Program guide > Access data with client applications > Use ObjectGridManager

Controlling the life cycle of an ObjectGrid

Use the ObjectGridManager interface to control the life cycle of an ObjectGrid instance using either a startup bean or a servlet.

Manage life cycle with a startup bean

A startup bean is used to control the life cycle of an ObjectGrid instance. A startup bean loads when an application starts. With a startup bean, code can run whenever an application starts or stops as expected. To create a startup bean, use the home com.ibm.websphere.startupservice.AppStartUpHome interface and use the remote com.ibm.websphere.startupservice.AppStartUp interface. Implement the start and stop methods on the bean. The start method is invoked whenever the application starts up. The stop method is invoked when the application shuts down. The start method is used to create ObjectGrid instances. The stop method is used to remove ObjectGrid instances. A code snippet that demonstrates this ObjectGrid life-cycle management in a startup bean follows:

public class MyStartupBean implements javax.ejb.SessionBean {
    private ObjectGridManager objectGridManager;

    /* The methods on the SessionBean interface have been
     * left out of this example for the sake of brevity */

    public boolean start(){
        // Starting the startup bean
        // This method is called when the application starts
        objectGridManager = ObjectGridManagerFactory.getObjectGridManager();
        try {
            // create 2 ObjectGrids and cache these instances
            ObjectGrid bookstoreGrid = 
                        objectGridManager.createObjectGrid("bookstore", true);
            bookstoreGrid.defineMap("book");
            ObjectGrid videostoreGrid = 
                        objectGridManager.createObjectGrid("videostore", true);
            // within the JVM,
            // these ObjectGrids can now be retrieved from the
            //ObjectGridManager using the getObjectGrid(String) method
        } catch (ObjectGridException e) {
            e.printStackTrace();
            return false;
        }

        return true;
    }

    public void stop(){
        // Stopping the startup bean
        // This method is called when the application is stopped
        try {
            // remove the cached ObjectGrids and destroy them
            objectGridManager.removeObjectGrid("bookstore", true);
            objectGridManager.removeObjectGrid("videostore", true);
        } catch (ObjectGridException e) {
            e.printStackTrace();
        }
    }
}

After the start method is called, the newly created ObjectGrid instances are retrieved from the ObjectGridManager interface. For example, if a servlet is included in the application, the servlet accesses the eXtreme Scale using the following code snippet:

ObjectGridManager objectGridManager = 
    ObjectGridManagerFactory.getObjectGridManager();
ObjectGrid bookstoreGrid = objectGridManager.getObjectGrid("bookstore");
ObjectGrid videostoreGrid = objectGridManager.getObjectGrid("videostore");

Manage life cycle with a servlet

To manage the life cycle of an ObjectGrid in a servlet, you can use the init method to create an ObjectGrid instance and the destroy method to remove the ObjectGrid instance. If the ObjectGrid instance is cached, it is retrieved and manipulated in the servlet code. Sample code that demonstrates ObjectGrid creation, manipulation, and destruction within a servlet follows:

public class MyObjectGridServlet extends HttpServlet implements Servlet {
    private ObjectGridManager objectGridManager;

    public MyObjectGridServlet() {
        super();
    }

    public void init(ServletConfig arg0) throws ServletException {
        super.init();
        objectGridManager = ObjectGridManagerFactory.getObjectGridManager();
        try {
            // create and cache an ObjectGrid named bookstore
            ObjectGrid bookstoreGrid = 
                        objectGridManager.createObjectGrid("bookstore", true);
            bookstoreGrid.defineMap("book");
        } catch (ObjectGridException e) {
            e.printStackTrace();
        }
    }

    protected void doGet(HttpServletRequest req, HttpServletResponse res)
        throws ServletException, IOException {
        ObjectGrid bookstoreGrid = objectGridManager.getObjectGrid("bookstore");
        Session session = bookstoreGrid.getSession();
        ObjectMap bookMap = session.getMap("book");
        // perform operations on the cached ObjectGrid
        // ...
    }

    public void destroy() {
        super.destroy();
        try {
            // remove and destroy the cached bookstore ObjectGrid
            objectGridManager.removeObjectGrid("bookstore", true);
        } catch (ObjectGridException e) {
            e.printStackTrace();
        }
    }
}

Parent topic:

Interacting with an ObjectGrid using ObjectGridManager

Related concepts

createObjectGrid methods

getObjectGrid methods

removeObjectGrid methods

Access the ObjectGrid shard

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