WebSphere Studio Application Developer Version 5 Programming Guide part 28 pptx

An application using DB Beans or tags can be generated for you by Application Developer using a wizard based on an SQL statement.. Generate Web pages from SQL queriesApplication Develope

244 WebSphere Studio Application Developer Version 5 Programming Guide

("getCustomer_java_lang_String customerID")));

itso.bank.model.Account[] methodResult1 = listAccountsBean.getAccounts (new java.lang.String(request.getParameter

("getCustomer_java_lang_String customerID")));

Tailoring the generated files

You could make the ListAccountsInputForm.html file look like the original

index.html file

Rename

Note that if you rename the files, you have to configure the initialization parameters of the controller servlet (ListAccountsController) in the web.xml

deployment descriptor

Running the generated application

Select the ListAccountsInputForm.html file and Run on Server (context) The application is published, the server is started, and the input page is displayed Enter a customer number (102) and click Submit The name of the customer and the accounts are displayed A sample run is shown in Figure 7-61

Figure 7-61 Sample JavaBean application run

In this chapter we learned about Application Developer’s facilities for creating static and dynamic Web applications We created a Web project and imported existing resources into it We then created static HTML pages, a cascading style sheet, servlets, JSPs, filters, and life-cycle listeners to complete the sample RedBank application, based on the MVC architectural pattern

We also used the JavaBean Web Pages Wizard to generate a Web application from a JavaBean

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Chapter 8. Developing Web

applications with database access

We have seen how to connect to databases and how to access them from a Java application Application Developer contains wizards to allow you to easily access databases from a Web application We now examine how to use those wizards, and how to test the resulting application

In this chapter, we go over the following topics:

򐂰 Accessing databases from a Web application

򐂰 Defining a data source in the server

򐂰 Testing the database application

򐂰 Accessing a database using DB Beans

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Accessing databases from a Web application

There are a number of ways that you can access databases from a Web application You can write your own Java classes and access the database via standard JDBC calls Alternatively, Application Developer supplies a library of database access beans called DB Beans These can be used in a JSP through the <useBean> tag and can also be accessed through a set of JSP tags supplied

in a tag library An application using DB Beans or tags can be generated for you

by Application Developer using a wizard based on an SQL statement

Which of these methods you choose depends on the nature of your application and the complexity of your database access From the perspective of separating the layers of your application, using separate JavaBeans for the database access may be more appropriate because you are not mixing presentation and database logic in the JSP as you do when using DB Beans or JSP tags

In the following sections we discuss the wizard that can be used to create a view bean or a taglib application starting from an SQL statement We then look a bit more closely at the DB Beans classes and JSP tags

Creating a Web project

In this section, we use a new ItsoProGuideDataBaseWeb project:

򐂰 Create a Web project named ItsoProGuideDataBaseWeb by following the instructions in “Creating a Web project” on page 185

򐂰 Use the existing ItsoProGuide enterprise application project and the default context root

򐂰 On the module dependencies page, select the ItsoProGuideJava.jar file and click Finish

򐂰 When prompted to repair the server configuration because a new project was added to the EAR file, click OK (Figure 8-1)

Figure 8-1 Repair server configuration

Generate Web pages from SQL queries

Application Developer provides a wizard to help you create a set of Web pages and supporting Java classes starting from an existing or new SQL query The wizard generates the required HTML pages, JSPs, and Java classes to quickly create a working skeleton application without you having to write any code You can then expand and modify the generated code to create the finished

application

To start the wizard, click File -> New -> Other In the New wizard, select Web in the left pane and Database Web Pages in the right pane, then click Next The first page of the wizard is displayed (Figure 8-2)

Figure 8-2 Create Database Web Pages wizard: select model

The following fields are available on this page:

򐂰 Destination folder—Folder where the generated Web pages are stored

򐂰 Java package—Package where Java classes are generated

򐂰 SQL Statement Type—The type of action to perform on the database

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򐂰 Model—There are two types of models that you can use:

IBM Database Access Tag Library: Two choices of tag library models are

available: Select Statement and Master Details Pattern – The Select Statement generation model creates an input form and a result table based on the given SQL query

– The Master Details Pattern produces a master results table as well as a details page that displays more information on a selected row of the master results table

Both of these use JSP tag libraries to access the data JSP tags are discussed in more detail in “Accessing a database using JSP taglib” on page 262

IBM Database Access Java Beans - Master Details Pattern: This model

generates Web pages that access database information using IBM Data Access Beans to separate the database interaction from the JSP page For this example we use this model

Clicking Next brings up the second wizard page (Figure 8-3)

Figure 8-3 Create Database Web Pages wizard: select SQL statement

You have two choices: use an existing SQL statement, or build a new one:

򐂰 If you already have an existing SQL statement in the statement folder of a database project, you can select it here and use that to generate the Web pages

򐂰 If you deselect Use Existing SQL Statement and click Next, you are prompted

to build an SQL statement in the same way as described in “Creating SQL statements” on page 165

We select the ListCredits SQL statement that we built in “Using SQL Query

Builder” on page 171 and click Next

Clicking Next displays the page where you decide how you want to access the database when the generated application is run (Figure 8-4) You can choose to use a direct connection or use a data source For a discussion about these two different ways of connecting, see “Data source versus direct connection” on page 141

Figure 8-4 Create Database Web Pages wizard: connection information

In this case we use the data source connection We specify the JNDI name of the data source, which in our case is jdbc/ejbbank

On the next three wizard pages you can view and change the pages that will be generated by the wizard

The first page is the View Bean Data Page, where you can specify the style sheet, error page, whether to store results in the session or request object, and whether or not to create a Front Controller, use an existing one, or not use one at all (Figure 8-5)

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Figure 8-5 Create Database Web Pages wizard: View Bean Data Page

The Store results option determines where the results from the query should be stored You can choose to store them in the session, in which case they will be available to other pages for the life of the session, or in the request You should

be aware of potential memory issues if you choose to store a large result set in the session

The front controller option decides if a controller servlet is generated or reused The controller servlet uses initialization parameters that specify for each action which JSP to call

On the following page, you see the HTML input form (Figure 8-6)

Figure 8-6 Create Database Web Pages wizard: design input form

Here you can make some changes to page and field properties Notice that the two input fields are automatically generated This is where the :type and

:lastname host variable values will come from

Select each host variable and change the label to the desired text, for example,

Transaction type and Last name

Once this and the following pages have been generated, you can make further changes using Page Designer

The next page shows the master result page The default is to use a table to display the result rows from the query (Figure 8-7)

Last name