Tuesday, October 10, 2017

Liferay 7 / DXP Modularity Introduction

Liferay 7 /DXP is new release from Liferay Inc. Liferay 7 / DXP came up with new architecture based development that is OSGi.

As we know OSGi (Open Services Gateway Initiative) is Dynamic Component Development for Java platform. Its modular framework, where we can compose the application into several module and the modules communicate each other.  Liferay 7 / DXP have OSGi support so we can develop liferay applications as OSGi modules.  Modularity is interesting feature and have many capabilities to make application into several modules.

Follow the bellow articles to know more about OSGi

Interesting features of OSGi

Reduce the complexity and make the application sampler
Easy Deployment of applications
Reasonability of the components and modules
Easy version management
Cross platform support we can run anywhere
Widely used platform now a days.

When we consider all above interesting features OSGi promising platform to deliver many interesting capabilities.

Liferay 7 / DXP have used OSGi modularity features to build and develop the Liferay 7/ DXPApplications.

OSGi specification available in two popular implementations such as Apache Felix and Eclipse Equinox.

Liferay 7 have used both implementation capabilities to strengthen the Liferay Modular Application development.

Traditional Web application development have application servers, which runs the web applications. It means, we will develop applications based on web application standards using some J2EE Web application frameworks. We will package these applications as WAR files and deploy into the Application Servers. This is basic web application development and runs the applications.

Whereas OSGi environment have OSGi container to run the OSGi applications.
OSGi applications can call it as OSGi bundles. OSGi bundles is JAR file, which consist of Java and other configuration files. These bundle developments follow the OSGi specification so that it can run in OSGi containers.

When we are talking about OSGi bundles, we use Component terminology many times.  Component is piece of code, which runs independently and deliver some reusable feature or task.

OSGi application composed of several components and these components are talk each other and all together deliver complex feature or task.

We package the group of components as bundle. Bundles is an OSGi application based on OSGi specification and runs in OSGi containers. Interesting feature of OSGi is application composed into small components.  

OSGi have other interesting artifact called OSGi Service Registry, which manage the component and its service registration and manage the references. OSGi component dependency management controlled via OSGi service registry. OSGi service registry implemented by OSGi Declarative Services and shorty we call it as DS.

We also have other implementation called Apache Blueprint, which is similar to DS.

Liferay 7 /DXP can use both implementation while develop Liferay Application Modules.

Structure of OSGi Module

As per OSGi module development, we have following pieces in the application.

Service API: Service API bundles container the all service interfaces

Service Provider: Service provider bundles provide the implementation for the interfaces which definer in the Service API

Service Client: It will consume the component services.

Liferay 7 / DXP module development follows the same structure while developing the Liferay 7/DXP application bundles.

Structure of a Modular App in Liferay 7 / DXP

As per OSGi, we can break the application into several bundles. Same way Liferay 7 / DXP have several bundles/modules.

The following are important parts or bundles in the Liferay 7 / DXP module development.


API contains all interfaces java classes. It is separated from implementation bundle.


Contains the service (business logic) and persistence implementations.


Web contains the presentation layer files such as HTML, JSP, CSS and JavaScript files.


Contains the tests. These are not included in the app for production.

Liferay Modular Architecture

Picture source form Liferay.com

Liferay 7/DXP have several layers in the architecture like Liferay Core, Foundation, and Web experience, Collaboration, Forms & Workflows and Independent Apps.

Liferay Core

Liferay Core consist of all core APIs and Liferay Kernel. Its basic components which will used by all other modules or layers in the Liferay portal.


This layer consist of Liferay building blocks implementation such as Users, Roles, Groups, Themes and Permission System.

Applications Layer

Liferay application layer separated with different group of modules and these all are independent apps separated from Liferay Core and Foundation. It uses the both Liferay Core and Foundation layer APIs and Its independent modules.

Liferay core and Foundation layers are packaged as WAR file deployed in the traditional application layer. Usually all these APIs and Implementations available in ROOT directory that deployed in Application server deployment directory.

Liferay independent Apps are made it as OSGi bundles, deployed in the OSGi container. All liferay bundles are found in OSGi directory of Liferay portal.

Liferay have provides the gateway which communicate with Liferay Core and Foundation layer to fulfill liferay application features.

Liferay 7 /DXP still support the plugins development and its deployment. This is a reason still we can see traditional application server. Liferay older versions migration to Liferay 7 / DXP possible through to keep traditional application server in the Liferay 7/DXP.

To customize or develop new features in Liferay 7/DXP, Developer follows the OSGi modularity specification to develop Liferay 7 / DXP apps.

Now all liferay applications possible through the OSGi bundles. Still some of the limitations for Liferay Themes, so we follows the Web based development for themes. Portlets, hooks can make it as OSGi bundles and themes can make it as WARs. Liferay 7 / DXP still support Plugins SDK so that we can develop liferay applications as plugin wars.

Liferay 7 / DXP suggested using OSGi Declarative Services (DS) framework to develop Liferay 7 application bundles. We can use Apache Blueprint framework as well.

Liferay have used Apache Gogo shell Command Line Interface to manage bundles, its means Activate/Deactivate Start/Stop bundles in the OSGi container. Bundles lifecycle controlled via Apache Gogo shell.

Interesting point is, we can disable/ enable Liferay features through Apache Gogo shell and we do not need to un-deploy or remove bundle from OSGi container. Just we can deactivate or activate is enough.

Liferay have provided good tools to develop Liferay 7/DXP modules. Follow the below articles to know more about Liferay 7/DXP Module Development. Follow below link to find more details about Liferay Application Development Tools



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