{"id":16302,"date":"2013-08-12T11:46:14","date_gmt":"2013-08-12T08:46:14","guid":{"rendered":"http:\/\/www.javacodegeeks.com\/?p=16302"},"modified":"2013-12-30T22:51:47","modified_gmt":"2013-12-30T20:51:47","slug":"ejb-passivation-and-activation-example","status":"publish","type":"post","link":"https:\/\/www.javacodegeeks.com\/2013\/08\/ejb-passivation-and-activation-example.html","title":{"rendered":"EJB passivation and activation example"},"content":{"rendered":"

In this tutorial we are going to see how activation and passivation works in a Stateful Java Enterprise Session Bean.<\/p>\n

1. Introduction<\/h2>\n

Stateful Session Beans usually hold information about a specific client, and holds that information throughout the whole session. It is a fact though, that client sessions tend to be active for a respectable amount of time, and of course many clients can be online the same time. As a result, it is a necessity for the EJB container to implement a mechanism that makes possible the releasing of resources that are not used at a given moment, and can be activated again when needed.<\/p>\n

Passivating a Session Bean means removing it from the Session EJB Cache of the container and storing all the necessary information and properties of the session bean in a file. Activating a session bean means reading the aforementioned file and restoring the passivated session bean in the cache. As you might imagine all the fields of a that session bean must be Serializable<\/a>.<\/p>\n

In this example we are going to create an EAR Project and an EJB Project that will host our Session Bean and a Dynamic Web Application that will host a Servlet, testing the aforementioned passivation and activation properties. We are going to use Eclipse Java EE IDE 4,3 Kepler and Glassfish 4.0 as our container.<\/p>\n

2. Create a new Enterprise Application Project<\/h2>\n

Create a new Enterprise Application Project named SatefulBeansEAR<\/code> .In Eclipse IDE select File -> New -> Enterprise Application Project and fill in the form and click Finish:<\/p>\n

\"new-ear-project\"<\/a><\/p>\n

3. Create a new EJB Projet<\/h2>\n

Create a new EJB Project called StatefulEJB. We are going to create our session bean on this. Go to File -> New -> EJB Project and fill out the form. Be careful to select “Add EAR Project” and Select “StatefulBeansEAR<\/code>” as EAR project name:<\/p>\n

\"new-ejb-project\"<\/a><\/p>\n

Click Next twice and choose to create EJB Client JAR, as well as to generate the ejb-jar.xml<\/code> deployment descriptor :<\/p>\n

\"ejb-client\"<\/a><\/p>\n

4. Create a Sateful Session Bean<\/h2>\n

Open StatefulEJB Project in the Project Explorer and in the folder ejbModule<\/code> create a new source package named com.javacodegeeks.enterprise.ejb<\/code>. In that package create a new Interface that will be a local view of the EJB:<\/p>\n

Passivation.java:<\/span><\/em><\/p>\n

package com.javacodegeeks.enterprise.ejb;\r\n\r\nimport javax.ejb.Local;\r\n\r\nimport com.javacodegeeks.enterprise.ejb.property.PropertyObject;\r\n\r\n@Local\r\npublic interface Passivation {\r\n\r\n\tvoid setPropertyObject(PropertyObject propertyObject);\r\n\r\n\tPropertyObject getPropertyObject();\r\n\r\n}<\/pre>\n
And here is the Session Bean:<\/p>\n
PassivationBean.java:<\/span><\/em><\/p>\n
package com.javacodegeeks.enterprise.ejb;\r\n\r\nimport javax.ejb.PostActivate;\r\nimport javax.ejb.PrePassivate;\r\nimport javax.ejb.Stateful;\r\n\r\nimport com.javacodegeeks.enterprise.ejb.property.PropertyObject;\r\n\r\n@Stateful\r\npublic class PassivationBean implements Passivation {\r\n\r\n\tprivate PropertyObject myProperty;\r\n\r\n\t@Override\r\n\tpublic void setPropertyObject(PropertyObject propertyObject) {\r\n\t\tthis.myProperty = propertyObject;\r\n\r\n\t}\r\n\r\n\t@Override\r\n\tpublic PropertyObject getPropertyObject() {\r\n\r\n\t\treturn this.myProperty;\r\n\t}\r\n\r\n\t@PrePassivate\r\n\tprivate void prePassivate(){\r\n\t    \/\/ Free resources \r\n\t    \/\/ ...\r\n\r\n\t    System.out.println(\"Passivating EJB. Property value: \" \r\n\t      + myProperty.getProperty());\r\n\t}\r\n\r\n\t@PostActivate\r\n\tprivate void postActivate(){\r\n\t    \/\/ Reactivate resources\r\n\t    \/\/ ...\r\n\r\n\t    System.out.println(\"Activating EJB. Property value: \" \r\n\t      + myProperty.getProperty());\r\n\t}\r\n}<\/pre>\n
In the above code :
 
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