DeviceResolverHandlerInterceptor.java

/*
 * Copyright 2010-2014 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.mobile.device;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;

/**
 * A Spring MVC interceptor that resolves the Device that originated the web request <i>before</i> any request handler is invoked.
 * The resolved Device is exported as a request attribute under the well-known name of {@link DeviceUtils#CURRENT_DEVICE_ATTRIBUTE}.
 * Request handlers such as @Controllers and views may then access the currentDevice to vary their control and rendering logic, respectively.
 * @author Keith Donald
 */
public class DeviceResolverHandlerInterceptor extends HandlerInterceptorAdapter {

	private final DeviceResolver deviceResolver;

	/**
	 * Create a device resolving {@link HandlerInterceptor} that defaults to a {@link LiteDeviceResolver} implementation.
	 */
	public DeviceResolverHandlerInterceptor() {
		this(new LiteDeviceResolver());
	}
	
	/**
	 * Create a device resolving {@link HandlerInterceptor}.
	 * @param deviceResolver the device resolver to delegate to in {@link #preHandle(HttpServletRequest, HttpServletResponse, Object)}.
	 */
	public DeviceResolverHandlerInterceptor(DeviceResolver deviceResolver) {
		this.deviceResolver = deviceResolver;
	}

	public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
		Device device = deviceResolver.resolveDevice(request);
		request.setAttribute(DeviceUtils.CURRENT_DEVICE_ATTRIBUTE, device);
		return true;
	}

}