Java中的 AnnotatedElement getDeclaredAnnotations() 方法及示例

Java.lang.AnnotatedElement 类的getDeclaredAnnotations()方法用于获取实现此接口的类中存在的已声明注释。该方法返回存在的已声明注释的数组。

句法：

public DeclaredAnnotation[] getDeclaredAnnotations()

参数：此方法不接受任何参数。

返回值：此方法返回存在的已声明注释的数组。

下面的程序演示了 getDeclaredAnnotations() 方法。

示例 1：

// Java program to demonstrate
// getDeclaredAnnotations() method
  
import java.util.*;
import java.lang.reflect.*;
import java.lang.annotation.*;
  
@Deprecated
public class Test {
  
    public Object obj;
  
    public static void main(String[] args)
        throws ClassNotFoundException
    {
        try {
  
            // returns the Class object
            // for this myAnnotatedElement
            AnnotatedElement myAnnotatedElement
                = Test.class;
  
            System.out.println(
                "AnnotatedElement represented"
                + " by myAnnotatedElement: "
                + myAnnotatedElement.toString());
  
            // Get the declared annotation
            // using getDeclaredAnnotations() method
            System.out.println(
                "DeclaredAnnotation of myAnnotatedElement: "
                + Arrays.toString(
                      myAnnotatedElement
                          .getDeclaredAnnotations()));
        }
        catch (Exception e) {
            System.out.println(e);
        }
    }
}

输出：

AnnotatedElement represented by myAnnotatedElement: class Test
DeclaredAnnotation of myAnnotatedElement: [@java.lang.Deprecated()]

示例 2：

// Java program to demonstrate
// getDeclaredAnnotations() method
  
import java.util.*;
import java.lang.reflect.*;
import java.lang.annotation.*;
  
// create a custom DeclaredAnnotation
@Retention(RetentionPolicy.RUNTIME)
@interface DeclaredAnnotation {
  
    // This declared annotation has two attributes.
    public String key();
  
    public String value();
}
  
// call DeclaredAnnotation for method
// and pass values for declared annotation
@DeclaredAnnotation(key = "GFG", value = "GeeksForGeeks")
public class Test {
  
    public Object obj;
  
    public static void main(String[] args)
        throws ClassNotFoundException
    {
  
        // returns the Class object
        // for this myAnnotatedElement
        AnnotatedElement myAnnotatedElement
            = Test.class;
  
        System.out.println(
            "AnnotatedElement represented"
            + " by myAnnotatedElement: "
            + myAnnotatedElement.toString());
  
        // Get the declared annotation
        // using getDeclaredAnnotations() method
        System.out.println(
            "DeclaredAnnotation of myAnnotatedElement: "
            + Arrays.toString(
                  myAnnotatedElement
                      .getDeclaredAnnotations()));
    }
}

输出：

AnnotatedElement represented by myAnnotatedElement: class Test
DeclaredAnnotation of myAnnotatedElement: [@DeclaredAnnotation(key=GFG, value=GeeksForGeeks)]

参考： https://docs.oracle.com/javase/9/docs/api/ Java/lang/reflect/AnnotatedElement.html#getDeclaredAnnotations–