Use of Synchronized in jsp/servlet

Can any one explain me the use of Synchronized in servlet/jsp which is multithreaded Is this correct synchronized should be used only when we want to pritect Static variable as they have only one copy but in case of instance variable they have seperate copy for each instance so no point of synchronized.
Thanks in advance

Hello again,
Take an external file for instance, you open a input stream to it and read data from it in your Java application. You can't have two threads reading at the same time, and one will likely block or throw an exception.
A better example is when your threads need to communicate with each other. If they all communicate via a set of variables that can be read and written to by any of them, then they should be synchronized. You should know if your threads need to communicate with each other? If they do not, there is no need for synchronisation.
What are your threads doing if you don't mind me asking?
I have to admit, I have had little experience using threads, and I have never needed to use threads in JSP (I don ot directly use servlets).
Regards,
Darren

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Thanks!
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Edited by: BobXu on Nov 17, 2008 2:27 PM
Edited by: BobXu on Nov 17, 2008 2:32 PM

Huh?
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I need some help pls
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package mypackage1;
import java.io.OutputStream;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.PrintWriter;
import java.io.IOException;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileReader;
import java.io.FileNotFoundException;
import java.io.Writer;
import java.sql.Connection;
import oracle.jdbc.*;
import oracle.jdbc.OracleResultSet;
import oracle.sql.BLOB;
import org.apache.log4j.Logger;
import Util_Connect.DataBase;
public class TestLOB
//static final Logger logger = Logger.getLogger("test");
public TestLOB()
public static void main(String args[])
TestLOB testLOB = new TestLOB();
testLOB.TestLOBInsert("c:\\my_data\\callcenterpilot.doc");
public void TestLOBInsert(String fileName)
Connection conn = getConnection("wizard");
BLOB blob = null;
try
conn.setAutoCommit(false);
String cmd = "SELECT * FROM so_cs.testlob WHERE docno = 1 FOR UPDATE";
PreparedStatement pstmt = conn.prepareStatement(cmd);
ResultSet rset = pstmt.executeQuery(cmd);
rset.next();
blob = ((OracleResultSet)rset).getBLOB(2);
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System.out.println("Document length = " + binaryFile.length());
FileInputStream instream = new FileInputStream(binaryFile);
OutputStream outstream = blob.getBinaryOutputStream();
int size = blob.getBufferSize();
byte[] buffer = new byte[size];
int length = -1;
while ((length = instream.read(buffer)) != -1)
outstream.write(buffer, 0, length);
instream.close();
outstream.close();
conn.commit();
closeConnection(conn);
catch (Exception ex)
System.out.println("Error =- > "+ex.toString());
private Connection getConnection(String dataBase)
Connection conn = null;
try
DriverManager.registerDriver(new OracleDriver());
conn = DriverManager.getConnection("jdbc:oracle:thin:@oraclu5:1600:dwz110","so_cs","so_cs");
catch (Exception ex)
System.out.println("Error getting conn"+ex.toString());
return conn;
private void closeConnection(Connection conn)
if (conn != null)
try
conn.close();
catch (Exception se)
System.out.println("Error closing connection in get last imei"+se.toString());
Works fine:
Here is the display servlet: Works when main class inserts file
package mypackage1;
import java.io.InputStream;
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.PrintWriter;
import java.io.IOException;
import java.io.OutputStream;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileReader;
import java.io.FileNotFoundException;
import java.io.Writer;
import java.sql.Connection;
import oracle.jdbc.*;
import oracle.jdbc.OracleResultSet;
import oracle.sql.BLOB;
import org.apache.log4j.Logger;
import Util_Connect.DataBase;
public class DisplayLOB extends HttpServlet
private static final String CONTENT_TYPE = "text/html; charset=windows-1252";
static final Logger logger = Logger.getLogger(DisplayLOB.class);
public void init(ServletConfig config) throws ServletException
super.init(config);
public void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
//response.setContentType(CONTENT_TYPE);
//PrintWriter out = response.getWriter();
Connection conn = null;
PreparedStatement pstmt = null;
try
conn = getConnection("wizard");
//out.println("<html>");
//out.println("<head><title>DisplayLOB</title></head>");
//out.println("<body>");
//out.println("<p>The servlet has received a POST. This is the reply.</p>");
InputStream is=null;
oracle.sql.BLOB blob=null;
response.setContentType("application/msword");
//response.setContentType("audio/mpeg");
OutputStream os = response.getOutputStream();
String term = "1";
String query = "SELECT docdetail FROM testlob WHERE docno = 1";
pstmt = conn.prepareStatement(query);
ResultSet rs = pstmt.executeQuery();
while (rs.next())
blob=((OracleResultSet)rs).getBLOB(1);
