Groovy's Sql doesn't see a database driver class specified in "buildscripts"

I specified the PostgresQL driver in the "buildsscripts" closure, as in Example 39.4. "Declaring external dependencies for the build script"

buildscript {
repositories { mavenCentral() }
dependencies { classpath group: 'postgresql', name: 'postgresql', version: '8.4-701.jdbc4' }
}

Gradle -s prints

> 15:29:59-tk@tk:~/workspace/b-one-crm> gradle -s -b build.gradle.groovy deployDb
> :deployDb
>
> FAILURE: Build failed with an exception.
>
> * Where:
> Build file '/home/tk/workspace/b-one-crm/build.gradle.groovy' line: 100
>
> * What went wrong:
> Execution failed for task ':deployDb'.
> Cause: java.lang.ClassNotFoundException: org.postgresql.Driver
>
> * Try:
> Run with -S option to get the full (very verbose) stacktrace.
>
> * Exception is:
> org.gradle.api.tasks.LocationAwareTaskExecutionException: Build file '/home/tk/workspace/b-one-crm/build.gradle.groovy' line: 100
> Execution failed for task ':deployDb'.
> at org.gradle.api.internal.tasks.DefaultTaskExecuter.executeActions(DefaultTaskExecuter.java:63)
> at org.gradle.api.internal.tasks.DefaultTaskExecuter.execute(DefaultTaskExecuter.java:41)
> at org.gradle.api.internal.project.taskfactory.PostExecutionAnalysisTaskExecuter.execute(PostExecutionAnalysisTaskExecuter.java:32)
> at org.gradle.api.internal.project.taskfactory.ExecutionShortCircuitTaskExecuter.execute(ExecutionShortCircuitTaskExecuter.java:50)
> at org.gradle.api.internal.tasks.SkipTaskExecuter.doExecute(SkipTaskExecuter.java:57)
> at org.gradle.api.internal.tasks.SkipTaskExecuter.execute(SkipTaskExecuter.java:35)
> at org.gradle.api.internal.tasks.ExecuteAtMostOnceTaskExecuter.execute(ExecuteAtMostOnceTaskExecuter.java:32)
> at org.gradle.api.internal.AbstractTask.execute(AbstractTask.java:231)
> at org.gradle.execution.DefaultTaskGraphExecuter.executeTask(DefaultTaskGraphExecuter.java:167)
> at org.gradle.execution.DefaultTaskGraphExecuter.doExecute(DefaultTaskGraphExecuter.java:160)
> at org.gradle.execution.DefaultTaskGraphExecuter.execute(DefaultTaskGraphExecuter.java:78)
> at org.gradle.execution.TaskNameResolvingBuildExecuter.execute(TaskNameResolvingBuildExecuter.java:161)
> at org.gradle.execution.DelegatingBuildExecuter.execute(DelegatingBuildExecuter.java:54)
> at org.gradle.initialization.DefaultGradleLauncher.doBuildStages(DefaultGradleLauncher.java:153)
> at org.gradle.initialization.DefaultGradleLauncher.doBuild(DefaultGradleLauncher.java:107)
> at org.gradle.initialization.DefaultGradleLauncher.run(DefaultGradleLauncher.java:75)
> at org.gradle.launcher.Main.execute(Main.java:93)
> at org.gradle.launcher.Main.main(Main.java:42)
> at org.gradle.launcher.GradleMain.main(GradleMain.java:49)
> Caused by: org.codehaus.groovy.runtime.InvokerInvocationException: java.lang.ClassNotFoundException: org.postgresql.Driver
> at org.gradle.api.internal.AbstractTask$ClosureTaskAction.execute(AbstractTask.java:445)
> at org.gradle.api.internal.AbstractTask$ClosureTaskAction.execute(AbstractTask.java:432)
> at org.gradle.api.internal.tasks.DefaultTaskExecuter.executeActions(DefaultTaskExecuter.java:55)
> ... 18 common frames omitted
> Caused by: java.lang.ClassNotFoundException: org.postgresql.Driver
> at Db.lookupVersion(/home/tk/workspace/b-one-crm/build.gradle.groovy:100)
> at Db$lookupVersion.callCurrent(Unknown Source)
> at Db.<init>(/home/tk/workspace/b-one-crm/build.gradle.groovy:87)
> at build_gradle_groovy_efff0db1333cb234a677f1a67e718f98$_run_closure1_closure7.doCall(/home/tk/workspace/b-one-crm/build.gradle.groovy:25)
> at build_gradle_groovy_efff0db1333cb234a677f1a67e718f98$_run_closure1.doCall(/home/tk/workspace/b-one-crm/build.gradle.groovy:23)
> ... 21 common frames omitted
>
> BUILD FAILED
>
> Total time: 2.024 secs

The buildscript is pasted below

import groovy.sql.Sql
import java.text.*

mixin()

def dbHost = 'db.example.com'
def application = 'crm'

buildscript {
repositories { mavenCentral() } }
dependencies { classpath group: 'postgresql', name: 'postgresql', version: '8.4-701.jdbc4' }
}

task deployDb << {

def databaseVersions = new XmlSlurper().parse('database-versions.xml')
def dbProjectEl = databaseVersions.project.find { it.@name as String == application }

dbProjectEl.database.each { database ->

Db db = new Db(database, dbHost)

println "database-scripts/$db.name, db.appliedScript: $db.appliedScript, db.versionScript: $db.versionScript"

("database-scripts/$db.name" as File).listFiles().sort{ it.name }.each { script ->

if(script.name.endsWith('.sql') && db.appliedScript < script.name && script.name <= db.versionScript) {

println "Updating script $script"

ant.exec(executable: './x', failonerror: 'true') { arg(line: "$db.host $db.user $db.name $script") }

println "successfully deploy database script $script"
}
}
}
}

def mixin() {

Number.metaClass.format << { fmt -> new DecimalFormat(fmt).format(delegate) }

Date.metaClass.format << { fmt -> new SimpleDateFormat(fmt).format(delegate) }

File.metaClass.recurse << { Closure include, Closure action -> delegate.recurse(include, include, action) }

File.metaClass.recurse << { Closure includeDirs, Closure includeFiles, Closure action ->
if(delegate.directory && delegate.name != '.svn' && includeDirs(delegate)) {
delegate.eachFile { it.recurse(includeDirs, includeFiles, action) }
} else if(includeFiles(delegate)) { action(delegate) }
}
}

class Db {
String driver
String host
String port
String name
String user
String password
String url
String versionScript
String appliedScript

Db(db, host) {
this.driver = 'org.postgresql.Driver'
this.host = host
this.port = '5432'
this.password = 'redacted'
this.name = db.@name as String
this.user = extractUser(db)
this.url = "jdbc:postgresql://$host:$port/$name"
this.versionScript = "${new Integer(db.@version as String).format("0000")}.sql"
this.appliedScript = "${lookupVersion().format("0000")}.sql"
}

def extractUser(db) {
def result = db.@user as String
if(! result) { def split = (db.@name as String).split(/_/) result = split.length > 1 ? split[1] : split[0] }
return result
}

int lookupVersion() {
def Sql sql = Sql.newInstance(url, user, password, driver)
try { return sql.firstRow("SELECT version FROM version").version as int } catch(org.postgresql.util.PSQLException e) {
if(e.message == 'ERROR: relation "version" does not exist') { return 9999 }
throw e
}
}

}

See mailing list thread [gradle-user] Question about the buildscripts own dependencies - "buildscript" for more details.