FormGenerator Part 2 : How to check inputs from CGI FORM / XHTML, WML or SVG by JSP / Japanese Shift_JIS, Chinese BIG5, GB2312 or Russian KOI8-R

How to check input of CGI FORM by JSP/Servlet on Apache Tomcat. XHTML, HDML/WML (WAP) or SVG by XML. Ready for Japanese Shift_JIS, Chinese BIG5, GB2312 or Russian KOI8-R. Better than JSP or XSLT.
Within the XML, you can write the code fragments for HTML, XHTML, HDML/WML (WAP phone) or SGV. Once the XML is parsed by this Java API, JSP/Servlet on Apache Tomcat can insert the arbitrary Strings into these code fragments. Then, this API merges them all and returns the concatenated String.

The code fragments in the XML are cached and re-used, i.e. the same XML will never been read more than once. This pooling mechanism results in the significant performance improvement.
Because of its high performance and simplicity, this API can be alternative to JSP or XSLT.

This is the Part 2 of FormGenerator. If you are not familiar with this Java API, please read from the previous page.

Related Pages:

• Previous Page (FormGenerator Part 1)
• API documentation for OOP FormGenerator
• form_gen_2_0.dtd (DTD for OOP FormGenerator)
• OOP Distributor : ESD, Shopping Cart for digital goods by OOP-Research

Very basic concept:

In this section, we will show you the very basic of this Java API. To make the things easier, the example in this section is meaningless. But, please don't be impatient. Later, you will see more interesting features.

Basically, the intended response from JSP/Servlet can be divided into the 2 categories. They are:

• static code fragment
• String to be inserted

• form_gen_2_0.dtd

• (docBase)/WEB-INF/classes

• (docBase)/WEB-INF/classes/hello.xml
• (docBase)/WEB-INF/classes/test/hello.xml

• getForm(String)

• (docBase)/WEB-INF/classes

• hello.xml
• test/hello.xml

• setDefaultValue("item","Hello")

• getMerged( )

• <ul><li>Hello</li></ul>

• reuseForm(Form)

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;

import com.oopreserch.web.*;

/**
 * @author Jun Inamori
 */
public class Hello extends HttpServlet{

    private static FormGenerator gen=null;

    public void init()
	throws ServletException{
	try{
	    gen=FormGenerator.getInstance();
	}
	catch(Exception ex){
	    ex.printStackTrace();
	    throw (new ServletException(ex));
	}
    }

    public void doPost(HttpServletRequest req, HttpServletResponse res)
	throws ServletException,IOException{
	try{
	    Form input=gen.getForm("test/hello.xml");
	    input.setDefaultValue("hello","Hello World");
	    String tag=input.getMerged();
	    gen.reuseForm(input);
	    req.setAttribute("tag",tag);
	    (req.getRequestDispatcher("hello.jsp")).forward(req,res);
	}
	catch(Exception ex){
	    throw (new ServletException(ex));
	}
    }

} //End of : Hello

One more basic:

Please be patient for a bit while. This section describes another basic of this Java API. It is...

• You can write the 2 set of code fragments into XML

• setDefaultValue("item","Hello",true)

• <ul><li>Hello</li></ul>

• getMerged( )

• setDefaultValue("item","Hello",false)

• <ul><li><font color="#ff0000">Hello</font></li></ul>

How to check input from CGI FORM:

First of all, the code fragment for the intended CGI FORM can be written in the XML. In the departing JSP, the tags for the CGI FORM will look like:

• setRequest(HttpServletRequest)

• isAllValid( )

• getMerged( )

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;

import com.oopreserch.web.*;

/**
 * @author Jun Inamori
 */
public class CgiCheck extends HttpServlet{

    private static FormGenerator gen=null;

    public void init()
	throws ServletException{
	try{
	    gen=FormGenerator.getInstance();
	}
	catch(Exception ex){
	    ex.printStackTrace();
	    throw (new ServletException(ex));
	}
    }

    public void doPost(HttpServletRequest req, HttpServletResponse res)
	throws ServletException,IOException{
	try{
	    Form input=gen.getForm("xml/cgi.xml");
	    input.setRequest(req);
	    if(!input.isAllValid()){

		// The tags for CGI FORM is available.
		// It includes all the parameter values
		// within the code fragments for the
		// invalid case.
		String tag=input.getMerged();

		// Don't forget this!
		gen.reuseForm(input);

		// The CGI FORM will be merged into the
		// response from another JSP...
		req.setAttribute("tag",tag);
		(req.getRequestDispatcher("again.jsp")).forward(req,res);
	    }
	    // Don't forget this!
	    gen.reuseForm(input);

	    // Then, this Servlet can do its own tasks.
	    // What it does depends on your web application...
	    .....
	    .....
	}
	catch(Exception ex){
	    throw (new ServletException(ex));
	}
    }

} //End of : CgiCheck

• FormValueVerifierFactory.properties

XML selection based on Locale:

Most web browsers (or WAP browsers) allows the users to select their preferable languages. When the web browser (or WAP browser) sends the HTTP request, the language preference is also sent as one of the header information. On the server side, this language preference can be used to send back the localized contents. For example, Apache HTTPD server (so called Apache web server) implements content negotiation, which selects the localized HTML file based on the language preference.

