JPA + MySQL: After Timeout --> use a local Connection - mysql

Question

as our connection is very unstable we have decided to switch to our local read-only database if a query times out.
But here is my problem: I do not get an exception when javax.persistence tries to query:
// Attribute
EntityManagerFactory entityManagerFactory;
EntityManager manager;
entityManagerFactory = Persistence
.createEntityManagerFactory("org.hibernate.tutorial.jpa");
manager = entityManagerFactory.createEntityManager();
try {
Query query = manager.createQuery(String.format(
"SELECT u FROM User u WHERE u.id = '%s'", 116));
User user = (User) query.getSingleResult();
manager.refresh(user);
System.out.println(user.getUsername());
} catch (org.hibernate.QueryTimeoutException ex) {
throw new QueryTimeoutException("timeout");
}
}
This is just a test to demonstrate my problem.
What am I missing?
Mysql: mysql-connector-java-5.1.16-bin.jar
JPA: javax.persistence_2.0.3.v201010191057.jar
Hibernate:
115 [main] INFO org.hibernate.annotations.common.Version - Hibernate Commons Annotations 3.2.0.Final
124 [main] INFO org.hibernate.cfg.Environment - Hibernate 3.6.7.Final
126 [main] INFO org.hibernate.cfg.Environment - hibernate.properties not found
129 [main] INFO org.hibernate.cfg.Environment - Bytecode provider name : javassist
132 [main] INFO org.hibernate.cfg.Environment - using JDK 1.4 java.sql.Timestamp handling
208 [main] INFO org.hibernate.ejb.Version - Hibernate EntityManager 3.6.7.Final
persistence.xml:
<properties>
<property name="hibernate.hbm2ddl.auto" value="valide"/>
<property name="hibernate.connection.url" value="jdbc:mysql:///database?zeroDateTimeBehavior=convertToNull"/>
<property name="hibernate.connection.username" value="user"/>
<property name="hibernate.connection.password" value="pass"/>
<property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver"/>
<property name="javax.persistence.query.timeout" value="1"/>
<property name="dialect" value="org.hibernate.dialect.MySQLDialect"/>
</properties>
Thank you
Tobias

Answer 1

Solution:
Class.forName("com.mysql.jdbc.Driver");
connection = DriverManager.getConnection("jdbc:mysql://server/database", "user", "pass");
Every time I want to start a query I test if the Connection is alive:
if (connection.isValid(1)) {
return true;
} else {
throw new NoConnectionException();

Answer 2

You may not be seeing a timeout because some DBs don't support that feature.
"javax.persistence.query.timeout query timeout in milliseconds
(Integer or String), this is a hint used by Hibernate but requires
support by your underlying database."
See http://docs.jboss.org/hibernate/entitymanager/3.6/reference/en/html/configuration.html for more details.
I'd be inclined to switch to the read only all the time if you can't guarantee a reliable connection.