java中自定义注解_JAVA_编程开发_程序员俱乐部

java 自定义注解中的三个主要注解：

   @Target:指示注释内容的上下文，有如下类型：

    

class="java"> /** Class, interface (including annotation type), or enum declaration */
    TYPE,

    /** Field declaration (includes enum constants) */
    FIELD,

    /** Method declaration */
    METHOD,

    /** Formal parameter declaration */
    PARAMETER,

    /** Constructor declaration */
    CONSTRUCTOR,

    /** Local variable declaration */
    LOCAL_VARIABLE,

    /** Annotation type declaration */
    ANNOTATION_TYPE,

    /** Package declaration */
    PACKAGE,

    /**
     * Type parameter declaration
     *
     * @since 1.8
     */
    TYPE_PARAMETER,

    /**
     * Use of a type
     *
     * @since 1.8
     */
    TYPE_USE

   @Retention：指示注释类型的注释多长时间为保留。如果不存在保留注释注释类型声明，保留策略默认为class，有如下类型

   

 /**
     * Annotations are to be discarded by the compiler.
     */
    SOURCE,

    /**
     * Annotations are to be recorded in the class file by the compiler
     * but need not be retained by the VM at run time.  This is the default
     * behavior.
     */
    CLASS,

    /**
     * Annotations are to be recorded in the class file by the compiler and
     * retained by the VM at run time, so they may be read reflectively.
     *
     * @see java.lang.reflect.AnnotatedElement
     */
    RUNTIME

   @Documented：指示类型的注释要由JavaDoc记录

   自定义的注解：
   

@Target({ElementType.FIELD,ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface AnnotationTest {
    public boolean isAnnotation() default false;

    public String name() default "";

    public String value () default "";
}

  使用：
  

@AnnotationTest(name = "wangxiangyang",isAnnotation = true)
    public void testAnnotation(){
        System.out.println("------------");
    }

    
  获取注解中的值：

   

try{

            Method method = LuceneTest.class.getDeclaredMethod("testAnnotation");
            if (method.isAnnotationPresent(AnnotationTest.class)){
                AnnotationTest annotationTest =  method.getAnnotation(AnnotationTest.class);
                System.out.println(annotationTest.isAnnotation());
                System.out.println(annotationTest.name());
                System.out.println(annotationTest.value());
                System.out.println(annotationTest.toString());
            }
        }catch (Exception e){
            e.printStackTrace();
        }