java.lang.reflect.Method.getAnnotation () method of the object exemplary method [reacquisition acquired annotation information on the object by the reflection method]

turn:

java.lang.reflect.Method.getAnnotation () method of Example

 

java.lang.reflect.Method.getAnnotation(Class <T> annotationClass)If such a method exists comment, annotation elements of the specified type is returned, otherwise null.

statement

The following is a java.lang.reflect.Method.getAnnotation(Class <T> annotationClass)statement of the method.

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

Java

parameter

• annotationClass - Classobject type of the corresponding comment.

return value

• If there is this element, the element annotation annotation type specified is returned, otherwise returns null.

abnormal

• NullPointerException - if the given annotation class is empty.

The following example shows java.lang.reflect.Method.getAnnotation(Class<T> annotationClass)the use of the method.

package sync;
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();
}

 

Java

Let's compile and run the above program, which will produce the following results -

name: getSampleMethod
value: Sample Method Annotation

Shell

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