Konda Reddy: April 2012

Wednesday, 25 April 2012

Tuning Performance of Java Web Application

Best Practices to improve performance in Servlets

1. Use init() method to cache static data
2. Use StringBuffer/StringBuilder rather than using + operator when you concatenate multiple strings
3. Use print() method rather than println() method
4. Use ServletOutputStream rather than PrintWriter to send binary data
5. Initialize the PrintWriter with proper size
6. Flush the data partly
7. Minimize code in the synchronized block
8. Set the content length
9. Release resources in destroy() method.
10. Implement getLastModified() method to use browser cache and server cache
11. Use application server caching facility
12. Use Mixed session mechanisms such as HttpSession with hidden fields
13. Remove HttpSession objects explicitly in your program whenever you finish the task
14. Reduce session time out value as much as possible
15. Use 'transient' variables to reduce serialization overhead if your HttpSession tracking mechanism uses serialization process.
16. Disable servlet auto reloading feature.
17. Use thread pool for your servlet engine and define the size as per application requirement.

Best Practices to improve Performance in JSP
1. Use jspInit() method to cache static data
2. Use StringBuffer rather than using + operator when you concatenate multiple strings
3. Use print() method rather than println() method
4. Use ServletOutputStream instead of JSPWriter to send binary data
5. Initialize the 'out' object (implicit object) with proper size in the page directive.
6. Flush the data partly
7. Minimize code in the synchronized block
8. Set the content length
9. Release resources in jspDestroy() method.
10. Give 'false' value to the session in the page directive to avoid session object creation.
11. Use include directive instead of include action when you want to include the child page content in the translation phase.
12. Avoid giving unnecessary scope in the 'useBean' action.
13. Do not use custom tags if you do not have reusability.
14. Use application server caching facility
15. Use Mixed session mechanisms such as 'session' with hidden fields
16. Use 'session' and 'application' as cache.
17. Use caching tags provided by different organizations like openSymphony.com
18. Remove 'session' objects explicitly in your program whenever you finish the task
19. Reduce session time out value as much as possible
20. Use 'transient' variables to reduce serialization overhead if your session tracking mechanism uses serialization process.
21. Disable JSP auto reloading feature.
22. Use thread pool for your JSP engine and define the size of thread pool as per application requirement.

Best practices to improve performance in JDBC

1. Get database connection from connection pool rather than getting it directly
2. Use batch transactions.
3. Choose right isolation level as per your requirement. TRANSACTION_READ_UNCOMMITED gives best performance for concurrent transaction based applications. TRANSACTION_NONE gives best performance for non-concurrent transaction based applications.
4. Your database server may not support all isolation levels, be aware of your database server features.
5. Use PreparedStatement when you execute the same statement more than once.
6. Use CallableStatement when you want result from multiple and complex statements for a single request.
7. Use batch update facility available in Statements.
8. Use batch retrieval facility available in Statements or ResultSet.
9. Set up proper direction for processing rows.
10. Use proper getXXX () methods.
11. Close ResultSet, Statement and Connection whenever you finish your work with them.
12. Write precise SQL queries.
13. Cache read-only and read-mostly tables data.

Performance improvement techniques in Object creation

1. Avoid creating objects in a loop.
2. Use String literals instead of String objects (created using the 'new' keyword) if the content is same.
3. Whenever you are done with an object make that reference null so that it is eligible for garbage collection.
4. Never keep inheriting chains long since it involves calling all the parent constructors all along the chain until the constructor for java.lang.Object is reached.
5. Use primitive data types rather than using wrapper classes.
6. Whenever possible avoid using class variables, use local variables since accessing local variables is faster than accessing class variables.
7. Another technique is Lazy object creation: i.e. delaying the memory allocation to an object till it is not being put into use. This way a lot of memory is saved till the object is actually put in to use.
Performance improvement techniques in Exceptions
1. In a catch block avoid using the generic class Exception. For each try block use specific catch blocks based on what can go wrong in your code.
2. Whenever you are using a throws clause always use the specific subclass of Exception like FileNotFoundException rather than using throws Exception.
3. Always use the finally block to release the resources like a database connection, closing a file or socket connection etc. This prevents resource leaks even if an exception occurs.
4. Do not use Exception handling in loops. It is better to place loops inside try/catch blocks than vice versa. Here is an code snippet that gives bench mark.

