Getting 'java.sql.SQLException: com.mysql.jdbc.Driver' with grails run-app (when BuildConfig.groovy doesn't need to be recompiled) - mysql

Question

I've upgraded my grails application from 1.3.9 to 2.2.3 and then to 2.3.3. I read the release and upgrade notes for 1.3.9->2.2.3 and then from 2.2.3->2.3.3
I am using OpenJDK 6, Jetty 6 and the plugin jetty 1.1, MySQL 5.5 and I have the connector library under lib
Now my issue is if I run grails clean and then grails run-app the application runs without any problems but if I stop it and run grails run-app again I get a gigantic error (see here: http://pastebin.com/36MpXhir)
I also found that changing something like adding a space somewhere in BuildConfig.groovy (anything that makes it be recompiled) makes the application run normally.
Looking at the stacktrace the first thing that puzzles me is
[02.12.13 16:13:59.919] [main] pool.ConnectionPool Unable to create initial connections of pool.
java.sql.SQLException: com.mysql.jdbc.Driver
at org.apache.tomcat.jdbc.pool.PooledConnection.connectUsingDriver(PooledConnection.java:254)
at org.apache.tomcat.jdbc.pool.PooledConnection.connect(PooledConnection.java:182)
at org.apache.tomcat.jdbc.pool.ConnectionPool.createConnection(ConnectionPool.java:701)
at org.apache.tomcat.jdbc.pool.ConnectionPool.borrowConnection(ConnectionPool.java:635)
at org.apache.tomcat.jdbc.pool.ConnectionPool.init(ConnectionPool.java:486)
at org.apache.tomcat.jdbc.pool.ConnectionPool.<init>(ConnectionPool.java:144)
at org.apache.tomcat.jdbc.pool.DataSourceProxy.pCreatePool(DataSourceProxy.java:116)
at org.apache.tomcat.jdbc.pool.DataSourceProxy.createPool(DataSourceProxy.java:103)
at org.apache.tomcat.jdbc.pool.DataSourceProxy.getConnection(DataSourceProxy.java:127)
at org.springframework.jdbc.datasource.LazyConnectionDataSourceProxy.afterPropertiesSet(LazyConnectionDataSourceProxy.java:162)
There are references to org.apache.tomcat even though I'm using jetty (and removed tomcat from BuildConfig.groovy).
Did anyone else encounter such a problem?

Answer 1

Don't put jar files in the lib directory if they're available in a public Maven repo. It's far better to download jars once and keep them in a local cache, and reuse them as needed.
The MySQL driver is used as the commented-out example in the generated BuildConfig.groovy - just un-comment it :) You might want to bump up the version to the latest, e.g.
dependencies {
runtime 'mysql:mysql-connector-java:5.1.27'
}
This is a good site for finding Maven artifacts: http://mvnrepository.com/artifact/mysql/mysql-connector-java
If you do have a jar that's not in a Maven repo (e.g. one with shared code at your company) then you can put it in the lib directory, but it's not auto-discovered. Run grails compile --refresh-dependencies to get it added to the classpath.

Answer 2

For me same error has occurred while running the Grails Application.Then I debug and view the code history of my code which was committed recently.
From that I found the issue that was:
Inside the controller file I send the instance with-out properly
Eg:
**def list=[personInstance.]---> error occurred.**
**render list as JSON**
Then I correct my mistake-->clean the app --> run the app
Now its working fine.