How to set multiple headers at once in Spring WebClient? - spring-boot

Question

I was trying to set headers to my rest client but every time I have to write
webclient.get().uri("blah-blah")
.header("key1", "value1")
.header("key2", "value2")...
How can I set all headers at the same time using headers() method?

Answer 1

If those headers change on a per request basis, you can use:
webClient.get().uri("/resource").headers(httpHeaders -> {
httpHeaders.setX("");
httpHeaders.setY("");
});
This doesn't save much typing; so for the headers that don't change from one request to another, you can set those as default headers while building the client:
WebClient webClient = WebClient.builder().defaultHeader("...", "...").build();
WebClient webClient = WebClient.builder().defaultHeaders(httpHeaders -> {
httpHeaders.setX("");
httpHeaders.setY("");
}).build();

Answer 2

The consumer is correct, though it's hard to visualize, esp. in that you can continue with additional fluent-composition method calls in the webclient construction, after you've done your work with the headers.
....suppose you have a HttpHeaders (or MutliValue map) holding your headers in scope. here's an example, using an exchange object from spring cloud gateway:
final HttpHeaders headersFromExchangeRequest = exchange.getRequest().headers();
webclient.get().uri("blah-blah")
.headers( httpHeadersOnWebClientBeingBuilt -> {
httpHeadersOnWebClientBeingBuilt.addAll( headersFromExchangeRequest );
}
)...
the addAll can take a multivalued map. if that makes sense. if not, let your IDE be your guide.
to make the consumer clearer, let's rewrite the above as follows:
private Consumer<HttpHeaders> getHttpHeadersFromExchange(ServerWebExchange exchange) {
return httpHeaders -> {
httpHeaders.addAll(exchange.getRequest().getHeaders());
};
}
.
.
.
webclient.get().uri("blah-blah")
.headers(getHttpHeadersFromExchange(exchange))
...

Answer 3

I found this problem came up again for me and this time I was writing groovy directly using WebClient. Again, the example I'm trying to drive is using the Consumer as the argument to the headers method call.
In groovy, the additional problem is that groovy closure syntax and java lambda syntax both use ->
The groovy version is here:
def mvmap = new LinkedMultiValueMap<>(headersAsMap)
def consumer = { it -> it.addAll(mvmap) } as Consumer<HttpHeaders>
WebClient client = WebClient.create(baseUrlAsString)
def resultAsMono = client.post()
.uri(uriAsString).accept(MediaType.APPLICATION_JSON)
.headers(consumer)
.body(Mono.just(payload), HashMap.class)
.retrieve()
.toEntity(HashMap.class)
The java version is here:
LinkedMultiValueMap mvmap = new LinkedMultiValueMap<>(headersAsMap);
Consumer<HttpHeaders> consumer = it -> it.addAll(mvmap);
WebClient client = WebClient.create(baseUrlAsString);
Mono<ResponseEntity<HashMap>> resultAsMono = client.post()
.uri(uriAsString).accept(MediaType.APPLICATION_JSON)
.headers(consumer)
.body(Mono.just(payload), HashMap.class)
.retrieve()
.toEntity(HashMap.class);

Answer 4

In Spring Boot 2.7.5:
webClient
.get()
.uri("blah-blah")
.headers(
httpHeaders -> {
httpHeaders.set("key1", "value1");
httpHeaders.set("key2", "value2");
})