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Tomcat 4.1.18 with JDK 1.4.1
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(Continued from previous part...)
You will get the following compilation error saying CacheBean is not resolvable:
org.apache.jasper.JasperException: Unable to compile class for JSP
An error occurred at line: 7 in the jsp file: /jsp/UseBeanModified.jsp
Generated servlet error:
[javac] Compiling 1 source file
D:\local\jakarta-tomcat-4.1.18\work\Standalone\localhost
\_\jsp\UseBeanModified_jsp.java:43: cannot resolve symbol
symbol : class CacheBean
location: class org.apache.jsp.UseBeanModified_jsp
CacheBean b = null;
^
The actual cause of this error is not the compiler. It is the Tomcat compilation environment.
Because you can compile the converted class, UseBeanModified_jsp.java, correctly in a command window
with the same class paths used by the Tomcat environment.
The only option left to use a JavaBean with Tomcat 4.1.18 and JDK 1.4.1 is to create your
JavaBean in a named package. The next section will give you an example.
JavaBean in a Named Package - TempratureConvertorBean.java
Creating JavaBean classes in named packages is very simple, just add a package
declaration statement at the beginning of the class. The following example shows
you a JavaBean classe defined in a package named as "herong":
/**
* TempratureConvertorBean.java
* Copyright (c) 2003 by Dr. Herong Yang. All rights reserved.
*/
package herong;
public class TempratureConvertorBean {
private double celsius = 0.0;
private double fahrenheit = 32.0;
public double getCelsius() {
return celsius;
}
public void setCelsius(double c) {
celsius = c;
fahrenheit = 1.8*c + 32.0;
}
public double getFahrenheit() {
return fahrenheit;
}
public void setFahrenheit(double f) {
fahrenheit = f;
celsius = (f-32.0)/1.8;
}
public String getInfo() {
return new String("My TempraturConvertorBean - Version 1.00");
}
}
Compile this source code, and copy the class file to the Tomcat class path.
Remember to store the class file under a sub directory named as "herong".
>\local\j2sdk1.4.1\bin\java TempratureConvertorBean.java
>copy TempratureConvertorBean.class
\local\jakarta-tomcat-4.1.18\webapps\root\web-inf\classes\herong
Now we are ready to test this JavaBean with an JSP page, TempratureConvertor.jsp:
<?xml version="1.0"?>
<jsp:root xmlns:jsp="http://java.sun.com/JSP/Page" version="1.2">
<!-- TempratureConvertor.jsp
Copyright (c) 2003 by Dr. Herong Yang
-->
<jsp:directive.page contentType="text/html"/>
<html><body>
<jsp:useBean id="b" class="herong.TempratureConvertorBean"/>
<jsp:expression>b.getInfo()</jsp:expression><br/>
Setting property "fahrenheit" to 70.0.<br/>
<jsp:setProperty name="b" property="fahrenheit" value="70.0"/>
Getting property "celsius" back:
<jsp:getProperty name="b" property="celsius"/>
<br/>
</body></html>
</jsp:root>
Open this JSP page with IE, you will get:
My TempraturConvertorBean - Version 1.00
Setting property "fahrenheit" to 70.0.
Getting property "celsius" back: 21.11111111111111
It works! Note that there is no need to use the import statement, if you use the
fully qualified class name in the jsp:useBean action element.
Conclusions:
- Using JavaBean classes in unnamed packages with Tomcat 4.1.18 and JDK 1.3.1
requires import directive elements in the JSP pages.
- There is no way to use JavaBean classes in unnamed packages with Tomcat 4.1.18
and JDK 1.4.1.
- There is no problem using JavaBean classes in named packages with Tomcat 4.1.18
and JDK 1.4.1.
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