Java Field getAnnotation()方法

java.lang.reflect.Field.getAnnotation(Class <T> annotationClass)方法返回指定类型的元素的注释，否则返回为null。

1 语法

public <T extends Annotation> T getAnnotation(Class<T> annotationClass)

2 参数

annotationClass ：如果给定的注释类为null。

3 返回值

该元素的注释指定的注释类型，如果存在于此元素，否则返回null。

4 示例 

package com.yiidian;

/**
 * 一点教程网： http://www.yiidian.com
 */
/**
 * Java Field getAnnotation()方法
 */
import java.lang.annotation.Annotation;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.reflect.Field;

public class GetAnnotation {

   public static void main(String[] args) throws NoSuchFieldException, SecurityException, IllegalArgumentException, IllegalAccessException {
      Field field = SampleClass.class.getField("sampleField");
      Annotation annotation = field.getAnnotation(CustomAnnotation.class);
      if(annotation instanceof CustomAnnotation){
         CustomAnnotation customAnnotation = (CustomAnnotation) annotation;
         System.out.println("name: " + customAnnotation.name());
         System.out.println("value: " + customAnnotation.value());
      }
   }
}

@CustomAnnotation(name="SampleClass",  value = "Sample Class Annotation")
class SampleClass {

   @CustomAnnotation(name="sampleClassField",  value = "Sample Field Annotation")
   public String sampleField;

   public String getSampleField() {
      return sampleField;
   }

   public void setSampleField(String sampleField) {
      this.sampleField = sampleField;
   }
}

@Retention(RetentionPolicy.RUNTIME)
@interface CustomAnnotation {
   public String name();
   public String value();
}

输出结果为：

name: sampleClassField
value: Sample Field Annotation