java - 在java中使用instanceof Void

Question

我想使用 void java 类型，但不能。这是我的代码，它是在所有具有 @TraceLog 注释的方法之后运行的一个方面

  @AfterReturning(value = "@annotation(log)", 
       returning = "returnValue", 
       argNames = "joinPoint, log, returnValue"
      )
    public void afterReturning(final JoinPoint joinPoint, final TraceLog log,
            final Object returnValue) {

            Class<?> returnType = ((MethodSignature) joinPoint.getSignature())
            .getReturnType();
           //It works when comperaing with string. But I want to write it with type of
           if ("void".equals(returnType.getName()) ) {
            //Do some log
         }
}

作为编码规则类不应按名称进行比较( http://cwe.mitre.org/data/definitions/486.html )，我尝试使用 (returnType instanceof Void) 但我面临这两个编译时Eclipse 中的错误:

- Incompatible conditional operand types Class<capture#5-of ?> and   Void
- The type Void is not generic; it cannot be parameterized with arguments <?>

我想知道如何解决它？!

Answer 1

你可以使用

if (Void.class.isAssignableFrom (returnType)) {

}

示例:

Class<?> returnType = Void.class;
if (Void.class.isAssignableFrom (returnType)) {
  System.out.println (returnType.getName ());
}

会打印

java.lang.Void