Performance improvement techniques in loops

1. Always use an int data type as the loop index variable whenever possible because it is efficient when compared to using byte or short data types. because when we use byte or short data type as the loop index variable they involve implicit type cast to int data type.
2. When using arrays it is always efficient to copy arrays using System.arraycopy() than using a loop.
3. Always avoid anything that can be done outside of the loop like method calls, assigning values to variables, or testing for conditions.
4. Method calls are very costly and you only make it worse by putting them in a loop. So as far as possible avoid method calls in a loop.
5. It is better to avoid accessing array elements in a loop the better option would be to use a temporary variables inside the loop and modify the array values out of the loop. It is fast to use a variable in a loop than accessing an array element.
6. Try to compare the terminating condition with zero if you use non-JIT or HotSpot virtual machine, here is an example to prove the point. JIT or HotSpot virtual machines are optimized for general loops so you do not have to bother about the terminating condition.

Reference: www.precisejava.com

Tips For Measuring Application Performance
Here are some of important points which should be considered while measuring application performance.

- Test systems should match production as closely as possible. Same hardware, OS, and software.
- Populate databases with the number of records expected in production.
An application may perform well with a small number of records in the database. Performance could degrade a great deal as the number of records in the table(s) increases
- Test HTTP requests with different request parameters.
Test with the extremes. A page which performs a search may perform well when the search criteria returns a small result set, but perform poorly when the search criteria returns a large result set.
- Simulate expected traffic over time including short term spikes.
A page which performs well with low request volume can cause the server to fail under higher request volume.
- Use Server load testing tools (like Apache Jakarta JMeter) to simulate heavy load.

Tomcat - Jboss Performance Tuning Tips

Apache Tomcat is an implmentation of the Java Servlet and JavaServer Pages technologies.
In production Enviroment, number of resources which can all impact application overall performance. Here are some important point which can help to improve Tomcat Performance.

Performance Tuning - Tomcat Configuration

Configure server.xml parameters as following.

-Set reloadable to false

When reloadable is true Tomcat tries to detect web application class changes and automatically reload any classes which change. Setting this to false removes a lot of unnecessary overhead in production.

-Set liveDeploy to false

liveDeploy controls whether your webapps directory is periodically checked for new web application directories and war files. This is done using a background thread. Set this to false and use the manager application or ant deploy tasks instead.

-Set debug to 0

Disable all debug output, unnecessary logging just adds overhead.

-Set swallowOutput to true

This makes sure all output to stdout or stderr for a web application gets directed to the web application log rather than the console or catalina.out. This makes it easier to troubleshoot web application problems.

Performance Tuning - Jasper 2 Configuration

Configure web.xml parameters as following.

-Set development to false

Disables JSP page out of date checks on each request and enables JSP background recompiles. development is set to true by default.

-Use JSP custom tag pooling

Object pooling of classes which implement custom tags significantly improves performance of JSP pages which use custom tag libraries. JSP custom tag pooling is enabled by default.

-Configure Jasper to fork javac compiles. (Do not set fork to true on MS Windows)

The JVM compiler javac has known memory leaks. Eliminates JVM memory usage and GC overhead of javac by configuring Jasper to fork javac when compiling JSP pages.

Make Textbox hidden/visible based on the DropDown selection using JavaScript

SOLUTION:

the following function will help you to solve this ......

function hideTextBox(dropDown1){
var valFromDropDown = dropDown1.value;
if(valFromDropDown == 'WRITE'){
document.forms[0].textBox1.style.visibility = "";
} else{
document.forms[0].textBox1.style.visibility = "hidden";
}
}

in the above example hideTextBox is the function name .....
and the input for this function is dropDown value selected......
in this example we are hiding the the text box if the drop down value is 'WRITE' else it will show the textbox......

the following Example.jsp page will clearly explain you how to implement this and please ignore this Symobl(--)inside the every tag Starting. i put this (--) for displaying html tags only kindly ignore that symbol

Example.jsp(please ignore this(--)symbol and try it it will surely work
--------------------------------------------------------------------

<%@taglib uri="/includes/struts-html.tld" prefix="html"%>
<%@taglib uri="/includes/struts-bean.tld" prefix="bean"%>
<%@taglib uri="/includes/struts-logic.tld" prefix="logic"%>



