I need to make a external API call from my Spring service. I am planning to return a Response object,
containing status code, actual json response. So that, the caller can decide how to decode the json based on the status code. Example - If status is 2xx - save the response, 4xx - log it in some error table etc.
I have done something like this. But, I am not sure whether the approach is correct or not.
Basically, I need to return the json and the status code for all status codes.
Wondering, how to achieve this with exchangeToMono.
The below code snippet works fine but I am not sure it's correct or not.
Appreciate any help or suggestions...
ResponseObj has two properties - statusCode and json.
public ResponseObj getExternalData() {
ResponseObj obj = new ResponseObj();
Mono<String> result = webclient.get().
.uri("/some/external/api")
.headers( //headers)
.exchangeToMono( response -> {
obj.setStatusCode(response.rawStatusCode());
return response.bodyToMono(String.class);
});
obj.setJson(result.block));
return obj;
}
Related
I'm looking for a simple example of error handling with WebFlux. I've read lots of stuff online, but can't find something that fits what I want.
I'm running with Spring Boot 2.45
I am calling services like this:
Mono<ResponseObject> mono = webClient.post()
.uri(url.toString())
.header("Authorization", authToken)
.body(Mono.just(contract), contract.getClass())
.retrieve()
.bodyToMono(ResponseObject.class);
All of my services return Json that is deserialized to ResposeObject which looks something like this:
"success" : true,
"httpStatus": 200,
"messages" : [
"Informational message or, if not 200, then error messages"
],
result: {
"data": {}
}
data is simply a map of objects that are the result of the service call.
If there is an error, obviously success is false.
When I eventually do a ResponseObject response = mono.block(), I want to get a ResponseObject each time, even if there was an error. My service returns a ResponseObject even if it returns an http status of 400, but WebFlux seems to intercept this and throws an exception. Obviously, there might also be 400 and 500 errors where the service wasn't even called. But I still want to wrap whatever message I get into a ResponseObject. How can I eliminate all exceptions and always get a ResponseObject returned?
Update
Just want to clarify that the service itself is not a Reactive Webflux service. It is not returning a Mono. Instead, it is calling out to other Restful services, and I want to do that using Webflux. So what I do is I call the external service, and then this service does a block(). In most cases, I'm calling multiple services, and then I do a Mono.zip and call block() to wait for all of them.
This seems to be what I want to do: Spring Webflux : Webclient : Get body on error, but still can't get it working. Not sure what exchange() is
Correct way of handling this is via .onErrorResume that allows you to subscribe to a fallback publisher using a function, when any error occurs. You can look at the generated exception and return a custom fallback response.
You can do something like this:
Mono<ResponseObject> mono = webClient.post()
.uri(url.toString())
.header("Authorization", authToken)
.bodyValue(contract)
.exchangeToMono(response -> {
if (response.statusCode().equals(HttpStatus.OK)) {
return response.bodyToMono(ResponseObject.class);
}
else if (response.statusCode().is4xxClientError()) {
return response.bodyToMono(ResponseObject.class);
}
else {
Mono<WebClientResponseException> wcre = response.createException();
// examine wcre and create custom ResponseObject
ResponseObject customRO = new ResponseObject();
customRO.setSuccess(false);
customRO.setHttpStatus(response.rawStatusCode());
// you can set more default properties in response here
return Mono.just( customRO );
}
});
Moreover, you should not be using .block() anywhere in your Java code. Just make sure to return a Mono<ResponseObject> from your REST controller. If you want to examine response before returning to client you can do so in a .map() hander like this at the end of pipeline (right after .onErrorResume handler)
.map(response -> {
// examine content of response
// in the end just return it
return response;
});
I am using the spring WebClient to make two calls in parallel.
One of the call results is passed back as a ResponseEntity, and the other result is inspected and then disregarded. Although the transactions are both successful, I see an IllegalReferenceCountException that occurs before any of the WebClient calls actually get executed.
What I see in my logging is that the container logs the exception, then my two HTTP requests get executed successfully, and one of these responses gets returned to the client.
