PART-4

PART-4

XSLT IN JSP USING BEAN

R.S.RAMASWAMY

As pointed out earlier, the most important requirement nowadays in designing web-applications is clean separation of code and presentation. In the above example of servlet, it will be seen how easily we have presented the result in table-form though there was no such code in java servlet's source-page. This is the chief merit of xslt approach. However, it can be refined still further by using jspbean for the logic and jsp page.

But, let us ponder over this option , for a while.As every developer would agree, it is much easier to develop and test our servlets , because they are compiled in jdk environment by ourselves. But , a JSP page can be developed and tested only in a jsp container like Tomcat.

If there are errors in our code, the Tomcat jsp compiler throws up a stack-trace 'at our face', and it is not easy to find the error from this trace. For trivial programs, it may not be too difficult but for a fairly complicated program, it is extremely frustrating , as the line numbers do not refer to jsp page atall. Each time to recompile our beans , put them in the proper folder and restart the tomcat is time-consuming and tiresome.On the other hand,

we do not need tomcat atall to test the result of our xsl .All that we require is jdk1.4.We can use the built-in xalan2 in jdk1.4 and any ordinary browser will do ,to see the result. The xalan processor is extremely fast and it is a very easy to examine the effect of various style-sheets on our xml document. We can do the testing by simple command-line:

>java org.apache.xalan.xslt

-in students.xml

-xsl xsl1.xsl

-out result.htm

By using doskey feature, we can just substitute various xsl files and see the effect in browser,immediately.. ( this extremely perceptive point is from page:119 of JAVA & XSLT by Eric Burke..OReilly pub.The author effectively argues in favour of a combination of servlet for creation of XML & TrAX.,as we have done already. )

It appears that both ASP.net and JSP suffer from this time-consuming shortcoming.If we adopt xslt , the problem is solved to a certain extent from the view of developer.But some other authors opine that XSLT is very slow and warn us to test the comparative performance before deciding.According to them, the worst feature of XSLT approach is that it is slow and takes up a lot of system resources.However, Burke argues that "Much too often many programmers focus on raw performance metrices without any consideration for ease of development or maintainability by non-experts. These decisions are hard and are often subjective, based on individual experience and preferences."

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Anyway, the traditional JSP approach is given below. We begin with the bean. We should always use package for jspbean. In other aspects, the bean code is hardly different from either the console-mode or servlet code. Place the beans classfile in e:\tomcat\webapps\root\web-inf\classes\ourbeans folder.

// traxjspbean.java

=====================

package ourbeans;

import java.io.*;

import javax.xml.transform.*;

import javax.xml.transform.stream.*;

public class traxjspbean

{

public traxjspbean() { }

public String callbean(String a,String b)

{

String r=" ";

try

{

TransformerFactory factory=

TransformerFactory.newInstance();

StreamSource xsl=new StreamSource(a);

Transformer transformer=

factory.newTransformer(xsl);

StreamSource xml=new StreamSource(b);

StreamResult result=

new StreamResult("g:\\tempor.htm");

transformer.transform(xml,result);

FileInputStream fis=

new FileInputStream("g:\\tempor.htm");

DataInputStream dis=

new DataInputStream(fis);

String s=dis.readLine();

while(s!=null)

{

r=r+s+"<br>";

s=dis.readLine();

}

System.out.println(r);

}catch(Exception e1)

System.out.println(""+e1); }

return r;

}

==========================================================

// traxjsp.htm

===============

<html>

<body>

<jsp:useBean id="bean1" class="ourbeans.traxjspbean" />

String s1=request.getParameter("combo1");

String s2=request.getParameter("combo2");

String a="http://localhost:8080/"+s1;

String b="http://localhost:8080/"+s2;

out.println(a);

out.println("<br>");

out.println(b);

String s=bean1.callbean(b,a);

out.println(s);

</body>

</html>

================================================================

// traxjsp.htm

====================

<html>

<body>

<form method=post

action='traxjsp.jsp'>

Select file

<option value="students.xml">students.xml

<option value="marks.xml">marks.xml

</select>

<br>

Select Style

<option value="xsl1.xsl">style1

<option value="xsl2.xsl">style2

<option value="xsl3.xsl">style3

</select>

<br>

</form>

</body>

</html>

Place the jsp & htm files in root folder.

Start the browser and give url as :

'http://localhost/traxjsp.htm' and we get correct result.

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At this point, it is worthwhile to point out that ,

if we follow a systematic method of encapsulating the logic in a class ( ie) bean, we can use it in :

a) console mode

b) stand-alone gui frame

c) client-server

d) RMI

e) servlet

f) JSP

g) EJB (Session-bean).

The essence of an Enterprise Application is in business-logic (algorithm)which can be tested even as a simple console program, as we did above in JAVA & C# too!

An IDE is just an artificat for making repetetive chores easier but can never be a substitute for business logic.

It is a moot point whether the essence of the success of Google is in its search algorithm or in its user interface!

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This tutorial has gotten to be too long and hence we will deal with JSTL (Java Standard Tag Library ) in the next issue and see how the XML tags in JSTL make the job still easier.

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