寻找带有注解的匿名类

huangapple
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英文:

Find anonymous classes by annotation

问题

有没有办法通过某个注解在一些 Java 反射库（如 Reflections）中找到匿名类？

我有以下代码：
它使用内部类（扩展自Object），并使用@DemoAnnotation进行了注解

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();
}

现在我想要找到项目中所有使用@DemoAnnotation注解的（匿名）类。

我尝试过使用 Reflections 库：但似乎无法找到匿名类（可以找到内部静态类）。

    @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：DemoUsageService$1的 javap 反编译器输出 看起来注解在其中。

Classfile /C:/Users/engelmann/git/experiment-anonymousclass-annotationscanning/target/classes/DemoUsageService$1.class
  Last modified 21.09.2020; size 1016 bytes
  MD5 checksum 2dcb03fe361641b6e04fbb62bbb6c971
  Compiled from "DemoUsageService.java"
class DemoUsageService$1
  minor version: 0
  major version: 55
  flags: (0x0020) ACC_SUPER
  this_class: #5                          // DemoUsageService$1
  super_class: #6                         // java/lang/Object
  interfaces: 0, fields: 2, methods: 1, attributes: 5
Constant pool:
   #1 = Fieldref           #5.#30         // DemoUsageService$1.this$0: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$1
   #6 = Class              #35            // java/lang/Object
   #7 = Utf8               content
   #8 = Utf8               Ljava/lang/String;
   #9 = Utf8               this$0
  #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$1;
  #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$0:LDemoUsageService;
  #31 = NameAndType        #11:#38        // "<init>":()V
  #32 = Utf8               myContent
  #33 = NameAndType        #7:#8          // content:Ljava/lang/String;
  #34 = Utf8               DemoUsageService$1
  #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$0;
    descriptor: LDemoUsageService;
    flags: (0x1010) ACC_FINAL, ACC_SYNTHETIC

  DemoUsageService$1(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$0: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$1;
            0      16     1 this$0   LDemoUsageService;
    MethodParameters:
      Name                           Flags
      this$0                         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$1
英文:

Is there a way to find anonymous classes by some annotation with some java reflection library like (Reflections)?

I have this code:
it use declare a inner class (extends Object) and annotated it with @DemoAnnotation

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

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

Now I want to find all (anonymous) classes in my project that are annotated with @DemoAnnotation.

I tried the Reflections Library: but it seams not to find anonymous classes (inner static classes are found).

    @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&lt;Class&lt;?&gt;&gt; result = reflections.getTypesAnnotatedWith(DemoAnnotation.class);
assertEquals(1, result.size()); //fails, because result.size == 0
//...
}

&lt;dependency&gt;
&lt;groupId&gt;org.reflections&lt;/groupId&gt;
&lt;artifactId&gt;reflections&lt;/artifactId&gt;
&lt;version&gt;0.9.12&lt;/version&gt;
&lt;/dependency&gt;

@chrylis -cautiouslyoptimistic: The javap decompiler output for DemoUsageService$1 looks like the annotation in there.

Classfile /C:/Users/engelmann/git/experiment-anonymousclass-annotationscanning/target/classes/DemoUsageService$1.class
Last modified 21.09.2020; size 1016 bytes
MD5 checksum 2dcb03fe361641b6e04fbb62bbb6c971
Compiled from &quot;DemoUsageService.java&quot;
class DemoUsageService$1
minor version: 0
major version: 55
flags: (0x0020) ACC_SUPER
this_class: #5                          // DemoUsageService$1
super_class: #6                         // java/lang/Object
interfaces: 0, fields: 2, methods: 1, attributes: 5
Constant pool:
#1 = Fieldref           #5.#30         // DemoUsageService$1.this$0:LDemoUsageService;
#2 = Methodref          #6.#31         // java/lang/Object.&quot;&lt;init&gt;&quot;:()V
#3 = String             #32            // myContent
#4 = Fieldref           #6.#33         // java/lang/Object.content:Ljava/lang/String;
#5 = Class              #34            // DemoUsageService$1
#6 = Class              #35            // java/lang/Object
#7 = Utf8               content
#8 = Utf8               Ljava/lang/String;
#9 = Utf8               this$0
#10 = Utf8               LDemoUsageService;
#11 = Utf8               &lt;init&gt;
#12 = Utf8               (LDemoUsageService;)V
#13 = Utf8               Code
#14 = Utf8               LineNumberTable
#15 = Utf8               LocalVariableTable
#16 = Utf8               this
#17 = Utf8               InnerClasses
#18 = Utf8               LDemoUsageService$1;
#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$0:LDemoUsageService;
#31 = NameAndType        #11:#38        // &quot;&lt;init&gt;&quot;:()V
#32 = Utf8               myContent
#33 = NameAndType        #7:#8          // content:Ljava/lang/String;
#34 = Utf8               DemoUsageService$1
#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$0;
descriptor: LDemoUsageService;
flags: (0x1010) ACC_FINAL, ACC_SYNTHETIC
DemoUsageService$1(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$0:LDemoUsageService;
5: aload_0
6: invokespecial #2                  // Method java/lang/Object.&quot;&lt;init&gt;&quot;:()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$1;
0      16     1 this$0   LDemoUsageService;
MethodParameters:
Name                           Flags
this$0                         final mandated
}
SourceFile: &quot;DemoUsageService.java&quot;
RuntimeVisibleTypeAnnotations:
0: #23(#24=s#25): CLASS_EXTENDS, type_index=65535
DemoAnnotation(
value=&quot;Test&quot;
)
EnclosingMethod: #27.#28                // DemoUsageService.doSomething
NestHost: class DemoUsageService
InnerClasses:
#5;                                     // class DemoUsageService$1

答案1

得分: 2

我以前从未使用过这个库，但在源代码中稍微查找了一下，似乎我可以使其工作（代码编写得很好，所以我很幸运）。我不知道是否有更好的方法，但是你可以看看以下代码：

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);
        }

    }

}

用法示例：

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()));
英文:

I never used this library before, but some poking here and there in the source code and it seems I can make it work (it is written in a nice fashion - so I was lucky, pretty much). I have no idea if there are better ways, but here you go:

static class TestScanner extends AbstractScanner {
@Override
public void scan(Object cls, Store store) {
String className = getMetadataAdapter().getClassName(cls);
try {
Class&lt;?&gt; 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);
}
}
}

And usage like:

    Reflections reflections = new Reflections(
new ConfigurationBuilder().setUrls(ClasspathHelper.forPackage(DemoUsageService.class.getPackageName()))
.setScanners(new TestScanner(), new SubTypesScanner(false), new TypeAnnotationsScanner()));
Set&lt;Class&lt;?&gt;&gt; result = reflections.getTypesAnnotatedWith(DemoAnnotation.class);
result.forEach(x -&gt; System.out.println(x.getName()));

huangapple
  • 本文由 发表于 2020年9月22日 00:22:30
  • 转载请务必保留本文链接：https://go.coder-hub.com/63996281.html
  • anonymous-inner-class
  • java
  • reflection
  • reflections
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