How do I handle error states inside a controller?
For example: My controller which accepts two headers. If both the headers are null then it's a problem so return response of type ErrorResponse else if all ok then return response of type customer.
However, there is a problem as we defined the handler method to return ResponseEntity<Customer>.
My controller:
#PostMapping("/generate/send")
fun handleRequest( #RequestHeader header1: String,
#RequestHeader header2: String): ResponseEntity<Customer> {
if(header1 == null && header2== null) { // ERROR if both header null
return ResponseEntity(ErrorResponse(""), HttpStatus.BAD_REQUEST )
}
return ResponseEntity(Customer(), HttpStatus.OK )
}
how do refactor my code to prevent this or handle this type of situation where I have to return a different type because of an error?
You can use ResponseEntity<?> to return either Customer or ErrorResponse like this.
#PostMapping("/generate/send")
fun handleRequest( #RequestHeader header1: String,
#RequestHeader header2: String): ResponseEntity<?> {
// ...
}
Related
I have the below controller
#RestController
#RequestMapping("/view")
public class ViewController {
#GetMapping(value = "/{channelId}/**")
public Mono<ResponseEntity<ViewResponse>> viewObject(#PathVariable(value = "channelId") String channelId) {
return redisController.getChannelData(channelInfoset, channelId).map(response -> {
Mono<ViewResponse> processOutput = processViewUrl(channelId); // returns object of Mono.just
return new ResponseEntity<>(processOutput, responseHeaders, HttpStatus.OK);
}}
The method which returns the mono object
private Mono<ViewResponse> processViewUrl(String channelId){
return Mono.just(new ViewResponse("val","temp",false));
}
This gives me an error saying
Incompatible types. Found: 'reactor.core.publisher.Mono<java.lang.Object>', required: 'reactor.core.publisher.Mono<org.springframework.http.ResponseEntity<com.api.model.ViewResponse>>'
What is wrong over here?
processOutput is a Mono<ViewResponse>, not a ViewResponse. To obtain a Mono<ResponseEntity<ViewResponse>>, you should map processOutput to a ResponseEntity:
return redisController.getChannelData(channelInfoset, channelId)
.map(response -> {
Mono<ViewResponse> processOutput = processViewUrl(channelId);
return processOutput.map(value -> new ResponseEntity(value, response.getHeaders(), HttpStatus.OK));
}}
Note that if there's no constraint over your processViewUrl method signature (API compliance, potential other async/complex implementation, etc.), I would recommend to change it to return directly a ViewResponse instead of a mono. Mono.just is not necessary here.
In general cases, Mono.just is required only when you want to provide a value to an operation that requires a publisher as input.
If you return directly a ViewResponse instead of a Mono<ViewResponse>, your initial code should work.
I am new to reactive programming concepts and trying to build one service that sends requests to a two backend service in parallel and combine those results.
Those two backend service has a different response structure and i have created a mapper method to convert all that into a common Response structure.
This is what i have right now and it is working when both the services return results.
public Mono<List<Response>> getRecords(String input){
List<Response> response = new ArrayList<>();
Mono<FirstApiResponse> gResp = this.firstWebClient.get().uri(uriBuilder -> uriBuilder
.path("/")
.queryParam("q", input)
.build()).retrieve()
.bodyToMono(FirstApiResponse.class).log()
.timeout(Duration.ofSeconds(50L));
Mono<SecondApiResponse> iResp = this.secondWebClient.get().uri(uriBuilder -> uriBuilder
.path("/search")
.queryParam("term", input)
.build()).retrieve()
.bodyToMono(SecondApiResponse.class).log().timeout(Duration.ofSeconds(50L));
return Mono.zip(firstResp,secResp).map(objects ->{
if(firstResp != null)
response.addAll(Mapper.convert(objects.getT1()));
if(secResp != null);
response.addAll(Mapper.convert(objects.getT2()));
return response;
});
}
public List<Response> convert(FirstApiResponse resp){
////
Mapping to Response object
////
return response;
}
public List<Response> convert(SecondApiResponse resp){
////
Mapping to Response object
////
return response;
}
I don't know if this is the right way to do it. Moreover, i want to make it in such a way that if there is any errors from any of this service, then it should still return the results from the other service. Right now it throws the exception and I am not able to figure out how to handle it properly
How to handle these errors in a proper way ?
