Spring Webclient : illegalargumentexception not enough variables to expand 'comment_count' - spring-boot

Question

I am using spring webclient to make a Facebook graph api request with url containing {comment_count}
But, getting this exception
java.lang.IllegalArgumentException: Not enough variable values available to expand reactive spring
Code Snippet :
import org.springframework.stereotype.Component;
import org.springframework.web.reactive.function.client.WebClient;
import reactor.core.publisher.Mono;
#Component
public class Stackoverflow {
WebClient client = WebClient.create();
public Mono<Post> fetchPost(String url) {
// Url contains "comments{comment_count}"
return client.get().uri(url).retrieve()
.bodyToMono(Post.class);
}
}
I know the solution with resttemplate, But i need to use spring webclient.

Answer 1

You can create your URL using UriComponentsBuilder as follows
webClient.get().uri(getFacebookGraphURI(3)).retrieve().bodyToMono(Object.class);
private URI getFacebookGraphURI(int comments){
return UriComponentsBuilder.fromHttpUrl("https://graph.facebook.com")
.pathSegment("v3.2", "PAGE_ID", "posts").queryParam("fields", "comments{comment_count}")
.queryParam("access_token", "acacaaac").build(comments);
}
OR
int commentsCount = 3; webClient.get().uri(UriComponentsBuilder.fromHttpUrl("https://graph.facebook.com")
.pathSegment("v3.2", "PAGE_ID", "posts").queryParam("fields", "comments{comment_count}")
.queryParam("access_token", "acacaaac").build().toString(),commentsCount).retrieve().bodyToMono(Object.class);

Answer 2

The solution I use is to disable the encoding in DefaultUriBuilderFactory
val urlBuilderFactory = DefaultUriBuilderFactory("https://foo.bar.com").apply {
encodingMode = EncodingMode.NONE
}
val wc = wcb
.clone()
.uriBuilderFactory(urlBuilderFactory)
.build()
It's in Kotlin, in Java you just have to use DefaultUriBuilderFactory#setEncodingMode(EncodingMode) with NONE as parameter.
Due to this change of behavior, you have to encode your query params yourself. To do so, I use the
val query = URLEncoder.encode(query_as_string, StandardCharsets.UTF_8.toString())
And I can perform call like this:
wc.get()
.uri { it
.path(graphqlEndpoints)
.queryParam("variables", query)
.build()
}
.retrieve()
.bodyToFlux<String>()
// ...
For Java (as per comment by Anurag below) it will be something like this:
var uriBuilderFactory = new DefaultUriBuilderFactory(baseUrl);
uriBuilderFactory.setEncodingMode(DefaultUriBuilderFactory.EncodingMode.NONE);
var wc = WebClient.builder()
.baseUrl(baseUrl)
.uriBuilderFactory(uriBuilderFactory)
// ... other options
.build();
wc.get()
.uri(uriBuilder -> uriBuilder
.path(path)
// value still needs to be URL-encoded as needed (e.g., if value is a JSON
.queryParam("param", value))
.build())
.retrieve()
.bodyToMono(...);
As noted above, you will still need to URL-encode the parameter value. With this approach, you are merely avoiding "double URL encoding" by replacing the urlBuilderFactory.