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failed to create a child event loop/failed to open a new selector/Too many open files

I am getting errors like "failed to create a child event loop/failed to open a new selector/Too many open files" when there are 30 or more concurrent requests...How to solve the above errors? Am I doing anything wrong? I am using Spring boot and Java cassandra driver. Below is the connection file:
public class Connection {
public static Session getConnection() {
final Cluster cluster = Cluster.builder().addContactPoint(ConnectionBean.getCASSANDRA_DB_IP())
.withQueryOptions(new QueryOptions().setConsistencyLevel(ConsistencyLevel.LOCAL_ONE))
.withCredentials(ConnectionBean.getCASSANDRA_USER(), ConnectionBean.getCASSANDRA_PASSWORD())
.withPoolingOptions(poolingOptions)
.build();
final Session session = cluster.connect(ConnectionBean.getCASSANDRA_DB_NAME());
return session;
}
}
Below is the ConnectionBean file which I used in Connection file:
public class ConnectionBean {
public static String CASSANDRA_DB_IP;
public static String CASSANDRA_DB_NAME;
public static String CASSANDRA_USER;
public static String CASSANDRA_PASSWORD;
public ConnectionBean() {
}
public ConnectionBean(String CASSANDRA_DB_IP,String CASSANDRA_DB_NAME,String CASSANDRA_USER,String CASSANDRA_PASSWORD) {
this.CASSANDRA_DB_IP=CASSANDRA_DB_IP;
this.CASSANDRA_DB_NAME=CASSANDRA_DB_NAME;
this.CASSANDRA_USER=CASSANDRA_USER;
this.CASSANDRA_PASSWORD=CASSANDRA_PASSWORD;
}
public static String getCASSANDRA_DB_IP() {
return CASSANDRA_DB_IP;
}
public static void setCASSANDRA_DB_IP(String cASSANDRA_DB_IP) {
CASSANDRA_DB_IP = cASSANDRA_DB_IP;
}
public static String getCASSANDRA_DB_NAME() {
return CASSANDRA_DB_NAME;
}
public static void setCASSANDRA_DB_NAME(String cASSANDRA_DB_NAME) {
CASSANDRA_DB_NAME = cASSANDRA_DB_NAME;
}
public static String getCASSANDRA_USER() {
return CASSANDRA_USER;
}
public static void setCASSANDRA_USER(String cASSANDRA_USER) {
CASSANDRA_USER = cASSANDRA_USER;
}
public static String getCASSANDRA_PASSWORD() {
return CASSANDRA_PASSWORD;
}
public static void setCASSANDRA_PASSWORD(String cASSANDRA_PASSWORD) {
CASSANDRA_PASSWORD = cASSANDRA_PASSWORD;
}
}
Below is the class from where ConnectionBean variables are initialized :
public class SecurityConfiguration extends WebSecurityConfigurerAdapter {
private static final String LOGIN_PROCESSING_URL = "/login";
private static final String LOGIN_FAILURE_URL = "/login?error";
private static final String LOGIN_URL = "/login";
#Autowired
private BCryptPasswordEncoder bCryptPasswordEncoder;
#Autowired
private DataSource dataSource;
#Value("${spring.queries.users-query}")
private String usersQuery;
#Value("${spring.queries.roles-query}")
private String rolesQuery;
#Value("${CASSANDRA_DB_IP}")
public String CASSANDRA_DB_IP;
#Value("${CASSANDRA_DB_NAME}")
public String CASSANDRA_DB_NAME;
#Value("${CASSANDRA_USER}")
public String CASSANDRA_USER;
#Value("${CASSANDRA_PASSWORD}")
public String CASSANDRA_PASSWORD;
#Override
protected void configure(AuthenticationManagerBuilder auth) throws Exception {
ConnectionBean cb = new ConnectionBean(CASSANDRA_DB_IP, CASSANDRA_DB_NAME, CASSANDRA_USER, CASSANDRA_PASSWORD);
auth.jdbcAuthentication().usersByUsernameQuery(usersQuery).authoritiesByUsernameQuery(rolesQuery)
.dataSource(dataSource).passwordEncoder(bCryptPasswordEncoder);
}
#Override
protected void configure(HttpSecurity http) throws Exception {
// Not using Spring CSRF here to be able to use plain HTML for the login page
http.csrf().disable()
// Register our CustomRequestCache, that saves unauthorized access attempts, so
// the user is redirected after login.
.requestCache().requestCache(new CustomRequestCache())
// Restrict access to our application.
.and().authorizeRequests()
// Allow all flow internal requests.
.requestMatchers(SecurityUtils::isFrameworkInternalRequest).permitAll()
// Allow all requests by logged in users.
.anyRequest().authenticated()
// Configure the login page.
.and().formLogin().loginPage(LOGIN_URL).permitAll().loginProcessingUrl(LOGIN_PROCESSING_URL)
.failureUrl(LOGIN_FAILURE_URL)
// Register the success handler that redirects users to the page they last tried
// to access
.successHandler(new SavedRequestAwareAuthenticationSuccessHandler())
// Configure logout
.and().logout().logoutSuccessUrl(LOGOUT_SUCCESS_URL);
}
/**
* Allows access to static resources, bypassing Spring security.
*/
#Override
public void configure(WebSecurity web) throws Exception {
web.ignoring().antMatchers(
// Vaadin Flow static resources
"/VAADIN/**",
// the standard favicon URI
"/favicon.ico",
// web application manifest
"/manifest.json", "/sw.js", "/offline-page.html",
// icons and images
"/icons/**", "/images/**",
// (development mode) static resources
"/frontend/**",
// (development mode) webjars
"/webjars/**",
// (development mode) H2 debugging console
"/h2-console/**",
// (production mode) static resources
"/frontend-es5/**", "/frontend-es6/**");
}
}
And finally, below is the class through which I am querying cassandra data:
public class getData {
Session session;
public getData(){
session = Connection.getConnection();
getDataTable();
}
private void getDataTable() {
try {
String query = "SELECT * FROM tableName";
ResultSet rs = session.execute(query);
for (Row row : rs) {
/*Do some stuff here using row*/
}
} catch (Exception e) {
e.printStackTrace();
}
}
}

