annotations-->注解的创建和使用

package annotation;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

//定义注解
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface UseCase
{
    public int id();
    
    public String description() default "no description";// 默认的描述
}

 

package annotation;

import java.util.List;

public class PasswordUtils
{
    // 使用注解
    @UseCase(id = 47, description = "passwords must contain at least one numeric")
    public boolean validatePassword(String password)
    {
        return password.matches("\\w*\\d\\w*");
    }
    
    @UseCase(id = 47)
    public String encryptPassword(String password)
    {
        return new StringBuilder(password).reverse().toString();
    }
    
    @UseCase(id = 47, description = "new passwords can't equal previously used ones")
    public boolean checkForNewPassword(List<String> prevPasswords, String password)
    {
        return !prevPasswords.contains(password);
    }
}

 

package annotation;

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

//注解处理器
public class UseCaseTracker
{
    public static void trackUseCases(java.util.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);
    }
}