Tomcat WebApp with embedded H2 : Database may be already in use: "Locked by another process"

Question

I'm working on a Maven Spring Boot web application using Hibernate on embedded H2 database. The application is deployed on Tomcat 8 application container using Maven goal tomcat7:redeploy from Maven Tomcat plugin (tomcat7-maven-plugin).

When I try to deploy this web application on Tomcat for the first time, I have no exception (after Tomcat restart).

But when I try to redeploy this web application on Tomcat, I have the following exception :

org.h2.jdbc.JdbcSQLException: Database may be already in use: "Locked by another process". Possible solutions: close all other connection(s); use the server mode; SQL statement: null/14cfb969fb93251ff134953c65dd1f05db2ecd34c6b [90020-145]

hibernate.cfg.xml

<?xml version='1.0' encoding='utf-8'?>

<!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">

<hibernate-configuration>

    <session-factory>

        <!-- Database connection settings -->
        <property name="connection.driver_class">org.h2.Driver</property>
        <property name="connection.url">jdbc:h2:file:d:/Profiles/mBaye/Developement/Run/spring-boot-web-seed-dev/db/springbootwebui;DB_CLOSE_DELAY=0;MVCC=TRUE</property>
        <property name="connection.username">sa</property>
        <property name="connection.password"/>

        <!-- JDBC connection pool (use the built-in) -->
        <property name="connection.pool_size">1</property>

        <!-- SQL dialect -->
        <property name="dialect">org.hibernate.dialect.H2Dialect</property>

        <!-- Disable the second-level cache  -->
        <property name="cache.provider_class">org.hibernate.cache.internal.NoCacheProvider</property>

        <!-- Echo all executed SQL to stdout -->
        <property name="show_sql">true</property>

        <!-- Drop and re-create the database schema on startup -->
        <!-- <property name="hbm2ddl.auto">create</property> -->
        <!-- Update the database schema on startup -->
        <property name="hbm2ddl.auto">update</property>

        <mapping resource="app/Greeting.hbm.xml"/>

    </session-factory>

</hibernate-configuration>

GreetingController.java

@Controller
public class GreetingController {

    private static Logger logger ;

    // A SessionFactory is set up once for an application
    private static final SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory();

    [...]

    private Greeting saveGreeting(Greeting greeting) {

        logger.info(new StringBuilder("greeting=").append(greeting.toString()).toString());

        Session session = null;
        Greeting ret = null;

        try {
            session = sessionFactory.openSession();
            session.beginTransaction();
            session.save( greeting );
            session.getTransaction().commit();
            // Return result
            ret = greeting ;
        } catch (Exception e) {
            logger.log(Level.SEVERE, new StringBuilder("Failed to save ").append(greeting.toString()).toString(), e);
        } finally {
            session.close();
        }

        if (ret != null) {
            logger.info(new StringBuilder("ret=").append(ret.toString()).toString());   
        } else {
            logger.info(new StringBuilder("ret=null").toString());
        }

        return ret ;
    }

    [...]
}

I read on other subjects that the database connections are closed automatically when the VM exits correctly (source: What is the proper way to close H2?)

I supposed, as the application is deployed on Tomcat, the database connections are hold by Tomcat.

I'd like to find a proper way to close all the database connections on Tomcat redeployment.

Thanks in advance.

Answer 1

Closing the connection also worked for me, had multiple connections open without realizing.

Answer 2

I finally found a solution ! :)

I changed the settings of the H2 database connection URL to :

<property name="connection.url">jdbc:h2:file:d:/Profiles/mBaye/Developement/Run/spring-boot-web-seed-dev/db/springbootwebui;MVCC=TRUE;DB_CLOSE_ON_EXIT=TRUE;FILE_LOCK=NO</property>

hibernate.cfg.xml

<?xml version='1.0' encoding='utf-8'?>

<!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">

<hibernate-configuration>

    <session-factory>

        <!-- Database connection settings -->
        <property name="connection.driver_class">org.h2.Driver</property>
        <property name="connection.url">jdbc:h2:file:d:/Profiles/mBaye/Developement/Run/spring-boot-web-seed-dev/db/springbootwebui;MVCC=TRUE;DB_CLOSE_ON_EXIT=TRUE;FILE_LOCK=NO</property>
        <property name="connection.username">sa</property>
        <property name="connection.password"/>

        <!-- JDBC connection pool (use the built-in) -->
        <property name="connection.pool_size">1</property>

        <!-- SQL dialect -->
        <property name="dialect">org.hibernate.dialect.H2Dialect</property>

        <!-- Disable the second-level cache  -->
        <property name="cache.provider_class">org.hibernate.cache.internal.NoCacheProvider</property>

        <!-- Echo all executed SQL to stdout -->
        <property name="show_sql">true</property>

        <!-- Drop and re-create the database schema on startup -->
        <!-- <property name="hbm2ddl.auto">create</property> -->
        <!-- Update the database schema on startup -->
        <property name="hbm2ddl.auto">update</property>

        <mapping resource="app/Greeting.hbm.xml"/>

    </session-factory>

</hibernate-configuration>

I'm not sure this is the best solution but it works.

Answer 3

H2 closes the Database when all connections are closed to it. Closing all connections from the connectionpool works for me.