MongoDB Connection Class in ServletContextListener-contextInitialized is not loading

Question

I am using Mongodb as Back-End database in a web project and i am trying to connect the MongoDB in contextInitialized() function but the tomcat server is not starting.But when i print some values or do some simple things rather than load a class in that function it works fine.I can't track what is happening.The code

@Override
    public void contextInitialized(ServletContextEvent contextEvent) {
        MongoDBClass.INSTANCE.getSomeDB().getCollection("UserDB");
        System.out.println("Context Created");//This is working
        context = contextEvent.getServletContext();
        context.getServerInfo();
        MongoDBClass.INSTANCE.getSomeDB().getCollection("UserDB");//Server loading and unable to start .
        }

MongoDBClass is as follows

public enum MongoDBClass {
    INSTANCE;
    private static final String MONGO_DB_HOST = "hostURL";
    private Mongo mongoObject;
    private DB someDB;
    String DB_NAME = null;
    MongoClientOptions options = null;

    MongoDBClass() {

        options = MongoClientOptions.builder().connectionsPerHost(100)
    .readPreference(ReadPreference.secondaryPreferred()).build();
    mongoObject = new MongoClient(new ServerAddress(MONGO_DB_HOST,27001),options);
         someDB = mongoObject.getDB(Nutans_Mongo.getNameOFDB());
}

please help me out Thanks Vicky

Answer 1

The problem in your code is MongoDBClass is not intialized because you are getting name of db which is not set during start the start of tomcat server `` set that first like @Override

public void contextInitialized(ServletContextEvent contextEvent) {
    Nutans_Mongo.setNameOFDB("someDBNAME"); //then intialize MongoDBCLass
    MongoDBClass.INSTANCE.getSomeDB().getCollection("UserDB");
    System.out.println("Context Created");//This is working
    context = contextEvent.getServletContext();
    context.getServerInfo();
    MongoDBClass.INSTANCE.getSomeDB().getCollection("UserDB");//Server loading and unable to start .
    }