为什么 reflections.getSubTypesOf(Object.class) 找不到枚举？

Question

如果我有

Reflections reflections = new Reflections("my.package", classLoader, new SubTypesScanner(false));

然后这会找到我的枚举 classes

Set<Class<? extends Enum>> enums = reflections.getSubTypesOf(Enum.class);

但这不是

Set<Class<?>> classes = reflections.getSubTypesOf(Object.class);

这有什么原因吗？

可重现的例子：

package cupawntae;

import org.reflections.Reflections;
import org.reflections.scanners.SubTypesScanner;

public class Reflector {
    public static void main(String[] args) {
        Reflections reflections = new Reflections("cupawntae", Reflector.class.getClassLoader(), new SubTypesScanner(false));
        System.out.println("Objects: " + reflections.getSubTypesOf(Object.class));
        System.out.println("Enums: " + reflections.getSubTypesOf(Enum.class));
        System.out.println("Enum's superclass: " + Enum.class.getSuperclass());
    }
}

枚举class:

package cupawntae;

public enum MyEnum {
}

输出：

Objects: [class cupawntae.Reflector]
Enums: [class cupawntae.MyEnum]
Enum's superclass: class java.lang.Object

Answer 1

这实际上是 documented behaviour，尽管可以说它不是特别清楚或直观：

be aware that when using the constructor new Reflections("my.package"), only urls with prefix 'my.package' will be scanned, and any transitive classes in other urls will not be scanned (for example if my.package.SomeClass extends other.package.OtherClass, than the later will not be scanned). in that case use the other constructors and specify the relevant packages/urls

编辑：该文档的 later revision 说：

Make sure to scan all the transitively relevant packages. for instance, given your class C extends B extends A, and both B and A are located in another package than C, when only the package of C is scanned - then querying for sub types of A returns nothing (transitive), but querying for sub types of B returns C (direct). In that case make sure to scan all relevant packages a priori.

在这种情况下，java.lang.Enum 被视为可传递的 class（如 other.package.OtherClass），因此不包括在扫描中，这意味着 class 是 Enum不包括在内。

类似地，如果我们在问题示例中使 Reflections 扩展目标包之外的内容，例如

public class Reflector extends Exception {

然后 class 不再在扫描中找到

Objects: []
Enums: [class cupawntae.MyEnum]
Enum's superclass: class java.lang.Object

为什么 reflections.getSubTypesOf(Object.class) 找不到枚举？

Why doesn't reflections.getSubTypesOf(Object.class) find enums?

java

reflection

enums

reflections