Introduction:
Liferay Model Listeners are event listeners which
will be invoked when the changes made in Model Object.
Each model object can have its own model listener to
listen changes in the model objects.
As for ORM concept any database interaction is
mapped to java POJO object that is we can call it as Model Object.
Before perform any database interaction first we
create or modify the model object then data will be stored or update in the
tables.
In the ORM concept each table row we can treat as
Model Object Instance that is called persistence object.
We can create our custom model listeners to existed
models which are in portal through Hook Plugin.
We have different model classes in portal like User, Role, Group, Layout, Address, and
Contact.
Apart from these we can also implement it for
portlet level model class like DLFileEntry,
JournalArticle and AssetEntry.
Note:
Before going implement model listener for any Model
which are in portal or portlet level Please check in liferay if they are
already existed or not. This you can search in portal.properties file
the property prefix is value.object.listener.
If already there make sure keep existed business
logic same and add your logic after that or create another model listener class
and configure it with comma separate value for above property.
Example
Properties for Model Listeners portal.properties
Pattern:
value.object.listeners.ActualModel
Class Name=Our Custom Listener class Name
|
Model
Listener to existed model objects which are in Portal level
value.object.listener.com.liferay.portal.model.Contact=
com.liferay.portal.model.ContactListener
value.object.listener.com.liferay.portal.model.Layout=
com.liferay.portal.model.LayoutListener,
com.liferay.portal.service.impl.LayoutSetPrototypeLayoutListener
value.object.listener.com.liferay.portal.model.LayoutSet=
com.liferay.portal.model.LayoutSetListener,
com.liferay.portal.service.impl.LayoutSetPrototypeLayoutSetListener
value.object.listener.com.liferay.portal.model.PortletPreferences=
com.liferay.portal.model.PortletPreferencesListener
value.object.listener.com.liferay.portal.model.User=
com.liferay.portal.model.UserListener
value.object.listener.com.liferay.portal.model.UserGroup=
com.liferay.portal.model.UserGroupListener
|
Note:
The above already existed in portal.properties file
Create
Custom Model Listener to existed model object which are in portlet level.
value.object.listener.com.liferay.portal.model.Address=
com.meera.model.listeners.AddressListener
value.object.listener.com.liferay.portal.model.Contact=
com.meera.model.listeners.ContactListener
value.object.listener.com.liferay.portlet.documentlibrary.model.DLFileEntry=
com.meera.model.listeners.DLFileEntryListener
|
Note:
The overriding of portal properties can be done
through Hook and we can use hook for existed models which are in liferay portal
level and portlet related models.
So if want know changes in the above models we need
create Model Listener and we can write some business logic to know all the
changes made in model like ADD, DELETE and UPDATE.
Any Model Listener that should implement the ModelListener
interface and it has some
abstracted methods and we need to implement it.
The
following are available methods in ModelListener
interface
public interface
ModelListener<T> {
public void
onAfterAddAssociation(
Object classPK,
String associationClassName,
Object
associationClassPK)
throws
ModelListenerException;
public void onAfterCreate(T
model) throws ModelListenerException;
public void onAfterRemove(T
model) throws ModelListenerException;
public void
onAfterRemoveAssociation(
Object classPK,
String associationClassName,
Object
associationClassPK)
throws
ModelListenerException;
public void onAfterUpdate(T
model) throws ModelListenerException;
public void
onBeforeAddAssociation(
Object classPK,
String associationClassName,
Object
associationClassPK)
throws
ModelListenerException;
public void onBeforeCreate(T
model) throws ModelListenerException;
public void onBeforeRemove(T
model) throws ModelListenerException;
public void
onBeforeRemoveAssociation(
Object classPK,
String associationClassName,
Object
associationClassPK)
throws
ModelListenerException;
public void onBeforeUpdate(T
model) throws ModelListenerException;
}
|
We have different named methods and these will be
invoked based on action performed in Model Object.
Like if any data added in table respective model
listener onAfterCreate(--) method will be invoked.
Similarly we have many methods based on action or
change respective methods will be invokes on behalf of Model object.
Real
time scenarios:
If any record add or delete for table based on this
some tome we may need to delete or add other records such scenarios we can use
model listeners.
To know more you can see source code in UserListener then we can understand importance of model listener.
If we want to track information in application then
we will use Model Listeners for example if we want track document library
information then we will create Model Listener for DLFileEntery then we can
track all information with respect to Document Library.
We
have two types of implementation
- Implement Model Listener for Existed Models
- Implement Model Listener for Plugin Portlet Models
Implement
Model Listener for Existed Models
We will use hook to existed model which are in
Portal Level or Portal Portlets Level.
Portal
Level Models Examples:
Role,
Group, Layout and Layoutset
|
Portlet
Level Models Examples
DLFileEntry,
Journal Articlle and AssetEntry
|
Steps:
1
Create Hook for Portal Properties
Step:
2
Add your Model Listener Implementation class name for
your existed Model in hook portal properties file.
Step:
3
Implement Model Listener interface Methods in Model Listener Implementation class.
Note:
Model Listener should be thread safe that is why we
have to implemented Message Bus concept to make it thread safe when concurrent actions performed in the model.
Message
Bus:
Message bus is one of the concepts in liferay so
that we can create some destinations and its respective listeners to send the information
and perform further actions through its respective listeners.
Whenever any event is generated we will post
information to configured destinations as soon as information posted in
destination respective liters will be listening and will perform further
activities.
