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JSF App slow with JPA connection

If you are working on Java Persistence API JPA on tomcat or any other web server this would be happening if you have multiple threads going off for connections.

The rule of thumb shall be to have one EntityManagerFactory and get EntityManagers out of it. Hence we would have one factory but multiple products that would take care of closing and managing them selves.

What are the signs:

1. Do you instantiate Persistence.createEntityManagerFactory(“name”) from multiple places?
2. What do you see on Process when you run

ps -aux | grep tomcat

Do you see multiple instances

If either or both of the above have yes, then here is the solution.

The first thing have single instance of ManagerFactory


package com.enderase.persistence;

import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;

/**
* Singlton implementation for EntityManagerFactory
*
* @author Kaleb Woldearegay<kaleb@gullele.com>
*/
public class HibernateUtil {
private static final EntityManagerFactory entityManagerFactory;

static {
try {
entityManagerFactory = Persistence.createEntityManagerFactory("jpa");
} catch (Throwable exception) {
//log your error here
throw new ExceptionInInitializerError(exception);
}
}

public static EntityManagerFactory getEntityManager() {
return entityManagerFactory;
}
}

Then make sure you are taking care of the instances of the EntityManagers that are created from the factory using

EntityManagerFactory entityManagerFactory = HibernateUtil.getEntityManager();
EntityManager em = entityManagerFactory.createEntityManager();

Make sure to close them appropriately after using them

This should pretty much take care of the problem

 

Showing error message on selectOneMenu while selecting default

So, we have a menu, brimmed with our objects from list/database. The intention would be creating a default “Select” kind of the first row and to brag on the user when s/he selects the default.

The trick is simple, create the first list with null object and label it as Select. Lets show it with simple example.
We want to have a list of programming languages on our select menu. And, the first would be a default object.

    //Actual domain class
    class Language{
        private String name;
        private String type;
        private boolan isCompiled;

       getters/setters goes here
   }
   //Bean class
   class someBean{
        private List languages;
        .
        .
        public String getLanguages(){
            //Let languages would be filled by some service or factory
            this.languages = someLanguageFactory.getAllLanguages(); 
           //Assign the first element as null
           this.languages.add(0, null);
       }
   }
   
   //JSF page
   :
   :
   <h:selectOneMenu id="selectLanguage" value="someBean.languages" 
     requred="true" ....

This should do the task, make the list required, and populate the first list null. So, during validation if the selection is null it would be rejected as we have told it to watch an eye on blank fields.