zoukankan      html  css  js  c++  java
  • Java Annotation,Java注解

    Annotation

    Annotaions (also known as metadata) provide a formalized way to add information to yourcode so that you can easily use that data at some later point.
    Defining annotationsHere is the definition of the annotation above. You can see that annotation definitions look a lot like interface definitions.

    In fact, they compile to class files like any other Java interface:Apart from the @ symbol, the definition of @Test is much like that of an empty interface.

    An annotation definition also requires the meta-annotations @Target and @Retention.

    @Target defines where you can apply this annotation(a method or a field, for example).

    @Retention defines whether the annotations are availablein the (SOURCE), in the classfiles (CLASS), or at run time(RUNTIME).

    e.g.:

    //UseCase.java
    
    package annotationtest;
    
    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 "没有描述";
    }
    
    //PasswordUtils.java
    
    package annotationtest;
    
    public class PasswordUtils {
    
    	@UseCase(id=1, description="validate 密码")
    	public boolean validatePassword(String password){
    		return true;
    	}
    	@UseCase(id=2, description="encrypt 密码")
    	public boolean encryptPassword(String password){
    		return true;
    	}
    	@UseCase(id=3, description="checkfor 密码")
    	public boolean checkforPassword(String password){
    		return true;
    	}	
    	
    }
    //Test.java
    
    package annotationtest;
    
    import java.lang.reflect.Method;
    
    public class Test {
    
    	/**
    	 * @param args
    	 */
    	public static void main(String[] args) {
    		
    		Method[] methods = PasswordUtils.class.getDeclaredMethods();
    
    		for (Method m : methods) {
    			UseCase uc= m.getAnnotation(UseCase.class);
    			System.out.println("id=" + uc.id()+",description="+uc.description());
    		}
    		
    	}
    
    }
    
    // from : thinking in java.
    

  • 相关阅读:
    arp攻击 (可查看同一局域网他人手机照片)
    SQL注入(转载)
    常见文件文件头文件尾格式总结及各类文件头
    CTF
    Base64,Base32,Base16进制的区别
    Maven学习总结(二):安装
    Maven学习总结(一):基本概念
    Myeclipse下集成SVN插件
    Windows下多个JDK版本之间的切换
    java线程的常用方法
  • 原文地址:https://www.cnblogs.com/wucg/p/1987842.html
Copyright © 2011-2022 走看看