How to access plain json body in Spring rest controller? - spring

Question

Having the following code:
#RequestMapping(value = "/greeting", method = POST, consumes = APPLICATION_JSON_VALUE, produces = APPLICATION_JSON_VALUE)
#ResponseBody
public String greetingJson(#RequestBody String json) {
System.out.println("json = " + json); // TODO json is null... how to retrieve plain json body?
return "Hello World!";
}
The String json argument is always null despite json being sent in the body.
Note that I don't want automatic type conversion, I just want the plain json result.
This for example works:
#RequestMapping(value = "/greeting", method = POST, consumes = APPLICATION_JSON_VALUE, produces = APPLICATION_JSON_VALUE)
#ResponseBody
public String greetingJson(#RequestBody User user) {
return String.format("Hello %s!", user);
}
Probably I can use the use the ServletRequest or InputStream as argument to retrieve the actual body, but I wonder if there is an easier way?

Answer 1

Best way I found until now is:
#RequestMapping(value = "/greeting", method = POST, consumes = APPLICATION_JSON_VALUE, produces = APPLICATION_JSON_VALUE)
#ResponseBody
public String greetingJson(HttpEntity<String> httpEntity) {
String json = httpEntity.getBody();
// json contains the plain json string
Let me know if there are other alternatives.

Answer 2

You can just use
#RequestBody String pBody

Answer 3

Only HttpServletRequest worked for me. HttpEntity gave null string.
import java.io.IOException;
import javax.servlet.http.HttpServletRequest;
import org.apache.commons.io.IOUtils;
#RequestMapping(value = "/greeting", method = POST, consumes = APPLICATION_JSON_VALUE, produces = APPLICATION_JSON_VALUE)
#ResponseBody
public String greetingJson(HttpServletRequest request) throws IOException {
final String json = IOUtils.toString(request.getInputStream(), StandardCharsets.UTF_8);
System.out.println("json = " + json);
return "Hello World!";
}

Answer 4

simplest way that works for me is
#RequestMapping(value = "/greeting", method = POST, consumes = MediaType.ALL_VALUE, produces = MediaType.APPLICATION_JSON_UTF8_VALUE)
#ResponseBody
public String greetingJson(String raw) {
System.out.println("json = " + raw);
return "OK";
}

Answer 5

If you have dozens of Methods that need to get HTTP body as JSON and convert it to custom data type, it is a better way to implement the support on the framework
public static class Data {
private String foo;
private String bar;
}
//convert http body to Data object.
//you can also use String parameter type to get the raw json text.
#RequestMapping(value = "/greeting")
#ResponseBody
public String greetingJson(#JsonBody Data data) {
System.out.println(data);
return "OK";
}
notice that we using user defined annotation #JsonBody.
// define custom annotation
#Retention(RetentionPolicy.RUNTIME)
#Target(ElementType.PARAMETER)
public #interface JsonBody {
String encoding() default "utf-8";
}
//annotation processor for JsonBody
#Slf4j
public class JsonBodyArgumentResolver implements HandlerMethodArgumentResolver {
#Override
public boolean supportsParameter(MethodParameter parameter) {
return parameter.getParameterAnnotation(JsonBody.class) != null;
}
#Override
public Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer, NativeWebRequest webRequest,
WebDataBinderFactory binderFactory) throws Exception {
JsonBody annotation = parameter.getParameterAnnotation(JsonBody.class);
assert annotation != null;
ServletRequest servletRequest = webRequest.getNativeRequest(ServletRequest.class);
if (servletRequest == null) {
throw new Exception("can not get ServletRequest from NativeWebRequest");
}
String copy = StreamUtils.copyToString(servletRequest.getInputStream(), Charset.forName(annotation.encoding()));
return new Gson().fromJson(copy, parameter.getGenericParameterType());
}
}
// register the annotation processor
#Component
public class WebConfig implements WebMvcConfigurer {
#Override
public void addArgumentResolvers(List<HandlerMethodArgumentResolver> resolvers) {
resolvers.add(new JsonBodyArgumentResolver());
}
}

Answer 6

As of 4.1 you can now use RequestEntity<String> requestEntity and access the body by requestEntity.getBody()
https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/http/RequestEntity.html