<script language="javascript">

function hideTextBox(dropDown1){
var valFromDropDown = dropDown1.value;
if(valFromDropDown == 'WRITE'){
document.forms[0].textBox1.style.visibility = "";
} else{
document.forms[0].textBox1.style.visibility = "hidden";
}
}

</script>




<table width="100%" border="0" cellspacing="0" cellpadding="0">

<tr>
<td width="20%">SelectProcess:
<td width="30%">
<html:select property="dropDown1" onchange="javascript:hideTextBox(this)">
<html:option value="READ">Read
<html:option value="WRITE">Write
<html:option value="OVERWRITE">OverWrite
</html:select>
<td width="20%">
<td width="30%">
</tr>

<tr>
<td width="20%">TextBox1:
<td width="30%">
<td width="30%"><html:text property="textBox1" maxlength="10" size="10">
</td>
<td width="20%">
<td width="30%">

</table>

</html:html>

--------------------------------------------------------------------------------------
from the above Example.jsp you can clearly understood how the function is implemented

note:

you have to declare these property in the form bean this is the example used in struts Frame work.

if you still having doubts write a comment on this.

Thanks

Download the CSV file using Servlets

import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class Csv
 */
@WebServlet("/Csv1")
public class Csv1 extends HttpServlet {
 private static final long serialVersionUID = 1L;

 /**
  * @see HttpServlet#HttpServlet()
  */
 public Csv1() {
  super();
  // TODO Auto-generated constructor stub
 }

 /**
  * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
  *      response)
  */
 protected void doGet(HttpServletRequest request,
   HttpServletResponse response) throws ServletException, IOException {
  // PrintWriter out = response.getWriter();
  Connection con = null;
  Statement stmt = null;
  ResultSet rs = null;
  try {
   Class.forName("com.mysql.jdbc.Driver");
   con = DriverManager.getConnection(
     "jdbc:mysql://localhost:3306/hibernate", "root", "root");
   stmt = con.createStatement();
   rs = stmt.executeQuery("SELECT * FROM employee");
   String filename = "d:\\csv\\myfile.csv";
   FileWriter fw = new FileWriter(filename);
   fw.append("Employee Code");
   fw.append(',');
   fw.append("Employee Name");
   fw.append('\n');

   while (rs.next()) {
    fw.append(rs.getObject(1).toString());
    fw.append(',');
    fw.append(rs.getObject(2).toString());
    fw.append('\n');
    fw.flush();
    // fw.close();
   }
   // out.println("<b>Csv file Successfully created.</b>");
   if (fw != null) {
    fw.close();
   }

  } catch (SQLException e) {
   throw new ServletException("Servlet Could not display records.", e);
  } catch (ClassNotFoundException e) {
   throw new ServletException("JDBC Driver not found.", e);
  } finally {
   try {
    if (rs != null) {
     rs.close();
     rs = null;
    }
    if (stmt != null) {
     stmt.close();
     stmt = null;
    }
    if (con != null) {
     con.close();
     con = null;
    }
   } catch (SQLException e) {
   }
  }

  File f = new File("d:\\csv\\myfile.csv");
  int length = 0;
  ServletOutputStream op = response.getOutputStream();
  ServletContext context = getServletConfig().getServletContext();
  String mimetype = context.getMimeType("text");
  //
  // Set the response and go!
  //
  //
  response.setContentType((mimetype != null) ? mimetype
    : "application/octet-stream");
  response.setContentLength((int) f.length());
  response.setHeader("Content-Disposition",
    "attachment; filename=d:\\csv1.csv");

  //
  // Stream to the requester.
  //
  byte[] bbuf = new byte[1024];
  DataInputStream in = new DataInputStream(new FileInputStream(f));

  while ((in != null) && ((length = in.read(bbuf)) != -1)) {
   op.write(bbuf, 0, length);
  }

  in.close();
  op.flush();
  op.close();
  // TODO Auto-generated method stub
 }

 /**
  * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
  *      response)
  */
 protected void doPost(HttpServletRequest request,
   HttpServletResponse response) throws ServletException, IOException {
  // TODO Auto-generated method stub
 }

