/*
* Copyright 2011 JBoss, by Red Hat, Inc
*
* 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.jboss.errai.bus.server.servlet;
import static org.jboss.errai.bus.server.io.MessageFactory.createCommandMessage;
import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.jboss.errai.bus.client.framework.ClientMessageBus;
import org.jboss.errai.bus.server.api.MessageQueue;
import org.jboss.errai.bus.server.api.QueueSession;
import org.jboss.errai.bus.server.service.ErraiServiceConfigurator;
/**
* The default DefaultBlockingServlet which provides the HTTP-protocol gateway
* between the server bus and the client buses.
*
* <h2>Configuration</h2>
*
* The DefaultBlockingServlet, as its name suggests, is normally configured as
* an HTTP Servlet in the <code>web.xml</code> file:
*
* <pre>
* {@code <servlet>}
* {@code <servlet-name>ErraiServlet</servlet-name>}
* {@code <servlet-class>org.jboss.errai.bus.server.servlet.DefaultBlockingServlet</servlet-class>}
* {@code <load-on-startup>1</load-on-startup>}
* {@code </servlet>}
*
* {@code <servlet-mapping>}
* {@code <servlet-name>ErraiServlet</servlet-name>}
* {@code <url-pattern>*.erraiBus</url-pattern>}
* {@code </servlet-mapping>}
* </pre>
*
* Alternatively, the DefaultBlockingServlet can be deployed as a Servlet
* Filter. This may be necessary in cases where an existing filter is configured
* in the web application, and that filter interferes with the Errai Bus
* requests. In this case, configuring DefaultBlockingServlet to handle
* {@code *.erraiBus} requests ahead of other filters in web.xml will solve the
* problem:
*
* <pre>
* {@code <filter>}
* {@code <filter-name>ErraiServlet</filter-name>}
* {@code <filter-class>org.jboss.errai.bus.server.servlet.DefaultBlockingServlet</filter-class>}
* {@code </filter>}
*
* {@code <filter-mapping>}
* {@code <filter-name>ErraiServlet</filter-name>}
* {@code <url-pattern>*.erraiBus</url-pattern>}
* {@code </filter-mapping>}
*
* {@code <!-- other filter-mapping and servlet-mapping elements go here -->}
* </pre>
*/
public class DefaultBlockingServlet extends AbstractErraiServlet implements Filter {
/**
* Called by the server (via the <tt>service</tt> method) to allow a servlet to handle a GET request by supplying
* a response
*
* @param httpServletRequest - object that contains the request the client has made of the servlet
* @param httpServletResponse - object that contains the response the servlet sends to the client
* @throws IOException - if an input or output error is detected when the servlet handles the GET request
* @throws ServletException - if the request for the GET could not be handled
*/
@Override
protected void doGet(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse)
throws ServletException, IOException {
pollForMessages(sessionProvider.getSession(httpServletRequest.getSession(),
httpServletRequest.getHeader(ClientMessageBus.REMOTE_QUEUE_ID_HEADER)),
httpServletRequest, httpServletResponse, ErraiServiceConfigurator.LONG_POLLING);
}
/**
* Called by the server (via the <code>service</code> method) to allow a servlet to handle a POST request, by
* sending the request
*
* @param httpServletRequest - object that contains the request the client has made of the servlet
* @param httpServletResponse - object that contains the response the servlet sends to the client
* @throws IOException - if an input or output error is detected when the servlet handles the request
* @throws ServletException - if the request for the POST could not be handled
*/
@Override
protected void doPost(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse)
throws ServletException, IOException {
final QueueSession session = sessionProvider.getSession(httpServletRequest.getSession(),
httpServletRequest.getHeader(ClientMessageBus.REMOTE_QUEUE_ID_HEADER));
service.store(createCommandMessage(session, httpServletRequest));
pollForMessages(session, httpServletRequest, httpServletResponse, false);
}
private void pollForMessages(QueueSession session, HttpServletRequest httpServletRequest,
HttpServletResponse httpServletResponse, boolean wait) throws IOException {
try {
// note about caching: clients now include a uniquifier in a request parameter called "z"
// so no-cache headers are now unnecessary.
httpServletResponse.setContentType("application/json");
final MessageQueue queue = service.getBus().getQueue(session);
ServletOutputStream outputStream = httpServletResponse.getOutputStream();
if (queue == null) {
switch (getConnectionPhase(httpServletRequest)) {
case CONNECTING:
case DISCONNECTING:
return;
}
sendDisconnectDueToSessionExpiry(outputStream);
return;
}
queue.heartBeat();
queue.poll(wait, outputStream);
outputStream.close();
}
catch (final Throwable t) {
t.printStackTrace();
writeExceptionToOutputStream(httpServletResponse, t);
}
}
@Override
public void init(FilterConfig filterConfig) throws ServletException {
init(filterConfig.getServletContext(), filterConfig.getInitParameter("service-locator"));
}
/**
* Services this request in the same way as it would be serviced if configured
* as a Servlet. Does not invoke any filters further down the chain. See the
* class-level comment for the reason why this servlet might be configured as a
* filter.
*/
@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
throws IOException, ServletException {
service(request, response);
}
}