无法获得通用的ResponseEntity< T>其中T是泛型类“SomeClass< SomeGenericType>” [英] Unable to get a generic ResponseEntity<T> where T is a generic class "SomeClass<SomeGenericType>"

问题描述

请帮我获得 ResponseEntity< T> ，其中 T 本身就是一个通用类型。正如我现在看到的那样，现在春天RestTemplate不支持这个功能。我使用的是Spring MVC 3.1.2版本。

这里是我的代码，我想使用：
代码：

  ResponseEntity< CisResponse< CisResponseEntity>> res = 
 this.restTemplate.postForEntity（
 this.rootURL，myRequestObj，CisResponse.class）; 
  

我得到这个错误：

 类型不匹配：无法从ResponseEntity转换< CisResponse> to 
 ResponseEntity< CisResponse< CisResponseEntity>> 
  

显而易见的错误，但我今天能如何解决它？

比我想得到我的通用响应类型：

  CisResponse< CisResponseEntity> myResponse = res.getBody（）; 
 CisResponseEntity entity = myResponse.getEntityFromResponse（）; 
  

现在，我使用这个解决方案，使用 postForObject（） postForEntity（）：

  CisResponse< CisResponseEntity> ; response = 
 this.restTemplate.postForObject（
 this.rootURL，myRequestObj，CisResponse.class）; 
  

解决方案

这是一个已知问题。现在通过引入 ParameterizedTypeReference 来解决它，它是一个参数化类型，您明确地继承以在运行时提供类型信息。这称为超类型令牌，并且围绕类型擦除工作，因为子类（在本例中为匿名）在运行时保留通用超类型的类型参数

。

>

但是，您不能使用 postForObject ，因为API仅支持 交换（） ：

  ResponseEntity< CisResponse< CisResponseEntity>> res = template.exchange（
 rootUrl，
 HttpMethod.POST，
 null，
 new ParameterizedTypeReference< CisResponse< CisResponseEntity>>（）{}）; 
  

请注意，最后一行显示了超级类型令牌：您不提供文字 CisResponse.class ，但是匿名实例化参数化类型 ParameterizedTypeReference< T> ，它可以在运行时期望提取子类型信息。您可以将超类型令牌视为 hacks ，以实现 Foo< Bar< Baz>> .class

$如果你的对象定义了一个 url BTW，那么在Java中，你不需要用这个前缀来访问实例变量： / code>和模板成员，只需以简单的名称访问它们，而不是像 this.url 和 this.template

Please help me to get a ResponseEntity<T> where T is itself a generic type. As I see it of now, this is not supported nowdays by spring RestTemplate. I'm using Spring MVC version 3.1.2

Here is my code, that I want to use: Code:

ResponseEntity<CisResponse<CisResponseEntity>> res =
         this.restTemplate.postForEntity(
             this.rootURL, myRequestObj, CisResponse.class);

I'm getting this error:

Type mismatch: cannot convert from ResponseEntity<CisResponse> to
ResponseEntity<CisResponse<CisResponseEntity>>

It's obvious error, but how I can workaround it today?

Than I do want to get my generic response type:

CisResponse<CisResponseEntity> myResponse= res.getBody();
CisResponseEntity entity = myResponse.getEntityFromResponse();

For now, I use this solution, with postForObject() and not postForEntity():

CisResponse<CisResponseEntity> response = 
          this.restTemplate.postForObject(
               this.rootURL,myRequestObj, CisResponse.class);

解决方案

This was a known issue. Now it's fixed with the introduction of ParameterizedTypeReference, which is a parameterized type that you explicitely inherit to supply type information at runtime. This is called a super-type token, and works around type erasure because subclasses (anoniymous in this case) keep the type arguments of the generic supertype at runtime.

However you can't use postForObject, because the API only supports exchange():

ResponseEntity<CisResponse<CisResponseEntity>> res = template.exchange(
        rootUrl,
        HttpMethod.POST,
        null,
        new ParameterizedTypeReference<CisResponse<CisResponseEntity>>() {});

Note that the last line demonstrates the idea of super type tokens: you don't supply the literal CisResponse.class, but an anonymous instantiation of the parameterized type ParameterizedTypeReference<T>, which at runtime can be expected to extract subtype information. You can think of super type tokens as hacks for achieving Foo<Bar<Baz>>.class

BTW, in Java you don't need to prefix access to instance variable with this: if your object defines a url and template members, just access them with their simple name, and not by prefixing like you do this.url and this.template

这篇关于无法获得通用的ResponseEntity< T>其中T是泛型类“SomeClass< SomeGenericType>”的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！