运行动态class加载时的时间注释扫描

Question

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objective是检查几个方法上的注解，如果注解上存在，我需要获取注解。

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

在上面的例子中，注释是在同一个文件中声明的。如果注释在不同的包中，我可以做类似

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")

如何获取方法上的注释。我认为下面的行在这种情况下不起作用

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

Answer 1

当注释动态加载到变量 Demo 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);

Answer 2

这种方法对我有用。希望这对某人有帮助。

 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);
          }
       }
     }

运行动态class加载时的时间注释扫描

run time annotation scanning when Dynamic class loading

java

class

methods

reflection

annotation-processing