自定义注解Demo

叁歲伎倆 2022-06-06 07:56 218阅读 0赞

1.自定义注解UseCase

package 注解;
    
    import static java.lang.annotation.ElementType.*;
    
    import java.lang.annotation.Retention;
    import static java.lang.annotation.RetentionPolicy.*;
    import java.lang.annotation.Target;
    
    @Target(value={METHOD})
    //注解信息保留到运行时
    @Retention(RUNTIME)
    public @interface UseCase {
    	public String hehe();
    	public int id();
    	public String description() default "no description";
    }

2.在示例类中使用自定义注解

package 注解;
    
    import java.util.List;
    
    public class PswUtils {
    	
    	@UseCase(id=47,description="pwd must contain at least one number", hehe = "1")
    	public boolean validPwd(String pwd){
    		return (pwd.matches("\\w*\\d\\w*"));
    	}
    	
    	@UseCase(id=48, hehe = "2")
    	public String encryptPassword(String pwd){
    		return new StringBuilder(pwd).reverse().toString();
    	}
    	
    	@UseCase(id=49,description="new pwd can't contain ...", hehe = "3")
    	public boolean checkForNewpwd(List<String> prePwd,String pwd){
    		return !prePwd.contains(pwd);
    	}
    }

3.编写注解处理器

package 注解处理器;
    
    import java.lang.reflect.Method;
    import java.util.ArrayList;
    import java.util.Collections;
    import java.util.List;
    
    import 注解.PswUtils;
    import 注解.UseCase;
    
    public class UseCaseTracker {
    	public static void
    		trackUseCases(List<?> useCases,Class<?> cl){
    		for(Method m:cl.getDeclaredMethods()){
    			UseCase uc = m.getAnnotation(UseCase.class);
    			if(uc!=null){
    				System.out.println("Found Use Case: id="+uc.id()+" annotion="+uc.description());
    				useCases.remove(new Integer(uc.id()));
    				useCases.remove(uc.hehe());
    			}
    		}
    		
    		for(Object i:useCases){
    			System.out.println("Warning:minssing the case = "+i);
    		}
    	}
    	
    	//main()方法
    	public static void main(String[] args) {
    		List<Integer> useCases = new ArrayList<Integer>();
    		Collections.addAll(useCases, 47,48,49,50);
    		trackUseCases(useCases, PswUtils.class);
    		System.out.println("##################");
    		List<String> uc = new ArrayList<String>();
    		Collections.addAll(uc, "1","2","3","4");
    		trackUseCases(uc, PswUtils.class);
    	}
    	
    }

4.输出结果

Found Use Case: id=47 annotion=pwd must contain at least one number
    Found Use Case: id=48 annotion=no description
    Found Use Case: id=49 annotion=new pwd can't contain ...
    Warning:minssing the case = 50
    ##################
    Found Use Case: id=47 annotion=pwd must contain at least one number
    Found Use Case: id=48 annotion=no description
    Found Use Case: id=49 annotion=new pwd can't contain ...
    Warning:minssing the case = 4