Allow specifying charset to use in ExchangeFilterFunctions#basicAuthentication

Prior to this commit, it was not possible to specify the character set
to use with ExchangeFilterFunctions#basicAuthentication.

To address that, this commit introduces a new

Closes gh-36777

Signed-off-by: Kai Zander <61500114+kzander91@users.noreply.github.com>

Author: kzander91

spring-webflux/src/main/java/org/springframework/web/reactive/function/client/ExchangeFilterFunctions.java

@@ -17,9 +17,11 @@
 package org.springframework.web.reactive.function.client;
 
 import java.nio.charset.Charset;
+import java.nio.charset.StandardCharsets;
 import java.util.function.Function;
 import java.util.function.Predicate;
 
+import org.jspecify.annotations.Nullable;
 import reactor.core.publisher.Mono;
 
 import org.springframework.core.io.buffer.DataBufferUtils;
@@ -34,6 +36,7 @@
  * @author Rob Winch
  * @author Arjen Poutsma
  * @author Sam Brannen
+ * @author Kai Zander
  * @since 5.0
  */
 public abstract class ExchangeFilterFunctions {
@@ -76,14 +79,32 @@ public static ExchangeFilterFunction statusError(Predicate<HttpStatusCode> statu
 	 * Return a filter that applies HTTP Basic Authentication to the request
 	 * headers via {@link HttpHeaders#setBasicAuth(String)} and
 	 * {@link HttpHeaders#encodeBasicAuth(String, String, Charset)}.
+	 * <p>{@linkplain StandardCharsets#ISO_8859_1 ISO-8859-1} is used to convert the credentials into an octet sequence.
 	 * @param username the username
 	 * @param password the password
 	 * @return the filter to add authentication headers with
 	 * @see HttpHeaders#encodeBasicAuth(String, String, Charset)
 	 * @see HttpHeaders#setBasicAuth(String)
 	 */
 	public static ExchangeFilterFunction basicAuthentication(String username, String password) {
-		String encodedCredentials = HttpHeaders.encodeBasicAuth(username, password, null);
+		return basicAuthentication(username, password, null);
+	}
+
+	/**
+	 * Return a filter that applies HTTP Basic Authentication to the request
+	 * headers via {@link HttpHeaders#setBasicAuth(String)} and
+	 * {@link HttpHeaders#encodeBasicAuth(String, String, Charset)}.
+	 * @param username the username
+	 * @param password the password
+	 * @param charset the charset to use to convert the credentials into an octet
+	 * sequence. Defaults to {@linkplain StandardCharsets#ISO_8859_1 ISO-8859-1}.
+	 * @return the filter to add authentication headers with
+	 * @since 7.0.8
+	 * @see HttpHeaders#encodeBasicAuth(String, String, Charset)
+	 * @see HttpHeaders#setBasicAuth(String)
+	 */
+	public static ExchangeFilterFunction basicAuthentication(String username, String password, @Nullable Charset charset) {
+		String encodedCredentials = HttpHeaders.encodeBasicAuth(username, password, charset);
 		return (request, next) ->
 				next.exchange(ClientRequest.from(request)
 						.headers(headers -> headers.setBasicAuth(encodedCredentials))

spring-webflux/src/test/java/org/springframework/web/reactive/function/client/ExchangeFilterFunctionsTests.java

@@ -43,6 +43,7 @@
  * Tests for {@link ExchangeFilterFunctions}.
  *
  * @author Arjen Poutsma
+ * @author Kai Zander
  */
 class ExchangeFilterFunctionsTests {
 
@@ -104,7 +105,7 @@ void basicAuthenticationUsernamePassword() {
 
 		ExchangeFunction exchange = r -> {
 			assertThat(r.headers().containsHeader(HttpHeaders.AUTHORIZATION)).isTrue();
-			assertThat(r.headers().getFirst(HttpHeaders.AUTHORIZATION)).startsWith("Basic ");
+			assertThat(r.headers().getFirst(HttpHeaders.AUTHORIZATION)).isEqualTo("Basic Zm9vOmJhcg==");
 			return Mono.just(response);
 		};
 
@@ -114,6 +115,23 @@ void basicAuthenticationUsernamePassword() {
 		assertThat(result).isEqualTo(response);
 	}
 
+	@Test
+	void basicAuthenticationUsernameAndUnicodePassword() {
+		ClientRequest request = ClientRequest.create(HttpMethod.GET, DEFAULT_URL).build();
+		ClientResponse response = mock();
+
+		ExchangeFunction exchange = r -> {
+			assertThat(r.headers().containsHeader(HttpHeaders.AUTHORIZATION)).isTrue();
+			assertThat(r.headers().getFirst(HttpHeaders.AUTHORIZATION)).isEqualTo("Basic Zm9vOvCfkqk=");
+			return Mono.just(response);
+		};
+
+		ExchangeFilterFunction auth = ExchangeFilterFunctions.basicAuthentication("foo", "\ud83d\udca9", StandardCharsets.UTF_8);
+		assertThat(request.headers().containsHeader(HttpHeaders.AUTHORIZATION)).isFalse();
+		ClientResponse result = auth.filter(request, exchange).block();
+		assertThat(result).isEqualTo(response);
+	}
+
 	@Test
 	void basicAuthenticationInvalidCharacters() {
 		ClientRequest request = ClientRequest.create(HttpMethod.GET, DEFAULT_URL).build();