SQLException w/ Tomcat 7.0 JDBC connection pool and MySql

Question

I'm trying to use the new Tomcat 7.0 JDBC connection pool and MySql. It says here that you can drop the latest tomcat-jdbc.jar into your tomcat/lib directory in a Tomcat 6.0 environment, and that's what I've done.

I'm using Spring to initialize and instantiate the DataSource per examples around the web:

<bean id="myDataSource" class="org.apache.tomcat.jdbc.pool.DataSource" destroy-method="close" 
p:driverClassName="${driver_class}"
p:url="${url}"
p:username="${username?root}"
p:password="${password}"
p:initialSize="10"
p:initSQL="SELECT DTS FROM DT_TM_TS FOR READ ONLY WITH UR"
p:minIdle="10"
p:maxIdle="100"
p:maxActive="100"
p:maxWait="6000"
p:jmxEnabled="true"
p:jdbcInterceptors="org.apache.tomcat.jdbc.pool.interceptor.ConnectionState;org.apache.tomcat.jdbc.pool.interceptor.StatementFinalizer"
p:removeAbandoned="true"
p:removeAbandonedTimeout="60"
p:logAbandoned="true"
p:testOnBorrow="true"
p:testOnReturn="false"
p:testWhileIdle="false"
p:useEquals="false"
p:fairQueue="false"
p:timeBetweenEvictionRunsMillis="30000"
p:minEvictableIdleTimeMillis="30000"
p:validationInterval="1800000"
p:validationQuery="SELECT DTS FROM DT_TM_TS FOR READ ONLY WITH UR"
/>   

However when I try to connect to the db it throws this exception:

java.sql.SQLException: "com.mysql.jdbc.Driver"
    at org.apache.tomcat.jdbc.pool.PooledConnection.connectUsingDriver(PooledConnection.java:243)
    at org.apache.tomcat.jdbc.pool.PooledConnection.connect(PooledConnection.java:176)
    at org.apache.tomcat.jdbc.pool.ConnectionPool.createConnection(ConnectionPool.java:647)
    at org.apache.tomcat.jdbc.pool.ConnectionPool.borrowConnection(ConnectionPool.java:589)
    at org.apache.tomcat.jdbc.pool.ConnectionPool.init(ConnectionPool.java:452)
    at org.apache.tomcat.jdbc.pool.ConnectionPool.<init>(ConnectionPool.java:130)
    at org.apache.tomcat.jdbc.pool.DataSourceProxy.createPool(DataSourceProxy.java:99)
    at org.apache.tomcat.jdbc.pool.DataSourceProxy.getConnection(DataSourceProxy.java:110)
    at org.hibernate.ejb.connection.InjectedDataSourceConnectionProvider.getConnection(InjectedDataSourceConnectionProvider.java:46)
    at org.hibernate.cfg.SettingsFactory.buildSettings(SettingsFactory.java:111)
    at org.hibernate.cfg.Configuration.buildSettings(Configuration.java:2101)
    at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1325)
    at org.hibernate.cfg.AnnotationConfiguration.buildSessionFactory(AnnotationConfiguration.java:867)
    at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:669)
    at org.hibernate.ejb.HibernatePersistence.createContainerEntityManagerFactory(HibernatePersistence.java:132)
    at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:225)
    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.afterPropertiesSet(AbstractEntityManagerFactoryBean.java:308)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1477)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1417)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:519)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:456)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:291)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:288)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:190)
    at org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor.findDefaultEntityManagerFactory(PersistenceAnnotationBeanPostProcessor.java:529)
    at org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor.findEntityManagerFactory(PersistenceAnnotationBeanPostProcessor.java:495)
    at org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor$PersistenceElement.resolveEntityManager(PersistenceAnnotationBeanPostProcessor.java:656)
    at org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor$PersistenceElement.getResourceToInject(PersistenceAnnotationBeanPostProcessor.java:629)
    at org.springframework.beans.factory.annotation.InjectionMetadata$InjectedElement.inject(InjectionMetadata.java:147)
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:84)
    at org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor.postProcessPropertyValues(PersistenceAnnotationBeanPostProcessor.java:338)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1074)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:517)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:456)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:291)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:288)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:190)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:580)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:895)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:425)
    at org.springframework.web.context.ContextLoader.createWebApplicationContext(ContextLoader.java:276)
    at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:197)
    at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:47)
    at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4135)
    at org.apache.catalina.core.StandardContext.start(StandardContext.java:4630)
    at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045)
    at org.apache.catalina.core.StandardHost.start(StandardHost.java:785)
    at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045)
    at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:445)
    at org.apache.catalina.core.StandardService.start(StandardService.java:519)
    at org.apache.catalina.core.StandardServer.start(StandardServer.java:710)
    at org.apache.catalina.startup.Catalina.start(Catalina.java:581)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:289)
    at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:414)
Caused by: java.lang.ClassNotFoundException: "com.mysql.jdbc.Driver"
    at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:248)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:247)
    at org.apache.tomcat.jdbc.pool.PooledConnection.connectUsingDriver(PooledConnection.java:236)
    ... 59 more

I've got mysql-connector-java-5.1.13-bin.jar in both the webapp WEB-INF/lib and tomcat/lib. I can connect fine specifying the driver details in persistence.xml (no DataSource/connection pooling).

Answer 1

There is actually a very simple workaround with Spring. Instead of having the Tomcat connection pool create the database connection and fail because of class loader shenanigans, let Spring create it and pass a reference to the connection pool.

<!-- Data source template for use in the connection pool. -->
<bean id="dataSourceTemplate" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
    <property name="driverClassName" value="${jdbc.driver}" />
    <property name="url" value="${jdbc.url}" />
    <property name="username" value="${jdbc.username}" />
    <property name="password" value="${jdbc.password}" />
</bean>

<!-- Connection pool as data source. -->
<bean id="dataSource" class="org.apache.tomcat.jdbc.pool.DataSource" destroy-method="close">
    <!-- Refer to a separately created bean as a data source template to work around a quirk of Tomcat's class loader. -->
    <property name="dataSource" ref="dataSourceTemplate" />
    ...
</bean>

Then the connection pool will actually use the database connection as a template for creating as many additional connections as it needs.

The best part is that you don't have to mess with tomcat/lib, which you may not even have access to.