Spring rest controller @RequestParam validation

Question

I want to validate the request param.I have gone through number of blogs and answer and did the same. Added @Validated on the controller class.

Method in controller:

public ResponseEntity<Employee> getHistory(
@Valid @Pattern(regexp = "^[A-Z]{2}[0-9]{6}[A-Z]{0,1}$", message = "Invalid 
emp") @NotNull(message = "input cannot be null") @RequestParam(name = "emp") 
String emp) { method body..........}

Controller Advice

@ExceptionHandler(value = {ConstraintViolationException.class})
@ResponseStatus(value = HttpStatus.BAD_REQUEST)
public String handleValidationFailure(ConstraintViolationException ex) {

  StringBuilder messages = new StringBuilder();

  for (ConstraintViolation<?> violation : ex.getConstraintViolations()) {
      messages.append(violation.getMessage() + "\n");
  }

  return messages.toString();
}

Config:

@Bean
public MethodValidationPostProcessor methodValidationPostProcessor() {
  return new MethodValidationPostProcessor();
}

After doing all this now I am getting a 404 error. "status":404,"error":"Not Found","message":"No message available"

Answer 1

You are missing @ResponseBody annotation over a method in controller advice. It causes an error, because Spring is trying to locate template with name returned as a String from this method, so during REST call you get something like this:

{
    "error": "Not Found", 
    "exception": "javax.validation.ConstraintViolationException", 
    "message": "No message available", 
    "path": "/history", 
    "status": 404, 
    "timestamp": 1502293311543
}

Adding @ResponseBody annotation to handleValidationFailure(ConstraintViolationException ex) method means that when you return a String it's not a template name but the response object itself.

Alternatively you can use ResponseEntity<String> as a return type in your advice method, e.g.

@ExceptionHandler(value = {ConstraintViolationException.class})
@ResponseStatus(value = HttpStatus.BAD_REQUEST)
public ResponseEntity<String> handleValidationFailure(ConstraintViolationException ex) {
    StringBuilder messages = new StringBuilder();

    for (ConstraintViolation<?> violation : ex.getConstraintViolations()) {
        messages.append(violation.getMessage());
    }

    return ResponseEntity.badRequest().body(messages.toString());
}

so you don't have to annotate method with @ResponseBody and Spring will now that your response is not a view name but response body itself. I hope it helps.

UPDATE

I assume you are calling incorrect endpoint. I have created a small Spring Boot application that replicates your problem using provided information:

https://github.com/wololock/rest-validation-demo

Feel free to clone it and run it. After running you can try calling /history endpoint with:

curl "localhost:8080/history?emp=AZ000001A"

and it will display in return:

{"id":"AZ000001A","name":"Joe Doe"}%

If you call this endpoint with emp that violates validation rules:

curl "localhost:8080/history?emp=sd"

you will get following response:

{"message":"Your request contains errors","errors":[{"getHistory.arg0":"Invalid emp"}]}

My assumption is that in your case you are calling your endpoint incorrectly. There is popular misunderstanding in using @RestController annotation. I saw people using it like @RestController("/someRootPath") and then they expected to have endpoints like

localhost:8080/someRootPath/...

which is not correct. Value passed to @RestController annotation is nothing else than:

The value may indicate a suggestion for a logical component name, to be turned into a Spring bean in case of an autodetected component.

You can always check console log to see what are the final mappings for your controllers, e.g.

2017-08-09 20:40:45.663  INFO 1340 --- [           main] s.w.s.m.m.a.RequestMappingHandlerAdapter : Looking for @ControllerAdvice: org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@6385cb26: startup date [Wed Aug 09 20:40:44 CEST 2017]; root of context hierarchy
2017-08-09 20:40:45.696  INFO 1340 --- [           main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/history],methods=[GET]}" onto public org.springframework.http.ResponseEntity<com.github.wololock.restvalidationdemo.Employee> com.github.wololock.restvalidationdemo.EmployeeController.getHistory(java.lang.String)
2017-08-09 20:40:45.698  INFO 1340 --- [           main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/error],produces=[text/html]}" onto public org.springframework.web.servlet.ModelAndView org.springframework.boot.autoconfigure.web.BasicErrorController.errorHtml(javax.servlet.http.HttpServletRequest,javax.servlet.http.HttpServletResponse)
2017-08-09 20:40:45.698  INFO 1340 --- [           main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/error]}" onto public org.springframework.http.ResponseEntity<java.util.Map<java.lang.String, java.lang.Object>> org.springframework.boot.autoconfigure.web.BasicErrorController.error(javax.servlet.http.HttpServletRequest)
2017-08-09 20:40:45.708  INFO 1340 --- [           main] o.s.w.s.h.BeanNameUrlHandlerMapping      : Mapped URL path [/employee] onto handler '/employee'
2017-08-09 20:40:45.714  INFO 1340 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/webjars/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2017-08-09 20:40:45.714  INFO 1340 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]

I hope it helps.