Overriding MVC Commands

MVC Commands are used to break up the controller layer of Liferay MVC applications into smaller, more digestible code chunks.

Sometimes you’ll want to override an MVC command, whether it’s in a Liferay application or another Liferay MVC application whose source code you don’t own. Since MVC commands are components registered in the OSGi runtime, you can simply publish your own customization of the component, give it a higher service ranking, and deploy it.

All existing components that reference the original MVC command service component (using a greedy reference policy) switch to reference your new one. Any existing reluctant references to the original command must be configured to reference the new one. Once they’re configured with the new service component, their JSP’s command URLs invoke the new custom MVC command.

Here are the customization options available for each Liferay MVC Command type:

• MVCActionCommand: Add logic
• MVCRenderCommand:
  • Add logic
  • Redirect to a different JSP
• MVCResourceCommand: Add logic

These tutorials demonstrate each MVC command customization option. Since the steps for adding logic are generally the same across MVC command types, start with adding logic.