Provide builder for ResponseEntity

This commit introduces a ResponseEntityBuilder, which allows for
building of a ResponseEntity through a fluent API.

Issue: SPR-11752

spring-web/src/main/java/org/springframework/http/ResponseEntityBuilder.java

@@ -0,0 +1,286 @@
+/*
+ * Copyright 2002-2014 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.http;
+
+import java.net.URI;
+import java.util.Set;
+
+/**
+ * A builder for {@link ResponseEntity} objects. Enforces common HTTP response practices
+ * through a fluent API.
+ *
+ * <p>This class is typically used in @Controller methods through a static import.
+ * For instance:
+ * <pre class="code">
+ * import static org.springframework.http.ResponseEntityBuilder.*;
+ *
+ * &#064;Controller
+ * public class MyController {
+ *
+ *     &#064;RequestMapping(value="/entity", method=RequestMethod.GET)
+ *     public ResponseEntity&lt;MyEntity&gt; myBean() {
+ *         MyEntity entity = ...
+ *         long lastModifiedDate = ...
+ *         ResponseEntity&lt;MyEntity&gt; responseEntity = status(HttpStatus.OK)
+ *             .header("Last-Modified", lastModifiedDate).body(entity);
+ *         return responseEntity;
+ *     }
+ * }</pre>
+ *
+ * Or, using some of the convenience methods:
+ *
+ * <pre class="code">
+ * ok().lastModified(lastModifiedDate).body(entity);
+ * </pre>
+ *
+ * @author Arjen Poutsma
+ * @since 4.1
+ * @see ResponseEntity
+ */
+public class ResponseEntityBuilder {
+
+	private ResponseEntityBuilder() {
+	}
+
+	/**
+	 * Creates a new {@code ResponseEntityBuilder} with the given status.
+	 * @param status the response status
+	 * @return the new response entity builder
+	 */
+	public static ResponseBodyBuilder status(HttpStatus status) {
+		return new DefaultResponseBuilder(status);
+	}
+
+	/**
+	 * Creates a new {@code ResponseEntityBuilder} with the given status.
+	 * @param status the response status
+	 * @return the new response entity builder
+	 */
+	public static ResponseBodyBuilder status(int status) {
+		return status(HttpStatus.valueOf(status));
+	}
+
+	/**
+	 * Creates a new {@code ResponseEntityBuilder} with the status set to
+	 * {@linkplain HttpStatus#OK OK}.
+	 * @return the new response entity builder
+	 */
+	public static ResponseBodyBuilder ok() {
+		return status(HttpStatus.OK);
+	}
+
+	/**
+	 * Creates a new {@code ResponseEntity} with the given body and the status set to
+	 * {@linkplain HttpStatus#OK OK}.
+	 * @return the new response entity
+	 */
+	public static ResponseHeadersBuilder ok(Object body) {
+		ResponseBodyBuilder builder = ok();
+		builder.body(body);
+		return builder;
+	}
+
+	/**
+	 * Creates a new {@code ResponseEntityBuilder} with a
+	 * {@linkplain HttpStatus#CREATED CREATED} status and a location header set to the
+	 * given URI.
+	 * @param location the location URI
+	 * @return the new response entity builder
+	 */
+	public static ResponseBodyBuilder created(URI location) {
+		ResponseBodyBuilder builder = status(HttpStatus.CREATED);
+		return builder.location(location);
+	}
+
+	/**
+	 * Creates a new {@code ResponseEntityBuilder} with an
+	 * {@link HttpStatus#ACCEPTED ACCEPTED} status.
+	 * @return the new response entity builder
+	 */
+	public static ResponseBodyBuilder accepted() {
+		return status(HttpStatus.ACCEPTED);
+	}
+
+	/**
+	 * Creates a new {@code ResponseEntityBuilder} with an
+	 * {@link HttpStatus#NO_CONTENT NO_CONTENT} status.
+	 * @return the new response entity builder
+	 */
+	public static ResponseHeadersBuilder noContent() {
+		return status(HttpStatus.NO_CONTENT);
+	}
+
+
+	/**
+	 * Defines a builder that adds headers to the response entity.
+	 * @param <B> the builder subclass
+	 */
+	public interface ResponseHeadersBuilder<B extends ResponseHeadersBuilder<B>> {
+
+		/**
+		 * Add the given, single header value under the given name.
+		 * @param headerName  the header name
+		 * @param headerValue the header value(s)
+		 * @return this builder