}

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app>
<servlet>
<servlet-name>csv1</servlet-name>
<servlet-class>Csv1</servlet-class>

</servlet>
<servlet-mapping>
<servlet-name>csv1</servlet-name>
<url-pattern>/csv1</url-pattern>

</servlet-mapping>


</web-app>

Thursday, 12 April 2012

How to write our own result type in struts2

Action Class

package com.lkr.action;


import com.lkr.service.UserService;
import com.lkr.vo.User;
import com.opensymphony.xwork2.ActionSupport;


public class GetImageAction extends ActionSupport {


 private static final long serialVersionUID = 1L;
 private UserService userService;
 private Long id;
 private User user;


 public Long getId() {
  return id;
 }


 public void setId(Long id) {
  this.id = id;
 }


 public UserService getUserService() {
  return userService;
 }


 public void setUserService(UserService userService) {
  this.userService = userService;
 }


 @Override
 public String execute() throws Exception {

  System.out.println("this is come from after display image jsp");
  user = userService.getUserById(id);
  return "imageBytesResult";
 }


 public String getContentDisposition() {
  return "";
 }

 public int getBufferSize() {
  return 4096;
 }
}

Result Type Class

package com.lkr.action;


import javax.servlet.http.HttpServletResponse;


import org.apache.struts2.ServletActionContext;


import com.opensymphony.xwork2.ActionInvocation;
import com.opensymphony.xwork2.Result;


public class ImageBytesResult implements Result {


 private static final long serialVersionUID = 1L;


 @Override
 public void execute(ActionInvocation invocation) throws Exception {
  GetImageAction action = (GetImageAction) invocation.getAction();
  HttpServletResponse response = ServletActionContext.getResponse();


  //response.setContentType(action.getContentType());
  //response.setContentLength(action.getContentLength());
  response.getOutputStream().write(action.getImageInBytes());
  response.getOutputStream().flush();
 }


}

Service

package com.lkr.service;


import java.util.List;

import com.lkr.dao.UserDAO;
import com.lkr.vo.User;


public class UserService{
 private UserDAO userDao;


 public UserDAO getUserDao() {
  return userDao;
 }


 public void setUserDao(UserDAO userDao) {
  this.userDao = userDao;
 }


 
 public User save(User user) throws Exception {


  return userDao.save(user);
 }



 public List<User> getAllUsers() throws Exception {


  return userDao.getAllUsers();
 }


 
 public User getUserById(long id) throws Exception {
  return userDao.getUserById(id);
 }
}

DAO

package com.lkr.dao;


import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.util.List;

import org.hibernate.Transaction;

import com.lkr.vo.User;


public class UserDAO {


 
 public User save(User user) throws Exception {
  Transaction tx=getSession().beginTransaction();
  getSession().save(user);
  
  tx.commit();
  return user;
 }


 
 public List<User> getAllUsers() throws Exception {
  List<User> allUsers = getSession().createQuery("from User").list();
  return allUsers;
 }


 
 public User getUserById(long id) throws Exception {
  User user = (User) getSession().get(User.class, new Long(id));
  // Convert BLOB to byte array
  user.setImageInBytes(getImageInBytes(user));
  user.setContentLength((int) user.getImage().length());
  return user;
 }


 public byte[] getImageInBytes(User user) {


  if (user.getImage() == null) {
   return new byte[0];
  }
  ByteArrayOutputStream baos = new ByteArrayOutputStream();
  try {
   InputStream is = user.getImage().getBinaryStream();
   byte[] buf = new byte[1024];
   int i = 0;
   while ((i = is.read(buf)) >= 0) {
    baos.write(buf, 0, i);
   }
   is.close();
  } catch (Exception ex) {
   ex.printStackTrace();
  }
  return baos.toByteArray();
 }
}

struts.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE struts PUBLIC
    "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
    "http://struts.apache.org/dtds/struts-2.0.dtd">


<struts>
 <constant name="struts.devMode" value="false" />
 <constant name="struts.custom.i18n.resources" value="global" />
 <constant name="struts.objectFactory" value="spring" />


 <package name="commonPackage" namespace="/" extends="struts-default">


  <result-types>
   <result-type name="imageBytesResult"
    class="com.lkr.action.ImageBytesResult" />
  </result-types>


