I want to use webflux to return a single result async. The response doesn't have an id of the object. So when I get the response async back from the remote reply, then I don't have a way to fetch that object from the database to get further information. So is there a way to pass my object id to the async response handler? I couldn't find any way. Here is my sample code
var monoReply = webClient.post().uri(url)
.header(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE)
.body(Mono.just(myRequestObject), MyRequest.class)
.retrieve()
.bodyToMono(MyResponse.class);
monoReply.subscribe(BanlawApiServiceImpl::handleLoginResponse);
private static String handleLoginResponse(MyResponse myResponse) {
String token = myResponse.getToken();
//now I want to know the id of the database object I am dealing with. Response doesn't
have that id
}
You need to continue async flow using flatMap and fetch object from the database. As result handleLoginResponse should return Mono<T>
webClient.post().uri(url)
.header(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE)
.body(Mono.just(myRequestObject), MyRequest.class)
.retrieve()
.bodyToMono(MyResponse.class)
.flatMap(response -> handleLoginResponse(response))
private static Mono<String> handleLoginResponse(MyResponse myResponse) {
...
}
Not sure why you are subscribing to the flow explicitly that usually is anti-pattern and should be avoided. In WebFlux subscription happens behind the scene.
Related
Scenario: need to get an access token from a service and pass it to a webclient call as below.
return someservice
.getToken() //returns token as Mono<String>,this itself is another webclient call
.flatMap(token -> {
return customWebclient.delete() //observe the delete method here
.uri(uri -> uri.path(/users)
.queryParam("id", id)
.build())
.headers(headers -> headers.setBearerAuth(token))
.header("Content-Type", MediaType.APPLICATION_JSON_VALUE)
.header("Accept", MediaType.APPLICATION_JSON_VALUE)
.retrieve()
.bodyToMono(new ParameterizedTypeReference<Map<String, Object>>() {
}).log();
}); // this return a Mono<Map<String, Object>>
I then need to block this final result and so I am using .toFuture().get() to get Map<String, Object>.
Now the issue is .get() call here is waiting indefinitely and the call to customWebClient call is never happening and if I get use .get(3000, TimeUnit.SECONDS), get() is throwing a TimedOutException and then calling the customWebClient call.
From what I understand, get() method should wait for Mono<Map<String, Object>> to resolve i.e, customWebclient call to happen and then return the result.
Using spring-boot-starter-webflux
Please help me with a solution.
I have also tried not nesting these calls and used toFuture().get() for both token and the Map, get() for token is waiting forever.
Other important point is that the same customWebclient call for get() method in same way as example is working fine.
Try with adding ".subscribeOn(Schedulers.boundedElastic())" before .toFuture().get(30L, TimeUnit.SECONDS).
In my project I have a requirement where I need to call a third party api authentic url to get the the access token. I need to set that access token in every subsequent request header .The access token has some lifetime and when the lifetime expired I need to regenerate the access token.
application.yml
I have hardcoded the client_id,client_secret,auth_url and grant_type .
AuthController.java
here I have created an endpoint to generate the access token.
**`AuthService.java`**
#Services
#Slf4j
public class AuthService{
#Autowired
private WebClient webClient;
static String accessToken="";
public Mono<SeekResponse> getAccessToken(AuthRequest authRequest) throws InvalidTokenException{
Mono<AuthResponse> authResponse=webClient.post()
.bodyValue(authRequest)
.accept(MediaType.APPLICATION_JSON)
.retrive()
.bodyToMono(AuthResponse.class);
authResponse.doOnNext(response->{
String value=response.getAccess_token();
accessToken=accessToken+value;
})
}
}
Although I have updated the "accessToken" value but it will return me null. I understand as I have made async call this value coming as null. I can't use blocking mechanism here.
Is there any other way to generate the access token and pass it as a header for the subsequent request for authentication. Or how can I use the accessToken value globally so that I can set those token value to my subsequent api request call.
I have tried with oAuth2 by following the below article:
https://medium.com/#asce4s/oauth2-with-spring-webclient-761d16f89cdd
But when I execute I am getting the below error :
"An expected CSRF token cannot found".
I'm also learning Webflux. Here's my thought. Please correct me if I'm wrong.
We are not going to rely on doOnNext() nor doOnSuccess() nor other similar method to try to work on an pre-defined variable accessToken (That's not a way to let Mono flow). What we should focus on is converting a mono to another mono, for example converting mono response to mono access token.
The way to do that is .flatmap()/.map()/.zipwith()/...
For example,
Mono<string> tokenMono = responseMono.flatmap(
// in the map or flatmap, we get the chance to operate on variables/objects.
resp -> {
string token = response.getAccess_token();
return Mono.just(token); // with Mono.just(), we are able to convert object to Mono again.
