/**
* Copyright 2009 Google 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.waveprotocol.box.server.rpc;
import com.google.common.base.Preconditions;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
import com.google.common.collect.Sets;
import com.google.inject.Inject;
import com.google.inject.Injector;
import com.google.inject.Singleton;
import com.google.inject.name.Named;
import com.google.inject.servlet.GuiceFilter;
import com.google.inject.servlet.GuiceServletContextListener;
import com.google.inject.servlet.ServletModule;
import com.google.protobuf.Descriptors;
import com.google.protobuf.Descriptors.MethodDescriptor;
import com.google.protobuf.Message;
import com.google.protobuf.RpcCallback;
import com.google.protobuf.Service;
import com.google.protobuf.UnknownFieldSet;
import com.glines.socketio.server.SocketIOInbound;
import com.glines.socketio.server.Transport;
import com.glines.socketio.server.transport.FlashSocketTransport;
import com.glines.socketio.server.transport.HTMLFileTransport;
import com.glines.socketio.server.transport.JSONPPollingTransport;
import com.glines.socketio.server.transport.XHRMultipartTransport;
import com.glines.socketio.server.transport.XHRPollingTransport;
import com.glines.socketio.server.transport.jetty.JettyWebSocketTransport;
import org.eclipse.jetty.http.ssl.SslContextFactory;
import org.eclipse.jetty.server.ssl.SslSelectChannelConnector;
import org.eclipse.jetty.server.Connector;
import org.eclipse.jetty.server.Server;
import org.eclipse.jetty.server.nio.SelectChannelConnector;
import org.eclipse.jetty.server.session.HashSessionManager;
import org.eclipse.jetty.servlet.DefaultServlet;
import org.eclipse.jetty.servlet.ServletHolder;
import org.eclipse.jetty.servlets.GzipFilter;
import org.eclipse.jetty.util.resource.ResourceCollection;
import org.eclipse.jetty.webapp.WebAppContext;
import org.eclipse.jetty.websocket.WebSocket;
import org.eclipse.jetty.websocket.WebSocketServlet;
import org.waveprotocol.box.common.comms.WaveClientRpc.ProtocolAuthenticate;
import org.waveprotocol.box.common.comms.WaveClientRpc.ProtocolAuthenticationResult;
import org.waveprotocol.box.server.CoreSettings;
import org.waveprotocol.box.server.authentication.SessionManager;
import org.waveprotocol.box.server.persistence.file.FileUtils;
import org.waveprotocol.box.server.util.NetUtils;
import org.waveprotocol.wave.model.util.Pair;
import org.waveprotocol.wave.model.wave.ParticipantId;
import org.waveprotocol.wave.util.logging.Log;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.net.SocketAddress;
import java.util.EnumSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import javax.annotation.Nullable;
import javax.servlet.DispatcherType;
import javax.servlet.ServletConfig;
import javax.servlet.ServletContextListener;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
/**
* ServerRpcProvider can provide instances of type Service over an incoming
* network socket and service incoming RPCs to these services and their methods.
*
*
*/
public class ServerRpcProvider {
private static final Log LOG = Log.get(ServerRpcProvider.class);
/**
* The buffer size is passed to implementations of {@link AbstractWaveSocketIOServlet} as init
* param. It defines the response buffer size.
*/
private static final int BUFFER_SIZE = 1024 * 1024;
private final InetSocketAddress[] httpAddresses;
private final Integer flashsocketPolicyPort;
private final ExecutorService threadPool;
private final SessionManager sessionManager;
private final org.eclipse.jetty.server.SessionManager jettySessionManager;
private Server httpServer = null;
private final boolean sslEnabled;
private final String sslKeystorePath;
private final String sslKeystorePassword;
// Mapping from incoming protocol buffer type -> specific handler.
private final Map<Descriptors.Descriptor, RegisteredServiceMethod> registeredServices =
Maps.newHashMap();
// List of webApp source directories ("./war", etc)
private final String[] resourceBases;
private final String sessionStoreDir;
/**
* Internal, static container class for any specific registered service
* method.