If getConnection() is being invoked for every request, you are creating a new Cluster instance each time.
This is discouraged because one connection is created between your client and a C* node for each Cluster instance, and for each Session a connection pool of at least one connection is created for each C* node.
If you are not closing your Cluster instances after a request completes, these connections will remain open. After a number of requests, you'll have so many connections open that you will run out of file descriptors in your OS.
To resolve this issue, create only one Cluster and Session instance and reuse it between requests. This strategy is outlined in 4 simple rules when using the DataStax drivers for Cassandra:
Use one Cluster instance per (physical) cluster (per application lifetime)
Use at most one Session per keyspace, or use a single Session and explicitely specify the keyspace in your queries

Access the session variable within a ServletContextListener

I am implementing an upload feature using Grails where basically a user gets to upload a text file and then the system will persist each line of that text file as a database record. While the uploading works fine, larger files take time to process and therefore they ask to have a progress bar so that users can determine if their upload is still processing or an actual error has occurred.
To do this, what I did is to create two URLs:
/upload which is the actual URL that receives the uploaded text file.
/upload/status?uploadToken= which returns the status of a certain upload based on its uploadToken.
What I did is after processing each line, the service will update a session-level counter variable:
// import ...
class UploadService {
Map upload(CommonsMultipartFile record, GrailsParameterMap params) {
Map response = [success: true]
try {
File file = new File(record.getOriginalFilename())
FileUtils.writeByteArrayToFile(file, record.getBytes())
HttpSession session = WebUtils.retrieveGrailsWebRequest().session
List<String> lines = FileUtils.readLines(file, "UTF-8"), errors = []
String uploadToken = params.uploadToken
session.status.put(uploadToken,
[message: "Checking content of the file of errors.",
size: lines.size(),
done: 0])
lines.eachWithIndex { l, li ->
// ... regex checking per line and appending any error to the errors List
session.status.get(uploadToken).done++
}
if(errors.size() == 0) {
session.status.put(uploadToken,
[message: "Persisting record to the database.",
size: lines.size(),
done: 0])
lines.eachWithIndex { l, li ->
// ... Performs GORM manipulation here
session.status.get(uploadToken).done++
}
}
else {
response.success = false
}
}
catch(Exception e) {
response.success = false
}
response << [errors: errors]
return response
}
}
Then create a simple WebSocket implementation that connects to the /upload/status?uploadToken= URL. The problem is that I cannot access the session variable on POGOs. I even change that POGO into a Grails service because I thought that is the cause of the issue, but I still can't access the session variable.
// import ...
#ServerEndpoint("/upload/status")
#WebListener
class UploadEndpointService implements ServletContextListener {
#OnOpen
public void onOpen(Session userSession) { /* ... */ }
#OnClose
public void onClose(Session userSession, CloseReason closeReason) { /* ... */ }
#OnError
public void onError(Throwable t) { /* ... */ }
#OnMessage
public void onMessage(String token, Session userSession) {
// Both of these cause IllegalStateException
def session = WebUtils.retrieveGrailsWebRequest().session
def session = RequestContextHolder.currentRequestAttributes().getSession()
// This returns the session id but I don't know what to do with that information.
String sessionId = userSession.getHttpSessionId()
// Sends the upload status through this line
sendMessage((session.get(token) as JSON).toString(), userSession)
}
private void sendMessage(String message, Session userSession = null) {
Iterator<Session> iterator = users.iterator()
while(iterator.hasNext()) {
iterator.next().basicRemote.sendText(message)
}
}
}
And instead, gives me an error:
Caused by IllegalStateException: No thread-bound request found: Are you referring to request attributes outside of an actual web request, or processing a request outside of the originally receiving thread? If you are actually operating within a web request and still receive this message, your code is probably running outside of DispatcherServlet/DispatcherPortlet: In this case,
use RequestContextListener or RequestContextFilter to expose the current request.
I already verified that the web socket is working by making it send a static String content. But what I want is to be able to get that counter and set it as the send message. I'm using Grails 2.4.4 and the Grails Spring Websocket plugin, while looks promising, is only available from Grails 3 onwards. Is there any way to achieve this, or if not, what approach should I use?