+		 * @see HttpHeaders#add(String, String)
+		 */
+		B header(String headerName, String... headerValues);
+
+		/**
+		 * Set the set of allowed {@link HttpMethod HTTP methods}, as specified by the
+		 * {@code Allow} header.
+		 * @param allowedMethods the allowed methods
+		 * @see HttpHeaders#setAllow(Set)
+		 */
+		B allow(Set<HttpMethod> allowedMethods);
+
+		/**
+		 * Sets the entity tag of the body, as specified by the {@code ETag} header.
+		 * @param eTag the new entity tag
+		 * @see HttpHeaders#setETag(String)
+		 */
+		B eTag(String eTag);
+
+		/**
+		 * Sets the time the resource was last changed, as specified by the
+		 * {@code Last-Modified} header.
+		 * <p>The date should be specified as the number of milliseconds since January 1, 1970 GMT.
+		 * @param lastModified the last modified date
+		 * @see HttpHeaders#setLastModified(long)
+		 */
+		B lastModified(long lastModified);
+
+		/**
+		 * Set the location of a resource, as specified by the {@code Location} header.
+		 * @param location the location
+		 * @see HttpHeaders#setLocation(URI)
+		 */
+		B location(URI location);
+
+		/**
+		 * Builds the response entity.
+		 * @return the response entity
+		 * @see ResponseBodyBuilder#body(Object)
+		 */
+		ResponseEntity<?> build();
+
+	}
+
+
+	/**
+	 * Defines a builder that adds a body to the response entity.
+	 */
+	public interface ResponseBodyBuilder extends ResponseHeadersBuilder<ResponseBodyBuilder> {
+
+		/**
+		 * Set the length of the body in bytes, as specified by the {@code Content-Length}
+		 * header.
+		 * @param contentLength the content length
+		 * @see HttpHeaders#setContentLength(long)
+		 */
+		ResponseBodyBuilder contentLength(long contentLength);
+
+		/**
+		 * Set the {@linkplain MediaType media type} of the body, as specified by the
+		 * {@code Content-Type} header.
+		 * @param contentType the content type
+		 * @see HttpHeaders#setContentType(MediaType)
+		 */
+		ResponseBodyBuilder contentType(MediaType contentType);
+
+		/**
+		 * Sets the body of the response entity and returns it.
+		 * @param body the body of the response entity
+		 * @param <T> the type of the body
+		 * @return the built response entity
+		 */
+		<T> ResponseEntity<T> body(T body);
+
+	}
+
+	private static class DefaultResponseBuilder implements ResponseBodyBuilder {
+
+		private final HttpStatus status;
+
+		private final HttpHeaders headers = new HttpHeaders();
+
+		private Object body = null;
+
+		public DefaultResponseBuilder(HttpStatus status) {
+			this.status = status;
+		}
+
+		@Override
+		public ResponseBodyBuilder header(String headerName, String... headerValues) {
+			for (String headerValue : headerValues) {
+				headers.add(headerName, headerValue);
+			}
+			return this;
+		}
+
+		@Override
+		public ResponseBodyBuilder allow(Set<HttpMethod> allowedMethods) {
+			headers.setAllow(allowedMethods);
+			return this;
+		}
+
+		@Override
+		public ResponseBodyBuilder contentLength(long contentLength) {
+			headers.setContentLength(contentLength);
+			return this;
+		}
+
+		@Override
+		public ResponseBodyBuilder contentType(MediaType contentType) {
+			headers.setContentType(contentType);
+			return this;
+		}
+
+		@Override
+		public ResponseBodyBuilder eTag(String eTag) {
+			headers.setETag(eTag);
+			return this;
+		}
+
+		@Override
+		public ResponseBodyBuilder lastModified(long date) {
+			headers.setLastModified(date);
+			return this;
+		}
+
+		@Override
+		public ResponseBodyBuilder location(URI location) {
+			headers.setLocation(location);
+			return this;
+		}
+
+
+		@Override
+		@SuppressWarnings("unchecked")
+		public ResponseEntity<?> build() {
+			return new ResponseEntity(body, headers, status);
+		}
+
+		@Override
+		public <T> ResponseEntity<T> body(T body) {
+			this.body = body;
+			return new ResponseEntity<T>(body, headers, status);
+		}
+
+	}
+
+}

spring-web/src/test/java/org/springframework/http/ResponseEntityBuilderTests.java