*/
static class RegisteredServiceMethod {
final Service service;
final MethodDescriptor method;
RegisteredServiceMethod(Service service, MethodDescriptor method) {
this.service = service;
this.method = method;
}
}
static class WebSocketConnection extends Connection {
private final WebSocketServerChannel socketChannel;
WebSocketConnection(ParticipantId loggedInUser, ServerRpcProvider provider) {
super(loggedInUser, provider);
socketChannel = new WebSocketServerChannel(this);
LOG.info("New websocket connection set up for user " + loggedInUser);
expectMessages(socketChannel);
}
@Override
protected void sendMessage(int sequenceNo, Message message) {
socketChannel.sendMessage(sequenceNo, message);
}
public WebSocketServerChannel getWebSocketServerChannel() {
return socketChannel;
}
}
static class SocketIOConnection extends Connection {
private final SocketIOServerChannel socketChannel;
SocketIOConnection(ParticipantId loggedInUser, ServerRpcProvider provider) {
super(loggedInUser, provider);
socketChannel = new SocketIOServerChannel(this);
LOG.info("New websocket connection set up for user " + loggedInUser);
expectMessages(socketChannel);
}
@Override
protected void sendMessage(int sequenceNo, Message message) {
socketChannel.sendMessage(sequenceNo, message);
}
public SocketIOServerChannel getWebSocketServerChannel() {
return socketChannel;
}
}
static abstract class Connection implements ProtoCallback {
private final Map<Integer, ServerRpcController> activeRpcs =
new ConcurrentHashMap<Integer, ServerRpcController>();
// The logged in user.
// Note: Due to this bug:
// http://code.google.com/p/wave-protocol/issues/detail?id=119,
// the field may be null on first connect and then set later using an RPC.
private ParticipantId loggedInUser;
private final ServerRpcProvider provider;
/**
* @param loggedInUser The currently logged in user, or null if no user is
* logged in.
* @param provider
*/
public Connection(ParticipantId loggedInUser, ServerRpcProvider provider) {
this.loggedInUser = loggedInUser;
this.provider = provider;
}
protected void expectMessages(MessageExpectingChannel channel) {
synchronized (provider.registeredServices) {
for (RegisteredServiceMethod serviceMethod : provider.registeredServices.values()) {
channel.expectMessage(serviceMethod.service.getRequestPrototype(serviceMethod.method));
LOG.fine("Expecting: " + serviceMethod.method.getFullName());
}
}
channel.expectMessage(Rpc.CancelRpc.getDefaultInstance());
}
protected abstract void sendMessage(int sequenceNo, Message message);
private ParticipantId authenticate(String token) {
HttpSession session = provider.sessionManager.getSessionFromToken(token);
ParticipantId user = provider.sessionManager.getLoggedInUser(session);
return user;
}
@Override
public void message(final int sequenceNo, Message message) {
if (message instanceof Rpc.CancelRpc) {
final ServerRpcController controller = activeRpcs.get(sequenceNo);
if (controller == null) {
throw new IllegalStateException("Trying to cancel an RPC that is not active!");
} else {
LOG.info("Cancelling open RPC " + sequenceNo);
controller.cancel();
}
} else if (message instanceof ProtocolAuthenticate) {
// Workaround for bug: http://codereview.waveprotocol.org/224001/
// When we get this message, either the connection will not be logged in
// (loggedInUser == null) or the connection will have been authenticated
// via cookies
// (in which case loggedInUser must match the authenticated user, and
// this message has no
// effect).
ProtocolAuthenticate authMessage = (ProtocolAuthenticate) message;
ParticipantId authenticatedAs = authenticate(authMessage.getToken());
Preconditions.checkArgument(authenticatedAs != null, "Auth token invalid");
Preconditions.checkState(loggedInUser == null || loggedInUser.equals(authenticatedAs),
"Session already authenticated as a different user");
loggedInUser = authenticatedAs;
LOG.info("Session authenticated as " + loggedInUser);
sendMessage(sequenceNo, ProtocolAuthenticationResult.getDefaultInstance());
} else if (provider.registeredServices.containsKey(message.getDescriptorForType())) {
if (activeRpcs.containsKey(sequenceNo)) {
throw new IllegalStateException(
"Can't invoke a new RPC with a sequence number already in use.");
} else {
final RegisteredServiceMethod serviceMethod =
provider.registeredServices.get(message.getDescriptorForType());
// Create the internal ServerRpcController used to invoke the call.
