Liferay is open source portal which follow JSR 168
and JSR 286 standards.
Liferay development can be achieved from Plugins SDK
it is Standard Development Kit for liferay portal.
Liferay Portal already has more components apart
form that if we want add anything to existed liferay portal we need to develop
Plugins.
To develop Plugins liferay have given Standard Development
Kit i.e. called Plugins SDK.
Liferay Portal can categorize into following parts.
- Portal Kernel
- Portal Implementation
- Portal Services
Portal
Kernel:
Portal Kernel is set of java classes and interfaces
which is core components of liferay portal. This kernel can available to outside
of portal. From this we can add or develop new things to liferay portal, means
out of box features we can develop. This kernel inherits from JSR 168 and JSR
286 features.
All classes and interfaces they are packaged in portal-keranl.jar in previous
version of liferay, now it is available inside portal-service.jar
Portal
Implementation
Portal Implementation is set of Implementation classes
which are derived from Liferay kernel specific to liferay portal use. This component
designed for liferay portal built in functionality. All these are packaged in
portal-impl.jar
Portal
Services
Portal services are is database services which
interact with liferay database means lportal database. Whenever we want connect
to portal database from Plugins we will use this service layer to connect to
liferay database.
What
is Liferay Portal?
Liferay implemented their own frameworks and component
in Portal Implementation layer and database services packaged as portal service
layer, if we combine these two then it will be become Liferay Portal and portal kernel
is common.
We can say like follows
Liferay
Kernel +Liferay Implementation +Liferay Services=Liferay Portal
To add new components or to modify exited competent
we need liferay support to outside, for this they have given Portal Kernel and
Portal services to outside availability means which is available to Plugins.
Liferay packaged Liferay Kernel and Liferay Services
in portal-services.jar
What is meaning of outside availability?
It is nothing but make it accessible their jar files
to other applications means these jar files available in application servers
global class path
In tomcat tomcat/lib/ext
this global class path if any jar available in this directory then any liferay plug-in
can use this classes and interfaces.
In Jboss jboss-7.1.1\modules\com\liferay\portal\main
When we look at these directories we can find portal-service.jar file. So we
can say this jar can available to any application that is deployed in server.
Note:
These directories we can see only in liferay
supported application servers, means we download liferay tomcat bundles or
liferay jobs bundles with these servers only we can see above directories.
The following diagram shows portal-service.jar
in tomcat/lib/ext
As of now we are talking about component and Plugins
What is Liferay Plugins?
Liferay Plugin is piece software or set of classes
which follows the standard defined by liferay.
A plug-in is a component which can change or modify
the behavior of liferay portal or it can add new behavior to portal.
We already said liferay is software which consist of
many components and feature so that we can use directly.
It is huge web application have many features and
can support many integration with other application.
Liferay have exposed entire their web application as
ROOT.war. This is completely liferay developed application
which can get from any bundles which we download form liferay web site.
ROOT.war can see in server’s deployment directory
In tomcat we can see ROOT.war file in Tomcat/webapp directory as follows
In JBOSS we can see in deployments directory
Well now liferay is already a huge web application
and liferay has exposed their core components in Global class path, so that we
can start customize or add new feature to the liferay.
To customize or develop new feature to liferay
portal we need Standard Development Kit that is called Plugins SDK.
Note:
Liferay portal is web application which contains
java classes, XML files, velocity files, property files and JSP pages.
Plugins
SDK consist of 5 main parts
- Portlet
- Hook
- Ext
- Theme
- Layout
When we open downloaded Plugins SDK then we
can see 5 main plugins.
Plugin
Portlet
Portlets are independent component which can add new
behavior or new feature to liferay portal.
It is very flexible components we can add or remove
very easy without effect the portal or server. We can develop portlet which can
use their own database tables or existed tables. Portlet can also connect to
other databases or liferay existed database.
As we discussed earlier portlet can use liferay kernel
and liferay services.
We have different kinds of portlet like Liferay MVC
portlet, Generic Portlet, Struts Portlet, JSF Portlet and Spring Portlet.
By default Liferay have own portlet frame work i.e. called
Liferay MVC frame work which have lot of support in liferay.
Out of box to support other frame work liferay
provide some bridges from which we can run any portlet like struts, spring and JSF
portlet.
Plugins have well appreciated feature is hot
deployment components, means when we deploy the portlet, we need not stop
server and change can apply immediately.
If we use Liferay
MVC portlet it is easy to create and very light weight.
Note:
In liferay development Liferay IDE supports only
Liferay MVC portlet and JSF portlet development. If you want use out box portlets
you need manually create portlet and need to add required jar files. Liferay has
very good support to JSF frame work portlet.
Advantages:
- Plug and play
- Hot deployment feature
- Can support any J2EE MVC frame work in out box.
- Once we developed in liferay we can run in other portals with minimum changes.
- These are very easy to migrate when we upgrade portal from one version to other versions.
Limitations
- From Plug-in portlet we can’t access portal implementation layer and we can’t change the existed behavior of liferay portal.
Hook
In liferay Hooks are special purpose plugin we can
change or modify the existed behavior of liferay portal. Hook can customize the
portal but some set of limitations.
Hook can modify the some of the things like
properties files, jsp, events and portal services.
Hooks can change the existed portal properties so
that we can see the change in portal behavior.
We can change existed portlet jsp pages so that we
can add or remove some code in JSP pages.
This is also hot deployment like portlet we need not
to stop server we can see the changes.
Advantages
- It can change the existed behavior of portal
- It is hot deployment component.
- Portal existed services also we can change
- These are very easy to migrate when we upgrade portal from one version to other versions.
Limitation
- We can’t modify or change the action classes or main core classes in liferay portal.
Ext
Ext is one of the plug-in in liferay portal which
have lot of ability can change anything in existed liferay portal.
We can change the portal implementation through ext
so that we can change existed behavior in lifery portal.
we can also create new features from ext. these are
not hot deployment so every modification we need to stop server and these Ext’s
are very tightly coupled component with liferay portal means which is not much flexible
when we add or remove .
Advantages
- It can change any part of liferay portal
Limitations
- These are not hot deployments components
- Very tightly coupled with liferay core portal
- Very tough when we migrate portal from one version to other version
Note:
In future
liferay may avoid ext completely.
Theme
Theme is the one of the plugin to change the look
and feel of portal. Means we can change CSS and java script files from theme.
Liferay portal is using velocity template when
portal is rendered in web page this velocity file have capability can
accommodate dynamic content like JSP pages.
From themes we can create new look and feel to
liferay portal and we can add new CSS and new velocity templates.
Themes also hot deployment component we can deploy
theme without down or stop server.
Layout
Layout can decide the page design. It can divide the
page into some section in that we can arrange the portlet to complete the web page.
Layouts also hot deployment components.
The following is example screen for
layouts
Important
Points
- Liferay have given Plugins SDK to develop liferay applications.
- Liferay plug-in portlets are very flexible and we can migrate very easy when we upgrade portal.
- We need to minimize development of Ext
- Liferay MVC frame work is very flexible to develop plug-in portlet and Liferay IDE has support to develop these portets.
- Liferay also have rich support to JSF portlet we can use JSF portlet too.
- Whe we use other frame work to develop portlet we need add some liferay bridges to support other frame work in liferay portal.
- All Plugins are hot deployments except ext. So we don’t need to stop server when we deploy the Plugins.
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Author
Meera
Prince
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