How to Handle HTTP 400 Errors in Spring MVC @ResponseBody Methods with String Return Type?

HTTP 400 Error Handling in Spring MVC's @ResponseBody Methods with String Return Type

When implementing an API using Spring MVC, it's crucial to handle errors gracefully. One common error code to respond to is HTTP 400, indicating a "bad request."

In your given scenario, where the match method returns a String wrapped in @ResponseBody, you may wonder how to respond with HTTP 400 error code. The traditional approach using ResponseEntity is not directly applicable here, as your method's return type is String.

To resolve this, consider changing the return type of your match method to ResponseEntity. This will provide you with the flexibility to handle HTTP status codes more explicitly.

Updated Method:

<code class="java">@RequestMapping(value = "/matches/{matchId}", produces = "application/json")
@ResponseBody
public ResponseEntity<String> match(@PathVariable String matchId) {
    String json = matchService.getMatchJson(matchId);
    if (json == null) {
        return new ResponseEntity<>(HttpStatus.BAD_REQUEST);
    }
    return new ResponseEntity<>(json, HttpStatus.OK);
}</code>

This modified approach allows you to return a ResponseEntity with an appropriate HTTP status code. If the matchId is invalid, you can return ResponseEntity with HTTP 400 status. For a valid request, you can return ResponseEntity with HTTP 200 status and the JSON response.

Spring 4.1 and Above:

Starting with Spring 4.1, the ResponseEntity class provides helper methods that you can use for a more concise approach:

Updated Method (Spring 4.1 ):

<code class="java">@RequestMapping(value = "/matches/{matchId}", produces = "application/json")
@ResponseBody
public ResponseEntity<String> match(@PathVariable String matchId) {
    String json = matchService.getMatchJson(matchId);
    if (json == null) {
        return ResponseEntity.status(HttpStatus.BAD_REQUEST).body(null);
    }
    return ResponseEntity.ok(json);
}</code>

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