AbstractEntityResponseBuilder.java

package net.eusashead.hateoas.response.impl;

/*
 * #[license]
 * spring-responseentitybuilder
 * %%
 * Copyright (C) 2013 Eusa's Head
 * %%
 * 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.
 * %[license]
 */

import javax.servlet.http.HttpServletRequest;

import net.eusashead.hateoas.header.ETagHeaderStrategy;
import net.eusashead.hateoas.header.impl.HashingETagHeaderStrategy;

import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;

public abstract class AbstractEntityResponseBuilder<T,V>
extends AbstractResponseBuilder<T>  {

	protected V entity;

	public AbstractEntityResponseBuilder(
			HttpServletRequest request) {
		super(request);
	}

	protected void setEntity(V entity) {
		this.entity = entity;
		assertEntity();
	}

	protected void assertEntity() {
		if (entity == null) {
			throw new IllegalArgumentException("Entity T cannot be null.");
		}
	}

	protected void setEtagHeader() {
		assertEntity();
		this.headers.setETag(new HashingETagHeaderStrategy().extract(entity).toString()); 
	}

	protected void setEtagHeader(ETagHeaderStrategy etagStrategy) {
		assertEntity();
		this.headers.setETag(etagStrategy.extract(entity).toString()); 
	}

	protected ResponseEntity<V> buildResponseEntity(V body) {
		
		// ResponseEntity to return
		ResponseEntity<V> responseEntity;

		// Check ETag against request value
		if (headers.getETag() != null && compareEtagWithIfNoneMatch(headers.getETag())) {
			// Return 304 Not Modified
			responseEntity = new ResponseEntity<V>(headers, HttpStatus.NOT_MODIFIED);
		} else {
			// Is it a HEAD or a GET
			if (request.getMethod().equals("HEAD")) {
				// Return 204 and the headers
				responseEntity = new ResponseEntity<V>(headers, HttpStatus.NO_CONTENT);
			} else if (request.getMethod().equals("GET")){
				// Return 200 and the entity
				responseEntity = new ResponseEntity<V>(body, headers, HttpStatus.OK);
			} else {
				throw new RuntimeException(String.format("esponseBuilder does not handle verb %s, only GET or HEAD.", request.getMethod()));
			}
		}

		// Return the ResponseEntity
		return responseEntity;
	}

}