强制Spring RestTemplate将纯文本处理为JSON? [英] Force spring RestTemplate to process plain text as JSON?

问题描述

Web API正在使用Content-Type:text/plain; charset=utf-8响应请求，但是消息的格式像是JSON，例如

A web API is responding to a request with Content-Type:text/plain; charset=utf-8, but the messageis formatted as if it were a JSON, eg.

{
"total": 168,
"page": 0,
"pageCount": 1,
...
}

在Spring中，此消息使用RestTemplate处理，并且JSON自动映射到ModelDto POJO，

In Spring, this message is processed with a RestTemplate and the JSON is automagically mapped into a ModelDto POJO,

restTemplate.getForObject(url, ModelDto::class.java) 

这会出现以下错误:

org.springframework.web.client.RestClientException:无法提取响应:没有为响应类型[class api.ModelDto]和内容类型[text/plain; charset = utf-8]找到合适的HttpMessageConverter

org.springframework.web.client.RestClientException: Could not extract response: no suitable HttpMessageConverter found for response type [class api.ModelDto] and content type [text/plain;charset=utf-8]

尽管Content-Type是纯文本的，有没有办法让spring将此消息视为JSON并解析为JSON?

Is there any way to have spring treat this message as if it were a JSON and parse it as such, despite the Content-Type being plaintext?

推荐答案

更新

因为AbstractHttpMessageConverter具有方法setSupportedMediaTypes可用于更改支持的媒体类型，所以无需创建自定义HttpMessageConverter:

There's no need to create a custom HttpMessageConverter since AbstractHttpMessageConverter has a method setSupportedMediaTypes which can be used to change supported media type:

MappingJackson2HttpMessageConverter converter = new MappingJackson2HttpMessageConverter();
converter.setSupportedMediaTypes(Arrays.asList(MediaType.TEXT_PLAIN, MediaType.APPLICATION_JSON));
restTemplate.getMessageConverters().add(0, converter);

---

我认为可以通过实现自己的HttpMessageConverter<T>来实现.

---

I think it's possible via implementing own HttpMessageConverter<T>.

RestTemplate使用它将原始响应转换为某种表示形式(例如POJO).由于它具有转换器列表，因此可以根据其类型(例如application/json等)找到用于特定响应的特定转换器.

RestTemplate uses it to convert a raw response to some representation (for instance, POJO). Since it has a list of converters, it finds specific converter for a particular response by its type (e.g application/json, etc).

因此，HttpMessageConverter<T>的实现应类似于默认的MappingJackson2HttpMessageConverter，但支持的媒体类型已更改:

So your implementation of HttpMessageConverter<T> should be something like default MappingJackson2HttpMessageConverter but with changed supported media type:

public class MappingJackson2HttpMessageConverter2 extends AbstractJackson2HttpMessageConverter {

    private String jsonPrefix;

    public MappingJackson2HttpMessageConverter2() {
        this(Jackson2ObjectMapperBuilder.json().build());
    }

    public MappingJackson2HttpMessageConverter2(ObjectMapper objectMapper) {
        // here changed media type
        super(objectMapper, MediaType.TEXT_PLAIN);
    }

    public void setJsonPrefix(String jsonPrefix) {
        this.jsonPrefix = jsonPrefix;
    }

    public void setPrefixJson(boolean prefixJson) {
        this.jsonPrefix = (prefixJson ? ")]}', " : null);
    }


    @Override
    protected void writePrefix(JsonGenerator generator, Object object) throws IOException {
        if (this.jsonPrefix != null) {
            generator.writeRaw(this.jsonPrefix);
        }
        String jsonpFunction =
                (object instanceof MappingJacksonValue ? ((MappingJacksonValue) object).getJsonpFunction() : null);
        if (jsonpFunction != null) {
            generator.writeRaw("/**/");
            generator.writeRaw(jsonpFunction + "(");
        }
    }

    @Override
    protected void writeSuffix(JsonGenerator generator, Object object) throws IOException {
        String jsonpFunction =
                (object instanceof MappingJacksonValue ? ((MappingJacksonValue) object).getJsonpFunction() : null);
        if (jsonpFunction != null) {
            generator.writeRaw(");");
        }
    }

}

然后您可以将其添加到RestTemplate对象:

Then you can add this to RestTemplate object:

restTemplate.getMessageConverters().add(0, new MappingJackson2HttpMessageConverter2());

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