on :start do
verifyParametersAndInitialize()
end

callback options:

1. :before, triggered before a task is invoked
2. :after, triggered after a task is invoked
3. :start, triggered before a top-level task is invoked via the command-line
4. :finish, triggered when a top-level task completes
5. :load, triggered after all recipes have loaded
6. :exit, triggered after all tasks have completed

Migrations are a beautiful way to properly version, co-ordinate and apply the changes you need to your various database environments.  I never knew of a way to do this in a non-rails environment, until now. Step in AutoPatch.

Some alternatives to AutoPatch exist such as migrate4j and Liquibase. Each with their own flavor of how to tackle the problem. AutoPatch was the winner for me as you don’t have to write your migrations in some custom DSL (xml in the case of Liquibase, or java for migrate4j). Our existing .sql scripts worked just fine!

Our shop is currently using Capistrano for deployments. Blending Autopatch with Capistrano was relatively straightforward. Below are two sample tasks that can be added to facilitate AutoPatch’s cmd line info and migrate calls.

desc "Display database migration levels."
task :dbinfo do
cmdAPClasspath = "#{deployDir}/applications/database/lib/oracle/ojdbc14_g.jar" \
+ ":#{deployDir}/dist/prepare/database" \
+ ":#{deployDir}/lib/java/tk-autopatch-1.2-b-cvs.jar" \
+ ":#{deployDir}/lib/java/log4j-1.2.8.jar" \
+ ":#{deployDir}/lib/java/commons-logging-1.0.3.jar" \
+ ":#{deployDir}/lib/java/commons-collections-3.2.1.jar" \
+ ":#{deployDir}/lib/java/commons-lang-2.2.jar" \
+ ":#{deployDir}/lib/java/tk-util-1.1.2.jar"
cmdAPPatchInfo = "java -cp #{cmdAPClasspath} " \
+ "com.tacitknowledge.util.migration.jdbc.MigrationInformation #{systemName}"
system(cmdAPPatchInfo)
end

desc "Apply database migrations."
task :dbmigrate do
cmdAPClasspath = "#{deployDir}/applications/database/lib/oracle/ojdbc14_g.jar" \
+ ":#{deployDir}/dist/prepare/database" \
+ ":#{deployDir}/lib/java/tk-autopatch-1.2-b-cvs.jar" \
+ ":#{deployDir}/lib/java/log4j-1.2.8.jar" \
+ ":#{deployDir}/lib/java/commons-logging-1.0.3.jar" \
+ ":#{deployDir}/lib/java/commons-collections-3.2.1.jar" \
+ ":#{deployDir}/lib/java/commons-lang-2.2.jar" \
+ ":#{deployDir}/lib/java/tk-util-1.1.2.jar"
cmdAPPatchInfo = "java -cp #{cmdAPClasspath} " \
+ "com.tacitknowledge.util.migration.jdbc.StandaloneMigrationLauncher #{systemName}"
system(cmdAPPatchInfo)
end

<project name="foo" basedir="." default="usage">

...

<target name="usage">
        <java classname="org.apache.tools.ant.Main">
            <arg value="-projecthelp"/>
            <classpath>
                <pathelement location="${lib.dir}/ant/ant.jar"/>
                <pathelement location="${lib.dir}/ant/ant-launcher.jar"/>
                <pathelement location="${lib.dir}/ant/xerces_2.8.0.jar"/>
            </classpath>
        </java>
    </target>

...

</project>