This is a pretty valid scenario and there are many ways to handle it. One crude way would be to use onErrorReturn a new Model which you can handle. It could be either an empty response or a wrapper around your model whichever seems fit for your scenario.
Mono<Wrapper<FirstApiResponse>> gResp = this.firstWebClient.get().uri(uriBuilder -> uriBuilder
.path("/")
.queryParam("q", input)
.build()).retrieve()
.bodyToMono(FirstApiResponse.class).log()
.map( response -> new Wrapper().withResponse(response))
.timeout(Duration.ofSeconds(50L))
.doOnError(throwable -> logger.error("Failed", throwable))
.onErrorReturn(new Wrapper().withError( YourDefaultErrorReponse(...));
Mono<SecondApiResponse> iResp = this.secondWebClient.get().uri(uriBuilder -> uriBuilder
.path("/search")
.queryParam("term", input)
.build())
.retrieve()
.bodyToMono(SecondApiResponse.class).log()
.map( response -> new Wrapper().withResponse(response))
.timeout(Duration.ofSeconds(50L))
..doOnError(throwable -> logger.error("Failed", throwable))
.onErrorReturn(new Wrapper().withError( YourDefaultErrorReponse(...))
Again there are ways to return a default response. A simple one would be to use something like a wrapper
public final class Wrapper<T> {
private T response ;
private Error error;
public Wrapper<T> withResponse ( T response ){
this.response = response;
return this;
}
public Wrapper<T> withError( Error error) {
this.error = error;
return this;
}
public Boolean hasError(){
return error != null ;
}
public T getResponse(){
return response;
}
}
I have a controller in my MVC 6 API project. There is a post method and what I want is to validate posted value and return some error back to a client if data are not valid.
[HttpPost]
public void Post([FromBody]PostedHistoricalEvent value)
{
if (!IsHistoricalEventValid(value))
{
//return error status code
}
}
Now I wonder why Post method in the default template does not have any returning type but void and how then one should return an error http status code with some message?
An action method that has no return type (void) will return an EmptyResult, or an 200 OK without a response body.
If you want to alter the response, then you can either change the return type and return an HttpStatusCodeResult:
public IActionResult Post(...)
{
// ...
return new HttpStatusCodeResult(400);
}
Or set it on the Controller.Response:
public void Post(...)
{
// ...
Response.StatusCode = 400;
}
I have a form and validation works. The problem comes in when a url parameter was added. The url parameter is a token and is required. So this is what my controller looks like:
#RequestMapping(value = "/resetpassword", method = RequestMethod.GET)
public String showResetForm(ResetPassword resetPassword, Model model,
#RequestParam(value = "token", required = true) String token,
#RequestParam(value = "msg", required = false) String msg){
model.addAttribute("token", token);
return "resetpassword";
}
#RequestMapping(value = "/resetpassword", method = RequestMethod.POST)
public String setPwd(#ModelAttribute("resetPassword") #Valid ResetPassword resetPassword,// RedirectAttributes reDirectAttr,
BindingResult bindingResult, Model model,
#RequestParam(value = "token", required = true) String token,
#RequestParam(value = "msg", required = false) String msg){
if (bindingResult.hasErrors()) {
//reDirectAttr.addFlashAttribute("org.springframework.validation.BindingResult.resetPassword",bindingResult);
//reDirectAttr.addFlashAttribute("resetPassword",resetPassword);
return "resetpassword?token="+token;
}
else {
if (token == null) {
// TODO: no token, what to do here??
return "redirect:/resetpassword?token=\"\"&msg=notoken";
}
ResetPasswordResponseDto response = super.resetUserPassword(
resetPassword.getUname(), resetPassword.getPassword(),
token);
if (response.getPasswordResetResult() == PasswordResetResult.SUCCESSFUL) {
// TODO: it worked, what now?