}
) // this example is not practical, as map() is better to do the same thing. flatmap with Mono.just() is meaningless here.
Mono<string> tokenMono2 = responseMono.map(
resp -> {
string token = response.getAccess_token();
return token;
}
)
Everything starting from Mono should be always Mono until subscribed or blocked. And they provide us ways to operate on those variables inside Mono<variables>. Those are map() flatmap(), zipwith(), etc.
https://stackoverflow.com/a/60105107/18412317
Referring to a point this author said, doOnNext() is for side effect such as logging.
It's hard to understand provided sample and implementation is not really reactive. The method returns Mono but at the same time throws InvalidTokenException or usage of onNext that is a so-called side-effect operation that should be used for logging, metrics, or other similar use cases.
The way you implement oauth flow for WebClient is to create filter, Client Filters.
Spring Security provides some boilerplates for common oauth flows. Check Spring Security OAuth2 for more details.
Here is an example of simple implementation of the client credential provider
private ServerOAuth2AuthorizedClientExchangeFilterFunction oauth(String clientRegistrationId, ClientConfig config) {
var clientRegistration = ClientRegistration
.withRegistrationId(clientRegistrationId)
.tokenUri(config.getAuthUrl() + "/token")
.clientId(config.getClientId())
.clientSecret(config.getClientSecret())
.authorizationGrantType(AuthorizationGrantType.CLIENT_CREDENTIALS)
.build();
var authRepository = new InMemoryReactiveClientRegistrationRepository(clientRegistration);
var authClientService = new InMemoryReactiveOAuth2AuthorizedClientService(authRepository);
var authClientManager = new AuthorizedClientServiceReactiveOAuth2AuthorizedClientManager(
authRepository, authClientService);
var oauth = new ServerOAuth2AuthorizedClientExchangeFilterFunction(authClientManager);
oauth.setDefaultClientRegistrationId(clientRegistrationId);
return oauth;
}
then you could use it in the WebClient
WebClient.builder()
.filter(oauth)
.build()
UPDATE
Here is an example of the alternative method without filters
AuthService
#Service
public class AuthService {
private final WebClient webClient;
public AuthService() {
this.webClient = WebClient.create("<url>/token");
}
public Mono<String> getAccessToken() {
return webClient.post()
.bodyValue()
.accept(MediaType.APPLICATION_JSON)
.retrieve()
.bodyToMono(AuthResponse.class)
.map(res -> res.getAccessToken());
}
}
ApiService
#Service
public class ApiService {
private final WebClient webClient;
private final Mono<String> requestToken;
public ApiService(AuthService authService) {
this.webClient = WebClient.create("<url>/api");
// cache for token expiration
this.requestToken = authService.getAccessToken().cache(Duration.ofMinutes(10));
}
public Mono<String> request() {
return requestToken
.flatMap(token ->
webClient.get()
.header(HttpHeaders.AUTHORIZATION, "Bearer " + token)
.accept(MediaType.APPLICATION_JSON)
.retrieve()
.bodyToMono(String.class)
);
}
}
I've been trying to follow the simplest tutorials out there for how to use WebClient, which I understand to be the next greatest thing compared to RestTemplate.
For example, https://www.baeldung.com/spring-5-webclient#4-getting-a-response
So when I try to do the same thing with https://petstore.swagger.io/v2/pet/findByStatus?status=available which is supposed to return some json,
WebClient webClient = WebClient.create();
webClient.get().uri("https://petstore.swagger.io/v2/pet/findByStatus?status=available").exchange().block();
I have absolutely no idea how to proceed from the resultant DefaultClientResponse object. It shouldn't be this convoluted to arrive at the physical response body, but I digress.
How do I get the response body with the code I provided?
In the form you currently have it, and explaining the behaviour..
WebClient webClient = WebClient.create();
webClient.get()
.uri("https://petstore.swagger.io/v2/pet/findByStatus?status=available")
.exchange()
.block();
the block() starts the request by internally synchronously subscribing to the Mono, and returns the resulting ClientResponse. You could also handle this asynchronously by calling subscribe() on the Mono returned by the exchange() method, instead of block().
In this current form, after the block() you now have all the metadata (ie. from the response header) about the response in a ClientResponse object, including the success status. This does not mean that the response body has finished coming through. If you don't care about the response payload, you could confirm the success and leave it at that.
If you further want to look at the response body, you need to convert the response body stream into some class. A this point you can decide whether you want to read everything into a single Mono with bodyToMono or into a stream of objects (Flux) with bodyToFlux, such as in the case where the response is a JSON array that can be parsed into individual separate Java objects.
