PortletMVC4Spring

PortletMVC4Spring is a way to develop portlets using the Spring Framework and the Model View Controller (MVC) pattern. While the Spring Framework supports developing servlet-based web applications using Spring Web MVC, PortletMVC4Spring supports developing portlet-based applications using MVC. You can build Spring Framework Liferay DXP portlets with features like these:

• Inversion of control (IoC) / dependency injection (DI)
• Annotations
• Security
• Binding and validation
• Multi-part file upload
• … and more

You’ll learn these things about PortletMVC4Spring:

• Developing a Portlet Using PortletMVC4Spring: Demonstrates creating and deploying a portlet using PortletMVC4Spring.

• Annotation-based Controller Development: Shows how to implement controllers using plain old Java objects (POJOs) and annotations.

Background: The PortletMVC4Spring project began as Spring Portlet MVC and was part of the Spring Framework. When the project was pruned from version 5.0.x of the Spring Framework under SPR-14129, it became necessary to fork and rename the project. This made it possible to improve and maintain the project for compatibility with the latest versions of the Spring Framework and the Portlet API.

Liferay adopted Spring Portlet MVC in March of 2019 and the project was renamed to PortletMVC4Spring.

If you’re familiar with Spring Web MVC, it’s helpful to compare it with PortletMVC4Spring. Portlet workflow differs from servlet workflow because a request to the portlet can have two distinct phases: the ACTION_PHASE and the RENDER_PHASE. The ACTION_PHASE is executed only once and is where any back-end changes or actions occur, such as making changes in a database. The RENDER_PHASE presents the portlet’s content to the user each time the display is refreshed. Thus for a single request, the ACTION_PHASE is executed only once, but the RENDER_PHASE may be executed multiple times. This provides (and requires) a clean separation between the activities that modify the system’s persistent state and the activities that generate content. The Portlet 2.0 Specification added two more phases: The event phase and the resource phase, both of which are supported by annotation-driven dispatching.

PortletMVC4Spring provides annotations that support requests from the render, action, event, and resource serving portlet phases; Spring Web MVC provides only a @RequestMapping annotation. Where a Spring Web MVC controller might have a single handler method annotated with @RequestMapping, an equivalent PortletMVC4Spring controller might have multiple handler methods, each using one of the phase annotations: @ActionMapping, @EventMapping, @RenderMapping, or @ResourceMapping.

The PortletMVC4Spring framework uses a DispatcherPortlet that dispatches requests to handlers, with configurable handler mappings and view resolution, just as the DispatcherServlet in the web framework does.

Note: For more information on portlets, portlet specifications, and how portlets differ from servlets, see Portlets.

Liferay also provides full-featured sample portlets that demonstrate using JSP and Thymeleaf view templates. They exercise many features that form-based portlet applications typically require.

Figure 1: This PortletMVC4Spring portlet enables users to enter job applications. It uses the Spring features mentioned above and handles requests from multiple portlet phases.

The samples are available here:

Source Code	Maven Central
applicant-jsp-portlet	com.liferay.portletmvc4spring.demo.applicant.jsp.portlet.war
applicant-thymeleaf-portlet	com.liferay.portletmvc4spring.demo.applicant.thymeleaf.portlet.war

Now that you have a basic understanding of PortletMVC4Spring portlets and how they compare to Spring Web MVC applications, it’s time to develop a PortletMVC4Spring portlet.