Better support for overriding base URI in WebClient

The base URI is ignored for requests that include a host.

WebClient exposes UriBuilder (rather than UriBuilderFactory) for
per-request URI building based on the base URI. That provides
full control to add or replace components of the base URI.

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

@@ -167,6 +167,11 @@ public class DefaultUriBuilderFactory implements UriBuilderFactory {
 		return new DefaultUriBuilder(uriTemplate);
 	}
 
+	@Override
+	public UriBuilder builder() {
+		return new DefaultUriBuilder("");
+	}
+
 
 	/**
 	 * {@link DefaultUriBuilderFactory} specific implementation of UriBuilder.
@@ -182,9 +187,11 @@ public class DefaultUriBuilderFactory implements UriBuilderFactory {
 
 		private UriComponentsBuilder initUriComponentsBuilder(String uriTemplate) {
 
-			UriComponentsBuilder result = baseUri.cloneBuilder();
-			UriComponents child = UriComponentsBuilder.fromUriString(uriTemplate).build();
-			result.uriComponents(child);
+			UriComponentsBuilder uriComponentsBuilder = UriComponentsBuilder.fromUriString(uriTemplate);
+			UriComponents uriComponents = uriComponentsBuilder.build();
+
+			UriComponentsBuilder result = (uriComponents.getHost() == null ?
+					baseUri.cloneBuilder().uriComponents(uriComponents) : uriComponentsBuilder);
 
 			if (shouldParsePath()) {
 				UriComponents uric = result.build();

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

@@ -30,14 +30,18 @@ package org.springframework.web.util;
 public interface UriBuilderFactory extends UriTemplateHandler {
 
 	/**
-	 * Return a builder that is initialized with the given URI string which may
-	 * be a URI template and represent full URI or just a path.
-	 * <p>Depending on the factory implementation and configuration, the builder
-	 * may merge the given URI string with a base URI and apply other operations.
-	 * Refer to the specific factory implementation for details.
-	 * @param uriTemplate the URI template to create the builder with
+	 * Return a builder initialized with the given URI string.
+	 * <p>Concrete implementations may apply further initializations such as
+	 * combining with a pre-configured base URI.
+	 * @param uriTemplate the URI template to initialize the builder with
 	 * @return the UriBuilder
 	 */
 	UriBuilder uriString(String uriTemplate);
 
+	/**
+	 * Return a builder to prepare a new URI.
+	 * @return the UriBuilder
+	 */
+	UriBuilder builder();
+
 }

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

@@ -41,40 +41,48 @@ public class DefaultUriBuilderFactoryTests {
 
 	@Test
 	public void baseUri() throws Exception {
-		DefaultUriBuilderFactory factory = new DefaultUriBuilderFactory("http://foo.com/bar?id=123");
-		URI uri = factory.uriString("/baz").port(8080).build();
-		assertEquals("http://foo.com:8080/bar/baz?id=123", uri.toString());
+		DefaultUriBuilderFactory factory = new DefaultUriBuilderFactory("http://foo.com/v1?id=123");
+		URI uri = factory.uriString("/bar").port(8080).build();
+		assertEquals("http://foo.com:8080/v1/bar?id=123", uri.toString());
+	}
+
+	@Test
+	public void baseUriWithFullOverride() throws Exception {
+		DefaultUriBuilderFactory factory = new DefaultUriBuilderFactory("http://foo.com/v1?id=123");
+		URI uri = factory.uriString("http://example.com/1/2").build();
+		assertEquals("Use of host should case baseUri to be completely ignored",
+				"http://example.com/1/2", uri.toString());
 	}
 
 	@Test
 	public void baseUriWithPathOverride() throws Exception {
-		DefaultUriBuilderFactory factory = new DefaultUriBuilderFactory("http://foo.com/bar");
-		URI uri = factory.uriString("").replacePath("/baz").build();
+		DefaultUriBuilderFactory factory = new DefaultUriBuilderFactory("http://foo.com/v1");
+		URI uri = factory.builder().replacePath("/baz").build();
 		assertEquals("http://foo.com/baz", uri.toString());
 	}
 
 	@Test
 	public void defaultUriVars() throws Exception {
-		DefaultUriBuilderFactory factory = new DefaultUriBuilderFactory("http://{host}/bar");
+		DefaultUriBuilderFactory factory = new DefaultUriBuilderFactory("http://{host}/v1");
 		factory.setDefaultUriVariables(singletonMap("host", "foo.com"));
 		URI uri = factory.uriString("/{id}").build(singletonMap("id", "123"));
-		assertEquals("http://foo.com/bar/123", uri.toString());
+		assertEquals("http://foo.com/v1/123", uri.toString());
 	}
 
 	@Test
 	public void defaultUriVarsWithOverride() throws Exception {
-		DefaultUriBuilderFactory factory = new DefaultUriBuilderFactory("http://{host}/bar");
+		DefaultUriBuilderFactory factory = new DefaultUriBuilderFactory("http://{host}/v1");
 		factory.setDefaultUriVariables(singletonMap("host", "spring.io"));
-		URI uri = factory.uriString("/baz").build(singletonMap("host", "docs.spring.io"));
-		assertEquals("http://docs.spring.io/bar/baz", uri.toString());
+		URI uri = factory.uriString("/bar").build(singletonMap("host", "docs.spring.io"));
+		assertEquals("http://docs.spring.io/v1/bar", uri.toString());
 	}
 
 	@Test
 	public void defaultUriVarsWithEmptyVarArg() throws Exception {
-		DefaultUriBuilderFactory factory = new DefaultUriBuilderFactory("http://{host}/bar");
+		DefaultUriBuilderFactory factory = new DefaultUriBuilderFactory("http://{host}/v1");
 		factory.setDefaultUriVariables(singletonMap("host", "foo.com"));
-		URI uri = factory.uriString("/baz").build();
-		assertEquals("Expected delegation to build(Map) method", "http://foo.com/bar/baz", uri.toString());
+		URI uri = factory.uriString("/bar").build();
+		assertEquals("Expected delegation to build(Map) method", "http://foo.com/v1/bar", uri.toString());
 	}
 
 	@Test