Quick n' easy way of generating pdf's on the fly using FOP and Java.

				


Quick n' easy way of generating pdf's on the fly using FOP and Java.



This article illustrates a very easy way of getting started with the print formatting objects
 using FOP. For more details on FOP check out the xml.apache.org. 
 All due credit goes to the guys who worked on the world's first FOP. These generic objects 
 give an easy access to generating professional pdf's on the fly from xml documents using 
 fop,xalan and xerces for DOM.

I used them for generating runtime agreements in pdf depending on the user selected 
channels,period,categories etc..for a licensing engine.

The example works on any environment with jdk1.2/1.3 installed. My contribution is a simple 
wrapper for the fop packages(org.apache.fop.apps.XMLFormatter) so that one can directly make 
use of the whole model by calling the methods XMLFormatter.formatToPDF() or XMLFormatter.formatToText().

Before starting lets see what FOP is all about. I reproduce below a snippet from the fop readme which says...
----------------------
 What is FOP?
 FOP is the world's first print formatter driven by XSL formatting
 objects. It is a Java application that reads a formatting object
 tree conforming to the XSL candidate release (21. November 2000) and
 then turns it into a PDF document or allows you to preview it
 directly on screen.
 FOP is part of Apache's XML project. The homepage of FOP is
 http:/xml.apache.org/fop
 HTML-Documentation can be found in the subdirectory docs/html-docs.
 A list of bugs, things worked on, and the names of the committers of
 this project can be found in the file status in root.
----------------------


How do i start?
Make sure the unzipped xalan.jar,xerces.jar,w3c.jar and fop.jar are in your class path. Also copy the 
sample xml xsl files into ur application directory and then copy paste the source code below which is an
 example of accessing the helper class XMLFormatter(wrapper for the conversion of xml and given xsl to 
 pdf/text). Make necessary changes for the file path of the xml,xsl and pdf/text in the example class given.
 Run the program...and the pdf/text would be generated at the path specified in the class.

Please use the sample xml,xsl and generated pdf's just as an example and not as standards for
writing your own xml or xsl. Comprehensive document is available at xml.apache.org for the various
formatting tags that can be used for building better pdf's. 

Here's the sample source code for invoking the wrapper...


/**
 * Test Class to call the wrappers for FOP objects
 * to generate pdf/text files. The inputs for conversion
 * are xml file name and xsl file name as well as the 
 * text/pdf file name to be rendered to.
 * @Class FormatterTest
 * @Created by/on M.Reddy 17/May/2001
 */
import java.util.*;
import java.io.*;
import org.apache.fop.apps.XMLFormatter;
public class FormatterTest{
//static constants storing the file paths for the xml,xsl and the pdf
private static final String XML_PATH = "c:/fop";
private static final String XSL_PATH = "c:/fop";
private static final String PDF_PATH = "c:/fop";
private static final String TEXT_PATH = "c:/fop";
public FormatterTest()	{}	// End Default Constructor
	
	
	//for rendering the given xml and xsl file to pdf file
	private void renderToPDF(String xmlfilename,String xslfilename,String pdffilename)
	{
		//construct arguments here
		String xmlFilePath ="file:///" + FormatterTest.XML_PATH + 
		 	File.separatorChar + xmlfilename;
		
 	String xslFilePath ="file:///" + FormatterTest.XSL_PATH + 
							File.separatorChar + xslfilename;
		
 	String pdfFilePath =FormatterTest.PDF_PATH + 
 	 	File.separatorChar + pdffilename;
		
		//for now use paths from arguments passed later retrieve from an init servlet
		String args[] = new String[3];
		args[0]=xmlFilePath;
		args[1]=xslFilePath;
		args[2]=pdfFilePath;
		
		try
		{
			XMLFormatter.format2Pdf( args );
		}catch(Exception e)
		{
			System.out.println("Exception in rendering to Pdf " + e.toString() );
		}
	}
//for rendering the given xml and xsl file to text file
	private void renderToText( String xmlfilename, String xslfilename ,String textfilename)
	{
		String xmlFilePath ="file:///" + FormatterTest.XML_PATH + 
							File.separatorChar + xmlfilename;
		
		String xslFilePath ="file:///" + FormatterTest.XSL_PATH + 
							File.separatorChar + xslfilename;
							
 	String textFilePath =FormatterTest.TEXT_PATH + 
							File.separatorChar + textfilename;
		
		
		String args[] = new String[2];
		
		args[0]=xmlFilePath;
		args[1]=xslFilePath;
		
		
		String data="";
		
		try
		{
			data = XMLFormatter.format( args );
			
			try {
				 byte b[] = data.getBytes();
				 FileOutputStream outstream = new FileOutputStream(textFilePath);
				 outstream.write(b);
				 outstream.close();						 
			} catch(java.io.IOException e) {
			 System.out.println("Cannot write to " + textFilePath);
			}
			
		}catch(Exception e)
		{
			System.out.println("Exception in rendering to Text " + e.toString() );
		}
	}
//helper class wrapper methods
//Test suite
	public static void main(String[] args)
	{
		try
		{
			new FormatterTest().renderToPDF("sample.xml","pdf.xsl","sample.pdf");
			//System.out.println("Successfully generated pdf....");
			
			new FormatterTest().renderToText("sample.xml","text.xsl","sample.txt");
			//System.out.println("Successfully generated text....");
			
		}catch (Exception e)
		{
			e.printStackTrace();
		}
	}
}


So guys..the above sample should work fine as long as the jars i mentioned are in your classpath. 
For making it easier on you i have included a batch file to get you started.
Be sure you edit the format.bat and give the right path to ur unzipped folder.
My suggestion is unzip the folder to root of c directory and then its as easy as it can get.
You can manipulate the xsl or xml file and also visit the FOP site for more advanced information. 
Happy Programming!!!



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