Is it possible to remove a key and value from a HashMap if its key is not available for a certain time
I have a requirement when I need to make sure that no user can do multiple logins So for this I made the login system centralized , which after the user successfully logs in, I store it in the Authenticator class , as shown below, and removing it from the HashMap when the user clicks on exit
public final class Authenticator {
private static Authenticator authenticator = null;
Map<String, String> usersStorage = new HashMap<String,String>();
private Authenticator() {}
public static Authenticator getInstance() {
if ( authenticator == null ) {
authenticator = new Authenticator();
}
return authenticator;
}
public Map<String, String> getusersStorage() {
return usersStorage;
}
}
That being said, everything works well.
I have some negative scenarios to handle and this
- User can close the browser without pressing "Exit" ( Ctrl + W / browser cross button )
In this case, you can remove the key and value from the HashMap if it has been idle for 15 minutes
please share your ideas on approaching this requirement.
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Basically you need session management. When the user is logged in, start a session and keep updating the session whenever the user takes any action on your website. And if a user is inactive for a certain amount of time (session time), remove that user from the session store.
If you are not interested in this session management and just want to use a "Map" type of technology, you can switch to any cache engine (eg EhCache). He will do what you asked. But I prefer session management for this particular scenario.
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Consider Google Guava. Cache classes are very versatile and also support timeout: https://code.google.com/p/guava-libraries/wiki/CachesExplained
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Typically for user centric applications, you will have an application server that takes care of session management if configured correctly, for example. Apache Tomcat will look for an attribute session-timeout
in web.xml
, which will look like this:
<session-config>
<session-timeout>30</session-timeout>
</session-config>
The value is taken in a matter of minutes.
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