How to get DB connection state using JPA?

Question

During the server start up(tomcat) I am creating an entitymangerfactory and storing into the memory. My question, is there any way I can check the connection state during this time?

What is happening now, it is creating an entitymangerfactory object during startup, but do not test whether has connected the database or not. With invalid configuration it is creating the entitymanagerfactory but when we are trying to execute some queries only then I am getting the exception.

What should I do if I want to check the connection state during server startup?

Thanks in advance

-regards, Somnath Guha

Have you tried connection.isValid(int Timeout)? This returns if the connection is valid by sending some query itself. — Sandiip Patil, Aug 06 '13 at 07:58

score 1 · Answer 1 · edited May 23 '17 at 12:05

You should create a servlet that implements the ServletContextListener,

web.xml:

<listener>
  <listener-class>test.JPACheckServlet</listener-class>
</listener>

the code:

public class JPACheckServlet implements ServletContextListener {
  public void contextInitialized(ServletContextEvent event) {
    here put the code for checking the connection and report status, logging...
  }
  public void contextDestroyed(ServletContextEvent event) {
    here to handle fancy shutdown situation, loggings, etc 
  }
}

Good thread to read: How do servlets work? Instantiation, sessions, shared variables and multithreading

score 0 · Answer 2 · answered Aug 06 '13 at 08:43

Let me rephrase your question: during startup I want to know if I will be able to successfully execute queries. Forget about connection state, that's your ultimate goal - to execute JPA persistence stuff and not get connection errors.

So... during startup after you create your factory, obtain an EntityManager and try to execute a simple fetch. Seems obvious, no?

How to get DB connection state using JPA?

2 Answers2