'hibernate.dialect' must be set when no Connection available - spring

Question

I am trying to run a hello world for: Spring/Hibernate with HSQLDB and C3PO connection pool.
the same code works with mySQL (only with different dialect and driver)
I have run the database and I can connect to it with the swing GUI. But when I try to run my application, I am getting a start up error.
Here are the details:
1: the error -
INFO: Initializing Spring root WebApplicationContext
[ERROR] [pool-2-thread-1 05:20:08] (JDBCExceptionReporter.java:logExceptions:101) Connections could not be acquired from the underlying database!
[ERROR] [pool-2-thread-1 05:20:08] (ContextLoader.java:initWebApplicationContext:220) Context initialization failed
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sessionFactory' defined in ServletContext resource [/WEB-INF/hibernate-context.xml]: Invocation of init method failed; nested exception is org.hibernate.HibernateException: 'hibernate.dialect' must be set when no Connection avalable
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1420)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:519)
...
...
2: hibernate-context.xml -
<tx:annotation-driven transaction-manager="transactionManager" />
<bean id="sessionFactory" class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean">
<property name="dataSource" ref="dataSource" />
<property name="packagesToScan" value="com.gleeb.sample.model" />
<property name="hibernateProperties">
<props>
<!-- <prop key="dialect">org.hibernate.dialect.MySQL5InnoDBDialect</prop> -->
<prop key="dialect">org.hibernate.dialect.HSQLDialect</prop>
<prop key="show_sql">false</prop>
<prop key="hbm2ddl.auto">create</prop>
</props>
</property>
</bean>
<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource"
destroy-method="close" p:driverClass="org.hsqldb.jdbc.JDBCDriver"
p:jdbcUrl="jdbc:hsqldb:hsql://localhost/testdb" p:user="sa"
p:password="" p:acquireIncrement="5" p:idleConnectionTestPeriod="60"
p:maxPoolSize="100" p:maxStatements="50" p:minPoolSize="10" />
<!-- Declare a transaction manager -->
<bean id="transactionManager"
class="org.springframework.orm.hibernate3.HibernateTransactionManager"
p:sessionFactory-ref="sessionFactory" />

Answer 1

As far as I can tell, it is not possible to pass in the dialect as a value set on the hibernateProperties field of a Spring Session Factory, at least if you are also using the configLocation property on it.
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.dialect">org.hibernate.dialect.DB2Dialect</property>
<property name="hibernate.search.autoregister_listeners">false</property>
[etc...]
My relevant session factory context config:
<bean id="sessionFactory" class="org.springframework.orm.hibernate4.LocalSessionFactoryBean">
<property name="configLocation">
<value>classpath:hibernate.cfg.xml</value>
</property>
<property name="dataSource" ref="dataSource"/>
<property name="hibernateProperties">
<props>
<!--<prop key="hibernate.dialect">org.hibernate.dialect.DB2Dialect</prop>-->
<prop key="hibernate.show_sql">true</prop>
<prop key="hibernate.format_sql">true</prop>
<prop key="hibernate.generate_statistics">false</prop>
<prop key="hibernate.default_schema">xxx</prop>
</props>
</property>
</bean>
If I uncomment the dialect prop in the context file, and comment it out from in the hibernate.cfg.xml file I encounter the same exception as the OP:
Caused by: org.hibernate.HibernateException: Connection cannot be null when 'hibernate.dialect' not set
However if I run with the above configuration (commented out in the context file, uncommented in the hibernate.cfg.xml), it works, and I see the formatted hibernate SQL, showing that the other hibernate properties are being set by the context file.

Answer 2

I have session factory properties with hibernate. prefix.
<property name="hibernateProperties">
<value>
hibernate.dialect=org.hibernate.dialect.HSQLDialect
hibernate.hbm2ddl.auto=update
hibernate.show_sql=false
hibernate.format_sql=false
</value>
</property>