java.lang.Class類的getAnnotationsByType()方法用於獲取此類中存在的指定注釋類型的注釋。該方法返回指定注釋類型的注釋數組。
用法:
public A[] getAnnotationsByType(Class<T> annotationClass)
參數:此方法接受參數注釋類,它是要獲取的注釋的類型。
返回值:此方法返回指定注釋類型的注釋數組。
異常:該方法拋出:
- NullPointerException :如果給定的注釋類為null。
下麵的程序演示了getAnnotationsByType()方法。
範例1:
// Java program to demonstrate
// getAnnotationsByType() method
import java.util.*;
import java.lang.annotation.*;
// create a custom Annotation
@Retention(RetentionPolicy.RUNTIME)
@interface Annotation {
// This annotation has two attributes.
public String key();
public String value();
}
// call Annotation for method
// and pass values for annotation
@Annotation(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 annotation
// using getAnnotationsByType() method
System.out.println(
"Annotation of myClass of type Annotation:"
+ Arrays.toString(
myClass
.getAnnotationsByType(
Annotation.class)));
}
}
輸出:
Class represented by myClass:class Test Annotation of myClass of type Annotation:[@Annotation(key=GFG, value=GeeksForGeeks)]
範例2:
// Java program to demonstrate
// getAnnotationsByType() 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 annotation
// using getAnnotationsByType() method
System.out.println(
"Annotation of myClass of type Deprecated:"
+ Arrays.toString(
myClass
.getAnnotationsByType(
Deprecated.class)));
}
catch (Exception e) {
System.out.println(e);
}
}
}
輸出:
Class represented by myClass:class Test Annotation of myClass of type Deprecated:[@java.lang.Deprecated()]
參考: https://docs.oracle.com/javase/9/docs/api/java/lang/Class.html#getAnnotationsByType-java.lang.Class-
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注:本文由純淨天空篩選整理自srinam大神的英文原創作品 Class getAnnotationsByType() method in Java with Examples。非經特殊聲明,原始代碼版權歸原作者所有,本譯文未經允許或授權,請勿轉載或複製。