Hot Deploy Versus Auto Deploy

As you develop plugins you’ll want to deploy them to your test servers and as you finish developing plugins you’ll want to deploy them to your production servers. There are hot deploy and auto deploy options to use in deploying your plugins. Most people confuse the two concepts, believing them to be one and the same. In reality, Liferay has TWO completely separate and different concepts for them.

How, you say? We’re glad you asked! This tutorial gives you a brief synopsis of each deployment method. Go ahead and get started by learning about the hot deployment method.

Using Hot Deployment

The first deployment method you’ll explore is hot deployment. You may be familiar with hot deployment in the context of Java EE application servers. In summary, you place an application artifact (WAR or EAR) file into a specifically configured directory, your application server (Tomcat, WebSphere, WebLogic, etc.) picks up that artifact, deploys it within the application server, and starts the application.

This model works really well for development purposes, since a server restart is not required to view updates from your code changes. This model also works for single node production deployments.

However, this model completely breaks down when you deploy to a multi-node production deployment. In a multi-node environment, you have many more constraints to deal with, that require you to:

  • Ensure the application archive is available to all nodes
  • Ensure the application deploys successfully across all nodes, simultaneously

Most application servers solve these constraints by using a master/slave type of design: an admin server with multiple managed servers. When you hot deploy a plugin, you use the admin server’s user interface, or vendor console tool like Wsadmin, to add the archive, select which managed servers should deploy it, and start the application. Application server vendors often have different names and tools for these modes and tools:

  • JBoss “domain” mode
  • WebLogic “production” mode
  • WebSphere deployment manager
  • Tomcat FarmWarDeployer

These modes and tools reside completely outside of Liferay Portal and are strictly in the application server’s realm. However, Liferay piggybacks off the application server’s hot deploy capability and performs additional initialization after a given application starts (e.g., via javax.servlet.ServletContextListener mechanisms).

There are some specific Liferay capabilities that won’t work unless your application server has hot deployment capabilities. Specifically, hot deploying custom JSPs in hooks won’t work, because Liferay’s JSP hook overriding capabilities depend on the application server’s ability to:

  • Deploy based on an exploded portal WAR
  • Load changes to JSP files at runtime

Application servers running in “production” and “domain” modes cannot support these abilities, because in these deployment models, most servers don’t use exploded WARs. As such, these application servers don’t support JSP reloading/recompilation in these modes. Even for Tomcat, it’s generally advisable to deactivate JSP reloading for production deployments.

So what do you do if you use hooks to override Liferay JSPs AND you must use non-exploded WAR deployments? The answer is simple: inject a pre-processing stage as part of your build process. You deploy the hooks, allowing them to make changes to the portal WAR file. Then you rebundle the portal WAR file and deploy it using the application server’s deployment tools. Of course, you still need to deploy your hook as well, but you no longer need to worry about the JSP overrides not being loaded by your application server.

Hopefully this whets your appetite for doing hot deployments. Stay hungry, as it’s time to explore auto deployment next.

Using Auto Deployment

The Liferay auto deployment feature is a mostly optional feature that works in conjunction with the hot deployment capabilities of your application server. Where Liferay’s hot deploy leverages the hot deploy capabilities of your app server and performs additional initializations, auto deploy injects the required JAR files and descriptors into your application’s archive file. Executing ant deploy invokes both hot deployment and auto deployment tasks for your plugin.

So how does auto deployment work with Liferay plugins? Auto deployment completes the following tasks:

  1. Picks up a Liferay recognized archive (e.g., *-portlet.*, *-theme.*, *-web.*, *.lpkg)
  2. Injects required libraries (e.g., util-java.jar, util-taglib.jar)
  3. Injects dependent JAR files (specified in
  4. Injects required taglib descriptors (e.g., liferay-theme.tld)
  5. Injects required deployment descriptors (e.g., app server specific descriptors)
  6. Injects any missing Liferay specific deployment descriptors (e.g., liferay-portlet.xml)

By relying on auto deployment to complete these tasks automatically, you save time and you don’t even have to learn all of Liferay’s deployment descriptors. However, this feature is incompatible with application server farms and multi-node modes.

So now you’re probably wondering how to configure your application server in these situations? The answer is simple: Do not use the auto deployment method at runtime; use it at build time.

The Liferay Plugins SDK allows you to preprocess your archives and inject all the required elements. You therefore bypass the auto deployer at runtime. You simply need to call the following Ant task:

ant direct-deploy

The direct-deploy Ant task creates an exploded WAR from which you can easily create a WAR file. The location of the exploded WAR depends on the deployment directory of the application server you’ve configured in your Plugins SDK environment. See the Developing with the Plugins SDK tutorials for instructions on configuring the Plugins SDK for your app server. The Plugins SDK’s provides a default deployment directory value for each supported app server. But you can override the default value by specifying your desired value for the app.server.[type].deploy.dir (replace [type] with your app server type) in your build.[username].properties file.

If you choose not to use the Liferay Plugins SDK to do direct deployment, you can examine the build-common.xml file in the Plugins SDK to see how Liferay invokes the deployer tools.

Terrific! You now know the differences between hot deploy and auto deploy. Understanding what’s going on during the deployment of your plugins is crucial for troubleshooting anything that goes wrong, and can help you simplify your deployment process and make it more efficient.

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