final ServerRpcController controller =
new ServerRpcControllerImpl(message, serviceMethod.service, serviceMethod.method,
loggedInUser, new RpcCallback<Message>() {
@Override
synchronized public void run(Message message) {
if (message instanceof Rpc.RpcFinished
|| !serviceMethod.method.getOptions().getExtension(Rpc.isStreamingRpc)) {
// This RPC is over - remove it from the map.
boolean failed = message instanceof Rpc.RpcFinished
? ((Rpc.RpcFinished) message).getFailed() : false;
LOG.fine("RPC " + sequenceNo + " is now finished, failed = " + failed);
if (failed) {
LOG.info("error = " + ((Rpc.RpcFinished) message).getErrorText());
}
activeRpcs.remove(sequenceNo);
}
sendMessage(sequenceNo, message);
}
});
// Kick off a new thread specific to this RPC.
activeRpcs.put(sequenceNo, controller);
provider.threadPool.execute(controller);
}
} else {
// Sent a message type we understand, but don't expect - erronous case!
throw new IllegalStateException(
"Got expected but unknown message (" + message + ") for sequence: " + sequenceNo);
}
}
@Override
public void unknown(int sequenceNo, String messageType, UnknownFieldSet message) {
throw new IllegalStateException(
"Got unknown message (type: " + messageType + ", " + message + ") for sequence: "
+ sequenceNo);
}
@Override
public void unknown(int sequenceNo, String messageType, String message) {
throw new IllegalStateException(
"Got unknown message (type: " + messageType + ", " + message + ") for sequence: "
+ sequenceNo);
}
}
/**
* Construct a new ServerRpcProvider, hosting on the specified
* WebSocket addresses.
*
* Also accepts an ExecutorService for spawning managing threads.
*/
public ServerRpcProvider(InetSocketAddress[] httpAddresses, Integer flashsocketPolicyPort,
String[] resourceBases, ExecutorService threadPool, SessionManager sessionManager,
org.eclipse.jetty.server.SessionManager jettySessionManager, String sessionStoreDir,
boolean sslEnabled, String sslKeystorePath, String sslKeystorePassword) {
this.httpAddresses = httpAddresses;
this.flashsocketPolicyPort = flashsocketPolicyPort;
this.resourceBases = resourceBases;
this.threadPool = threadPool;
this.sessionManager = sessionManager;
this.jettySessionManager = jettySessionManager;
this.sessionStoreDir = sessionStoreDir;
this.sslEnabled = sslEnabled;
this.sslKeystorePath = sslKeystorePath;
this.sslKeystorePassword = sslKeystorePassword;
}
/**
* Constructs a new ServerRpcProvider with a default ExecutorService.
*/
public ServerRpcProvider(InetSocketAddress[] httpAddresses, Integer flashsocketPolicyPort,
String[] resourceBases, SessionManager sessionManager,
org.eclipse.jetty.server.SessionManager jettySessionManager, String sessionStoreDir,
boolean sslEnabled, String sslKeystorePath, String sslKeystorePassword) {
this(httpAddresses, flashsocketPolicyPort, resourceBases, Executors.newCachedThreadPool(),
sessionManager, jettySessionManager, sessionStoreDir, sslEnabled, sslKeystorePath,
sslKeystorePassword);
}
@Inject
public ServerRpcProvider(@Named(CoreSettings.HTTP_FRONTEND_ADDRESSES) List<String> httpAddresses,
@Named(CoreSettings.FLASHSOCKET_POLICY_PORT) Integer flashsocketPolicyPort,
@Named(CoreSettings.RESOURCE_BASES) List<String> resourceBases,
SessionManager sessionManager, org.eclipse.jetty.server.SessionManager jettySessionManager,
@Named(CoreSettings.SESSIONS_STORE_DIRECTORY) String sessionStoreDir,
@Named(CoreSettings.ENABLE_SSL) boolean sslEnabled,
@Named(CoreSettings.SSL_KEYSTORE_PATH) String sslKeystorePath,
@Named(CoreSettings.SSL_KEYSTORE_PASSWORD) String sslKeystorePassword) {
this(parseAddressList(httpAddresses), flashsocketPolicyPort, resourceBases
.toArray(new String[0]), sessionManager, jettySessionManager, sessionStoreDir,