return "redirect:/login";
} else if (response.getPasswordResetResult() == PasswordResetResult.INVALID_TOKEN) {
// TODO: bad token
return "redirect:/resetpassword?token="+token+"&msg=badtoken";
} else if (response.getPasswordResetResult() == PasswordResetResult.OUT_OF_POLICY_PW) {
// TODO: out of policy pw
return "redirect:/resetpassword?token="+token+"&msg=outofpolicy";
} else if (response.getPasswordResetResult() == PasswordResetResult.LDAP_FAILURE) {
// TODO: other failure
return "redirect:/resetpassword?token="+token+"&msg=error";
}
}
return "redirect:/resetpassword?token="+token+"&msg=error";
//return new RedirectView("resetpassword?token=\"\"&msg=notoken");
}
So I tried a bunch of things but nothing seems to work. Here is what I would like to happen when the view is requested /resetpassword?token=1232453 the view is displayed. Then if the form has errors the url parameter persists in the url and the form displays the errors. Right now I get an error saying that the template cannot be resolved. Ok fair enough, so I tried doing a redirect instead
return "redirect:/resetpassword?token="+token;
and that seems to work, however the URL parameter is lost and the view loses the bindingResult errors. In the code, I posted I also tried FlashAttributes but I just get an error "Validation failed for object='resetPassword'. Error count: 4" which is correct but I need it to show the form and the errors I coded with Thymeleaf. Any help or suggestions would be great!
Resources I have looked at:
Spring - Redirect after POST (even with validation errors)
&
SpringMVC controller: how to stay on page if form validation error occurs
Have you tried returning a ModelAndView instead of just the redirect string? Attributes on the model will be available as URL query parameters.
ModelAndView redirect = new ModelAndView("redirect:/resetpassword");
redirect.addObject("token", token);
redirect.addObject("msg", "error");
return redirect;
I have the following jQuery script:
$(document).ready(function() {
$("#resendActivationEmailLink").bind("click", function(event) {
$.get($(this).attr("href"), function() {
$("#emailNotActivated").html("<span>not yet activated. email sent!</span>");
}, "html");
event.preventDefault();
});
});
Basically, when a user clicks a link the following server-side method is invoked:
#RequestMapping(value = "/resendActivationEmail/{token}", method = RequestMethod.GET, produces = "application/json")
public #ResponseBody
String resendActivationEmail(#PathVariable("token") String token) {
preferencesService.resendActivationEmail(token);
return "dummy";
}
and some business logic is executed on the server but there is no real outcome from the server to be used on the client/browser side apart from an ajax success or an ajax failure.
Now what I am really not sure about is what my server-side method is supposed to return!
Currently it just returns the string dummy but of course this is only temporary. Should I go for no return type (void) or null or something else??
Note that I can change the datatype parameter of the jQuery get method.
EDIT:
I have altered my server-side method as follows:
#RequestMapping(value = "/resendActivationEmail/{token}", method = RequestMethod.GET)
public #ResponseBody void resendActivationEmail(#PathVariable("token") String token) {
preferencesService.resendActivationEmail(token);
}
#ResponseBody is required because this is an ajax call.
There is no point in returning a dummy value in this case. If you are not doing anything with the return value, then you can just do something like this:
#RequestMapping(value="/resendActivationEmail/{token}", method=RequestMethod.GET)
#ResponseStatus(org.springframework.http.HttpStatus.NO_CONTENT)
public void resendActivationEmail(#PathVariable String token) {
preferencesService.resendActivationEmail(token);
}
There will be a 204 response code instead of a 200 but that should be fine.
I'm assuming you are returning JSON from the server (from your server code: produces = "application/json").
Since you don't care about what gets returned, i.e. you are not handling the return value in your callback function, after $.get, then you can just return "{}", or if you want to handle the response you can go with something like:
{ "success": true }
// or
{ "error": "Error messages here" }