If the shouldBackfill() function returns false, then I execute one HTTP request and return that response (and the IllegalReferenceCountException does not occur).
I was initially thinking that I should release the reference in the second response that I disregard.
If I attempt to call releaseBody() directly on the WebClient response. (See https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/web/reactive/function/client/ClientResponse.html), this does not help. I assume now that the container is detecting that the WebClient request that I disregarded is in an illegal state, hence the error detection. But what I don't understand is that the actual request occurs AFTER the IllegalReferenceCountException gets logged.
Any ideas here on how to get around this? I am wondering if the exception is actually NOT any kind of leak.
The code looks like this:
fun execute(routeHttpRequest: RouteHttpRequest): Mono<ResponseEntity<String>> =
propertyRepository.getProperty(routeHttpRequest.propertyId.orDefault())
.flatMap {
val status = it.getOrElse { unknownStatus(routeHttpRequest.propertyId.orDefault()) }
val response1 = execute(routeHttpRequest, routingRepository.webClientFor(routeHttpRequest))
if (shouldBackfill(routeHttpRequest, status.type())) {
val response2 =
execute(routeHttpRequest, routingRepository.shadowOrBackfillWebClientFor(routeHttpRequest))
zip(response1, response2).map { response ->
compare(routeHttpRequest, response.t1, response.t2, status.type())
response.t1 // response.t2 is NOT returned here..
}
} else response1
}
// This function returns a wrapper on a spring Webclient that makes an HTTP post.
//
private fun execute(routeHttpRequest: RouteHttpRequest, client: Mono<MyWebClient>) =
client
.flatMap { dataService.execute(routeHttpRequest, it) }
.subscribeOn(Schedulers.elastic()) // TODO: consider a dedicated executor here?
private fun shouldBackfill(routeHttpRequest: RouteHttpRequest, migrationStatus: MigrationStatusType): Boolean {
... this logic returns true when we should execute 2 requests in parallel
}
Here's the exception and partial trace:
io.netty.util.IllegalReferenceCountException: refCnt: 0, decrement: 1
at io.netty.util.internal.ReferenceCountUpdater.toLiveRealRefCnt(ReferenceCountUpdater.java:74)
at io.netty.util.internal.ReferenceCountUpdater.release(ReferenceCountUpdater.java:138)
at io.netty.buffer.AbstractReferenceCountedByteBuf.release(AbstractReferenceCountedByteBuf.java:100)
at io.netty.util.ReferenceCountUtil.release(ReferenceCountUtil.java:88)
Sorry for not posting the exact code. Fix- I was passing the incoming http request org.springframework.core.io.buffer.DataBuffer directly to the WebClient request body. This was intentional because my application is acting as a proxy service. The problem came up when I attempted to make two outbound WebClient calls in parallel - the container was trying to release the underlying buffer twice, and the IllegalReferenceCountException occurs. My fix was to just copy the DataBuffer byte array into a new buffer before sending the request along to it's destination.
I am calling a micro-service in my rest controller. It works fine when ever there is a successful response from the Micro-service but if there is some error response I fails to pass on the error response back to user. Below is the sample code.
#GetMapping("/{id}/users/all")
public Mono<Employee> findAllProfiles(#PathVariable("id") UUID organisationId,
#RequestHeader(name = "Authorization", required = false) String oauthJwt) {
return webClient.get().uri(prepareUrl("{id}/users/all"), organisationId)
.header("Authorization", oauthJwt).accept(MediaType.APPLICATION_JSON)
.exchange().then(response -> response.bodyToMono(Employee.class));
}
Now if there is any JSON response with error code then web client does not pass on the error response to the controller due to which no information is propagated to the api end user.
You should be able to chain methods from the Mono API. Look for "onError" to see a number of options which allow you to define the behavior when there is an error.