Much thanks to the answer to this question that helped me greatly solving my problem.
I just modified my UploadEndpointService the same as the one on that answer and instead of making it as a service class, I reverted it back into a POGO. I also configured it's #Serverendpoint annotation and added a configurator value. I also added a second parameter to the onOpen() method. Here is the edited class:
import grails.converters.JSON
import grails.util.Environment
import javax.servlet.annotation.WebListener
import javax.servlet.http.HttpSession
import javax.servlet.ServletContext
import javax.servlet.ServletContextEvent
import javax.servlet.ServletContextListener
import javax.websocket.CloseReason
import javax.websocket.EndpointConfig
import javax.websocket.OnClose
import javax.websocket.OnError
import javax.websocket.OnMessage
import javax.websocket.OnOpen
import javax.websocket.server.ServerContainer
import javax.websocket.server.ServerEndpoint
import javax.websocket.Session
import org.apache.log4j.Logger
import org.codehaus.groovy.grails.commons.GrailsApplication
import org.codehaus.groovy.grails.web.json.JSONObject
import org.codehaus.groovy.grails.web.servlet.GrailsApplicationAttributes
import org.springframework.context.ApplicationContext
#ServerEndpoint(value="/ep/maintenance/attendance-monitoring/upload/status", configurator=GetHttpSessionConfigurator.class)
#WebListener
class UploadEndpoint implements ServletContextListener {
private static final Logger log = Logger.getLogger(UploadEndpoint.class)
private Session wsSession
private HttpSession httpSession
#Override
void contextInitialized(ServletContextEvent servletContextEvent) {
ServletContext servletContext = servletContextEvent.servletContext
ServerContainer serverContainer = servletContext.getAttribute("javax.websocket.server.ServerContainer")
try {
if (Environment.current == Environment.DEVELOPMENT) {
serverContainer.addEndpoint(UploadEndpoint)
}
ApplicationContext ctx = (ApplicationContext) servletContext.getAttribute(GrailsApplicationAttributes.APPLICATION_CONTEXT)
GrailsApplication grailsApplication = ctx.grailsApplication
serverContainer.defaultMaxSessionIdleTimeout = grailsApplication.config.servlet.defaultMaxSessionIdleTimeout ?: 0
} catch (IOException e) {
log.error(e.message, e)
}
}
#Override
void contextDestroyed(ServletContextEvent servletContextEvent) {
}
#OnOpen
public void onOpen(Session userSession, EndpointConfig config) {
this.wsSession = userSession
this.httpSession = (HttpSession) config.getUserProperties().get(HttpSession.class.getName())
}
#OnMessage
public void onMessage(String message, Session userSession) {
try {
Map params = new JSONObject(message)
if(httpSession.status == null) {
params = [message: "Initializing file upload.",
size: 0,
token: 0]
sendMessage((params as JSON).toString())
}
else {
sendMessage((httpSession.status.get(params.token) as JSON).toString())
}
}
catch(IllegalStateException e) {
}
}
#OnClose
public void onClose(Session userSession, CloseReason closeReason) {
try {
userSession.close()
}
catch(IllegalStateException e) {
}
}
#OnError
public void onError(Throwable t) {
log.error(t.message, t)
}
private void sendMessage(String message, Session userSession=null) {
wsSession.basicRemote.sendText(message)
}
}
The real magic happens within the onOpen() method. There is where the accessing of the session variable takes place.

Play2.5 Java WebSockets

Play 2.5 Highlights states
Better control over WebSocket frames
The Play 2.5 WebSocket API gives you direct control over WebSocket frames. You can now send and receive binary, text, ping, pong and close frames. If you don’t want to worry about this level of detail, Play will still automatically convert your JSON or XML data into the right kind of frame.
However
https://www.playframework.com/documentation/2.5.x/JavaWebSockets has examples around LegacyWebSocket which is deprecated
What is the recommended API/pattern for Java WebSockets? Is using
LegacyWebSocket the only option for java websockets?
Are there any examples using new Message types ping/pong to implement a heartbeat?

