From 435a8d85c373626a1a548526fdf12a102c61d55c Mon Sep 17 00:00:00 2001 From: xuxin <840198532@qq.com> Date: Thu, 2 Apr 2026 14:17:14 +0800 Subject: [PATCH] =?UTF-8?q?=E8=BF=9B=E9=98=B6day12-=E6=B3=A8=E8=A7=A3?= =?UTF-8?q?=E8=A7=A3=E6=9E=90=E7=9B=B8=E5=85=B3API?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- .../com/inmind/{ => annotation03}/Demo08.java | 2 +- .../src/com/inmind/annotation03/Demo09.java | 67 +++++++++++++++++++ .../com/inmind/annotation03/MyAnnotation.java | 3 + .../src/com/inmind/annotation03/Student.java | 4 +- 4 files changed, 74 insertions(+), 2 deletions(-) rename javaSE-day12/src/com/inmind/{ => annotation03}/Demo08.java (93%) create mode 100644 javaSE-day12/src/com/inmind/annotation03/Demo09.java diff --git a/javaSE-day12/src/com/inmind/Demo08.java b/javaSE-day12/src/com/inmind/annotation03/Demo08.java similarity index 93% rename from javaSE-day12/src/com/inmind/Demo08.java rename to javaSE-day12/src/com/inmind/annotation03/Demo08.java index 46c7efd..2394bff 100644 --- a/javaSE-day12/src/com/inmind/Demo08.java +++ b/javaSE-day12/src/com/inmind/annotation03/Demo08.java @@ -1,4 +1,4 @@ -package com.inmind; +package com.inmind.annotation03; /* 元注解:用来修饰注解的注解 @Target:设置某一个注解的作用范围 diff --git a/javaSE-day12/src/com/inmind/annotation03/Demo09.java b/javaSE-day12/src/com/inmind/annotation03/Demo09.java new file mode 100644 index 0000000..f0c440e --- /dev/null +++ b/javaSE-day12/src/com/inmind/annotation03/Demo09.java @@ -0,0 +1,67 @@ +package com.inmind.annotation03; + +import java.lang.reflect.InvocationTargetException; +import java.lang.reflect.Method; + +/* + +Anontation：所有注解类型的公共接口，类似所有类的父类是Object。 + +AnnotatedElement接口：定义了与注解解析相关的方法，常用方法以下四个： + +1. boolean isAnnotationPresent(Class annotationClass); + 判断当前对象是否有指定的注解，有则返回true，否则返回false。 + +2. T getAnnotation(Class annotationClass); + 获得当前对象上指定的注解对象。 + +3. Annotation[] getAnnotations(); + 获得当前对象及其从父类上继承的所有的注解对象。 + +4. Annotation[] getDeclaredAnnotations(); + 获得当前对象上所有的注解对象，不包括父类的。 + +注意：我们之前学习的所有的反射API基本都是实现了AnnotatedElement接口，反射API都可解析注解！！！！！ + */ +public class Demo09 { + public static void main(String[] args) throws NoSuchMethodException, InstantiationException, IllegalAccessException, InvocationTargetException { + /* + 需求： + 1.使用反射获取私有的show方法上的MyAnnotation的注解的value属性值 + 2.将value的值作为show方法的参数，让show方法执行起来 + 解析： + 1.获取私有的show方法的Method对象 + 2.判断下该show方法上，是否有MyAnnotation注解 + 3.如果有该注解，获取MyAnnotation的注解对象，并获取注解中的value属性值 + 4.调用Mehotd对象的invoke方法，将value的值作为参数执行起来 + */ + + //1.获取私有的show方法的Method对象 + Class clazz = Student.class; + Method showMethod = clazz.getDeclaredMethod("show", int.class); + + /* + 2.判断下该show方法上，是否有MyAnnotation注解 + boolean isAnnotationPresent(Class annotationClass);判断当前对象是否有指定的注解，有则返回true，否则返回false。 + */ + boolean flag = showMethod.isAnnotationPresent(MyAnnotation.class); + System.out.println(flag); + + /* + 3.如果有该注解，获取MyAnnotation的注解对象，并获取注解中的value属性值 + T getAnnotation(Class annotationClass);获得当前对象上指定的注解对象 + */ + if (flag) { + MyAnnotation annotation = showMethod.getAnnotation(MyAnnotation.class); + int value = annotation.value(); + System.out.println(value); + /* + 4.调用Mehotd对象的invoke方法，将value的值作为参数执行起来 + */ + showMethod.setAccessible(true); + Object result = showMethod.invoke(clazz.newInstance(), value); + System.out.println(result); + } + + } +} diff --git a/javaSE-day12/src/com/inmind/annotation03/MyAnnotation.java b/javaSE-day12/src/com/inmind/annotation03/MyAnnotation.java index 8b89024..47a811e 100644 --- a/javaSE-day12/src/com/inmind/annotation03/MyAnnotation.java +++ b/javaSE-day12/src/com/inmind/annotation03/MyAnnotation.java @@ -1,6 +1,8 @@ package com.inmind.annotation03; import java.lang.annotation.ElementType; +import java.lang.annotation.Retention; +import java.lang.annotation.RetentionPolicy; import java.lang.annotation.Target; import java.util.ArrayList; @@ -21,6 +23,7 @@ import java.util.ArrayList; 6.注解在使用时，属性值必须赋值，默认值可以覆盖 */ @Target(value = {ElementType.TYPE,ElementType.FIELD,ElementType.METHOD,ElementType.CONSTRUCTOR}) +@Retention(RetentionPolicy.RUNTIME)//让当前的注解在运行时也有效，便于反射技术 public @interface MyAnnotation { public static final int age = 1;//注解中的常量 String name() default "张三";//name属性 diff --git a/javaSE-day12/src/com/inmind/annotation03/Student.java b/javaSE-day12/src/com/inmind/annotation03/Student.java index 095c9ce..ffb23be 100644 --- a/javaSE-day12/src/com/inmind/annotation03/Student.java +++ b/javaSE-day12/src/com/inmind/annotation03/Student.java @@ -1,5 +1,7 @@ package com.inmind.annotation03; +import org.junit.Test; + @MyAnnotation(name = "李四",value = 1) public class Student { //属性（成员变量） @@ -24,7 +26,7 @@ public class Student { System.out.println("无参无返回值的show方法执行了"); } - @MyAnnotation(1) + @MyAnnotation(100) private int show(int i){ System.out.println("有参有返回值的show方法执行了"); return i+100;