Content-Type: application/json

{
 "question": "aaa",
 "fromUser": "bbb"
}

Content-Type: application/xml

<?xml version='1.0' encoding="utf-8"?> 
<Request>
 <question>aaa</question>
 <fromUser>bbb</fromUser>
</Request>

public interface HttpMessageConverter<T> {
 boolean canRead(Class<?> clazz, MediaType mediaType);
 boolean canWrite(Class<?> clazz, MediaType mediaType);
 List<MediaType> getSupportedMediaTypes();
 T read(Class<? extends T> clazz, HttpInputMessage inputMessage)
   throws IOException, HttpMessageNotReadableException;
 void write(T t, MediaType contentType, HttpOutputMessage outputMessage)
   throws IOException, HttpMessageNotWritableException;
}

@Configuration
public class WebConfig extends WebMvcConfigurerAdapter {
    /**
     * 自定義message_convert
     */
    @Override
    public void extendMessageConverters(List<HttpMessageConverter<?>> converters) {
       // 把converter添加到converters的最后（SpringBoot會(huì)使用第一個(gè)匹配到的Converter）
       converters.add(new XxxConverter());
       // 把converter添加到converters的最前面
       // converters.add(0, new XxxConverter());
    }
}

public class XxxConverter implements HttpMessageConverter<Serializable> {
    public static final String CUSTOM_MEDIA = "application/custom-media";
    @Override
    public boolean canRead(Class<?> clazz, MediaType mediaType) {
        return true;
    }
    @Override
    public boolean canWrite(Class<?> clazz, MediaType mediaType) {
        return true;
    }
    @Override
    public List<MediaType> getSupportedMediaTypes() {
        return Lists.newArrayList(MediaType.parseMediaType(CUSTOM_MEDIA));
    }
    @Override
    public Serializable read(Class<? extends Serializable> clazz, HttpInputMessage inputMessage) throws IOException, HttpMessageNotReadableException {
        return null;
    }
    @Override
    public void write(Serializable serializable, MediaType contentType, HttpOutputMessage outputMessage) throws IOException, HttpMessageNotWritableException {
    }
}

@RestController
@RequestMapping(produces = CUSTOM_MEDIA, consumes = CUSTOM_MEDIA)
@Validated
public class HomeController {
    @GetMapping(HOME)
    JsonResult info(@RequestHeader("userId") Long userId) {
        return JsonResult.ok();
    }
}

public class XxxConverter implements HttpMessageConverter<Serializable> {
 ......
    @Override
    public void write(Serializable serializable, MediaType contentType, HttpOutputMessage outputMessage) throws IOException, HttpMessageNotWritableException {
        // 最后把Content-Type改成APPLICATION_JSON_UTF8_VALUE，要不然請(qǐng)求方會(huì)無(wú)法解析
        ((ServletServerHttpResponse) outputMessage)
        .getServletResponse().setHeader("Content-Type",APPLICATION_JSON_UTF8_VALUE);
    }
}