Accessing Databases from Web Applications

Populating the Example Database

Creating a Data Source in the Application Server

Accessing Databases from Web Applications

Data that is shared between web components and is persistent between invocations ofa web application is usually maintained in a database. To maintain a catalogof books, the Duke’s Bookstore examples described in ChaptersChapter 4, Java Servlet Technology throughChapter 15, Internationalizing and Localizing Web Applications usethe Java DB database included with the Application Server.

To access the data in a database, web applications use the newJava Persistence API (seeChapter 24, Introduction to the Java Persistence API). SeeChapter 25, Persistence in the Web Tier to learn how the Duke’s Bookstore applicationsuse this API to access the book data.

To run the Duke’s Bookstore applications, you need to first populate the databasewith the book data and create a data source in the ApplicationServer. The rest of this section explains how to perform these tasks.

Populating the Example Database

When you deploy any of the Duke’s Bookstore applications usingant deploy, the database isautomatically populated at the same time. If you want to populate thedatabase separately from the deploy task or are using NetBeans IDE to deploythe application, follow these steps:

1. In a terminal window, go to thebooks directory or any one of thebookstore1 throughbookstore6 example directories.

2. Start the Java DB database server. For instructions, seeStarting and Stopping the Java DB Database Server. You don’t have to do this if you are using NetBeans IDE. It starts the database server automatically.

3. Typeant create-tables. This task runs a command to read the filetut-install/examples/common/sql/javadb/tutorial.sql and execute the SQL commands contained in the file.

4. At the end of the processing, you should see the following output:

   ...[sql] 181 of 181 SQL statements executed successfully

When you are runningcreate-tables, don’t worry if you see a message thatan SQL statement failed. This usually happens the first time you run thecommand because it always tries to delete an existing database table first beforeit creates a new one. The first time through, there is no tableyet, of course.

Creating a Data Source in the Application Server

ADataSource object has a set of properties that identify and describe thereal world data source that it represents. These properties include information such asthe location of the database server, the name of the database, the networkprotocol to use to communicate with the server, and so on.

Data sources in the Application Server implement connection pooling. To define the Duke’sBookstore data source, you use the installed Derby connection pool namedDerbyPool.

You create the data source using the Application Server Admin Console, following thisprocedure:

1. Expand the Resources node.

2. Expand the JDBC node.

3. Select the JDBC Resources node.

4. Click the New... button.

5. Typejdbc/BookDB in the JNDI Name field.

6. ChooseDerbyPool for the Pool Name.

7. Click OK.

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