  <action name="addUserData" class="com.lkr.action.UserAction">
   <result name="input">
    WEB-INF/jsp/imageUploader.jsp
   </result>
  </action>
  <action name="displayFullImage" class="com.lkr.action.FullImageAction">
   <result name="input">
    WEB-INF/jsp/dispalyFullImage.jsp
   </result>
  </action>


  <action name="getImage" class="com.lkr.action.GetImageAction">
   <result name="imageBytesResult" type="imageBytesResult">
   </result>
  </action>
 </package>


</struts>

If you are directly getting Byte[] from the database then you don't need to convert Blob to Byte[]

Saturday, 7 April 2012

Creating Pdf By Using Struts2

Struts Framework and Stream Result type configuration for the Action to send binary stream to the browser as PDF
content type

In this example I shall be showing step by step ways to follow through various pieces of code to process or achieve
an objective of presenting binary content type to browser based client and this is presented to the client with the
same name as mentioned in struts.xml configuration file.

Struts.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC
    "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
    "http://struts.apache.org/dtds/struts-2.0.dtd">
<struts>
  <package name="stream-example" namespace="/sample-stream"
                 extends="struts-default">
    <action name="pdfAction" class="com.lkr.struts2.pdf.GeneratingPdfAction" 
                        method="generatingPdf">
       <result name="test-stream" type="stream">
         <param name="inputName">fileStream</param>
  <param name="contentType">application/pdf</param>
         <param name="contentDisposition">filename="test.pdf"</param>
       </result>
    </action>
  </package>
</struts>

Action class "GeneratingPdfAction.java" is having a generatingPdf method that assigns an input stream to a private

instance variable, this variable is mentioned as the inputName param value to the result tag.

In this example, the inputName param is having value as fileStream, that is defined as an instance variable

in Action class.

GeneratingPdfAction

package com.lkr.struts2.pdf;
import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Date;
import java.util.List;
import com.itextpdf.text.Anchor;
import com.itextpdf.text.BadElementException;
import com.itextpdf.text.BaseColor;
import com.itextpdf.text.Chapter;
import com.itextpdf.text.Document;
import com.itextpdf.text.DocumentException;
import com.itextpdf.text.Element;
import com.itextpdf.text.Font;
import com.itextpdf.text.ListItem;
import com.itextpdf.text.Paragraph;
import com.itextpdf.text.Phrase;
import com.itextpdf.text.Section;
import com.itextpdf.text.pdf.PdfPCell;
import com.itextpdf.text.pdf.PdfPTable;
import com.itextpdf.text.pdf.PdfWriter;

public class GeneratingPdfAction {
 private InputStream fileStream;
 private static String FILE = "c:/temp/FirstPdf.pdf";
 private static Font catFont = new Font(Font.FontFamily.TIMES_ROMAN, 18,
   Font.BOLD);
 private static Font redFont = new Font(Font.FontFamily.TIMES_ROMAN, 12,
   Font.NORMAL, BaseColor.RED);
 private static Font subFont = new Font(Font.FontFamily.TIMES_ROMAN, 16,
   Font.BOLD);
 private static Font smallBold = new Font(Font.FontFamily.TIMES_ROMAN, 12,
   Font.BOLD);

 public void setFileStream(InputStream arg) {
  fileStream = arg;
 }

 public InputStream getFileStream() {
  return fileStream;
 }


 public String generatingPdf() throws Exception {
  
  try {
   Document document = new Document();
   PdfWriter.getInstance(document, new FileOutputStream(FILE));
   document.open();
   addMetaData(document);
   addTitlePage(document);
   addContent(document);
   document.close();
  } catch (Exception e) {
   e.printStackTrace();
  }
  try{
   fileStream = new DataInputStream(
     new FileInputStream(FILE));
  } catch (IOException ioEx) {
   ioEx.printStackTrace();
  }
  
  return "test-stream";
 }
 
 private static void addMetaData(Document document) {
  document.addTitle("My first PDF");
  document.addSubject("Using iText");
  document.addKeywords("Java, PDF, iText");
  document.addAuthor("Konda Reddy. Lingamdinne");
  document.addCreator("Konda Reddy. Lingamdinne");
 }

