java.lang.reflect.Method.getAnnotation(Class <T> annotationClass)
方法如果存在這樣的註釋,則返回指定型別的元素的注釋,否則為null
。
以下是java.lang.reflect.Method.getAnnotation(Class <T> annotationClass)
方法的宣告。
public <T extends Annotation> T getAnnotation(Class<T> annotationClass)
引數
Class
物件對相應的注釋型別。返回值
null
。異常
以下範例顯示java.lang.reflect.Method.getAnnotation(Class<T> annotationClass)
方法的用法。
import java.lang.annotation.Annotation;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.reflect.Method;
public class MethodDemo {
public static void main(String[] args) {
Method[] methods = SampleClass.class.getMethods();
Annotation annotation = methods[0].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 {
private String sampleField;
@CustomAnnotation(name="getSampleMethod", value = "Sample Method Annotation")
public String getSampleField() {
return sampleField;
}
public void setSampleField(String sampleField) {
this.sampleField = sampleField;
}
}
@Retention(RetentionPolicy.RUNTIME)
@interface CustomAnnotation {
public String name();
public String value();
}
讓我們編譯並執行上面的程式,這將產生以下結果 -
name: getSampleMethod
value: Sample Method Annotation