The official documentation on this is disappointingly very sparse. Perhaps in Play 2.6 we'll see an update to this. However, I will provide an example below on how to configure a chat websocket in Play 2.5, just to help out those in need.
Setup
AController.java
#Inject
private Materializer materializer;
private ActorRef chatSocketRouter;
#Inject
public AController(#Named("chatSocketRouter") ActorRef chatInjectedActor) {
this.chatSocketRouter = chatInjectedActor;
}
// Make a chat websocket for a user
public WebSocket chatSocket() {
return WebSocket.Json.acceptOrResult(request -> {
String authToken = getAuthToken();
// Checking of token
if (authToken == null) {
return forbiddenResult("No [authToken] supplied.");
}
// Could we find the token in the database?
final AuthToken token = AuthToken.findByToken(authToken);
if (token == null) {
return forbiddenResult("Could not find [authToken] in DB. Login again.");
}
User user = token.getUser();
if (user == null) {
return forbiddenResult("You are not logged in to view this stream.");
}
Long userId = user.getId();
// Create a function to be run when we initialise a flow.
// A flow basically links actors together.
AbstractFunction1<ActorRef, Props> getWebSocketActor = new AbstractFunction1<ActorRef, Props>() {
#Override
public Props apply(ActorRef connectionProperties) {
// We use the ActorRef provided in the param above to make some properties.
// An ActorRef is a fancy word for thread reference.
// The WebSocketActor manages the web socket connection for one user.
// WebSocketActor.props() means "make one thread (from the WebSocketActor) and return the properties on how to reference it".
// The resulting Props basically state how to construct that thread.
Props properties = ChatSocketActor.props(connectionProperties, chatSocketRouter, userId);
// We can have many connections per user. So we need many ActorRefs (threads) per user. As you can see from the code below, we do exactly that. We have an object called
// chatSocketRouter which holds a Map of userIds -> connectionsThreads and we "tell"
// it a lightweight object (UserMessage) that is made up of this connecting user's ID and the connection.
// As stated above, Props are basically a way of describing an Actor, or dumbed-down, a thread.
// In this line, we are using the Props above to
// reference the ActorRef we've just created above
ActorRef anotherUserDevice = actorSystem.actorOf(properties);
// Create a lightweight object...
UserMessage routeThisUser = new UserMessage(userId, anotherUserDevice);
// ... to tell the thread that has our Map that we have a new connection
// from a user.
chatSocketRouter.tell(routeThisUser, ActorRef.noSender());
// We return the properties to the thread that will be managing this user's connection
return properties;
}
};
final Flow<JsonNode, JsonNode, ?> jsonNodeFlow =
ActorFlow.<JsonNode, JsonNode>actorRef(getWebSocketActor,
100,
OverflowStrategy.dropTail(),
actorSystem,
materializer).asJava();
final F.Either<Result, Flow<JsonNode, JsonNode, ?>> right = F.Either.Right(jsonNodeFlow);
return CompletableFuture.completedFuture(right);
});
}
// Return this whenever we want to reject a
// user from connecting to a websocket