@@ -0,0 +1,133 @@
+/*
+ * Copyright 2002-2014 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.http;
+
+import java.net.URI;
+import java.net.URISyntaxException;
+import java.util.Collections;
+import java.util.List;
+
+import static org.junit.Assert.*;
+import org.junit.Test;
+import static org.springframework.http.ResponseEntityBuilder.*;
+
+public class ResponseEntityBuilderTests {
+
+	@Test
+	public void normal() {
+		String headerName = "My-Custom-Header";
+		String headerValue1 = "HeaderValue1";
+		String headerValue2 = "HeaderValue2";
+		Object entity = new Object();
+
+		ResponseEntity<Object> responseEntity =
+				status(HttpStatus.OK).header(headerName, headerValue1, headerValue2).body(entity);
+
+		assertNotNull(responseEntity);
+		assertEquals(HttpStatus.OK, responseEntity.getStatusCode());
+		assertTrue(responseEntity.getHeaders().containsKey(headerName));
+		List<String> list = responseEntity.getHeaders().get(headerName);
+		assertEquals(2, list.size());
+		assertEquals(headerValue1, list.get(0));
+		assertEquals(headerValue2, list.get(1));
+		assertEquals(entity, responseEntity.getBody());
+	}
+
+	@Test
+	public void okNoBody() {
+		ResponseEntity<?> responseEntity = ok().build();
+
+		assertNotNull(responseEntity);
+		assertEquals(HttpStatus.OK, responseEntity.getStatusCode());
+		assertNull(responseEntity.getBody());
+	}
+
+	@Test
+	public void okEntity() {
+		Object entity = new Object();
+		ResponseEntity<Object> responseEntity = ok(entity).build();
+
+		assertNotNull(responseEntity);
+		assertEquals(HttpStatus.OK, responseEntity.getStatusCode());
+		assertEquals(entity, responseEntity.getBody());
+	}
+
+	@Test
+	public void createdLocation() throws URISyntaxException {
+		URI location = new URI("location");
+		ResponseEntity<?> responseEntity = created(location).build();
+
+		assertNotNull(responseEntity);
+		assertEquals(HttpStatus.CREATED, responseEntity.getStatusCode());
+		assertTrue(responseEntity.getHeaders().containsKey("Location"));
+		assertEquals(location.toString(),
+				responseEntity.getHeaders().getFirst("Location"));
+		assertNull(responseEntity.getBody());
+	}
+
+	@Test
+	public void acceptedNoBody() throws URISyntaxException {
+		ResponseEntity<?> responseEntity = accepted().build();
+
+		assertNotNull(responseEntity);
+		assertEquals(HttpStatus.ACCEPTED, responseEntity.getStatusCode());
+		assertNull(responseEntity.getBody());
+	}
+
+	@Test
+	public void noContent() throws URISyntaxException {
+		ResponseEntity<?> responseEntity = ResponseEntityBuilder.noContent().build();
+
+		assertNotNull(responseEntity);
+		assertEquals(HttpStatus.NO_CONTENT, responseEntity.getStatusCode());
+		assertNull(responseEntity.getBody());
+	}
+
+	@Test
+	public void headers() throws URISyntaxException {
+		String eTag = "\"foo\"";
+		URI location = new URI("location");
+		long contentLength = 67890;
+		MediaType contentType = MediaType.TEXT_PLAIN;
+
+		ResponseEntity<?> responseEntity = ResponseEntityBuilder.ok().
+				allow(Collections.singleton(HttpMethod.GET)).
+				eTag(eTag).
+				lastModified(12345L).
+				location(location).
+				contentLength(contentLength).
+				contentType(contentType).
+				build();
+
+		assertNotNull(responseEntity);
+		assertEquals(HttpStatus.OK, responseEntity.getStatusCode());
+		HttpHeaders responseHeaders = responseEntity.getHeaders();
+
+		assertEquals("GET", responseHeaders.getFirst("Allow"));
+		assertEquals(eTag, responseHeaders.getFirst("ETag"));
+		assertEquals("Thu, 01 Jan 1970 00:00:12 GMT",
+				responseHeaders.getFirst("Last-Modified"));
+		assertEquals(location.toASCIIString(),
+				responseHeaders.getFirst("Location"));
+		assertEquals(String.valueOf(contentLength), responseHeaders.getFirst("Content-Length"));
+		assertEquals(contentType.toString(), responseHeaders.getFirst("Content-Type"));
+
+		assertNull(responseEntity.getBody());
+	}
+
+
+}