Gradle: cannot execute sql, driver not found - gradle

Question

I have got the following gradle script. It results in No suitable driver found error which I found strange.
buildscript {
repositories{
maven {
url = 'http://localhost:8090/nexus/content/groups/public/'
}
}
dependencies {
classpath 'com.oracle:ojdbc6:11.2.0.4.0'
}
}
task sql << {
def url = 'jdbc:oracle:thin:#' + project.properties['db_hostname'] + ':' + project.properties['db_port'] + ':' + project.properties['db_sid']
println 'sql, db url:' + url
def driverName = 'oracle.jdbc.OracleDriver'
Class.forName(driverName).newInstance();
groovy.sql.Sql sql = groovy.sql.Sql.newInstance(
url,
project.properties['db_username'],
project.properties['db_password'],
driverName
)
}
The error is:
Tasks to be executed: [task ':sql']
:sql (Thread[main,5,main]) started.
:sql
Executing task ':sql' (up-to-date check took 0.0 secs) due to:
Task has not declared any outputs.
truncating, db url:jdbc:oracle:thin:#LOCALHOST:1521:orcl
:sql FAILED
:sql (Thread[main,5,main]) completed. Took 0.105 secs.
FAILURE: Build failed with an exception.
* Where:
Build file '/home/fran/projects/jua/build.gradle' line: 49
* What went wrong:
Execution failed for task ':sql'.
> No suitable driver found for jdbc:oracle:thin:#LOCALHOST:1521:orcl
* Try:
Run with --debug option to get more log output.

Answer 1

The driver jar is being loaded in a different classloader context than the Sql class. To fix it, try adding this:
// Add jars resolved by buildscript classpath configuration to the classloader which Sql will use
URLClassLoader loader = groovy.sql.Sql.class.classLoader
project.buildscript.configurations.classpath.each { File file ->
loader.addURL(file.toURL())
}
prior to the call to Sql.newInstance(). It will make all your classpath dependencies available to the Groovy classloader which loads the Sql class. The Class.forName() should not be neccesary.
See the discussion here for more information:
http://gradle.1045684.n5.nabble.com/using-jdbc-driver-in-a-task-fails-td1435189.html

Answer 2

For me that didn't work (Gradle 2.12).
But instead of performing:
Class.forName("org.h2.Driver")
I did:
groovy.sql.loadDriver("org.h2.Driver")
The Groovy Sql.loadDriver method does some nifty classloader stuff.

Answer 3

You should use something like this:
configurations {
db2database
}
buildscript {
dependencies {
classpath('com.ibm.db2:db2jcc4:10.5.5')//db2 driver for gradle task
}
}
dependencies {
db2database "com.ibm.db2:db2jcc4:10.5.5" //db2 driver for configuration
}
//load drivers for gradle tasks
configurations.db2database.each {
GroovyObject.class.classLoader.addURL(it.toURI().toURL())
}
....
Sql sql = Sql.newInstance(
envProps.getProperty('dbUri'),
envProps.getProperty('dbUsername'),
envProps.getProperty('dbPassword'),
envProps.getProperty('dbDriverClassName')
)
println sql.rows("SELECT * FROM TEST.TEST")