private CompletionStage<F.Either<Result, Flow<JsonNode, JsonNode, ?>>> forbiddenResult(String msg) {
final Result forbidden = Results.forbidden(msg);
final F.Either<Result, Flow<JsonNode, JsonNode, ?>> left = F.Either.Left(forbidden);
return CompletableFuture.completedFuture(left);
}
ChatSocketActor.java
public class ChatSocketActor extends UntypedActor {
private final ActorRef out;
private final Long userId;
private ActorRef chatSocketRouter;
public ChatSocketActor(ActorRef out, ActorRef chatSocketRouter, Long userId) {
this.out = out;
this.userId = userId;
this.chatSocketRouter = chatSocketRouter;
}
public static Props props(ActorRef out, ActorRef chatSocketRouter, Long userId) {
return Props.create(ChatSocketActor.class, out, chatSocketRouter, userId);
}
// Add methods here handling each chat connection...
}
ChatSocketRouter.java
public class ChatSocketRouter extends UntypedActor {
public ChatSocketRouter() {}
// Stores userIds to websockets
private final HashMap<Long, List<ActorRef>> senders = new HashMap<>();
private void addSender(Long userId, ActorRef actorRef){
if (senders.containsKey(userId)) {
final List<ActorRef> actors = senders.get(userId);
actors.add(actorRef);
senders.replace(userId, actors);
} else {
List<ActorRef> l = new ArrayList<>();
l.add(actorRef);
senders.put(userId, l);
}
}
private void removeSender(ActorRef actorRef){
for (List<ActorRef> refs : senders.values()) {
refs.remove(actorRef);
}
}
#Override
public void onReceive(Object message) throws Exception {
ActorRef sender = getSender();
// Handle messages sent to this 'router' here
if (message instanceof UserMessage) {
UserMessage userMessage = (UserMessage) message;
addSender(userMessage.userId, userMessage.actorRef);
// Watch sender so we can detect when they die.
getContext().watch(sender);
} else if (message instanceof Terminated) {
// One of our watched senders has died.
removeSender(sender);
} else {
unhandled(message);
}
}
}
Example
Now whenever you want to send a client with a websocket connection a message you can do something like:
ChatSenderController.java
private ActorRef chatSocketRouter;
#Inject
public ChatSenderController(#Named("chatSocketRouter") ActorRef chatInjectedActor) {
this.chatSocketRouter = chatInjectedActor;
}
public static void sendMessage(Long sendToId) {
// E.g. send the chat router a message that says hi
chatSocketRouter.tell(new Message(sendToId, "Hi"));
}
ChatSocketRouter.java
#Override
public void onReceive(Object message) throws Exception {
// ...
if (message instanceof Message) {
Message messageToSend = (Message) message;
// Loop through the list above and send the message to
// each connection. For example...
for (ActorRef wsConnection : senders.get(messageToSend.getSendToId())) {
// Send "Hi" to each of the other client's
// connected sessions
wsConnection.tell(messageToSend.getMessage());
}
}
// ...
}
Again, I wrote the above to help out those in need. After scouring the web I could not find a reasonable and simple example. There is an open issue for this exact topic. There are also some examples online but none of them were easy to follow. Akka has some great documentation but mixing it in with Play was a tough mental task.
Please help improve this answer if you see anything that is amiss.

