找不到适合响应类型的 HttpMessageConverter - 自定义 RestTemplate

Question

首先，抱歉可能重复。我发现了一些关于类似问题的问题。但是，我仍然无法弄清楚我的具体情况出了什么问题。

因此，来自服务器的示例 json：

[
  {
    "_id": "55f9690f30ef6f210e2dc3a5",
    "ID": "74c4bf82-9f78-4df5-b9d7-6547e2a55eaa",
    "Name": "myLand, Saarbrücken",
    "__v": 0,
    "Shops": [
      {
        "ID": "b8eacee1-b2c6-48aa-ac6f-2e7fbe3a5d68",
        "Name": "ARA",
        "_id": "55f9690f30ef6f210e2dc3a6",
        "News": [
          {
            "ID": "d79b7f51-7d5c-4bd6-9321-e40c6e93788c",
            "ValidFrom": "2015-01-08T00:00:00",
            "ValidTo": "2015-09-30T00:00:00",
            "_id": "55f9690f30ef6f210e2dc3a7",
            "Texts": [
              {
                "ID": "TITLE",
                "Value": "11. Wochenspiegel Firmenlauf",
                "_id": "55f9690f30ef6f210e2dc3a9"
              },
              {
                "ID": "BODY",
                "Value": "Wir gratulieren zur ersten und gleich sehr erfolgreichen Teilnahme am 11.Wochenspiegel Firmenlauf in Dillingen,\r\nunsere Teams vom “Outlet center Wadgassen“ haben ihren Lauf mit tollen Zeiten abgeschlossen und hatten trotz\r\nhohen Temperaturen einen wunderbaren Tag – wie man sehen kann. Wir freuen uns schon jetzt auf nächstes Jahr!",
                "_id": "55f9690f30ef6f210e2dc3a8"
              }
            ]
          }
        ],
        "Texts": [
          {
            "ID": "DESCRIPTION",
            "Value": "Mit Tradition in die Zukunft Seit sechs Jahrzehnten steht ara für vielfältige Schuhmode erstklassiger Qualität,",
            "_id": "55f9690f30ef6f210e2dc3aa"
          }
        ]
      }
    ]
  }
]

我生成了名为 Mall 的类（以及其余数据结构的所有子类）：

public class Mall
{

    private String Id;
    private String ID;
    private String Name;
    private int V;
    private List<Shop> Shops = new ArrayList<Shop>();
    private Map<String, Object> additionalProperties = new HashMap<String, Object>();

    /**
     * @return The Id
     */
    public String getId()
    {
        return Id;
    }

    /**
     * @param Id The _id
     */
    public void setId(String Id)
    {
        this.Id = Id;
    }

    /**
     * @return The ID
     */
    public String getID()
    {
        return ID;
    }

    /**
     * @param ID The ID
     */
    public void setID(String ID)
    {
        this.ID = ID;
    }

    /**
     * @return The Name
     */
    public String getName()
    {
        return Name;
    }

    /**
     * @param Name The Name
     */
    public void setName(String Name)
    {
        this.Name = Name;
    }

    /**
     * @return The V
     */
    public int getV()
    {
        return V;
    }

    /**
     * @param V The __v
     */
    public void setV(int V)
    {
        this.V = V;
    }

    /**
     * @return The Shops
     */
    public List<Shop> getShops()
    {
        return Shops;
    }

    /**
     * @param Shops The Shops
     */
    public void setShops(List<Shop> Shops)
    {
        this.Shops = Shops;
    }

    public Map<String, Object> getAdditionalProperties()
    {
        return this.additionalProperties;
    }

    public void setAdditionalProperty(String name, Object value)
    {
        this.additionalProperties.put(name, value);
    }

}

服务器返回内容类型的文本/纯文本。为了修改内容类型，我编写了简单的扩展类：

public class RestTemplateJSON extends RestTemplate
{

    @Override
    protected <T> T doExecute(URI url, HttpMethod method, RequestCallback requestCallback,
                              ResponseExtractor<T> responseExtractor) throws RestClientException
    {

        //logger.info(RestTemplateJSON.class.getSuperclass().getSimpleName() + ".doExecute() is overridden");

        Assert.notNull(url, "'url' must not be null");
        Assert.notNull(method, "'method' must not be null");
        ClientHttpResponse response = null;
        try
        {
            ClientHttpRequest request = createRequest(url, method);
            if (requestCallback != null)
            {
                requestCallback.doWithRequest(request);
            }
            response = request.execute();

            // Set ContentType to JSON
            response.getHeaders().setContentType(MediaType.APPLICATION_JSON);

            if (!getErrorHandler().hasError(response))
            {
                logResponseStatus(method, url, response);
            } else
            {
                handleResponseError(method, url, response);
            }
            if (responseExtractor != null)
            {
                return responseExtractor.extractData(response);
            } else
            {
                return null;
            }
        }
        catch (IOException ex)
        {
            throw new ResourceAccessException("I/O error on " + method.name() +
                    " request for \"" + url + "\":" + ex.getMessage(), ex);
        }
        finally
        {
            if (response != null)
            {
                response.close();
            }
        }

    }

    private void logResponseStatus(HttpMethod method, URI url, ClientHttpResponse response)
    {
        //if (logger.isDebugEnabled())
        {
            try
            {
                System.out.println(method.name() + " request for \"" + url + "\" resulted in " +
                        response.getRawStatusCode() + " (" + response.getStatusText() + ")");
            }
            catch (IOException e)
            {
                // ignore
            }
        }
    }

    private void handleResponseError(HttpMethod method, URI url, ClientHttpResponse response) throws IOException
    {
        getErrorHandler().handleError(response);
    }
}

最后，这就是我尝试使用我的网络服务的方式：

RestTemplateJSON restTemplate = new RestTemplateJSON();
restTemplate.getMessageConverters().add(new MappingJackson2HttpMessageConverter());
Mall mall = restTemplate.getForObject(url, Mall.class);

但是，我仍然遇到相同的异常：

无法提取响应：找不到适合响应类型 [mmrestspringtest.Mall.Mall] 和内容类型 [application/json] 的 HttpMessageConverter

据我所知，如果我更改内容类型，应该没问题。你能告诉我我做错了什么吗？

Answer 1

所以，我终于想通了。json中有数组，所以我想把它映射到Mall[]，而不是Mall。我提供了错误的类，应该有：

RestTemplateJSON restTemplate = new RestTemplateJSON();
restTemplate.getMessageConverters().add(new MappingJackson2HttpMessageConverter());
Mall[] malls = restTemplate.getForObject(url, Mall[].class);