password muset contain at least one numeric")
    public boolean encryptPassword(String password){
        return (password.matches("\\w*\\d\\w*"));
    }
    
    @UseCase(id=49, description="password muset contain at least one numeric")
    public boolean checkForNewPassword(String password){
        return (password.matches("\\w*\\d\\w*"));
    }
}