sslEnabled, sslKeystorePath, sslKeystorePassword);
}
public void startWebSocketServer(final Injector injector) {
httpServer = new Server();
List<SelectChannelConnector> connectors = getSelectChannelConnectors(httpAddresses);
if (connectors.isEmpty()) {
LOG.severe("No valid http end point address provided!");
}
for (SelectChannelConnector connector : connectors) {
httpServer.addConnector(connector);
}
final WebAppContext context = new WebAppContext();
context.setParentLoaderPriority(true);
if (jettySessionManager != null) {
// This disables JSessionIDs in URLs redirects
// see: http://stackoverflow.com/questions/7727534/how-do-you-disable-jsessionid-for-jetty-running-with-the-eclipse-jetty-maven-plu
// and: http://jira.codehaus.org/browse/JETTY-467?focusedCommentId=114884&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-114884
jettySessionManager.setSessionIdPathParameterName(null);
context.getSessionHandler().setSessionManager(jettySessionManager);
}
final ResourceCollection resources = new ResourceCollection(resourceBases);
context.setBaseResource(resources);
addWebSocketServlets();
try {
final Injector parentInjector = injector;
final ServletModule servletModule = getServletModule(parentInjector);
ServletContextListener contextListener = new GuiceServletContextListener() {
private final Injector childInjector = parentInjector.createChildInjector(servletModule);
@Override
protected Injector getInjector() {
return childInjector;
}
};
context.addEventListener(contextListener);
context.addFilter(GuiceFilter.class, "/*", EnumSet.allOf(DispatcherType.class));
context.addFilter(GzipFilter.class, "/webclient/*", EnumSet.allOf(DispatcherType.class));
httpServer.setHandler(context);
httpServer.start();
restoreSessions();
} catch (Exception e) { // yes, .start() throws "Exception"
LOG.severe("Fatal error starting http server.", e);
return;
}
LOG.fine("WebSocket server running.");
}
private void restoreSessions() {
try {
HashSessionManager hashSessionManager = (HashSessionManager) jettySessionManager;
hashSessionManager.setStoreDirectory(FileUtils.createDirIfNotExists(sessionStoreDir,
"Session persistence"));
hashSessionManager.setSavePeriod(60);
hashSessionManager.restoreSessions();
} catch (Exception e) {
LOG.warning("Cannot restore sessions");
}
}
public void addWebSocketServlets() {
// Servlet where the websocket connection is served from.
ServletHolder wsholder = addServlet("/socket", WaveWebSocketServlet.class);
// TODO(zamfi): fix to let messages span frames.
wsholder.setInitParameter("bufferSize", "" + BUFFER_SIZE);
// Servlet where the websocket connection is served from.
ServletHolder sioholder = addServlet("/socket.io/*", WaveSocketIOServlet.class );
// TODO(zamfi): fix to let messages span frames.
sioholder.setInitParameter("bufferSize", "" + BUFFER_SIZE);
// Set flash policy server parameters
String flashPolicyServerHost = "localhost";
StringBuilder flashPolicyAllowedPorts = new StringBuilder();
/*
* Loop through addresses, collect list of ports, and determine if we are to use "localhost"
* of the AnyHost wildcard.
*/
for (InetSocketAddress addr: httpAddresses) {
if (flashPolicyAllowedPorts.length() > 0) {
flashPolicyAllowedPorts.append(",");
}
flashPolicyAllowedPorts.append(addr.getPort());
if (!addr.getAddress().isLoopbackAddress()) {
// Until it's possible to pass a list of address, this is the only valid alternative.
flashPolicyServerHost = "0.0.0.0";
}
}
sioholder.setInitParameter(FlashSocketTransport.PARAM_FLASHPOLICY_SERVER_HOST,
flashPolicyServerHost);
sioholder.setInitParameter(FlashSocketTransport.PARAM_FLASHPOLICY_SERVER_PORT,
""+flashsocketPolicyPort);
// TODO: Change to use the public http address and all other bound addresses.
