Using JavaBean Objects in Scripting Elements

JSP Tutorials - Herong's Tutorial Examples

∟JavaBean Objects and "useBean" Action Elements

∟Using JavaBean Objects in Scripting Elements

This section provides a tutorial example on how to use JavaBean objects in scripting elements. A JavaBean is really just Java class object, which can be used in any scripting elements.

As I mentioned in the previous section, JavaBean is just a normal Java object with some special methods. Once a JavaBean is created, we should be able to use it as Java object in any scripting elements.

Here is a sample page to show you how to use a JavaBean as a Java object. It is using the same JavaBean class, herong.DemoBean, as provided in the previous section.

<?xml version="1.0"?>
<jsp:root xmlns:jsp="http://java.sun.com/JSP/Page" version="2.3">
<!-- BeanAsObject.jspx
 - Copyright (c) 2006 HerongYang.com. All Rights Reserved.
-->
<jsp:directive.page contentType="text/html"/>
<html><body>
<jsp:useBean id="b" class="herong.DemoBean"/>
<jsp:setProperty name="b" property="author" value="Someone"/>
Line 11: author =
<jsp:expression>b.getAuthor()</jsp:expression><br/>

<jsp:scriptlet><![CDATA[b.setTotal(10);]]></jsp:scriptlet>
Line 12: total =
<jsp:getProperty name="b" property="total"/><br/>

<jsp:scriptlet><![CDATA[b.setSize(15);]]></jsp:scriptlet>
Line 13: size =
<jsp:getProperty name="b" property="size"/><br/>
Line 14: size =
<jsp:scriptlet><![CDATA[out.println(b.getSize());]]></jsp:scriptlet>
<br/>

<jsp:scriptlet><![CDATA[
   Object o = pageContext.findAttribute("b");
   String s = ((herong.DemoBean)o).getSize();
   out.println("Line 15: size = "+s);
]]></jsp:scriptlet><br/>
</body></html>
</jsp:root>

Open this JSP page with IE, you will get:

Line 11: author = Someone
Line 12: total = int: 10
Line 13: size = int: 15
Line 14: size = int: 15
Line 15: size = int: 15

Note that:

Line 11 tells us that we can use an expression element to get the property value.
Line 12 tells us that if we use scriptlet element, we can call a specific version of setTotal method. Remember setProperty failed on "total" in the previous example.
Line 15 tells us that we also retrieve the object back from pageContext, because useBean element store the JavaBean object in pageContext.