Add queryParamIfPresent to UriComponentsBuilder

See gh-25951

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

@@ -21,6 +21,7 @@ import java.util.Collection;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
+import java.util.Optional;
 
 import org.springframework.lang.Nullable;
 import org.springframework.util.MultiValueMap;
@@ -334,6 +335,12 @@ public class DefaultUriBuilderFactory implements UriBuilderFactory {
 			return this;
 		}
 
+		@Override
+		public DefaultUriBuilder queryParamIfPresent(String name, Optional<?> optionalValue) {
+			this.uriComponentsBuilder.queryParamIfPresent(name, optionalValue);
+			return this;
+		}
+
 		@Override
 		public DefaultUriBuilder queryParam(String name, @Nullable Collection<?> values) {
 			this.uriComponentsBuilder.queryParam(name, values);

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

@@ -19,6 +19,7 @@ package org.springframework.web.util;
 import java.net.URI;
 import java.util.Collection;
 import java.util.Map;
+import java.util.Optional;
 
 import org.springframework.lang.Nullable;
 import org.springframework.util.MultiValueMap;
@@ -185,6 +186,15 @@ public interface UriBuilder {
 	 */
 	UriBuilder queryParam(String name, Object... values);
 
+	/**
+	 * Delegates to {@link #queryParam(String, Object...)} or {@link #queryParam(String, Object...)} if and only if optionalValue has a value.
+	 * No action will be taken, and the query parameter name will not be added, if optionalValue is empty.
+	 * @param name the query parameter name
+	 * @param optionalValue an Optional, either empty or holding the query parameter value.
+	 * @return
+	 */
+	UriBuilder queryParamIfPresent(String name, Optional<?> optionalValue);
+
 	/**
 	 * Variant of {@link #queryParam(String, Object...)} with a Collection.
 	 * <p><strong>Note: </strong> please, review the Javadoc of

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

@@ -27,6 +27,7 @@ import java.util.Deque;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
@@ -708,6 +709,20 @@ public class UriComponentsBuilder implements UriBuilder, Cloneable {
 		return this;
 	}
 
+	@Override
+	public UriComponentsBuilder queryParamIfPresent(String name, Optional<?> optionalValue) {
+		if (optionalValue.isPresent()) {
+			Object value = optionalValue.get();
+			if (value instanceof Collection) {
+				queryParam(name, (Collection) value);
+			}
+			else {
+				queryParam(name, value);
+			}
+		}
+		return this;
+	}
+
 	@Override
 	public UriComponentsBuilder queryParam(String name, @Nullable Collection<?> values) {
 		return queryParam(name, (CollectionUtils.isEmpty(values) ? EMPTY_VALUES : values.toArray()));

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

@@ -18,11 +18,13 @@ package org.springframework.web.util;
 
 import java.net.URI;
 import java.net.URISyntaxException;
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
+import java.util.Optional;
 
 import org.junit.jupiter.api.Test;
 
@@ -204,6 +206,33 @@ class UriComponentsBuilderTests {
 		assertThat(uri.toString()).isEqualTo(httpUrl);
 	}
 
+
+	@Test
+	void queryParamIfPresent() {
+		UriComponentsBuilder builder = UriComponentsBuilder.newInstance();
+		UriComponents result = builder.queryParamIfPresent("baz", Optional.of("qux")).queryParamIfPresent("foo", Optional.empty()).build();
+
+		assertThat(result.getQuery()).isEqualTo("baz=qux");
+		MultiValueMap<String, String> expectedQueryParams = new LinkedMultiValueMap<>(1);
+		expectedQueryParams.add("baz", "qux");
+		assertThat(result.getQueryParams()).isEqualTo(expectedQueryParams);
+	}
+
+	@Test
+	void queryParamIfPresentCollection() {
+		Collection<String> c = new ArrayList<>();
+		c.add("foo");
+		c.add("bar");
+		UriComponentsBuilder builder = UriComponentsBuilder.newInstance();
+		UriComponents result = builder.queryParamIfPresent("baz", Optional.of(c)).build();
+
+		assertThat(result.getQuery()).isEqualTo("baz=foo&baz=bar");
+		MultiValueMap<String, String> expectedQueryParams = new LinkedMultiValueMap<>(1);
+		expectedQueryParams.add("baz", "foo");
+		expectedQueryParams.add("baz", "bar");
+		assertThat(result.getQueryParams()).isEqualTo(expectedQueryParams);
+	}
+
 	@Test  // SPR-10539
 	void fromUriStringIPv6Host() {
 		UriComponents result = UriComponentsBuilder