The language preference is also available for JSP/Servlet programming. From the given instance of HttpServletRequest, JSP/Servlet can get the instance of java.util.Locale. And the instance of Locale tells the JSP/Servlet which language the user likes. For example, in the MVC (model-view-controller) design, the following Servlet switches the HTTP request to the Localized JSP:

import java.io.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;

/**
 * @author Jun Inamori
 */
public class Switch extends HttpServlet{

    public void doPost(HttpServletRequest req, HttpServletResponse res)
	throws ServletException,IOException{
	Locale loc=req.getLocale();
	String lang=loc.getLanguage();
	if(lang!=null && lang.equalsIgnoreCase("fr")){
	    (req.getRequestDispatcher("french.jsp")).forward(req,res);
	    return;
	}
	(req.getRequestDispatcher("english.jsp")).forward(req,res);
    }

} //End of : Switch

import java.io.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;

/**
 * @author Jun Inamori
 */
public class BadSwitch extends HttpServlet{

    public void doPost(HttpServletRequest req, HttpServletResponse res)
	throws ServletException,IOException{
	Locale loc=req.getLocale();
	String lang=loc.getLanguage();
	(req.getRequestDispatcher("result_"+lang+".jsp")).forward(req,res);
    }

} //End of : BadSwitch

• getForm(String,Locale)

• (docBase)/WEB-INF/classes

• language code
• country code

• http://www.ics.uci.edu/pub/ietf/http/related/iso639.txt

• http://www.chemie.fu-berlin.de/diverse/doc/ISO_3166.html

• language code is ja
• country code is JP

• foo_ja_JP.xml
• foo_ja.xml
• foo.xml

import java.io.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;

/**
 * @author Jun Inamori
 */
public class GoodSwitch extends HttpServlet{

    private static FormGenerator gen=null;

    public void init()
	throws ServletException{
	try{
	    gen=FormGenerator.getInstance();
	}
	catch(Exception ex){
	    ex.printStackTrace();
	    throw (new ServletException(ex));
	}
    }

    public void doPost(HttpServletRequest req, HttpServletResponse res)
	throws ServletException,IOException{
	Locale loc=req.getLocale();
	Form form=gen.getForm("hello",loc);
	String html=form.getMerged();

	// Each XML can specify the Content-Type
	// followed by the appropriate charset extension.
	String type=form.getContentType();

	// Don't forget this!
	gen.reuseForm(form);

	// Set the Content-Type header with
	// the appropriate charset extension.
	res.setContentType(type);

	//HTTP 1.1
	res.setHeader("Cache-Control","no-cache");
	//HTTP 1.0
	res.setHeader("Pragma","no-cache");
	//prevents caching at the proxy server
	res.setDateHeader ("Expires", 0);

    }

} //End of : GoodSwitch

• hello_fr.xml
• hello_en.xml
• hello.xml

How to escape the special characters:

As described in the previous sections, you can insert the arbitrary String into the pre-defined code fragments. Then, the instance of Form can merge them all and return the concatenated String.

Please consider what will happen if the String to be inserted includes the special characters such as < or >. The concatenated String will be invalid as the HTML (or HDML/WML in case of WAP phone) code, which will result in the corrupted String on the web browser.

To avoid such a problems, the String to be inserted should be escaped, i.e. all the special characters within the original String should be replaced with the corresponding escaped characters. And this is the responsibility of the implementation of FormValueEscaper interface.

The implementation of this interface will be used by the instance of Form to escape the String to be inserted. The list of the available implementations should be listed in:

• FormValueEscaperFactory.properties

• no-argument public constructor
• getEscaped(String)

• EscapeForHtml
• EscapeForHdml
• EscapeForXml
• EscapeForWml

• FormValueEscaperFactory.properties

• UrlEncodeAscii

• UrlEncodeAscii

   protected String charset="ISO-8859-1";

Line breaks within HTML, HDML, WML or XHTML:

As described in the previous sections, you can insert the arbitrary String into the pre-defined code fragments. Then, the instance of Form can merge them all and return the concatenated String.

Please consider what will happen if the String to be inserted includes the line separators. As you know, most mark-up languages treat them as just single space character. As a result, the inserted String will be shown without any line breaks on the web browser.
To be shown with lines breaks, the line separators in the String must be replaced with the tags for lines break, such as <br>. And this is the responsibility of the implementation of FormValueBreaker.

The implementation of this interface will be used by the instance of Form to replace the line separators. The list of the available implementations should be listed in:

• FormValueBreakerFactory.properties

• no-argument public constructor
• getBreaked(String)

• BreakForHtml
• BreakForXml

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