java - 为什么 "Integer.TYPE"在注释 "attribute value must be constant"中显示错误

Question

我创建了一个注释:

@Target(ElementType.FIELD )
@Retention( RetentionPolicy.RUNTIME )
public @interface Test
{
    Class something();
}

但是当我使用 Integer.TYPE (对于 int 的返回类型)调用它时，它会显示错误。

public class TestA
{
    @Test(Integer.TYPE)
    public int id;
}

Answer 1

Class is not commensurate with the value Integer.TYPE

It is a compile-time error if the element type is not commensurate with the element value. An element type T is commensurate with an element value V if and only if one of the following is true:

• [...]

• If T is Class or an invocation of Class (§4.5), then V is a class literal (§15.8.2).

来自Integer的源代码

public static final Class<Integer>  TYPE = (Class<Integer>) Class.getPrimitiveClass("int");

表达式Integer#TYPE不是类文字。如果您想要的话，Integer.class 或 int.class 都可以。