Cannot load JDBC driver class 'com.mysql.jdbc.GoogleDriver'

Question

I am facing a very bizarre problem where my App Engine server can't load its Cloud SQL's GoogleDriver, here's the error (It happens right after I run "mvn appengine:update").

org.springframework.transaction.CannotCreateTransactionException: Could not open Hibernate Session for transaction; nested exception is org.hibernate.exception.GenericJDBCException: Cannot open connection
        at org.springframework.orm.hibernate3.HibernateTransactionManager.doBegin(HibernateTransactionManager.java:596)
        ...
Caused by: org.apache.commons.dbcp.SQLNestedException: Cannot load JDBC driver class 'com.mysql.jdbc.GoogleDriver'
        at org.apache.commons.dbcp.BasicDataSource.createConnectionFactory(BasicDataSource.java:1429)
        at org.apache.commons.dbcp.BasicDataSource.createDataSource(BasicDataSource.java:1371)
        at org.apache.commons.dbcp.BasicDataSource.getConnection(BasicDataSource.java:1044)
        at org.springframework.orm.hibernate3.LocalDataSourceConnectionProvider.getConnection(LocalDataSourceConnectionProvider.java:81)
        at org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:446)
        ... 48 more
Caused by: java.lang.ClassNotFoundException: com.mysql.jdbc.GoogleDriver

appengine.properties

################### MySQL Configuration - Google Cloud App Engine ##########################
jdbc.driverClassName=com.mysql.jdbc.GoogleDriver
jdbc.url=jdbc:google:mysql://mytestapp:testdb?user=someuser
jdbc.username=someuser
jdbc.password=******
jdbc.dialect=org.hibernate.dialect.MySQLDialect

In my Spring context file I have:

<context:property-placeholder location="classpath:appengine.properties" />
<bean
    id="dataSource"
    class="org.apache.commons.dbcp.BasicDataSource"
    destroy-method="close" >

    <property
        name="driverClassName"
        value="${jdbc.driverClassName}" />
    <property
        name="url"
        value="${jdbc.url}" />
    ...

Any ideas?

==

Just to confirm, I had already configured my appengine-web.xml and it doesn't help at all:

<?xml version="1.0" encoding="utf-8"?>
<appengine-web-app xmlns="http://appengine.google.com/ns/1.0">
    <application>mytestapp</application>
    <version>1</version>
    <threadsafe>true</threadsafe>
    <sessions-enabled>true</sessions-enabled>

    <system-properties>
        <property name="java.util.logging.config.file" value="WEB-INF/logging.properties"/>
    </system-properties>

    <use-google-connector-j>true</use-google-connector-j>
</appengine-web-app>

--

I couldn't move forward due to some incompatibility between hibernate jar versions so I kept trying through the actual release pipeline (Jenkins + Maven + build + test + deploy), I had to add the Compute Engine VM's IP address to the list of authorized IPs of the Cloud SQL Instance in order to run my unit tests and deploy it to the application (but, if I keep this approach, I can only use the MySQL driver and URL instead of the GoogleDriver and URL. So this is getting tricky...).

I have these properties in a Production.properties file that is loaded by my Spring MVC config file:

################### MySQL Configuration - Google Cloud App Engine ##########################
jdbc.driverClassName=com.mysql.jdbc.GoogleDriver
jdbc.url=jdbc:google:mysql://*******testapp:testsqldb?user=root
jdbc.username=root
jdbc.password=*****
jdbc.dialect=org.hibernate.dialect.MySQLDialect

Is there an easy way to dynamically switch between external and GAE Cloud SQL connection details without using this approach?

if (SystemProperty.environment.value() ==
SystemProperty.Environment.Value.Production) {
    // Connecting from App Engine.

Any ideas?

Answer 1

• The class is not automatically available in the App Engine runtime. You must enable it by adding <use-google-connector-j>true</use-google-connector-j> to your appengine-web.xml. This is documented at: https://cloud.google.com/appengine/docs/java/cloud-sql/#enable_connector_j

Edited to add (from comments below):

• Also, when connecting to Cloud SQL from GAE you should leave the password field empty.
• You should also make sure that if your code is running outside GAE (eg on your workstation, on GCE, on a Jenkins build) it uses stock MySQL connector as the Google connector is only available on GAE.
• You might also want too look into using the stock MySQL driver, which works both from GAE and other connections. There is a demo of this at https://github.com/GoogleCloudPlatform/appengine-cloudsql-native-mysql-hibernate-jpa-demo-java