Q:

How to access plain json body in Spring rest controller?

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?

A:

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.

A:

You can just use 
@RequestBody String pBody

A:

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!";
}

