Java中的类 getDeclaredAnnotations() 方法和示例

Java.lang.Class 类的getDeclaredAnnotations()方法用于获取此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.annotation.*;
  
@Deprecated
public class Test {
  
    public Object obj;
  
    public static void main(String[] args)
        throws ClassNotFoundException
    {
        try {
            // returns the Class object for this class
            Class myClass = Test.class;
  
            System.out.println(
                "Class represented by myClass: "
                + myClass.toString());
  
            // Get the declared annotation
            // using getDeclaredAnnotations() method
            System.out.println(
                "DeclaredAnnotation of myClass: "
                + Arrays.toString(
                      myClass.getDeclaredAnnotations()));
        }
        catch (Exception e) {
            System.out.println(e);
        }
    }
}

输出：

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

示例 2：

// Java program to demonstrate
// getDeclaredAnnotations() method
  
import java.util.*;
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 class
        Class myClass = Test.class;
  
        System.out.println(
            "Class represented by myClass: "
            + myClass.toString());
  
        // Get the declared annotation
        // using getDeclaredAnnotations() method
        System.out.println(
            "DeclaredAnnotation of myClass: "
            + Arrays.toString(
                  myClass.getDeclaredAnnotations()));
    }
}

输出：

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

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