Format Collection query param in UriComponentsBuilder

See gh-34311

Signed-off-by: Mengqi Xu <[email protected]>

Author: remeio

spring-web/src/main/java/org/springframework/web/util/HierarchicalUriComponents.java

@@ -22,6 +22,7 @@
 import java.net.URISyntaxException;
 import java.nio.charset.Charset;
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
 import java.util.Objects;
@@ -47,6 +48,7 @@
  * @author Rossen Stoyanchev
  * @author Phillip Webb
  * @author Sam Brannen
+ * @author Mengqi Xu
  * @since 3.1.3
  * @see <a href="https://tools.ietf.org/html/rfc3986#section-1.2.3">Hierarchical URIs</a>
  */
@@ -1090,6 +1092,9 @@ public QueryUriTemplateVariables(UriTemplateVariables delegate) {
 			if (ObjectUtils.isArray(value)) {
 				value = StringUtils.arrayToCommaDelimitedString(ObjectUtils.toObjectArray(value));
 			}
+			if (value instanceof Collection<?> coll) {
+				value = StringUtils.collectionToCommaDelimitedString(coll);
+			}
 			return value;
 		}
 	}

spring-web/src/test/java/org/springframework/web/util/UriComponentsTests.java

@@ -23,6 +23,7 @@
 import java.net.URI;
 import java.util.Arrays;
 import java.util.Collections;
+import java.util.List;
 
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
@@ -42,6 +43,7 @@
  * @author Arjen Poutsma
  * @author Phillip Webb
  * @author Rossen Stoyanchev
+ * @author Mengqi Xu
  */
 class UriComponentsTests {
 
@@ -153,6 +155,26 @@ void expandWithFragmentOrder(ParserType parserType) {
 		assertThat(uri.toUriString()).isEqualTo("https://example.com/foo#bar");
 	}
 
+	@Test
+	void expandQueryParamWithArray() {
+		UriComponents uri = UriComponentsBuilder.fromPath("/hello")
+				.queryParam("name", "{name}")
+				.build();
+		uri = uri.expand(Collections.singletonMap("name", new String[]{"foo", "bar"}));
+
+		assertThat(uri.toString()).hasToString("/hello?name=foo,bar");
+	}
+
+	@Test
+	void expandQueryParamWithList() {
+		UriComponents uri = UriComponentsBuilder.fromPath("/hello")
+				.queryParam("name", "{name}")
+				.build();
+		uri = uri.expand(Collections.singletonMap("name", List.of("foo", "bar")));
+
+		assertThat(uri.toString()).hasToString("/hello?name=foo,bar");
+	}
+
 	@ParameterizedTest // SPR-12123
 	@EnumSource
 	void port(ParserType parserType) {