Java Specification Request (JSR) 286 introduced event-based coordination for portlets. JSR 286 allows portlets to send and receive events. Some portlets can define events to be published, and other portlets define which ones can receive such events. IBM® Rational® Application Developer provides the tools to create such events for portlets. In this part you will see how to enable event handling, for portlets in Rational Application Developer. These event-enabled portlets are wired together at run time to create a connection between the portlets. This tutorial, which is Part 4 of a five-part series, concentrates on enabling events for existing portlets, creation of new event-enabled portlets, and wiring together two event-enabled portlets so they can share data.

• The first portlet, the Deals portlet, acts as an event publisher portlet i.e. it will emit an event to transfer data.
• The second portlet, the ContactInformation portlet, acts as an Event Subscriber portlet, which receive an event and invoke a method that processes the exchanged data.

This is the flow of events:

1. The Deals portlet publishes an event to pass the Contact Name to the ContactInformation portlet.
2. The ContactInformation portlet receives an event to invoke a method that processes the data, for example, the Contact Name.
3. Based on the Contact Name, an appropriate SDO method is invoked to fetch information from the CONTACT_PERSON DB2 table.

Create a new portlet

To enable eventing (event handling) between two portlets, the first step is to create a new portlet:

1. Right-click on the DealsProject and select New > Portlet.
2. Enter ContactInformation as the portlet name.
3. Also, make sure that the portlet type is set to Faces Portlet. (See Figure 1.)

4. Click Next, and make sure that the Generate a custom portlet class option is checked, as Figure 2 shows.

5. Click Finish.

This will create a JSP called ContactInformationView.jsp and a portlet class named ContactInformationPortlet.java. Now that you have two portlets in place, you can enable them for \event handling (called eventing in the JSR).

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Enable the source portlet to publish an event

To enable the Deals portlet to publish an event, follow these steps:

1. Open the DealsView.jsp file.
2. In the palette view, locate Event Source Trigger in the Portlet drawer.
3. Click Event Source Trigger and drag it onto the Name expression in the Contact Name column, as shown in Figure 3.

This invokes the Insert Event Source Trigger dialog window shown in Figure 4.

4. Click the New Event button to create a new event to publish.
5. In the "Event – Enable this portlet to Publish events" dialog window that opens, for Event Name, enter ContactId, as shown in Figure 5.

6. Click Finish to populate the Insert Event Source Trigger window shown in Figure 6.

7. Type #{vardealsInformationList.CONTACT_ID} in the Value to Send field.
8. Click Finish.

The NAME field will be hyperlinked, as shown in Figure 7.

Also notice how the Deals portlet node is decorated with a Publish event icon (blue arrow preceded by a yellow flag) in the Enterprise Explorer view. The event name is listed below it as shown in Figure 8.

9. Save the file.

Now you will need to create a JavaServer Faces Managed Bean to hold the data being exchanged between portlets through eventing.

10. Right-click the Java Resources node, and select New > Class, as shown in Figure 9.

11. Specify the Package as com.ibm and Name as ContactBean, as shown in Figure 10.
12. Click Finish.

13. When the ContactBean.java file has been created and opens in the editor, replace its contents with the code in Listing 1.

      package com.ibm;

   public class ContactBean {
	long id;
	String picURL;
	public long getId() {
		return id;
	}
	public void setId(long id) {
		this.id = id;
	}
	public String getPicURL() {
		return picURL;
	}
	public void setPicURL(String picURL) {
		this.picURL = picURL;
	}
    }

14. Open the DealsView.jsp file.
15. 15.In the Page Data View, right-click on Faces Managed Bean and choose New > Faces Managed Bean as shown in Figure 11.

16. Specify Name as contactbean, Class as com.ibm.ContactBean, and for Scope, select Session from the context menu, as shown in Figure 12.

17. Click Finish.

Create an SDO Relational Record

Enabling the ContactInformation portlet for eventing is a two-step process. First, you need to create an SDO Relational Record using the DB2 table CONTACT_PERSON, and then you need to enable ContactInformation to receive an event.

Note:
Creation of a Services Data Object (SDO) has nothing to do with event enabling. You are creating an SDO because of the requirements of your use case.

To create a SDO Relational Record, follow these steps:

1. Open ContactInformationView.jsp in the Page Designer, and open the Page Data view.
2. Right-click on SDO Relational Records, and choose New > SDO Relational Record.

3. In the Add Relational Record dialog window, provide contactInformation as the name, and click Next.

4. For table, choose the CONTACT_PERSON table under the ADMINISTRATOR schema, and click Next (see Figure 15).

5. Choose all the columns, as shown Figure 16, and click Finish.

As Figure 17 shows, a new Relational Record is created under the SDO Relational Records node in the Page Data view.

Generate JSP code

Now that you have created the SDO Relational Record, you need to drag the Relational Record to the portlet JSP to be able to use data from the CONTACT_PERSON table:

1. Drag the contactInformation (CONTACT_PERSON) node to the portlet JSP (ContactInformationView.jsp) to invoke the Insert Record dialog window shown in Figure 18.

