Using Java Objects as JavaBeans

JSP Tutorials - Herong's Tutorial Examples

∟JavaBean Objects and "useBean" Action Elements

∟Using Java Objects as JavaBeans

This section provides a tutorial example on how to use a regular Java object as JavaBean using the 'setProperty' action elements. This requires the Java object to be added to 'pageContext' attribute collection.

Now we know that a JavaBean is just a normal Java object with some specially named methods, and stored in pageContext's attribute collection. We can use the useBean to create a JavaBean and use it any way we wanted.

The next question is: can we create any object and put it into pageContext's attribute collection, and use setProperty elements? The answer is yes. Here is my sample JSP page to show you this:

<?xml version="1.0"?>
<jsp:root xmlns:jsp="http://java.sun.com/JSP/Page" version="2.1">
<!-- ObjectAsBean.jspx
 - Copyright (c) 2006 HerongYang.com. All Rights Reserved.
-->
<jsp:directive.page contentType="text/html"/>
<html><body>
<jsp:scriptlet><![CDATA[
   herong.DemoBean b = new herong.DemoBean();
   pageContext.setAttribute("b", b, PageContext.PAGE_SCOPE);
]]></jsp:scriptlet>

<jsp:setProperty name="b" property="author" value="Unknown"/>
Line 21: author = <jsp:expression>b.getAuthor()</jsp:expression><br/>

Line 22: total = <jsp:expression>b.getTotal()</jsp:expression><br/>

<jsp:scriptlet><![CDATA[b.setSize(15);]]></jsp:scriptlet>
Line 23: size = <jsp:expression>b.getSize()</jsp:expression><br/>

Line 24: size =
<jsp:scriptlet>out.println(b.getSize());</jsp:scriptlet><br/>

<jsp:scriptlet><![CDATA[
   java.util.Date d = new java.util.Date();
   pageContext.setAttribute("d", d, PageContext.PAGE_SCOPE);
]]></jsp:scriptlet>

<jsp:setProperty name="d" property="time" value="1000000000000"/>
Line 25: time = <jsp:expression>d.getTime()</jsp:expression><br/>

</body></html>
</jsp:root>

Open this JSP page with a Web browser, you will get:

Line 21: author = Unknown
Line 22: total = 1
Line 23: size = int: 15
Line 24: size = int: 15
Line 25: time = 1000000000000

Note that:

Line 25 tells us that we can even create a Date object and make it available a JavaBean. Its setTime and getTime methods are used provide the time property.

Notice that, I am not using "getProperty" action elements in this example. Why? Because it does work not in Tomcat. See next tutorial for more details.