/*
* Copyright (C) 2012 Red Hat, Inc. and/or its affiliates.
*
* 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 java.util.concurrent.TimeUnit;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletConfig;
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.api.QueueSession;
import org.jboss.errai.bus.server.QueueUnavailableException;
import org.jboss.errai.bus.server.api.MessageQueue;
import org.jboss.errai.bus.server.io.OutputStreamWriteAdapter;
/**
* The default DefaultBlockingServlet which provides the HTTP-protocol gateway
* between the server bus and the client buses.
* <p/>
* <h2>Configuration</h2>
* <p/>
* The DefaultBlockingServlet, as its name suggests, is normally configured as
* an HTTP Servlet in the <code>web.xml</code> file:
* <p/>
* <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>
* <p/>
* 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:
* <p/>
* <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 {
private static final long serialVersionUID = 1L;
@Override
public void init(ServletConfig config) throws ServletException {
super.init(config);
}
@Override
public void initAsFilter(FilterConfig config) throws ServletException {
super.initAsFilter(config);
}
/**
* 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(final HttpServletRequest httpServletRequest, final HttpServletResponse httpServletResponse)
throws ServletException {
pollForMessages(sessionProvider.createOrGetSession(httpServletRequest.getSession(true),
getClientId(httpServletRequest)),
httpServletRequest, httpServletResponse, isLongPollingEnabled(), isSSERequest(httpServletRequest));
}
/**
* 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(final HttpServletRequest httpServletRequest, final HttpServletResponse httpServletResponse) throws ServletException {
final QueueSession session = sessionProvider.createOrGetSession(httpServletRequest.getSession(true),
getClientId(httpServletRequest));
if (failFromMissingCSRFToken(httpServletRequest)) {
prepareTokenChallenge(httpServletRequest, httpServletResponse);
return;
}
try {
service.store(createCommandMessage(session, httpServletRequest));
}
catch (IOException ioe) {
log.debug("Problem when storing message", ioe);
}
catch (QueueUnavailableException e) {
try {
sendDisconnectDueToSessionExpiry(httpServletResponse);
}
catch (IOException ioe) {
log.debug("Failed to inform client that session expired", ioe);
}
return;
}
pollForMessages(session, httpServletRequest, httpServletResponse, shouldWait(httpServletRequest), false);
}
private void pollForMessages(final QueueSession session, final HttpServletRequest httpServletRequest,
final HttpServletResponse httpServletResponse, boolean wait, final boolean sse) {
try {
if (sse) {
prepareSSE(httpServletResponse);
}
else {
prepareCometPoll(httpServletResponse);
}
final MessageQueue queue = service.getBus().getQueue(session);
if (queue == null) {
switch (getConnectionPhase(httpServletRequest)) {
case CONNECTING:
case DISCONNECTING:
return;
case NORMAL:
case UNKNOWN:
break;
}
sendDisconnectDueToSessionExpiry(httpServletResponse);
return;
}
queue.heartBeat();
final ServletOutputStream outputStream = httpServletResponse.getOutputStream();
if (sse) {
while (!queue.isStale()) {
try {
prepareSSEContinue(httpServletResponse);
queue.poll(TimeUnit.MILLISECONDS, getSSETimeout(), new OutputStreamWriteAdapter(outputStream));
outputStream.write(SSE_TERMINATION_BYTES);
outputStream.flush();
queue.heartBeat();
}
catch (IOException e) {
log.debug("SSE problem when polling for new messages", e);
outputStream.close();
return;
}
}
}
else if (wait) {
queue.poll(TimeUnit.MILLISECONDS, getLongPollTimeout(), new OutputStreamWriteAdapter(outputStream));
}
else {
queue.poll(new OutputStreamWriteAdapter(outputStream));
}
}
catch (final IOException io) {
log.debug("Problem when polling for new messages", io);
}
catch (final Throwable t) {
try {
writeExceptionToOutputStream(httpServletResponse, t);
}
catch (IOException e) {
log.debug("Couldn't write exception to output stream", e);
}
}
}
@Override
public void init(final FilterConfig filterConfig) throws ServletException {
super.initAsFilter(filterConfig);
}
/**
* 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(final ServletRequest request, final ServletResponse response, final FilterChain chain)
throws IOException, ServletException {
service(request, response);
}
}