泛型与Spring REST模板 [英] Generics with Spring RESTTemplate

问题描述

我有这样一个类：

  public class Wrapper< T> {
 
私人字符串消息; 
私人T数据; 
 
 public String getMessage（）{
 return message; 
} 
 
 public void setMessage（String message）{
 this.message = message; 
} 
 
 public T getData（）{
 return data; 
} 
 
 public void setData（T data）{
 this.data = data; 
} 
 
} 
  

我使用resttemplate如下：

  ... 
 Wrapper< Model> response = restTemplate.getForObject（URL，Wrapper.class，myMap）; 
 Model model = response.getData（）; 
 ... 
  

然而它会抛出：

  ClassCastException 
  

我读到：<在尝试在java中使用Jackson时出现问题，但没有帮助。有一些话题与我的问题等有关： https://jira.springsource.org/browse/ SPR-7002 和 https://jira.springsource.org/browse/SPR-7023

任何想法？

PS：我的错误是：

  java.lang.ClassCastException：java.util.LinkedHashMap不能转换为abcdModel 
  

我认为resttemplate无法理解我的泛型变量，也许它将它接受为Object而不是泛型T.因此它变成了LinkedHashMap。您可以从此处进行阅读它说，从什么时候解释到：

JSON类型| Java类型

object | LinkedHashMap

解决方案

3.2 M2中引入了ParameterizedTypeReference来解决此问题。

  Wrapper< Model> response）= restClient.exchange（loginUrl，
 HttpMethod.GET，
 null，
 new ParameterizedTypeReference< Wrapper< Model>>（）{}）。getBody（）; 
  

但是，postForObject / getForObject变体没有引入。

I have a class like that:

public class Wrapper<T> {

 private String message;
 private T data;

 public String getMessage() {
    return message;
 }

 public void setMessage(String message) {
    this.message = message;
 }

 public T getData() {
    return data;
 }

 public void setData(T data) {
    this.data = data;
 }

}

and I use resttemplate as follows:

...
Wrapper<Model> response = restTemplate.getForObject(URL, Wrapper.class, myMap);
Model model = response.getData();
...

However it throws a:

ClassCastException

I read that: Issue when trying to use Jackson in java but didn't help. There are some topics related to my problem etc.: https://jira.springsource.org/browse/SPR-7002 and https://jira.springsource.org/browse/SPR-7023

Any ideas?

PS: My error is that:

java.lang.ClassCastException: java.util.LinkedHashMap cannot be cast to a.b.c.d.Model

I think resttemplate can not understand my generic variable and maybe it accepts it as an Object instead of generic T. So it becomes a LinkedHashMap. You can read from it here It says that when explaining from what it marshalls to:

JSON Type | Java Type

object | LinkedHashMap

解决方案

ParameterizedTypeReference has been introduced in 3.2 M2 to workaround this issue.

Wrapper<Model> response = restClient.exchange(loginUrl, 
                          HttpMethod.GET, 
                          null, 
                          new ParameterizedTypeReference<Wrapper<Model>>() {}).getBody();

However, the postForObject/getForObject variant was not introduced.

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