package annotationTest;

import java.lang.annotation.*;

@Documented
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface MethodInfo {
    String author() default "Jerry";
    String version() default "1.0";
    String date();
    String comment();
}

package annotationTest;

// Jerry change for demo

public class AnnotationExample {
    @Override
    @MethodInfo(author = "xxx",version = "1.0",date = "2015/03/26",comment = "override toString()")
    public String toString() {
        return "AnnotationExample{}";
    }

    @Deprecated
    @MethodInfo(comment = "deprecated method", date = "2015/03/26")
    public static void oldMethod() {
        System.out.println("old method, don't use it.");
    }

    @MethodInfo(author = "Pankaj", comment = "Main method", date = "Nov 17 2012", version = "1.0")
    public static void genericsTest() {
        oldMethod();
    }
}

@annotationTest.MethodInfo(version="1.0", author="xxx", date="2015/03/26", comment="override toString()") in method:public java.lang.String annotationTest.AnnotationExample.toString()


Method with revision no 1.0 = public java.lang.String annotationTest.AnnotationExample.toString()
@annotationTest.MethodInfo(version="1.0", author="Pankaj", comment="Main method", date="Nov 17 2012") in method:public static void annotationTest.AnnotationExample.genericsTest()


Method with revision no 1.0 = public static void annotationTest.AnnotationExample.genericsTest()
@java.lang.Deprecated(forRemoval=false, since="") in method:public static void annotationTest.AnnotationExample.oldMethod()
@annotationTest.MethodInfo(version="1.0", author="Jerry", comment="deprecated method", date="2015/03/26") in method:public static void annotationTest.AnnotationExample.oldMethod()


Method with revision no 1.0 = public static void annotationTest.AnnotationExample.oldMethod()

package annotationTest;

import java.lang.annotation.Documented;
import java.lang.annotation.Inherited;
import java.lang.annotation.*;

@Target({ElementType.METHOD,ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Documented
public @interface Description {
   String desc();
   String author();
   int age() default 18;
}

package annotationTest;

import java.lang.annotation.Annotation;
import java.lang.reflect.Method;

@Description(author = "Jerry", desc = "Class annotation", age = 35)
public class People {
  
  @Description(author = "Jerry 2", desc = "method annotation", age = 35)
  public void hello(){
    
  }
  
  @SuppressWarnings({ "rawtypes", "unchecked" })
  public static void main(String[] arg){
          try {
              // 使用类加载器加载类
              Class c = Class.forName("annotationTest.People");
              // 找到类上面的注解
              boolean isExist = c.isAnnotationPresent(Description.class);
              // 上面的这个方法是用这个类来判断这个类是否存在Description这样的一个注解
              if (isExist) {
                  // 拿到注解实例，解析类上面的注解
                  
                Description d = (Description) c.getAnnotation(Description.class);
                  System.out.println(d.desc());
              }
              
            //获取所有的方法
              Method[] ms = c.getMethods();
              // 遍历所有的方法
              for (Method m : ms) {
                  boolean isExist1 = m.isAnnotationPresent(Description.class);
                  if (isExist1) {
                      Description d1=m.getAnnotation(Description.class);
                      System.out.println(d1.desc());
                  }
              }
              
            //另一种解析方法
              for (Method m : ms) {
                  //拿到方法上的所有的注解
                  Annotation[] as=m.getAnnotations();
                  for (Annotation a : as) {
                      //用二元操作符判断a是否是Description的实例
                      if (a instanceof Description) {
                          Description d=(Description) a;
                          System.out.println(d.desc());
                      }
                  }
              }
              
              
          } catch (ClassNotFoundException e) {
              e.printStackTrace();
          }
      }
  }