反射获取泛型+获取注解

反射获取泛型

1. // method.getGenericParameterTypes();   获取泛型的参数信息
   // method.getGenericExceptionTypes()    获取泛型的异常信息
   // method.getGenericReturnType();       获取泛型的返回信息
   // 如果有就开始循环遍历       ParameterizedType   参数化类型
   // 开始强转成泛型  .getActualTypeArguments();      获取它真实的参数类型
   

2. public class Test05 {
   
       public void test01(Map<String,User> map, List<User> list){
           System.out.println("test01");
       }
   
       public Map<String,User> test02(){
           System.out.println("test02");
           return null;
       }
   
       public static void main(String[] args) throws NoSuchMethodException {
           // 用反射获取方法
           Method method = Test05.class.getMethod("test01", Map.class, List.class);
           // method.getGenericParameterTypes();   获取泛型的参数信息
           // method.getGenericExceptionTypes()    获取泛型的异常信息
           // method.getGenericReturnType();       获取泛型的返回信息
           Type[] genericParameterTypes = method.getGenericParameterTypes();
           for (Type genericParameterType : genericParameterTypes) {
               // 打印参数信息
               System.out.println("#"+genericParameterType);
               // 判断这个对象是否有泛型
               // 如果有就开始循环遍历       ParameterizedType   参数化类型
               if (genericParameterType instanceof ParameterizedType){
                   // 开始强转成泛型  .getActualTypeArguments();      获取它真实的参数类型
                   Type[] actualTypeArguments = ((ParameterizedType) genericParameterType).getActualTypeArguments();
                   for (Type actualTypeArgument : actualTypeArguments) {
                       System.out.println(actualTypeArgument);
                   }
               }
           }
           System.out.println("========================");
           method = Test05.class.getMethod("test02",null);
           Type genericReturnType = method.getGenericReturnType();
           if (genericReturnType instanceof ParameterizedType){
               Type[] actualTypeArguments = ((ParameterizedType) genericReturnType).getActualTypeArguments();
               for (Type actualTypeArgument : actualTypeArguments) {
                   System.out.println(actualTypeArgument);
               }
           }
       }
   }
   

反射获取注解

1. 对象.getAnnotations();		获取注解
   输出出来的是注解的类信息；下面是获取注解的值
   /**
   * 反射获取注解的值
   * 首先获取反射的类,根据类进行获取反射的值
   * 强转成反射的类   里面有value方法  就能获取反射的值
   */
   TableWen tableWen = (TableWen) c1.getAnnotation(TableWen.class);
   System.out.println(tableWen.value());
   
   // 反射获取属性的值
   Field[] declaredFields = c1.getDeclaredFields();
   for (Field declaredField : declaredFields) {
   	ColumnWen c = (ColumnWen) declaredField.getAnnotation(ColumnWen.class);
   	System.out.println("长度是：" + c.length() + "，名字是：" + c.name() + "，类型是：" + c.type());
   }
   

2. 本类的信息

   public class Test06反射获取注解 {
       public static void main(String[] args) throws ClassNotFoundException {
           // 反射来获取注解
           Class c1 = Class.forName("com.lening.reflection.Student");
           Annotation[] annotations = c1.getAnnotations();
           for (Annotation annotation : annotations) {
               System.out.println(annotation);
           }
   
           /**
            * 反射获取注解的值
            * 首先获取反射的类,根据类进行获取反射的值
            * 强转成反射的类   里面有value方法  就能获取反射的值
            */
           TableWen tableWen = (TableWen) c1.getAnnotation(TableWen.class);
           System.out.println(tableWen.value());
   
           // 反射获取属性的值
           Field[] declaredFields = c1.getDeclaredFields();
           for (Field declaredField : declaredFields) {
               ColumnWen c = (ColumnWen) declaredField.getAnnotation(ColumnWen.class);
               System.out.println("长度是：" + c.length() + "，名字是：" + c.name() + "，类型是：" + c.type());
           }
       }
   }
   
   @TableWen("db_Wen")
   class Student {
       @ColumnWen(name = "name", type = "varChar", length = 3)
       private String name;
       @ColumnWen(name = "age", type = "Integer", length = 4)
       private int age;
       @ColumnWen(name = "uuid", type = "Integer", length = 5)
       private int id;
   
       public String getName() {
           return name;
       }
   
       public void setName(String name) {
           this.name = name;
       }
   
       public int getAge() {
           return age;
       }
   
       public void setAge(int age) {
           this.age = age;
       }
   
       public int getId() {
           return id;
       }
   
       public void setId(int id) {
           this.id = id;
       }
   
       public Student(String name, int age, int id) {
           this.name = name;
           this.age = age;
           this.id = id;
       }
   
       public Student() {
       }
   
       @Override
       public String toString() {
           return "Student{" +
                   "name='" + name + '\'' +
                   ", age=" + age +
                   ", id=" + id +
                   '}';
       }
   }
   
   @Target(ElementType.TYPE)
   @Retention(RetentionPolicy.RUNTIME)
   @interface TableWen {
       String value();
   }
   
   @Target(ElementType.FIELD)
   @Retention(RetentionPolicy.RUNTIME)
   @interface ColumnWen {
       String name();
   
       String type();
   
       int length();
   }