2. Uncheck the column CONTACT_ID and click Finish.

Notice that the code is generated in the portlet JSP.

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Enable the target portlet to receive the event information

Now that you have created and generated the code to use data from the CONTACT_PERSON table, you need to put together a final piece: passing a contact ID to the ContactInformation portlet. This contact ID will be used to fetch a record of a particular person from the CONTACT_PERSON table to display the relevant information in the ContactInformation portlet. Recall that the Deals portlet publishes an event by the name of ContactId to pass the contact ID. Now you need to enable the ContactInformation portlet so that it subscribes to that event.

1. Locate the ContactInformation portlet under Portlet Deployment Descriptor in the Enterprise Explorer.
2. Right-click on the portlet, and select Event > Enable this Portlet to Process Event (see Figure 19).

This invokes the "Events – Enable this Portlet to Process events" dialog window.

3. Select ContactId from the Event Name drop-down menu, as shown in Figure 20.

4. Click Finish.

Notice that the ContactId event node under the ContactInformation portlet node is decorated with a Subscribe event icon (yellow flag preceded by green arrow), as shown in Figure 21.

The previous action also generates a processEvent method in the ContactInformationPortlet.java, the portlet class for the ContactInformation portlet. Listing 2 shows the generated code.

public void processEvent(EventRequest request, 
			EventResponse response) throws 
			PortletException, java.io.IOException {	
     super.processEvent(request, response);
     FacesContext facesContext = FacesContext.getCurrentInstance();
     Event sampleEvent = request.getEvent();
     if(sampleEvent.getName().toString().equals("ContactId")) {
	 Object sampleProcessObject = sampleEvent.getValue();
	}
    facesContext.release();
   }

The processEvent method is invoked for each event targeted to the portlet, with an EventRequest and EventResponse object.

Listing 3 modifies the code in Listing 2 to add the business logic to the processEvent method.

    public void processEvent(EventRequest request, 
			    EventResponse response) throws 
			    PortletException, java.io.IOException {	
	super.processEvent(request, response);
	FacesContext facesContext = FacesContext.getCurrentInstance();
	Event sampleEvent = request.getEvent();
	if(sampleEvent.getName().toString().equals("ContactId")) {
	 Object sampleProcessObject = sampleEvent.getValue();
	 Application app = facesContext.getApplication();
	 ValueBinding binding = app.createValueBinding("#       
                              {contactbean}");
	 ContactBean mybean =(ContactBean) binding.getValue 
                            (facesContext);
	 mybean.setId(Long.parseLong(sampleProcessObject.toString()));
	}

In this listing, the code simply gets an instance of Faces managed bean, ContactBean, that you created earlier. This instance contains the contact ID that is transferred by the Deals portlet through eventing. The instance of the ContactBean, itself, is stored in a session variable so that it can be reused across the portlets, spanning different requests.

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Wire the portlets together

To exchange data on invocation of events, you need to wire the portlets together so that they can exchange data.

1. Perform the Run on Server operation on the project as you did earlier. Figure 22 shows how the rendered portlets look in the browser.

2. Now, to wire the portlets together, click the Edit Page option from the Actions menu, as shown in Figure 23.

Note:
This Edit Page option is present only when the theme is the PageBuilder one that is included with IBM® WebSphere® Portal, Version 7.0. For any custom themes, you can wire together the portlets by using the portal administration console wiring tool.

3. Right-click on the small arrow symbol for the drop-down menu (shown in Figure 24) at the top-left of the Deals portlet window, and choose the Edit Wiring menu item.

4. Choosing the Edit Wiring menu item brings up the Wiring interface shown in Figure 26. The interface shows the available events that can be wired together. In this interface, you will find the events that you created earlier.
5. In the Wiring interface, choose the {http://DealsProject/}/ContactId publisher event under the Deals icon that appears under the Select content to send heading.
6. Choose the {http://DealsProject/}/ContactId subscriber event under the ContactInformation icon that appears under the Select a widget to receive content heading
7. Click Done.

8. Click the Save & Exit button.
9. Now click on the individual Contact Names in the Deals portlet, and you will see the relevant information displayed in the Contact Information portlet (Figure 27).

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Next in this series

This concludes Part 4 of this five-part series. Part 5 shows how to create portlets that can fetch data from IBM® Connections.

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• For details, read Coordination between portlets in the JSR286 Java Portlet specification.
  
  
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About the author

Gaurav Bhattacharjee is a technical lead in the IBM India Software Labs in Delhi, India. He works with the Rational Application Developer Portal Tooling team in the IBM Software Group, IBM Collaboration Solutions.

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Table of contents

• Create a new portlet
• Enable the source portlet to publish an event
• Enable the target portlet to receive the event information
• Wire the portlets together
• Next in this series
• Download
• Resources
• About the author
• Comments

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