 private static void addTitlePage(Document document)
   throws DocumentException {
  Paragraph preface = new Paragraph();
  // We add one empty line
  addEmptyLine(preface, 1);
  // Lets write a big header
  preface.add(new Paragraph("Title of the document", catFont));

  addEmptyLine(preface, 1);
  // Will create: Report generated by: _name, _date
  preface.add(new Paragraph(
    "Report generated by: " + System.getProperty("user.name") + ", " + new Date(), //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
    smallBold));
  addEmptyLine(preface, 3);
  preface.add(new Paragraph(
    "This document describes something which is very important ",
    smallBold));

  addEmptyLine(preface, 8);

  preface.add(new Paragraph(
    "This document is a preliminary version and not subject to your license agreement or any other agreement with vogella.de ;-).",
    redFont));

  document.add(preface);
  // Start a new page
  document.newPage();
 }

 private static void addContent(Document document) throws DocumentException {
  Anchor anchor = new Anchor("First Chapter", catFont);
  anchor.setName("First Chapter");

  // Second parameter is the number of the chapter
  Chapter catPart = new Chapter(new Paragraph(anchor), 1);

  Paragraph subPara = new Paragraph("Subcategory 1", subFont);
  Section subCatPart = catPart.addSection(subPara);
  subCatPart.add(new Paragraph("Hello"));

  subPara = new Paragraph("Subcategory 2", subFont);
  subCatPart = catPart.addSection(subPara);
  subCatPart.add(new Paragraph("Paragraph 1"));
  subCatPart.add(new Paragraph("Paragraph 2"));
  subCatPart.add(new Paragraph("Paragraph 3"));

  // Add a list
  Paragraph paragraph = new Paragraph();
  addEmptyLine(paragraph, 5);
  subCatPart.add(paragraph);

  // Add a table
  createTable(subCatPart);

  // Now add all this to the document
  document.add(catPart);

  // Next section
  anchor = new Anchor("Second Chapter", catFont);
  anchor.setName("Second Chapter");

  // Second parameter is the number of the chapter
  catPart = new Chapter(new Paragraph(anchor), 1);

  subPara = new Paragraph("Subcategory", subFont);
  subCatPart = catPart.addSection(subPara);
  subCatPart.add(new Paragraph("This is a very important message"));

  // Now add all this to the document
  document.add(catPart);

 }

 private static void createTable(Section subCatPart)
   throws BadElementException {
  PdfPTable table = new PdfPTable(3);

  // t.setBorderColor(BaseColor.GRAY);
  // t.setPadding(4);
  // t.setSpacing(4);
  // t.setBorderWidth(1);

  PdfPCell c1 = new PdfPCell(new Phrase("Table Header 1"));
  c1.setHorizontalAlignment(Element.ALIGN_CENTER);
  table.addCell(c1);

  c1 = new PdfPCell(new Phrase("Table Header 2"));
  c1.setHorizontalAlignment(Element.ALIGN_CENTER);
  table.addCell(c1);

  c1 = new PdfPCell(new Phrase("Table Header 3"));
  c1.setHorizontalAlignment(Element.ALIGN_CENTER);
  table.addCell(c1);
  table.setHeaderRows(1);

  table.addCell("1.0");
  table.addCell("1.1");
  table.addCell("1.2");
  table.addCell("2.1");
  table.addCell("2.2");
  table.addCell("2.3");

  subCatPart.add(table);

 }

 private static void addEmptyLine(Paragraph paragraph, int number) {
  for (int i = 0; i < number; i++) {
   paragraph.add(new Paragraph(" "));
  }
 }

}

web.xml

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE web-app
    PUBLIC "-//Sun Microsystems, 
    Inc.//DTD Web Application 2.3//EN"
    "http://java.sun.com/dtd/web-app_2_3.dtd">

<web-app>
    <display-name>Struts 2 Stream Result type</display-name>
  <filter>
  <filter-name>sample-filter</filter-name>
  <filter-class> 
    org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter
  </filter-class>
  </filter>
  <filter-mapping>
    <filter-name>sample-filter</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>
</web-app>

This example application creates PDF file and reads the PDF file from the path mentioned in the Action class and

generatingPdf method.
This result type definition in struts.xml file sends those to the client as downloadable file name.

English to Telugu Dictionary Powered by Tamilcube.com