A Comprehensive Guide to IBM WebSphere Host Publisher Version 3.5

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5. Scenario 5: Accessing Host Publisher EJB from user EJBs.

6. Scenario 6: Accessing Host Publisher EJB from user EJBs with chaining.

7. Scenario 7: Changing Host Publisher EJB from EJB session stateful to

stateless.

Note: EJB support is provided for database and host Integration Objects; in

these scenarios, we are only using host Integration Objects.

17.4.1 Scenario 1: Accessing Host Publisher EJB from local JSPs

This scenario illustrates and guides you through the process of implementing a

simple Host Publisher application using Host Publisher EJB support and JSPs

created to instantiate the EJB Access Bean in order to locally access the Host

Publisher EJB. The scenario is shown in Figure 17-8.

Note: The procedure to access Host Publisher EJB from local servlets is very

similar, but will not be shown in this scenario.

Figure 17-8 Accessing Host Publisher EJB from a local JavaServer Page (JSP)

In this scenario, the request flow goes las follows (see Figure 17-8):

1. The JSP is accessed from the Web browser, for example via URL or a POST

operation. The JSP instantiates the EJB Access Bean (a JavaBean). The EJB

Access Bean was previously generated by Host Access (Studio) when you

saved the Integration Object. Also, the interface that the EJB Access Bean

provides is similar to the one provided by the Integration Object (setters,

doHPTransaction and getters methods).

2. When the execution method is invoked in the EJB Access Bean, it

communicates with the Host Publisher EJB (a session stateful EJB) via

RMI/IIOP. That is, the EJB Access Bean provides the EJB client code and it

will use the provided JNDI by default to locate the Host Publisher EJB.

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Note: Since the communication between the EJB Access Bean and the Host

Publisher EJB is local in this scenario, the TCP/IP stack is not used and

therefore provides better performance.

3. The Host Publisher EJB instantiates the Integration Object (a JavaBean)

using the setters, doHPTransaction and getters methods.

4. The Integration Object executes the host application transaction via the Telnet

3270 (or 5250) transport and passes the response back to the Host Publisher

EJB.

For this scenario, we assume that the Integration Object has already been

created and EJB support files have been generated using the procedure

described in 17.3, “Adding EJB support to Integration Objects” on page 509.

Sample JSP

You can create JSPs to instantiate, drive and render the EJB Access Bean output

properties in the same way that the original Integration Objects are used. The

difference is in using the proper Java Bean name. For example, the EJB Access

Bean will have a name of the form <IOName>Access0.jar for an Integration

Object with name <IOname>.

In this scenario, the Integration Object name is Hobj01.jar and therefore its

associated EJB Access Bean name will be Hobj01Access0.jar, where Access0 is

the default suffix. However, you can change the suffix value if required when

creating your Integration Object and EJB support files.

The sample JSP to invoke the EJB Access Bean is shown in Figure 17-9 on

page 516.

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Figure 17-9 Sample JSP used to invoke the EJB Access Bean

The sample JSP was created using the Host Publisher Studio (see Chapter 10,

“Creating applications” on page 301). However, the JSP can be created using

other tools and editors, for example, WebSphere Studio (see Chapter 15,

“Integration Objects and WebSphere Studio” on page 405).

Transferring and deploying applications using EJB Access

In this section, we show you how to transfer and deploy your application using

JSPs in a local environment.

Step 1: Transfer and deploy the application

Transfer and deployment of Host Publisher applications that are created using

EJB Access Beans are the same as transfer and deployment of Host Publisher

applications using the Integration Object directly.

<HTML>

<%@ page contentType="text/html;charset=ISO-8859-1" %>

<TITLE> EJBSample1Output</TITLE>

BODY>

<H1> EJBSample2 Result page</H1>

<br>

<jsp:useBean id="Hobj01Access0" type="IntegrationObject.Hobj01Access0"

class="IntegrationObject.Hobj01Access0" scope="request">

<jsp:setProperty name="Hobj01Access0" property="*" />

</jsp:useBean>

<% Hobj01Access0.setHPubErrorPage("EJBSample1Error.jsp"); %>

<% Hobj01Access0.setHPubStartPoolName("hpool01"); %>

<% Hobj01Access0.doHPTransaction(request, response); %>

<%

if (Hobj01Access0.getHPubErrorOccurred() != 0) {

// Error page redirection already done by IO

return;

}

%>

<P>Account: <%= Hobj01Access0.getAccountOut() %>

<P>Surname: <%= Hobj01Access0.getSurnameOut() %>

<P>Firstname: <%= Hobj01Access0.getFirstnameOut() %>

<P>Address: <%= Hobj01Access0.getAddressOut() %>

</BODY>

</HTML>