is=blob.getBinaryStream();
int pos=0;
int length=0;
byte[] b = new byte[blob.getChunkSize()];
while((length=is.read(b))!= -1)
pos+=length;
os.write(b);
}//try
catch (Exception se)
se.printStackTrace();
finally
try
pstmt.close();
catch (Exception ex)
System.out.println("Error closing pstmt "+ex.toString());
//out.println("</body></html>");
//out.close();
private Connection getConnection(String dataBase)
Connection conn = null;
try
conn = DataBase.getPoolConnection(dataBase);
catch (Exception se)
logger.fatal("Error getting connection: ",se);
return conn;
private void closeConnection(Connection conn)
if (conn != null)
try
conn.close();
catch (Exception se)
logger.error("Error closing connection in get last imei",se);
Here is JSP/Servlet
<%@ page import="org.apache.log4j.*"%>
<%@ page contentType="text/html; charset=ISO-8859-1" %>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
<title>untitled</title>
<title>Wizard SMS Interface</title>
<link rel='stylesheet' type='text/css' href='main1.css'>
<script language='JavaScript' src='copyright.js'></script>
</head>
<pre>
<%
//HTTP 1.1
response.setHeader("Cache-Control","no-cache");
//HTTP 1.0
response.setHeader("Pragma","no-cache");
//prevents caching at the proxy server
response.setDateHeader ("Expires", 0);
Logger logger = Logger.getLogger("co.za.mtn.wizard.administration.admin01.jsp");
%>
</pre>
<body>
<FORM ACTION="/WizardAdministration/uploadfile"
METHOD="POST"
ENCTYPE="multipart/form-data">
<INPUT TYPE="FILE" NAME="example">
<INPUT TYPE="SUBMIT" NAME="button" VALUE="Upload">
</FORM>
</body>
</html>
<font> <b>Copyright ©
<script>
var LMDate = new Date( document.lastModified );
year = LMDate.getYear();
document.write(display(year));
</script>
Mobile Telephone Networks.
<p align="left"><i><b><font face="Georgia, Times New Roman, Times, serif" size="1"></font></b></i></p>
package co.za.mtn.wizard.admin;
import java.io.InputStream;
import java.util.Enumeration;
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.PrintWriter;
import java.io.IOException;
import java.io.OutputStream;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileReader;
import java.io.FileNotFoundException;
import java.io.Writer;
import java.sql.Connection;
import oracle.jdbc.OracleResultSet;
import oracle.sql.BLOB;
import org.apache.log4j.Logger;
import Util_Connect.DataBase;
public class UploadFile extends HttpServlet
private static final String CONTENT_TYPE = "text/html; charset=windows-1252";
//static final Logger logger = Logger.getLogger(UploadFile.class);
public void init(ServletConfig config) throws ServletException
super.init(config);
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
String headerName = null;
Enumeration en = request.getHeaderNames();
try
while ( en.hasMoreElements() )
Object ob = en.nextElement();
headerName = ob.toString();
System.out.println("Value for headerNAme is >"+headerName+"<");
String aaa = request.getHeader(headerName);
System.out.println("Value for aa is >"+aaa+"<");
catch (Exception ex)
System.out.println("Error in extracting request headers"+ex.toString());
Connection conn = getConnection("wizard");
BLOB blob = null;
try
conn.setAutoCommit(false);
String cmd = "SELECT * FROM so_cs.testlob WHERE docno = 1 FOR UPDATE";
PreparedStatement pstmt = conn.prepareStatement(cmd);
ResultSet rset = pstmt.executeQuery(cmd);
rset.next();
blob = ((OracleResultSet)rset).getBLOB(2);
//File binaryFile = new File("h:\\callcenterpilot.doc");
//System.out.println("Document length = " + binaryFile.length());
//FileInputStream instream = new FileInputStream(binaryFile);
response.setHeader("Content-Type","application/vnd.ms-word");
String contentType = request.getContentType();
System.out.println("Content type received in servlet is >"+contentType+"<");
ServletInputStream instream = request.getInputStream();
OutputStream outstream = blob.getBinaryOutputStream();
int size = blob.getBufferSize();
byte[] buffer = new byte[size];
int length = -1;
while ((length = instream.read(buffer)) != -1)
outstream.write(buffer, 0, length);
instream.close();
outstream.close();
conn.commit();
closeConnection(conn);
response.setContentType(CONTENT_TYPE);
PrintWriter out = response.getWriter();
catch (Exception ex)
System.out.println("Error =- > "+ex.toString());
//out.println("</body></html>");
//out.close();
private Connection getConnection(String dataBase)
Connection conn = null;
try
conn = DataBase.getPoolConnection(dataBase);
catch (Exception se)
System.err.println("Error getting connection: "+se.toString());
return conn;
private void closeConnection(Connection conn)
if (conn != null)
try
conn.close();
catch (Exception se)
System.err.println("Error closing connection in get last imei"+se.toString());
This is what the display servlet is showing when the JSP/Servlet insert the document
-----------------------------7d31422224030e
Content-Disposition: form-data; name="example"; filename="H:\(your name) Skills Matrix.doc"
Content-Type: application/msword
�� ࡱ � > ��
Tks
Andre

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Use of Synchronized in jsp/servlet

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