Hibernate: Using two different DataBase schemas in the same application

Context
I'm creating a database environment where I'd like to split data in several different schemas to be used for different groups of users. Although, one of these databases should be shared to everyone due to it contains common entities.
Suppose databases:
DB1 - Common entities;
Wheels entity
DB2 - Group "A";
Cars entity
DB3 - Group "B";
Motorcycles entity
I have three different projects:
Project 1:
Wheels bean
Project 2:
Cars constructor
Project 3:
Motorcycles constructor
Problem
I'm trying to access wheels (Project 1) from projects/schemas (2,"A") and (3,"B")
First question: Is it possible?
Second: How can I do it?
hibernate.cfg.xml in project 2 is configured to
<property name="hibernate.connection.url">jdbc:mysql://99.999.999.99:3306/DB2</property>
This necessarily must restrict all the connections to DB2, or there's another way to add a new connection or work with all databases in 3306 port, or at least DB1?
Mapping the entities from project1 in project 2 seems not to be succeeded too, like:
<mapping class="com.company.project1.Wheels"
package="com.company.project1.Wheels" resource="com/company/project1/Wheels.hbm.xml"/>
Configuration
Eclipse Indigo
MySql 5.5
Hibernate 3.0 (mapping through xml instead annotations)
Win 7
Thanks for helping!

You can use #Table(catalog="") to specify database to which they belong to and then also can make relation across database.
in your case Wheel maps to DB1, Car to DB2 and MotorCycle to DB3 using catalog attribute.
i have used this solution with MySQL and MSSQL and works perfectly fine. only constraint this has all three DB has to be in same database server and user which is being used to access db should have appropriate permission to all DB.
As this solution just adds schema name against table in all queries.

I would divide my project in multiple self sustained projects. The Wheel project will be self sufficient project which takes care of Wheel entity.
Project 1: Wheel
This project will define Hibernate entities and DAO to access / modify wheel definitions.
Also I would configure a separate datasource in this project which points to DB1.
Entity classes:
#Entity
public class Wheel {
}
DAO classes:
#Repository
public class WheelDAO {
#Persistence
private EntityManager em;
}
Basically the idea is to separate application at DAO level. And manage transactions at Service level. Imaging WheelDAO (wired to DB1 datasource) and CarDAO (wired to DB2 datasource) and inject these in CarService.
DB1 DB2 DB2
| | |
WheelDAO CarDAO MotorcycleDAO
\_____________/ |
\_____|__________________________/
| |
| |
CarService MotorCycleService
I suggest to use Spring as IOC container to manage these dependency. Although you can achieve this without using Spring too.

