ResponseEntity with builder methods

ResponseEntity.java

/*
 * Copyright 2002-2012 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 sample2;

import java.net.URI;
import java.util.Arrays;
import java.util.LinkedHashSet;
import java.util.Set;

import org.springframework.http.HttpEntity;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpMethod;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.util.MultiValueMap;
import org.springframework.util.ObjectUtils;

/**
 * Extension of {@link HttpEntity} that adds a {@link HttpStatus} status code.
 *
 * <p>Returned by {@link org.springframework.web.client.RestTemplate#getForEntity}:
 * <pre class="code">
 * ResponseEntity&lt;String&gt; entity = template.getForEntity("http://example.com", String.class);
 * String body = entity.getBody();
 * MediaType contentType = entity.getHeaders().getContentType();
 * HttpStatus statusCode = entity.getStatusCode();
 * </pre>
 * <p>Can also be used in Spring MVC, as a return value from a @Controller method:
 * <pre class="code">
 * &#64;RequestMapping("/handle")
 * public ResponseEntity&lt;String&gt; handle() {
 *   HttpHeaders responseHeaders = new HttpHeaders();
 *   responseHeaders.set("MyResponseHeader", "MyValue");
 *   return new ResponseEntity&lt;String&gt;("Hello World", responseHeaders, HttpStatus.CREATED);
 * }
 * </pre>
 *
 * @author Arjen Poutsma
 * @since 3.0.2
 * @see #getStatusCode()
 */
public class ResponseEntity<T> extends HttpEntity<T> {

	private final HttpStatus statusCode;


	/**
	 * Create a new {@code ResponseEntity} with the given status code, and no body nor headers.
	 * @param statusCode the status code
	 */
	public ResponseEntity(HttpStatus statusCode) {
		super();
		this.statusCode = statusCode;
	}

	/**
	 * Create a new {@code ResponseEntity} with the given body and status code, and no headers.
	 * @param body the entity body
	 * @param statusCode the status code
	 */
	public ResponseEntity(T body, HttpStatus statusCode) {
		super(body);
		this.statusCode = statusCode;
	}

	/**
	 * Create a new {@code HttpEntity} with the given headers and status code, and no body.
	 * @param headers the entity headers
	 * @param statusCode the status code
	 */
	public ResponseEntity(MultiValueMap<String, String> headers, HttpStatus statusCode) {
		super(headers);
		this.statusCode = statusCode;
	}

	/**
	 * Create a new {@code HttpEntity} with the given body, headers, and status code.
	 * @param body the entity body
	 * @param headers the entity headers
	 * @param statusCode the status code
	 */
	public ResponseEntity(T body, MultiValueMap<String, String> headers, HttpStatus statusCode) {
		super(body, headers);
		this.statusCode = statusCode;
	}


	/**
	 * Return the HTTP status code of the response.
	 * @return the HTTP status as an HttpStatus enum value
	 */
	public HttpStatus getStatusCode() {
		return this.statusCode;
	}

	@Override
	public boolean equals(Object other) {
		if (this == other) {
			return true;
		}
		if (!(other instanceof ResponseEntity)) {
			return false;
		}
		ResponseEntity<?> otherEntity = (ResponseEntity<?>) other;
		return (ObjectUtils.nullSafeEquals(this.statusCode, otherEntity.statusCode) && super.equals(other));
	}

	@Override
	public int hashCode() {
		return super.hashCode() * 29 + ObjectUtils.nullSafeHashCode(this.statusCode);
	}

	@Override
	public String toString() {
		StringBuilder builder = new StringBuilder("<");
		builder.append(this.statusCode.toString());
		builder.append(' ');
		builder.append(this.statusCode.getReasonPhrase());
		builder.append(',');
		T body = getBody();
		HttpHeaders headers = getHeaders();
		if (body != null) {
			builder.append(body);
			if (headers != null) {
				builder.append(',');
			}
		}
		if (headers != null) {
			builder.append(headers);
		}
		builder.append('>');
		return builder.toString();
	}


	public static <T> Builder<T> ok() {
		return new Builder<T>(null, null, HttpStatus.OK);
	}

	public static <T> Builder<T> ok(T body) {
		return new Builder<T>(body, null, HttpStatus.OK);
	}

	public static <T> Builder<T> created(URI location) {
		return new Builder<T>(null, null, HttpStatus.CREATED).location(location);
	}

	public static <T> Builder<T> created(URI location, T body) {
		return new Builder<T>(body, null, HttpStatus.CREATED).location(location);
	}

	public static <T> Builder<T> accepted() {
		return new Builder<T>(null, null, HttpStatus.ACCEPTED);
	}

	public static <T> Builder<T> accepted(T body) {
		return new Builder<T>(body, null, HttpStatus.ACCEPTED);
	}

	public static <T> HeadersBuilder<T> noContent() {
		return new HeadersBuilder<T>(null, null, HttpStatus.NO_CONTENT);
	}

	public static <T> Builder<T> status(HttpStatus status) {
		return new Builder<T>(null, null, status);
	}

	public static <T> Builder<T> status(HttpStatus status, T body) {
		return new Builder<T>(body, null, status);
	}


