Question

I’m using Grails 2.0, and I’m having trouble getting the code to recognize an external library. Specifically the MySQL Driver.

Basically the trouble happens whenever I try to change my DataSource from HSQLDB to MySql. I downloaded the connector jar (5.0.8) and put it in the (project)/lib directory. I’ve verified that the com.mysql.jdbc.Driver.class file is located in the .jar.

Every time I try to run the app I get the error:

Caused by ClassNotFoundException: com.mysql.jdbc.Driver

Any help is greatly appreciated.

dataSource {
    pooled = true
    //driverClassName = "org.h2.Driver"
    //username = "sa"
    //password = ""
    driverClassName = "com.mysql.jdbc.Driver"
    username = "bob"
    password = "password"
}
hibernate {
    cache.use_second_level_cache = true
    cache.use_query_cache = true
    cache.region.factory_class = 'net.sf.ehcache.hibernate.EhCacheRegionFactory'
}
// environment specific settings
environments {
    development {
        dataSource {
            //dbCreate = "create-drop" // one of 'create', 'create-drop', 'update', 'validate', ''
            //url = "jdbc:h2:mem:devDb;MVCC=TRUE"
            dbCreate = "update" // one of 'create', 'create-drop', 'update', 'validate', ''
            url = "jdbc:mysql://localhost:3306/tekevent"
        }
    }
    test {
        dataSource {
            dbCreate = "create-drop"
            url = "jdbc:h2:mem:testDb;MVCC=TRUE"
        }
    }
    production {
        dataSource {
            dbCreate = "update"
            url = "jdbc:h2:prodDb;MVCC=TRUE"
            pooled = true
            properties {
               maxActive = -1
               minEvictableIdleTimeMillis=1800000
               timeBetweenEvictionRunsMillis=1800000
               numTestsPerEvictionRun=3
               testOnBorrow=true
               testWhileIdle=true
               testOnReturn=true
               validationQuery="SELECT 1"
            }
        }
    }
}

Answer 1

Delete the jar and use a dependency declaration in BuildConfig.groovy instead. Rather than having multiple copies of many jars, it’s far better to download each once and cache them in your Ivy cache and reference them from there.

BuildConfig.groovy has an example for MySQL already; just uncomment it and update the version if needed. Also make sure that the mavenCentral() repository is uncommented:

repositories {
    ...
    mavenCentral()
}

dependencies {
   ...
   runtime 'mysql:mysql-connector-java:5.1.16'
}