Scripting Ant tasks with BSF

Today I wrote a couple of custom Ant tasks in Groovy, using the Scriptdef optional task. I had never used scripting languages within Ant (nor was I familiar with task development for that matter), but it proved to be really quick and straightforward.

Here is a very simple example: I wanted to configure the load order for a Weblogic deployment, but it is not feasible with BEA's wldeploy task. The workaround is to do it programmatically through the JMX API:

<!-- Sets the load order on a Weblogic deployment -->
<scriptdef name="wlSetLoadOrder" language="groovy" classpath="${weblogic.home}/server/lib/weblogic.jar">
  <!-- The name of the deployment -->
  <attribute name="name" />
  <!-- The load order -->
  <attribute name="loadOrder" />
  <!-- The admin URL of the domain -->
  <attribute name="adminUrl" />
  <!-- A weblogic user with administration rights -->
  <attribute name="user" />
  <!-- The user's password -->
  <attribute name="password" />
  <![CDATA[
    import java.util.Hashtable
    import javax.naming.Context
    import javax.naming.InitialContext
    import weblogic.management.MBeanHome
    import weblogic.management.deploy.DeployerRuntime
    import weblogic.management.deploy.DeploymentData
    import org.apache.tools.ant.BuildException

    try {
      int loadOrder = Integer.parseInt(attributes["loadorder"])
      self.log("Configuring load order " + loadOrder + " for " + attributes["name"])

      // Connect to the MBean server
      def ctx = new InitialContext(new Hashtable(
        (Context.PROVIDER_URL) : attributes["adminurl"],
        (Context.INITIAL_CONTEXT_FACTORY) : "weblogic.jndi.WLInitialContextFactory",
        (Context.SECURITY_PRINCIPAL) : attributes["user"],
        (Context.SECURITY_CREDENTIALS) : attributes["password"]))
      def adminHome = ctx.lookup(MBeanHome.ADMIN_JNDI_NAME)

      // Lookup the deployment's ApplicationMBean
      def appMBean = adminHome.getMBean(attributes["name"], "Application")

      // Set the JMX attribute
      appMBean.setLoadOrder(loadOrder)
    } catch (NumberFormatException e) {
      throw new BuildException("Invalid value for loadOrder: " + attributes["loadorder"])
    }
  ]]>
</scriptdef>

This new task is unsurprisingly invoked like any regular Ant task:

<wlSetLoadOrder name="myKillerApp" loadorder="200"
  adminurl="t3://localhost:7001" user="admin" password="weblogic"
/>

Notes:

• this works for Weblogic 8.1. I have not tried with later versions, but it can probably be easily adapted.
  
• you will need to put the appropriate dependencies in Ant's classpath, namely: Groovy, Commons Logging and BSH. See this page.