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EduBw
Asked: 2022-07-19 06:16:04 +0800 CST 2022-07-19 06:16:04 +0800 CST

Spring catch error before controller

  • 772

I have some web-rest services in Spring and they accept a body. If a malicious user creates an incorrect body:

{
 \"usuario": "blabla"
}

Spring handles the exception automatically by returning the error:

 "code": "UNKNOWN_ERROR",
   "message": "JSON parse error: Unexpected character ('\\' (code 92)): was expecting double-quote to start field name; nested exception is com.fasterxml.jackson.core.JsonParseException: Unexpected character ('\\' (code 92)): was expecting double-quote to start field name\n at [Source: java.io.PushbackInputStream@3fb5605c; line: 2, column: 4]",
   "type": "T",
   "component": "UNKNOWN_COMPONENT",
   "application": "Mweb",
   "timeStamp": "2022-02-18T13:15:39.224Z",
   "errors": [{"code": "UNKNOWN_ERROR"}],
   "stackTrace":    [
            {
         "methodName": "readJavaType",
         "fileName": "AbstractJackson2HttpMessageConverter.java",
         "lineNumber": 240
      },
            {
         "methodName": "read",
         "fileName": "AbstractJackson2HttpMessageConverter.java",
         "lineNumber": 225
      },
            {
         "methodName": "readWithMessageConverters",
         "fileName": "AbstractMessageConverterMethodArgumentResolver.java",
         "lineNumber": 201
      },
            {
         "methodName": "readWithMessageConverters",
         "fileName": "RequestResponseBodyMethodProcessor.java",
         "lineNumber": 150
      },
            {
         "methodName": "resolveArgument",
         "fileName": "RequestResponseBodyMethodProcessor.java",
         "lineNumber": 128
      }
   ]
}

Since the app fails before it reaches my controller, when it tries to create the input object, I need to return a "custom" message first.

I have read and tried to use:

@RestControllerAdvice
public class GlobalExceptionHandler {

/**
 * Se captura el tipo de error.
 * @param e objeto capturado
 * @return salida del metodo.
 */
@ExceptionHandler(HttpMessageNotReadableException.class)
public ResponseEntity<myException> handleException(Exception e){
return crearException(e,Constantes.INTERNAL_SERVER_CODE, Constantes.EXCEPTION_HANDLER_JSON);
 }

/**
 * Metodo auxiliar para crear el objeto del error
 * @param e objeto capturado
 * @return objeto del error.
 */
private ResponseEntity<myException> crearException()......

The problem is that it doesn't fit inside the method.

I have chosen the HttpMessageNotReadableException because in the Java console it is the first cause by that appears as an error.

java

1 Answers

  1. Best Answer

    To handle the exception HttpMessageNotReadableException, create a class that inherits from ResponseEntityExceptionHandlerand override the method handleHttpMessageNotReadablewith your custom response. A possible example:

    @ControllerAdvice
public class RestExceptionHandler extends ResponseEntityExceptionHandler {
    @Override
    protected ResponseEntity<Object> handleHttpMessageNotReadable(HttpMessageNotReadableException ex, HttpHeaders headers, HttpStatus status, WebRequest request) {
        return new ResponseEntity<>(sendCustomMessage(), HttpStatus.BAD_REQUEST);
    }

    private Map<String, String> sendCustomMessage() {
        return Map.of("Error", "Entrada Errónea");
    }
}
    • 2