Polish contribution

Closes gh-13208

spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/web/client/LocalHostUriTemplateHandler.java

@@ -70,11 +70,11 @@ public class LocalHostUriTemplateHandler extends RootUriTemplateHandler {
 	 * @param handler the delegate handler
 	 * @since 2.0.3
 	 */
-	public LocalHostUriTemplateHandler(Environment environment, String scheme, UriTemplateHandler handler) {
+	public LocalHostUriTemplateHandler(Environment environment, String scheme,
+			UriTemplateHandler handler) {
 		super(handler);
 		Assert.notNull(environment, "Environment must not be null");
 		Assert.notNull(scheme, "Scheme must not be null");
-		Assert.notNull(handler, "Handler must not be null");
 		this.environment = environment;
 		this.scheme = scheme;
 	}

spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/web/client/LocalHostUriTemplateHandlerTests.java

 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,13 +16,21 @@
 
 package org.springframework.boot.test.web.client;
 
+import java.net.URI;
+import java.util.HashMap;
+import java.util.Map;
+
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.ExpectedException;
 
 import org.springframework.mock.env.MockEnvironment;
+import org.springframework.web.util.UriTemplateHandler;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.BDDMockito.given;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
 
 /**
  * Tests for {@link LocalHostUriTemplateHandler}.
@@ -91,4 +99,18 @@ public class LocalHostUriTemplateHandlerTests {
 		assertThat(handler.getRootUri()).isEqualTo("http://localhost:8080/foo");
 	}
 
+	@Test
+	public void expandShouldUseCustomHandler() {
+		MockEnvironment environment = new MockEnvironment();
+		UriTemplateHandler uriTemplateHandler = mock(UriTemplateHandler.class);
+		Map<String, ?> uriVariables = new HashMap<>();
+		URI uri = URI.create("http://www.example.com");
+		given(uriTemplateHandler.expand("https://localhost:8080/", uriVariables))
+				.willReturn(uri);
+		LocalHostUriTemplateHandler handler = new LocalHostUriTemplateHandler(
+				environment, "https", uriTemplateHandler);
+		assertThat(handler.expand("/", uriVariables)).isEqualTo(uri);
+		verify(uriTemplateHandler).expand("https://localhost:8080/", uriVariables);
+	}
+
 }

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/client/RootUriTemplateHandler.java

 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -38,6 +38,7 @@ public class RootUriTemplateHandler implements UriTemplateHandler {
 	private final UriTemplateHandler handler;
 
 	protected RootUriTemplateHandler(UriTemplateHandler handler) {
+		Assert.notNull(handler, "Handler must not be null");
 		this.rootUri = null;
 		this.handler = handler;
 	}