Chapter 16: JavaServer Pages: Part II

Writing JavaBeans

1. Write a bean. A bean is a reusable, platform independent component.
2. Place the code in this directory: C:\Program Files\Apache Group\Tomcat 4.1\webapps\ROOT\WEB-INF\classes
3. At the DOS prompt, compile the file with: javac -d . name.java. Note: if javac is not in your classpath, follow the instructions here
4. Place a jsp file in C:\Program Files\Apache Group\Tomcat 4.1\webapps\ROOT or any of its subdirectories.
5. Start Apache Tomcat. Note: it is very important to start Tomcat after the WEB-INF\classes directory has been created so that Tomcat can find relevant packages.
6. Load the above .jsp file into Apache Tomcat.

Relevant JSP Commands

• <jsp:useBean id="beanName" class="package.class" />
• <jsp:getProperty id="beanName" property="propertyName" />
• <jsp:setProperty id="beanName" property="propertyName" value="newValue" />

JavaBean Scope

The scope attribute specifies how long a bean exists in memory. The scopes will be demonstrated with Counter.java.

• Page Scope (the default). Example.
• Request Scope. The bean is kept alive when the following is encountered: <jsp:forward page="relativeURL" />
• Session Scope. The bean is in scope until the browser session is closed. Example.
• Application Scope. The bean is in scope until Apache Tomcat is restarted. Example.

Shopping Cart Example

• ShopCart.java
• example6.html
• example6-1.jsp
• example6-2.jsp

Exercise

• Make the above Shopping Cart Example work on your laptop: 3 points.
• Look at and understand the four files that make up the Shopping Cart Example. Be able to answer questions that Jack and John ask you about the code. 2 points.