However, in your case, you just want to see the JSON as-is. So converting to a String is sufficient. You would just use bodyToMono which would return a Mono object.
WebClient webClient = WebClient.create();
String responseJson = webClient.get()
.uri("https://petstore.swagger.io/v2/pet/findByStatus?status=available")
.exchange()
.block()
.bodyToMono(String.class)
.block();
Here you use block() to wait for the response payload to arrive and be parsed into a String, but you could also subscribe to the Mono to receive it reactively when it is complete.
One thing to note is that retrieve() can be used instead of exchange() to shortcut the ClientResponse. In this case you let default behavior handle error responses. Using exchange() puts all the responsibility on the application for responding to error responses on the ClientResponse. Read more in the Javadoc. The retrieve() version would look as follows. No need to block() as you only care about the response data.
WebClient webClient = WebClient.create();
String responseJson = webClient.get()
.uri("https://petstore.swagger.io/v2/pet/findByStatus?status=available")
.retrieve()
.bodyToMono(String.class)
.block();
Here is how you make a request with RestTemplate
String json = new RestTemplate()
.getForEntity("https://petstore.swagger.io/v2/pet/findByStatus?status=available")
.getBody();
Here is how you make a request with requests
import requests
json = requests.get("https://petstore.swagger.io/v2/pet/findByStatus?status=available")
.content
Here is how you make a request with WebClient
String json = WebClient.create()
.get()
.uri("https://petstore.swagger.io/v2/pet/findByStatus?status=available")
.exchange()
.block()
.bodyToMono(String.class)
.block();
I am trying to send an object to the endpoint but I do not understand why I can't do it with .get(), why .post() has to be used? What if the endpoint method takes an object and does something with it and returns an object? I may want to send an object to the endpoint which takes the object as an argument. Is there a way to do it? How to pass a customer object to getCustomer() endpoint.
WebClient.create("http://localhost:8080")
.get()//why this can not be used? why post has to be used?
.uri("client/getCustomer")
.contentType(MediaType.APPLICATION_JSON)
.bodyValue(customer)//with .get() body cannot be passed.
.retrieve()
.bodyToMono(Customer.class);
#GET
#Path("/getCustomer")
#Produces(MediaType.APPLICATION_JSON)
#Consumes(MediaType.APPLICATION_JSON)
public Customer getCustomer(Customer customer) {
//do something
return customer;
}
Edited
In GET methods, the data is sent in the URL. just like:
http://www.test.com/users/1
In POST methods, The data is stored in the request body of the
HTTP request.
Therefore we should not expect .get() method to have .bodyValue().
Now if you wanna send data using GET method, you should send them in the URL, like below snippet
WebClient.create("http://localhost:8080")
.get()
.uri("client/getCustomer/{customerName}" , "testName")
.retrieve()
.bodyToMono(Customer.class);
Useful Spring webClient sample:
spring 5 WebClient and WebTestClient Tutorial with Examples
Further information about POST and GET
HTTP Request Methods
I am working in a Spring #Component class and I am trying to get the HTTP status code of a particular URL for further processing. I have a function as follows:
fun getStatus() : String
{
val webClient = WebClient.create("https://stackoverflow.com")
val result = webClient.get()
.exchange().map { res -> res.rawStatusCode() }
println(result)
return "statusGotten"
}
However, rather than getting the Int value of the status code (e.g. 200, or 401), I am simply getting: "MonoMap".
I am new to both Spring and Web Programming in general, so I'm a little confused how to proceed from here. I'm aware that "result" is being returned as a "Mono", but I'm less clear about what a "Mono" is, or how I might transform it into something with more scrutable properties, as even looking at "result" in the debugger doesn't shed any light as to whether the HTTP request was actually sent or was successful:
Am I calling the webclient incorrectly? Or merely failing to parse the resultant data in a meaningful way? Any suggestions on how or where I might learn more about the underlying topics would be much appreciated as well.
If you need a blocking way to do this is easy just
#Test
public void myTest(){
WebClient client = WebClient.builder().baseUrl("https://stackoverflow.com/").build();
ClientResponse resp = client
.get()
.uri("questions/")
.exchange()
.block();
System.out.println("Status code response is: "+resp.statusCode());
}
But for this you can use directly the RestTemplate instead the webclient... the recomended way to do this is non blocking what means you should return a Mono with the status and consume outside your method like for example:
public Mono<HttpStatus> myMethod(){
WebClient client = WebClient.builder().baseUrl("https://stackoverflow.com/").build();
return client
.get()
.uri("questions/")
.exchange()
.map( clientResp -> clientResp.statusCode());
}
The way of consume this Mono depends of your code...