在应用程序库中没有合适的jar驱动程序

Question

在Mule ESB 3.7.0 CE上我已经配置了一个C3P0连接:

<bean id="dbConnection"
    class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
    <property name="persistenceUnitName" value="${diap6.centraleurope.company}" />
    <property name="persistenceXmlLocation" value="${db.persistence.xml}" />
    <property name="jpaVendorAdapter">
        <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
            <property name="generateDdl" value="false" />
            <property name="showSql" value="${diap6.centraleurope.show_sql}" />
        </bean>
    </property>
    <property name="persistenceUnitPostProcessors">
        <list>
            <ref bean="entitiesCompanyLoader" />
        </list>
    </property>
    <property name="jpaProperties">
        <props>
            <prop key="hibernate.connection.provider_class">org.hibernate.connection.C3P0ConnectionProvider
            </prop>
            <prop key="hibernate.connection.driver_class">oracle.jdbc.OracleDriver</prop>
            <prop key="hibernate.connection.url">${diap6.centraleurope.url}</prop>
            <prop key="hibernate.connection.username">t6valce</prop>
            <prop key="hibernate.connection.password">t6valce</prop>
            <prop key="hibernate.hbm2ddl.auto">false</prop>
            <prop key="hibernate.show_sql">${diap6.centraleurope.show_sql}</prop>
            <prop key="hibernate.dialect">org.hibernate.dialect.Oracle9iDialect</prop>
            <prop key="hibernate.c3p0.acquire_increment">2</prop>
            <prop key="hibernate.c3p0.idle_test_period">60</prop>
            <prop key="hibernate.c3p0.timeout">15</prop>
            <prop key="hibernate.c3p0.max_size">10</prop>
            <prop key="hibernate.c3p0.max_statements">50</prop>
            <prop key="hibernate.c3p0.min_size">0</prop>
            <prop key="hibernate.c3p0.maxIdleTime">360</prop>
            <prop key="hibernate.c3p0.preferredTestQuery">SELECT 1 from dual</prop>
            <prop key="hibernate.c3p0.idleConnectionTestPeriod">30</prop>
            <prop key="hibernate.c3p0.acquireRetryDelay">1000</prop>
            <prop key="hibernate.connection.autoReconnect">true</prop>
            <prop key="hibernate.cache.use_second_level_cache">false</prop>
            <prop key="hibernate.cache.use_query_cache">false</prop>
            <prop key="hibernate.cache.region.factory_class">net.sf.ehcache.hibernate.SingletonEhCacheRegionFactory
            </prop>
        </props>
    </property>
</bean>

如果我把驱动类jar ojdbc6.jar放在apps/myapp/lib上，我在应用程序启动时得到这个错误:

    WARN  2015-10-16 11:26:01,691 [C3P0PooledConnectionPoolManager[identityToken->z8kfsx9ctrp0kk4mc5wl|456c58cd]-HelperThread-#0] com.mchange.v2.resourcepool.BasicResourcePool: com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask@13c79966 -- Acquisition Attempt Failed!!! Clearing pending acquires. While trying to acquire a needed new resource, we failed to succeed more than the maximum number of allowed acquisition attempts (30). Last acquisition attempt exception:
java.sql.SQLException: No suitable driver
        at java.sql.DriverManager.getDriver(DriverManager.java:315) ~[?:1.8.0_60]
        at com.mchange.v2.c3p0.DriverManagerDataSource.driver(DriverManagerDataSource.java:285) ~[c3p0-0.9.5.jar:0.9.5]
        at com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:175) ~[c3p0-0.9.5.jar:0.9.5]
        at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:220) ~[c3p0-0.9.5.jar:0.9.5]
        at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:206) ~[c3p0-0.9.5.jar:0.9.5]
        at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:200) ~[c3p0-0.9.5.jar:0.9.5]
        at com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1127) ~[c3p0-0.9.5.jar:0.9.5]
        at com.mchange.v2.resourcepool.BasicResourcePool.doAcquireAndDecrementPendingAcquiresWithinLockOnSuccess(BasicResourcePool.java:1114) ~[c3p0-0.9.5.jar:0.9.5]
        at com.mchange.v2.resourcepool.BasicResourcePool.access$800(BasicResourcePool.java:44) ~[c3p0-0.9.5.jar:0.9.5]
        at com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask.run(BasicResourcePool.java:1855) ~[c3p0-0.9.5.jar:0.9.5]
        at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:696) ~[mchange-commons-java-0.2.9.jar:0.2.9]

如果我把jar放到mule系统库:mule-standalone-3.7.0/lib/opt中，就会找到驱动程序，并且应用程序可以正常启动。

我更喜欢将驱动程序与应用程序捆绑在一起，但似乎不可能。你有什么解决办法吗?谢谢。

Answer 1

我认为这取决于类加载器问题。c3p0库在mule-standalone-3.7.0/lib/opt上，因此，当它调用java.sql.DriverManager.getDriver时，类加载器会检查mule上下文，而驱动程序是由应用程序级别的不同类加载器加载的。如果我把oracle驱动程序放在mule-standalone-3.7.0/lib/opt上，c3p0和oracle驱动程序都属于同一个类加载器，getDriver()方法工作得很好。