Note:
service.properties
file
will be created after run the service-builder for the portlet.
One more important thing is when we re-run service
builder then service.propertis file overridden with default properties file and
make sure the property spring.config should have messaging-spring.xml
path.
When you run service builder again need to add above
file path in list of to spring-config property.
Assume
we want Track Document Library Information
Create brand new liferay hook project for portal
properties file.
Add following code in liferay-hook.xml file (/WEB-INF/liferay-hook.xml)
<hook>
<portal-properties>portal.properties</portal-properties>
</hook>
|
Add following property in hook portal.properties file (/WEB-INF/src/portal.properties)
value.object.listener.com.liferay.portlet.documentlibrary.model.DLFileEntry=
com.meera.model.listeners.DLFileEntryListener |
Implement Model Listener for DLFileEntry
We already know we need to implement all the methods
which are present in the ModelListener interface and we need
to implement in our Custom Model Listener class
Example Model Listener class as follows
package
com.meera.model.listeners;
import
com.liferay.portal.ModelListenerException;
import
com.liferay.portal.kernel.log.Log;
import
com.liferay.portal.kernel.log.LogFactoryUtil;
import
com.liferay.portal.model.BaseModelListener;
import
com.liferay.portlet.documentlibrary.model.DLFileEntry;
public class DLFileEntryListener extends
BaseModelListener<DLFileEntry> {
public void
onBeforeCreate(DLFileEntry dlFileEntry) throws
ModelListenerException {
_log.info("This method
will be called before create document");
}
public void
onBeforeRemove(DLFileEntry dlFileEntry) throws
ModelListenerException {
_log.info("This method
will be called before DELETE document");
}
public void
onBeforeUpdate(DLFileEntry newDLFileEntry) throws
ModelListenerException {
_log.info("This method
will be called before UPDATE document");
}
private static Log _log =LogFactoryUtil.getLog(DLFileEntryListener.class);
}
|
Note:
When you use Document Library portlet then these
methods will be called and you can information in log file or server console.
Implement
Model Listener for Plugin Portlet Models
When we work with Plugin portlet some time we need
create our own enmities in Plugin portlet and we may have our own model classes.
Whenever we want create model listener in Plugin
portlet we will use service.properties file to configure our custom model listener
on behalf of our model class.
Assume we have Student MVC Portlet and have Student
Entity
Steps:
Create Liferay MVC Portlet
Create service builder and define your entity in service.xml
Run service builder then all service layer classes
and its configuration files will be created.
In the service.properties file configure
our custom model listener on behalf of our model class
com.meera.dbservice.model.StudentModel=
com.meera.model.listeners.StudentModelListener
|
Implement our model listener and that should
implement the Model Listener interface
Example
package com.meera.model.listeners;
import
com.liferay.portal.ModelListenerException;
import
com.liferay.portal.kernel.log.Log;
import
com.liferay.portal.kernel.log.LogFactoryUtil;
import
com.liferay.portal.model.BaseModelListener;
import
com.liferay.portlet.documentlibrary.model.DLFileEntry;
public class StudentModelListener
extends
BaseModelListener<DLFileEntry> {
public void
onBeforeCreate(DLFileEntry dlFileEntry) throws
ModelListenerException {
_log.info("This method
will be called before create Student");
}
public void
onBeforeRemove(DLFileEntry dlFileEntry) throws
ModelListenerException {
_log.info("This method
will be called before DELETE Student");
}
public void
onBeforeUpdate(DLFileEntry newDLFileEntry) throws
ModelListenerException {
_log.info("This method
will be called before UPDATE Student");
}
private static Log _log =LogFactoryUtil.getLog(DLFileEntryListener.class);
}
|
Portlet
Development using Model Listeners
Assume we will find the information which is going
on Document Library Portlet.
We need to implement model listener for DLFileEntry
Model so that we can track all information.
Download
Liferay Model Listener Example Portlet
https://sourceforge.net/projects/meeralferay/files/LiferayModelListenerPortlet/
Environment:
Liferay
IDE 2.x+Eclipse (Kepler) +Liferay Plugins SDK 6.2+Tomcat 7.x Liferay Portal
Bundle
Important
Points
We have implemented DLFileEntry Model Leister
to find information in Document Library Model class.
We have created Hook for the portlet and we
configured model listener information in Hook portal.properties file.
For the storing information we have defined one
entity in service.xml file
Once we run service builder to portlet then we will
get required configuration files and java classes to perform CRUD operation on
table.
We have used Message Bus destinations and it
Listeners to post data and store the data in the table.
We have configured destinations and its listeners in
messaging-spring.xml
file which in /WEB-INF/src/META-INF/ directory.
We need to specify the messafing-config.xml file information
in service.properties
file which is in /WEB-INF/src/service.properties
service.properties
file will be created after run the service builder and when we’re run service
builder it will be revert back it default configuration so make sure for each
re run service
builder again add messaging-spring.xml information in service.propertires
file.
Deployment
and its Working.
Download portlet you can source or war file to
deploy into liferay portal as your convenient.
Once portlet successfully deployed drag the portlet
in any desired page. Portlet is available in sample category.
Now login as admin go to Document Library portlet
add some documents and Update the documents.
Now come to our portlet and click on Document
Library Records and you can see all information.
Similarly in the portlet we have document download
page you can download any document again see the Document Library Records page you can see downloaded information.
Portlet
Screens:
Default
Page
Document
download screen
Document Library Information Screen
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