java.lang.Class类的getDeclaredAnnotationsByType()方法用于获取存在于此类中的指定声明注释类型的声明注释。该方法为指定的声明的注释类型返回声明的注释的数组。
用法:
public A[] getDeclaredAnnotationsByType(Class<T> declared annotationClass)
参数:此方法接受一个声明的注释类型的参数,该参数是要获取的声明注释的类型。
返回值:此方法为指定的声明的注释类型返回声明的注释的数组。
异常:该方法抛出:
- NullPointerException :如果给定的声明注释类为null。
下面的程序演示了getDeclaredAnnotationsByType()方法。
范例1:
// Java program to demonstrate
// getDeclaredAnnotationsByType() 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 getDeclaredAnnotationsByType() method
System.out.println(
"DeclaredAnnotation of myClass of type DeclaredAnnotation:"
+ Arrays.toString(
myClass
.getDeclaredAnnotationsByType(
DeclaredAnnotation.class)));
}
}
输出:
Class represented by myClass:class Test
DeclaredAnnotation of myClass of type DeclaredAnnotation:[@DeclaredAnnotation(key=GFG, value=GeeksForGeeks)]
范例2:
// Java program to demonstrate
// getDeclaredAnnotationsByType() 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 getDeclaredAnnotationsByType() method
System.out.println(
"DeclaredAnnotation of myClass of type Deprecated:"
+ Arrays.toString(
myClass
.getDeclaredAnnotationsByType(
Deprecated.class)));
}
catch (Exception e) {
System.out.println(e);
}
}
}
输出:
Class represented by myClass:class Test
DeclaredAnnotation of myClass of type Deprecated:[@java.lang.Deprecated()]
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注:本文由纯净天空筛选整理自srinam大神的英文原创作品 Class getDeclaredAnnotationsByType() method in Java with Examples。非经特殊声明,原始代码版权归原作者所有,本译文未经允许或授权,请勿转载或复制。