sioholder.setInitParameter(FlashSocketTransport.PARAM_FLASHPOLICY_DOMAIN, "*");
sioholder.setInitParameter(FlashSocketTransport.PARAM_FLASHPOLICY_PORTS,
flashPolicyAllowedPorts.toString());
// Serve the static content and GWT web client with the default servlet
// (acts like a standard file-based web server).
addServlet("/static/*", DefaultServlet.class);
addServlet("/webclient/*", DefaultServlet.class);
}
public ServletModule getServletModule(final Injector injector) {
return new ServletModule() {
@Override
protected void configureServlets() {
// We add servlets here to override the DefaultServlet automatic registered by WebAppContext
// in path "/" with our WaveClientServlet. Any other way to do this?
// Related question (unanswered 08-Apr-2011)
// http://web.archiveorange.com/archive/v/d0LdlXf1kN0OXyPNyQZp
for (Pair<String, ServletHolder> servlet : servletRegistry) {
String url = servlet.getFirst();
@SuppressWarnings("unchecked")
Class<HttpServlet> clazz = (Class<HttpServlet>) servlet.getSecond().getHeldClass();
Map<String,String> params = servlet.getSecond().getInitParameters();
serve(url).with(clazz,params);
bind(clazz).in(Singleton.class);
}
}
};
}
private static InetSocketAddress[] parseAddressList(List<String> addressList) {
if (addressList == null || addressList.size() == 0) {
return new InetSocketAddress[0];
} else {
Set<InetSocketAddress> addresses = Sets.newHashSet();
for (String str : addressList) {
if (str.length() == 0) {
LOG.warning("Encountered empty address in http addresses list.");
} else {
try {
InetSocketAddress address = NetUtils.parseHttpAddress(str);
if (!addresses.contains(address)) {
addresses.add(address);
} else {
LOG.warning(
"Ignoring duplicate address in http addresses list: Duplicate entry '" + str
+ "' resolved to " + address.getAddress().getHostAddress());
}
} catch (IOException e) {
LOG.severe("Unable to process address " + str, e);
}
}
}
return addresses.toArray(new InetSocketAddress[0]);
}
}
/**
* @return a list of {@link SelectChannelConnector} each bound to a host:port
* pair form the list addresses.
*/
private List<SelectChannelConnector> getSelectChannelConnectors(
InetSocketAddress[] httpAddresses) {
List<SelectChannelConnector> list = Lists.newArrayList();
String[] excludeCiphers = {"SSL_RSA_EXPORT_WITH_RC4_40_MD5", "SSL_RSA_EXPORT_WITH_DES40_CBC_SHA",
"SSL_DHE_RSA_EXPORT_WITH_DES40_CBC_SHA", "SSL_RSA_WITH_DES_CBC_SHA",
"SSL_DHE_RSA_WITH_DES_CBC_SHA", "TLS_DHE_RSA_WITH_AES_128_CBC_SHA",
"SSL_DHE_RSA_WITH_3DES_EDE_CBC_SHA", "TLS_DHE_RSA_WITH_AES_256_CBC_SHA"};
SslContextFactory sslContextFactory = null;
if (sslEnabled) {
Preconditions.checkState(sslKeystorePath != null && !sslKeystorePath.isEmpty(),
"SSL Keystore path left blank");
Preconditions.checkState(sslKeystorePassword != null && !sslKeystorePassword.isEmpty(),
"SSL Keystore password left blank");
sslContextFactory = new SslContextFactory(sslKeystorePath);
sslContextFactory.setKeyStorePassword(sslKeystorePassword);
sslContextFactory.setAllowRenegotiate(false);
sslContextFactory.setExcludeCipherSuites(excludeCiphers);
}
for (InetSocketAddress address : httpAddresses) {
SelectChannelConnector connector;
if (sslEnabled) {
connector = new SslSelectChannelConnector(sslContextFactory);
} else {
connector = new SelectChannelConnector();
}
connector.setHost(address.getAddress().getHostAddress());
connector.setPort(address.getPort());
connector.setMaxIdleTime(0);
list.add(connector);
}
return list;
}
@SuppressWarnings("serial")
@Singleton
public static class WaveWebSocketServlet extends WebSocketServlet {
ServerRpcProvider provider;
@Inject
public WaveWebSocketServlet(ServerRpcProvider provider) {
super();
this.provider = provider;
}
@Override
