Add RequestPostProcessor

Fixes gh-81

spring-web-reactive/src/main/java/org/springframework/web/client/reactive/DefaultHttpRequestBuilder.java

@@ -38,6 +38,7 @@ import org.springframework.http.HttpMethod;
 import org.springframework.http.MediaType;
 import org.springframework.http.client.reactive.ClientHttpRequest;
 import org.springframework.http.client.reactive.ClientHttpRequestFactory;
+import org.springframework.util.Assert;
 import org.springframework.web.client.RestClientException;
 
 /**
@@ -137,6 +138,21 @@ public class DefaultHttpRequestBuilder implements HttpRequestBuilder {
 		return this;
 	}
 
+	/**
+	 * Allows performing more complex operations with a strategy. For example, a
+	 * {@link RequestPostProcessor} implementation might accept the arguments of
+	 * username and password and set an HTTP Basic authentication header.
+	 *
+	 * @param postProcessor the {@link RequestPostProcessor} to use. Cannot be null.
+	 *
+	 * @return this instance for further modifications.
+	 */
+	public DefaultHttpRequestBuilder apply(RequestPostProcessor postProcessor) {
+		Assert.notNull(postProcessor, "`postProcessor` is required");
+		postProcessor.postProcess(this);
+		return this;
+	}
+
 	public ClientHttpRequest build(ClientHttpRequestFactory factory) {
 		ClientHttpRequest request = factory.createRequest(this.httpMethod, this.url, this.httpHeaders);
 		request.getHeaders().putAll(this.httpHeaders);

spring-web-reactive/src/main/java/org/springframework/web/client/reactive/RequestPostProcessor.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright 2002-2016 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.web.client.reactive;
+
+/**
+ * Allows post processing the {@link DefaultHttpRequestBuilder} for strategy for
+ * performing more complex operations.
+ *
+ * @author Rob Winch
+ * @see DefaultHttpRequestBuilder#apply(RequestPostProcessor)
+ */
+public interface RequestPostProcessor {
+
+	/**
+	 * Implementations can modify the {@link DefaultHttpRequestBuilder} passed
+	 * in.
+	 *
+	 * @param toPostProcess
+	 *            the {@link DefaultHttpRequestBuilder} to be modified.
+	 */
+	void postProcess(DefaultHttpRequestBuilder toPostProcess);
+}

spring-web-reactive/src/test/java/org/springframework/web/client/reactive/DefaultHttpRequestBuilderTests.java

@@ -0,0 +1,52 @@
+/*
+ * Copyright 2002-2016 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.web.client.reactive;
+
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.springframework.http.HttpMethod;
+
+/**
+ *
+ * @author Rob Winch
+ *
+ */
+public class DefaultHttpRequestBuilderTests {
+	private DefaultHttpRequestBuilder builder;
+
+	@Before
+	public void setup() {
+		builder = new DefaultHttpRequestBuilder(HttpMethod.GET, "https://example.com/foo");
+	}
+
+	@Test
+	public void apply() {
+		RequestPostProcessor postProcessor = mock(RequestPostProcessor.class);
+
+		builder.apply(postProcessor);
+
+		verify(postProcessor).postProcess(builder);
+	}
+
+	@Test(expected = IllegalArgumentException.class)
+	public void applyNullPostProcessorThrowsIllegalArgumentException() {
+		builder.apply(null);
+	}
+}