What you need is just a db connection factory which allows you to use db that you want when you need it.
Take a look at the class below which you can adapte to resolve your issue
import java.net.URL;
import java.util.HashMap;
import javax.security.auth.login.Configuration;
public class HibernateUtil {
private static Log log = LogFactory.getLog(HibernateUtil.class);
private static HashMap<String, SessionFactory> sessionFactoryMap = new HashMap<String, SessionFactory>();
public static final ThreadLocal sessionMapsThreadLocal = new ThreadLocal();
public static Session currentSession(String key) throws HibernateException {
HashMap<String, Session> sessionMaps = (HashMap<String, Session>) sessionMapsThreadLocal.get();
if(sessionMaps == null) {
sessionMaps = new HashMap();
sessionMapsThreadLocal.set(sessionMaps);
}
// Open a new Session, if this Thread has none yet
Session s = (Session) sessionMaps.get(key);
if(s == null) {
s = ((SessionFactory) sessionFactoryMap.get(key)).openSession();
sessionMaps.put(key, s);
}
return s;
}
public static Session currentSession() throws HibernateException {
return currentSession("");
}
public static void closeSessions() throws HibernateException {
HashMap<String, Session> sessionMaps = (HashMap<String, Session>) sessionMapsThreadLocal.get();
sessionMapsThreadLocal.set(null);
if(sessionMaps != null) {
for(Session session : sessionMaps.values()) {
if(session.isOpen())
session.close();
}
;
}
}
public static void closeSession() {
HashMap<String, Session> sessionMaps = (HashMap<String, Session>) sessionMapsThreadLocal.get();
sessionMapsThreadLocal.set(null);
if(sessionMaps != null) {
Session session = sessionMaps.get("");
if(session != null && session.isOpen())
session.close();
}
}
public static void buildSessionFactories(HashMap<String, String> configs) {
try {
// Create the SessionFactory
for(String key : configs.keySet()) {
URL url = HibernateUtil.class.getResource(configs.get(key));
SessionFactory sessionFactory = new Configuration().configure(url).buildSessionFactory();
sessionFactoryMap.put(key, sessionFactory);
}
} catch(Exception ex) {
ex.printStackTrace(System.out);
log.error("Initial SessionFactory creation failed.", ex);
throw new ExceptionInInitializerError(ex);
} // end of the try - catch block
}
public static void buildSessionFactory(String key, String path) {
try {
// Create the SessionFactory
URL url = HibernateUtil.class.getResource(path);
SessionFactory sessionFactory = new Configuration().configure(url).buildSessionFactory();
sessionFactoryMap.put(key, sessionFactory);
} catch(Throwable ex) {
log.error("Initial SessionFactory creation failed.", ex);
throw new ExceptionInInitializerError(ex);
} // end of the try - catch block
}
public static void closeSession(String key) {
HashMap<String, Session> sessionMaps = (HashMap<String, Session>) sessionMapsThreadLocal.get();
if(sessionMaps != null) {
Session session = sessionMaps.get(key);
if(session != null && session.isOpen())
session.close();
}
}
} // end of the class
http://www.java-forums.org/

Tomcat persistent and user specific session counter

I need to make persistent and user specific session counter. I made this
package my.package;
import javax.servlet.http.HttpSessionListener;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSession;
import java.util.HashMap;
public class SessionCounter implements HttpSessionListener {
private static HashMap activeSessions;
public SessionCounter() {
//How to restore session count?
activeSessions = new HashMap();
}
public void sessionCreated(HttpSessionEvent se) {
HttpSession session = se.getSession();
String userName = session.getAttribute("username");
Integer count = (Integer) activeSessions.get(userName);
if (count != null) {
activeSessions.put(userName, Integer.valueOf(count.intValue() + 1));
} else {
activeSessions.put(userName, new Integer(1));
}
}
public void sessionDestroyed(HttpSessionEvent se) {
HttpSession session = se.getSession();
String userName = session.getAttribute("username");
Integer count = (Integer) activeSessions.get(userName);
if (count != null && count.intValue() > 0) {
activeSessions.put(userName, Integer.valueOf(count.intValue() - 1));
}
}
public static HashMap getActiveSessions() {
return activeSessions;
}
}
Session are active even after restart tomcat but session count stored in my activeSessions variable is lost. How can I restore the session count after restart?

When Tomcat is shut down (i.e, by the shutdown script and not by killing the process) all sessions a serialized and restored when it is started the next time.
An HttpSessionListener will always be recreated, therefore your HashMap gets newly instantiated and the information is lost. You will have to write a model that implements serialiable, that holds your data, and store it to the disk when Tomcat is shutdown.