java - 如何让Java代理和反射协同工作？

Question

我有一个项目( https://github.com/zhihan/janala2-gradle )，它使用 java-agent 进行在线检测。我尝试为运行时反射提供一个注释类。程序因 NoClassDefFoundError 崩溃

Exception in thread "main" java.lang.NoClassDefFoundError: janala/logger/DJVM
at com.sun.proxy.$Proxy0.<clinit>(Unknown Source)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:408)
at java.lang.reflect.Proxy.newProxyInstance(Proxy.java:739)
at sun.reflect.annotation.AnnotationParser$1.run(AnnotationParser.java:305)
at sun.reflect.annotation.AnnotationParser$1.run(AnnotationParser.java:303)
at java.security.AccessController.doPrivileged(Native Method)
at sun.reflect.annotation.AnnotationParser.annotationForMap(AnnotationParser.java:303)
at sun.reflect.annotation.AnnotationParser.parseAnnotation2(AnnotationParser.java:293)
at sun.reflect.annotation.AnnotationParser.parseAnnotations2(AnnotationParser.java:120)
at sun.reflect.annotation.AnnotationParser.parseSelectAnnotations(AnnotationParser.java:101)
at sun.reflect.annotation.AnnotationType.<init>(AnnotationType.java:139)
at sun.reflect.annotation.AnnotationType.getInstance(AnnotationType.java:85)
at sun.reflect.annotation.AnnotationParser.parseAnnotation2(AnnotationParser.java:266)
at sun.reflect.annotation.AnnotationParser.parseAnnotations2(AnnotationParser.java:120)
at sun.reflect.annotation.AnnotationParser.parseAnnotations(AnnotationParser.java:72)
at java.lang.reflect.Executable.declaredAnnotations(Executable.java:546)
at java.lang.reflect.Executable.getAnnotation(Executable.java:520)
at java.lang.reflect.Method.getAnnotation(Method.java:607)
at janala.utils.ClassRunner.run(ClassRunner.java:20)
at janala.utils.ClassRunner.main(ClassRunner.java:33)

错误的调用点很简单

Test annotation = method.getAnnotation(Test.class);

如果我更改程序以首先检测类，请将检测的类写入 .class 文件，然后使用相同的类路径运行该程序。然后就可以正常运行了。

注释声明为

public class Annotations {

   /**
   * A CATG test.
   */
  @Retention(RetentionPolicy.RUNTIME)
  @Target(ElementType.METHOD)
  public @interface Test {}
}

而注解的使用就像

  @Test
  public void testAnd() {

Answer 1

好吧，事实证明原因在堆栈跟踪中

at com.sun.proxy.$Proxy0.<clinit>(Unknown Source)

代理类由 JVM 自动生成，作为反射支持的一部分。默认情况下，检测器会检测所有内容。过滤这个包就可以解决问题。