通过注释查找匿名类

Question

有没有办法通过一些注释和一些 java 反射库（Reflections）找到匿名的 classes？

我有这个代码： 它使用声明一个内部 class（扩展对象）并用 @DemoAnnotation

注释它

public class DemoUsageService {

    public void doSomething() {
        this.test(new @DemoAnnotation(value="Test") Object() {
            String content = "myContent";
        });
    }
}

@Retention(RUNTIME)
@Target({ElementType.TYPE_USE})
public @interface DemoAnnotation {
   String value();
}

现在我想在我的项目中找到所有用 @DemoAnnotation.

注释的（匿名）classes

我尝试了 Reflections 库：但它找不到匿名 classes（找到了内部静态 classes）。

    @Test
    public void testFindAnnotatedClasses() throws Exception {
        
        Reflections reflections = new Reflections(
                new ConfigurationBuilder()
                        .setUrls(ClasspathHelper.forPackage(DemoUsageService.class.getPackageName()))
                        .setScanners(
                                new SubTypesScanner(false),
                                new TypeAnnotationsScanner()));
        
        Set<Class<?>> result = reflections.getTypesAnnotatedWith(DemoAnnotation.class);
        assertEquals(1, result.size()); //fails, because result.size == 0
        //...
    }

<dependency>
    <groupId>org.reflections</groupId>
    <artifactId>reflections</artifactId>
    <version>0.9.12</version>
</dependency>

@chrylis -cautiouslyoptimistic：javap 反编译器输出 DemoUsageService 看起来像那里的注释。

Classfile /C:/Users/engelmann/git/experiment-anonymousclass-annotationscanning/target/classes/DemoUsageService.class
  Last modified 21.09.2020; size 1016 bytes
  MD5 checksum 2dcb03fe361641b6e04fbb62bbb6c971
  Compiled from "DemoUsageService.java"
class DemoUsageService
  minor version: 0
  major version: 55
  flags: (0x0020) ACC_SUPER
  this_class: #5                          // DemoUsageService
  super_class: #6                         // java/lang/Object
  interfaces: 0, fields: 2, methods: 1, attributes: 5
Constant pool:
   #1 = Fieldref           #5.#30         // DemoUsageService.this[=15=]:LDemoUsageService;
   #2 = Methodref          #6.#31         // java/lang/Object."<init>":()V
   #3 = String             #32            // myContent
   #4 = Fieldref           #6.#33         // java/lang/Object.content:Ljava/lang/String;
   #5 = Class              #34            // DemoUsageService
   #6 = Class              #35            // java/lang/Object
   #7 = Utf8               content
   #8 = Utf8               Ljava/lang/String;
   #9 = Utf8               this[=15=]
  #10 = Utf8               LDemoUsageService;
  #11 = Utf8               <init>
  #12 = Utf8               (LDemoUsageService;)V
  #13 = Utf8               Code
  #14 = Utf8               LineNumberTable
  #15 = Utf8               LocalVariableTable
  #16 = Utf8               this
  #17 = Utf8               InnerClasses
  #18 = Utf8               LDemoUsageService;
  #19 = Utf8               MethodParameters
  #20 = Utf8               SourceFile
  #21 = Utf8               DemoUsageService.java
  #22 = Utf8               RuntimeVisibleTypeAnnotations
  #23 = Utf8               LDemoAnnotation;
  #24 = Utf8               value
  #25 = Utf8               Test
  #26 = Utf8               EnclosingMethod
  #27 = Class              #36            // DemoUsageService
  #28 = NameAndType        #37:#38        // doSomething:()V
  #29 = Utf8               NestHost
  #30 = NameAndType        #9:#10         // this[=15=]:LDemoUsageService;
  #31 = NameAndType        #11:#38        // "<init>":()V
  #32 = Utf8               myContent
  #33 = NameAndType        #7:#8          // content:Ljava/lang/String;
  #34 = Utf8               DemoUsageService
  #35 = Utf8               java/lang/Object
  #36 = Utf8               DemoUsageService
  #37 = Utf8               doSomething
  #38 = Utf8               ()V
{
  java.lang.String content;
    descriptor: Ljava/lang/String;
    flags: (0x0000)

  final DemoUsageService this[=15=];
    descriptor: LDemoUsageService;
    flags: (0x1010) ACC_FINAL, ACC_SYNTHETIC

  DemoUsageService(DemoUsageService);
    descriptor: (LDemoUsageService;)V
    flags: (0x0000)
    Code:
      stack=2, locals=2, args_size=2
         0: aload_0
         1: aload_1
         2: putfield      #1                  // Field this[=15=]:LDemoUsageService;
         5: aload_0
         6: invokespecial #2                  // Method java/lang/Object."<init>":()V
         9: aload_0
        10: ldc           #3                  // String myContent
        12: putfield      #4                  // Field java/lang/Object.content:Ljava/lang/String;
        15: return
      LineNumberTable:
        line 7: 0
        line 8: 9
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
            0      16     0  this   LDemoUsageService;
            0      16     1 this[=15=]   LDemoUsageService;
    MethodParameters:
      Name                           Flags
      this[=15=]                         final mandated
}
SourceFile: "DemoUsageService.java"
RuntimeVisibleTypeAnnotations:
  0: #23(#24=s#25): CLASS_EXTENDS, type_index=65535
    DemoAnnotation(
      value="Test"
    )
EnclosingMethod: #27.#28                // DemoUsageService.doSomething
NestHost: class DemoUsageService
InnerClasses:
  #5;                                     // class DemoUsageService

Answer 1

我以前从未使用过这个库，但在源代码中到处翻找了一下，看来我可以让它工作（它以一种很好的方式编写 - 所以我很幸运，非常）。我不知道是否有更好的方法，但是给你：

static class TestScanner extends AbstractScanner {

    @Override
    public void scan(Object cls, Store store) {

        String className = getMetadataAdapter().getClassName(cls);

        try {
            Class<?> c = Class.forName(className);
            if (c.isAnonymousClass()) {
                for (Annotation ann : c.getAnnotatedSuperclass().getAnnotations()) {
                    store.put(Utils.index(TypeAnnotationsScanner.class), ann.annotationType().getName(), className);
                }

            }
        } catch (ClassNotFoundException e) {
            throw new RuntimeException(e);
        }

    }

}

用法如：

    Reflections reflections = new Reflections(
        new ConfigurationBuilder().setUrls(ClasspathHelper.forPackage(DemoUsageService.class.getPackageName()))
                                  .setScanners(new TestScanner(), new SubTypesScanner(false), new TypeAnnotationsScanner()));

    Set<Class<?>> result = reflections.getTypesAnnotatedWith(DemoAnnotation.class);
    result.forEach(x -> System.out.println(x.getName()));

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