动态类加载时运行时注释扫描

时间:2017-12-05 21:30:48

标签: java class methods reflection annotation-processing

import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.reflect.Method;

// declare a new annotation
@Retention(RetentionPolicy.RUNTIME)
@interface Demo {
   String str();
   int val();
}

public class PackageDemo {

   // set values for the annotation
   @Demo(str = "Demo Annotation", val = 100)
   // a method to call in the main
   public static void example() {
      PackageDemo ob = new PackageDemo();

      try {
         Class c = ob.getClass();

         // get the method example
         Method m = c.getMethod("example");

         // get the annotation for class Demo
         Demo annotation = m.getAnnotation(Demo.class);

         // print the annotation
         System.out.println(annotation.str() + " " + annotation.val());
      } catch (NoSuchMethodException exc) {
         exc.printStackTrace();
      }
   }
   public static void main(String args[]) {
      example();
   }
}

我的目标是检查几个方法的注释,如果注释中存在注释,我需要获取注释。

Demo annotation = m.getAnnotation(Demo.class);

在上面的示例中,注释在同一文件中声明。如果注释位于不同的包中,我可以执行类似

的操作
import com.this.class.DemoClass
try {
         Class c = ob.getClass();

         // get the method example
         Method m = c.getMethod("example");

         // get the annotation for class Demo
         Demo annotation = m.getAnnotation(Demo.class);

但是如果我想像

那样动态加载DemoClass / AnnotationClass
Class<?> Demo = Class.forName("com.this.class.DemoClass")

如何获取方法的注释。我认为以下行在这种情况下不起作用

Demo annotation = m.getAnnotation(Demo.class);

2 个答案:

答案 0 :(得分:1)

这种方法对我有用。希望这有助于某人。

 DemoClass= (Class<Annotation>) Class.forName("com.this.class.DemoClass");
    if (method.isAnnotationPresent(DemoClass)) {
       for (Annotation annotation : method.getAnnotations()) {
       Class<? extends Annotation> annotationType = annotation.annotationType();      
       if (annotationType.getName() == "com.this.class.DemoClass") {
          for (Method annotationMethod : annotationType.getDeclaredMethods()) {
          value= annotationMethod.invoke(annotation, (Object[]) null);
          }
       }
     }

答案 1 :(得分:0)

当注释动态加载到变量Demo中时,然后使用该变量获取注释:

Class<?> Demo = Class.forName("com.this.class.DemoClass");
Demo annotation = m.getAnnotation(Demo);