For example, if you wanted to return an "empty" Employee, you could do the following:
.exchange()
.then(response -> response.bodyToMono(Employee.class))
.onErrorReturn(new Employee());
How can I return a list of error messages from Web Api 2 with 400 Bad Request status code? See the example below. Usually I use BadRequest method to return the 400 status code but it doesn't have any overload where it accepts a collection of string. It has an overload where it accepts ModelStateDisctionary. Does it mean I will have to create ModelStateDictionary from a list of error messages?
[Route("")]
[HttpPost]
public IHttpActionResult Add(Object data)
{
var valid = _serviceLayer.Validate(data);
if(!valid)
{
var errors = valid.Errors;
// errors is an array of string
// How do I return errors with Bad Request status code here?
}
var updatedObject = _serviceLayer.Save(data);
return Ok(updatedObject);
}
As per Mike's comment, I am going to add a new class implementing IHttpActionResult to return a list of error messages with 400 Bad Request. Thanks Mark
I have a servicestack service which when called via the browser (restful) Url ex:http://localhost:1616/myproducts, it works fine.
The service method has RedisCaching enabled. So first time it hits the data repository and caches it for subsequent use.
My problem is when I try calling it from a c# client via Soap12ServiceClient. It returns the below error:
Error in line 1 position 183. Expecting element '<target response>'
from namespace 'http://schemas.datacontract.org/2004/07/<target namespace>'..
Encountered 'Element' with name 'base64Binary',
namespace 'http://schemas.microsoft.com/2003/10/Serialization/'.
Below is my Client code:
var endpointURI = "http://mydevelopmentapi.serverhostingservices.com:1616/";
using (IServiceClient client = new Soap12ServiceClient(endpointURI))
{
var request = new ProductRequest { Param1 = "xy23432"};
client.Send<ProductResponse>(request);
}
It seems that the soapwsdl used is giving the problem, but I appear to have used the defaults as generated by servicestack..
Any help will be much appreciated.
Update
I was able over come this error by changing the cache code at the service end:
Code that returned error at client end:
return RequestContext.ToOptimizedResultUsingCache(this.CacheClient, cacheKey,
() =>
new ProductResponse(){CreateDate = DateTime.UtcNow,
products = new productRepository().Getproducts(request)
});
Code that works now:
var result = this.CacheClient.Get<ProductResponse>(cacheKey);
if (result == null)
{
this.CacheClient.Set<ProductResponse>(cacheKey, productResult);
result = productResult;
}
return result;
But I am still curious to know why the first method (RequestContext.ToOptimizedResultUsingCache) returned error at c# client?
But I am still curious to know why the first method (RequestContext.ToOptimizedResultUsingCache) returned error at c# client?
From what I can tell, the ToOptimizedResultUsingCache is trying to pull a specific format (xml, html, json, etc) out of the cache based on the RequestContext's ResponseContentType (see code here and here). When using the Soap12ServiceClient the ResponseContentType is text/html (not sure if this is correct/intentional within ServiceStack). So what ToOptimizedResultUsingCache is pulling out of the cache is a string of html. The html string is being returned to the Soap12ServiceClient and causing an exception.
By pulling directly out of the cache you are bypassing ToOptimizedResultUsingCache's 'format check' and returning something the Soap12ServiceClient can handle.
** If you are using Redis and creating your key with UrnId.Create method you should see a key like urn:ProductResponse:{yourkey}.html
Thanks for your response paaschpa.
I revisited the code and I was able to fix it. Since your response gave me the direction, I have accepted your answer. Below is my fix.
I moved the return statement from RequestContext to the response DTO.
Code which throws error when used via c# client (code was returning entire requestcontext):
return RequestContext.ToOptimizedResultUsingCache(this.CacheClient, cacheKey,
() =>
new ProductResponse(){CreateDate = DateTime.UtcNow,
products = new productRepository().Getproducts(request)
});
Fixed Code (return moved to response DTO):
RequestContext.ToOptimizedResultUsingCache(this.CacheClient, cacheKey,
() => {
return new ProductResponse(){CreateDate = DateTime.UtcNow,
products = new productRepository().Getproducts(request)
}
});