	/**
	 * Abstract base class for {@link Builder} and {@link HeadersBuilder}.
	 */
	public static abstract class AbstractBuilder<T, B extends AbstractBuilder<T, B>> extends ResponseEntity<T> {

		public AbstractBuilder(T body, MultiValueMap<String, String> headers, HttpStatus statusCode) {
			super(body, (headers == null ? new HttpHeaders() : headers), statusCode);
		}

		/**
		 * Add the given, single header value under the given name.
		 * @param headerName the header name
		 * @param headerValues the header value(s)
		 * @return a new builder
		 * @see HttpHeaders#add(String, String)
		 */
		public B header(String headerName, String... headerValues) {
			HttpHeaders newHeaders = newHeaders();
			for (String headerValue : headerValues) {
				newHeaders.add(headerName, headerValue);
			}
			return newBuilder(newHeaders);
		}

		/**
		 * Set the set of allowed {@link HttpMethod HTTP methods}, as specified by the
		 * {@code Allow} header.
		 * @param allowedMethods the allowed methods
		 * @return a new builder
		 * @see HttpHeaders#setAllow(Set)
		 */
		public B allow(HttpMethod... allowedMethods) {
			HttpHeaders newHeaders = newHeaders();
			newHeaders.setAllow(new LinkedHashSet<HttpMethod>(Arrays.asList(allowedMethods)));
			return newBuilder(newHeaders);
		}

		/**
		 * Sets the entity tag of the body, as specified by the {@code ETag} header.
		 * @param eTag the new entity tag
		 * @return a new builder
		 * @see HttpHeaders#setETag(String)
		 */
		public B eTag(String eTag) {
			HttpHeaders newHeaders = newHeaders();
			newHeaders.setETag(eTag);
			return newBuilder(newHeaders);
		}

		/**
		 * 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
		 * @return a new builder
		 * @see HttpHeaders#setLastModified(long)
		 */
		public B lastModified(long lastModified) {
			HttpHeaders newHeaders = newHeaders();
			newHeaders.setLastModified(lastModified);
			return newBuilder(newHeaders);
		}

		/**
		 * Set the location of a resource, as specified by the {@code Location} header.
		 * @param location the location
		 * @return a new builder
		 * @see HttpHeaders#setLocation(URI)
		 */
		public B location(URI location) {
			HttpHeaders newHeaders = newHeaders();
			newHeaders.setLocation(location);
			return newBuilder(newHeaders);
		}

		protected final HttpHeaders newHeaders() {
			HttpHeaders headers = new HttpHeaders();
			headers.putAll(getHeaders());
			return headers;
		}

		protected abstract B newBuilder(HttpHeaders newHeaders);

	}


	/**
	 * Builder that can be used to create {@link ResponseEntity} instances that do not
	 * contain a body.
	 */
	public static class HeadersBuilder<T> extends AbstractBuilder<T, HeadersBuilder<T>> {

		public HeadersBuilder(T body, MultiValueMap<String, String> headers, HttpStatus statusCode) {
			super(body, headers, statusCode);
		}

		@Override
		protected HeadersBuilder<T> newBuilder(HttpHeaders newHeaders) {
			return new HeadersBuilder<T>(getBody(), newHeaders, getStatusCode());
		}

	}

	/**
	 * Builder that can be used to create {@link ResponseEntity} instances that do
	 * contain a body.
	 */
	public static class Builder<T> extends AbstractBuilder<T, Builder<T>> {

		public Builder(T body, MultiValueMap<String, String> headers, HttpStatus statusCode) {
			super(body, headers, statusCode);
		}

		@Override
		protected Builder<T> newBuilder(HttpHeaders newHeaders) {
			return new Builder<T>(getBody(), newHeaders, getStatusCode());
		}

		/**
		 * Set the length of the body in bytes, as specified by the {@code Content-Length}
		 * header.
		 * @param contentLength the content length
		 * @return a new builder
		 * @see HttpHeaders#setContentLength(long)
		 */
		public Builder<T> contentLength(long contentLength) {
			HttpHeaders newHeaders = newHeaders();
			newHeaders.setContentLength(contentLength);
			return newBuilder(newHeaders);
		}

		/**
		 * Set the {@linkplain MediaType media type} of the body, as specified by the
		 * {@code Content-Type} header.
		 * @param mediaType the content media type
		 * @return a new builder
		 * @see HttpHeaders#setContentType(MediaType)
		 */
		public Builder<T> contentType(MediaType mediaType) {
			HttpHeaders newHeaders = newHeaders();
			newHeaders.setContentType(mediaType);
			return newBuilder(newHeaders);
		}

	}

}

ResponseEntityUsage.java

package sample2;

import org.springframework.http.MediaType;


public class ResponseEntityUsage {

	public ResponseEntity<Void> a() {
		return ResponseEntity.ok();
	}

	public ResponseEntity<?> a2() {
		return ResponseEntity.ok();
	}

	public ResponseEntity<String> b() {
		return ResponseEntity.ok("test");
	}

	public ResponseEntity<String> c() {
		String body = "";
		return ResponseEntity.ok(body).contentType(MediaType.APPLICATION_JSON);
	}

}