public WebSocket doWebSocketConnect(HttpServletRequest request, String protocol) {
ParticipantId loggedInUser =
provider.sessionManager.getLoggedInUser(request.getSession(false));
WebSocketConnection connection = new WebSocketConnection(loggedInUser, provider);
return connection.getWebSocketServerChannel();
}
}
@SuppressWarnings("serial")
@Singleton
public static class WaveSocketIOServlet extends HttpServlet {
ServerRpcProvider provider;
@Inject
public WaveSocketIOServlet(ServerRpcProvider provider) {
super();
this.provider = provider;
}
AbstractWaveSocketIOServlet socketIOServlet = new AbstractWaveSocketIOServlet( new Transport[] {
new XHRMultipartTransport(), new XHRPollingTransport(), new FlashSocketTransport(),
new JettyWebSocketTransport(), new JSONPPollingTransport(), new HTMLFileTransport()}) {
@Override
protected SocketIOInbound doSocketIOConnect(HttpServletRequest request) {
ParticipantId loggedInUser = provider.sessionManager.getLoggedInUser(
request.getSession(false));
SocketIOConnection connection = new SocketIOConnection(loggedInUser, provider);
return connection.getWebSocketServerChannel();
}
};
@Override
public void init(ServletConfig config) throws ServletException {
socketIOServlet.init(config);
}
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
socketIOServlet.service(req, resp);
}
@Override
public void service(ServletRequest req, ServletResponse res)
throws ServletException, IOException {
socketIOServlet.service(req, res);
}
}
/**
* Returns the socket the WebSocket server is listening on.
*/
public SocketAddress getWebSocketAddress() {
if (httpServer == null) {
return null;
} else {
Connector c = httpServer.getConnectors()[0];
return new InetSocketAddress(c.getHost(), c.getLocalPort());
}
}
/**
* Stops this server.
*/
public void stopServer() throws IOException {
try {
httpServer.stop(); // yes, .stop() throws "Exception"
} catch (Exception e) {
LOG.warning("Fatal error stopping http server.", e);
}
LOG.fine("server shutdown.");
}
/**
* Register all methods provided by the given service type.
*/
public void registerService(Service service) {
synchronized (registeredServices) {
for (MethodDescriptor methodDescriptor : service.getDescriptorForType().getMethods()) {
registeredServices.put(methodDescriptor.getInputType(),
new RegisteredServiceMethod(service, methodDescriptor));
}
}
}
/**
* Set of servlets
*/
List<Pair<String, ServletHolder>> servletRegistry = Lists.newArrayList();
/**
* Add a servlet to the servlet registry. This servlet will be attached to the
* specified URL pattern when the server is started up.
*
* @param urlPattern the URL pattern for paths. Eg, '/foo', '/foo/*'.
* @param servlet the servlet class to bind to the specified paths.
* @param initParams the map with init params, can be null or empty.
* @return the {@link ServletHolder} that holds the servlet.
*/
public ServletHolder addServlet(String urlPattern, Class<? extends HttpServlet> servlet,
@Nullable Map<String, String> initParams) {
ServletHolder servletHolder = new ServletHolder(servlet);
if (initParams != null) {
servletHolder.setInitParameters(initParams);
}
servletRegistry.add(new Pair<String, ServletHolder>(urlPattern, servletHolder));
return servletHolder;
}
/**
* Add a servlet to the servlet registry. This servlet will be attached to the
* specified URL pattern when the server is started up.
* @param urlPattern the URL pattern for paths. Eg, '/foo', '/foo/*'.
* @param servlet the servlet class to bind to the specified paths.
* @return the {@link ServletHolder} that holds the servlet.
*/
public ServletHolder addServlet(String urlPattern, Class<? extends HttpServlet> servlet) {
return addServlet(urlPattern, servlet, null);
}
}