json spring mvc java

@RequestMapping(value = "/rest/create/document", produces = "text/plain;charset=UTF-8")
@ResponseBody
public String create(Document document, HttpServletRespone respone) throws UnsupportedEncodingException {

    Document newDocument = DocumentService.create(Document);

    return jsonSerializer.serialize(newDocument);
}

<mvc:annotation-driven>
  <mvc:message-converters register-defaults="true">
    <bean class="org.springframework.http.converter.StringHttpMessageConverter">
      <property name="supportedMediaTypes" value = "text/plain;charset=UTF-8" />
    </bean>
  </mvc:message-converters>
</mvc:annotation-driven>

Or code-based configuration:
@Configuration
@EnableWebMvc
public class WebConfig extends WebMvcConfigurerAdapter {

  private static final Charset UTF8 = Charset.forName("UTF-8");

  @Override
  public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
    StringHttpMessageConverter stringConverter = new StringHttpMessageConverter();
    stringConverter.setSupportedMediaTypes(Arrays.asList(new MediaType("text", "plain", UTF8)));
    converters.add(stringConverter);

    // Add other converters ...
  }
}