Question

I’m currently experiencing an interesting problem.

My Situation:

• I am currently developing a web service (I’m using VAADIN for programming with JAVA in eclipse)
• My database behind is java derby
• I am using hibernate for my database
• I’m currently deploying it on Tomcat v7.0

My Problem:

• When I change something in my code (doesn’t matter what), the server should reload it without the need of being restarted – I guess that’s the overall expected behaviour
• The server reloads the application successfull, but if I try to click on something (so after the reloading), e.g. the login-Button, I get an error

Error Message:

Cause: org.hibernate.exception.GenericJDBCException: Could not open
connection] with root cause ERROR XSDB6: Another instance of Derby may
have already booted the database C:\HTML-Ausgabe\database\DocumentDB.
at org.apache.derby.iapi.error.StandardException.newException(Unknown
Source) …

My Thoughts on this

It seems that somehow on the reloading process the connection/context to hibernate doesnt get destroyed/closed and so the error occures when the server tries to reconnect to the database

My Code

I have a class, called Hibernate Listener:

public class HibernateListener implements ServletContextListener {

    public void contextInitialized(ServletContextEvent event) {
        HibernateUtil.getSessionFactory(); // Just call the static initializer of that class    
    }

    public void contextDestroyed(ServletContextEvent event) {
        HibernateUtil.getSessionFactory().close(); // Free all resources
    }
}

My hibernate.cfg.xml:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
    <session-factory>
        <property name="hibernate.connection.driver_class">org.apache.derby.jdbc.EmbeddedDriver</property>
        <property name="hibernate.connection.url">jdbc:derby:C:\HTML-Ausgabe\database\DocumentDB;create=true</property>
        <property name="hibernate.dialect">org.hibernate.dialect.DerbyDialect</property>
        <property name="hibernate.current_session_context_class">thread</property>
        <property name="hibernate.hbm2ddl.auto">create-drop</property>
        <property name="hibernate.show_sql">true</property>

        <mapping class="view.model.database.User"/>
        <mapping class="view.model.database.Document"/>
        <mapping class="view.model.database.Version"/>
        <mapping class="view.model.database.VersionData"/>
    </session-factory>
</hibernate-configuration>

My (VAADIN) web.xml, in which I added a “listener” for the upper shown HibernateListener (check the text at listener ):

<?xml version="1.0" encoding="UTF-8"?>
<web-app id="WebApp_ID" version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
    <display-name>Bachelorprojekt</display-name>
    <context-param>
        <description>Vaadin production mode</description>
        <param-name>productionMode</param-name>
        <param-value>false</param-value>
    </context-param>
    <servlet>
        <servlet-name>Bachelorprojekt Application</servlet-name>
        <servlet-class>com.vaadin.terminal.gwt.server.ApplicationServlet</servlet-class>
        <init-param>
            <description>Vaadin application class to start</description>
            <param-name>application</param-name>
            <param-value>view.view.WebsiteFrame</param-value>
        </init-param>
    </servlet>
    <servlet-mapping>
        <servlet-name>Bachelorprojekt Application</servlet-name>
        <url-pattern>/*</url-pattern>
    </servlet-mapping>

    <listener>
        <listener-class>view.model.database.HibernateListener</listener-class>
    </listener>
    <welcome-file-list>
        <welcome-file>index.html</welcome-file>
        <welcome-file>index.htm</welcome-file>
        <welcome-file>index.jsp</welcome-file>
        <welcome-file>default.html</welcome-file>
        <welcome-file>default.htm</welcome-file>
        <welcome-file>default.jsp</welcome-file>
    </welcome-file-list>
</web-app>

I did research, posted also on the hibernate forum (still without even a single answer 🙁 ) and now did not find a matching theme on this website. So I hope I didn’t do something wrong.

If anyone of you could help me somehow, I would be really happy. Currently I dont know what to change to stop this error happening. And, of course, I cant always restart the whole server later when my application is on the internet, if I change one line of code.

Thanks a lot for every answer and thought that you’re sharing with me.

Answer 1

I found the solution to my problem.

First of all, it was an apache derby problem, as I forced it to close with

public void contextDestroyed(ServletContextEvent event) {
    HibernateUtil.getSessionFactory().close(); // Free all resources
    try {
          DriverManager.getConnection("jdbc:derby:;shutdown=true");
    } catch (SQLException e) {}
    }
}

it worked fine for me.

Now I swichted my database vom apache derby to mysql and noticed that the problem, described in my question above, didn’t occur anymore.

So, lesson learned: Don’t use apache derby. I hope this helps someone else someday. Thanks a lot for your help.