Problem in concurrent access of a single method

Question

Hi,
I have one servlet named "Controllerservlet.java" and a jsp page "Inward jsp".
Now from this jsp user enters data which are being passed to controller servlet 's "insertData" method which is a synchronized method then it stores the query result in a variable "query_result" whatever it is ( if it throws exception "duplicate value insertion.... this will be assigned to query_result).
now when only one user is using then it is working fine.But when two user tried to enter the same data simultaneously then in one sceen it showed error message "Can't insert Duplicate value " and in others's it didn't show anything but inserted data.
I know that when i think data is being entered simultaneously then it is actually not simultaneously for computer.but according to me it shud have shown in one screen "successfully entered" and in other error message "Duplicate value....".
this is my servlets code
private synchronized void insertData(HttpServletRequest req, HttpServletResponse res)
             String date = req.getParameter("date");
             String department[] = req.getParameterValues("Department");
             String main_Building[] = req.getParameterValues("Main_Building");
             String Other = req.getParameter("Other");
             String Roll_No = req.getParameter("Roll_No");
             String Receiver = req.getParameter("Receiver");
             String subject = req.getParameter("subject");
              String buttontype = req.getParameter("buttontype");
             String entrytype = req.getParameter("type");
             String query="";
             String query_result="";
             String source="";
             String Department="",Main_Building="";
             if(department!=null && !department[0].equals("Select"))Department=department[0];
             if(department!=null)
            for (int i=1;i<department.length;i++)
                    Department+=","+department;
if(!Department.equals("")) source= Department;
if(main_Building!=null && !main_Building[0].equals("Select"))
Main_Building=main_Building[0];
if(main_Building!=null)
for (int i=1;i<main_Building.length;i++)
Main_Building+=","+main_Building[i];
if(!Main_Building.equals(""))
if(source.length()!=0)
source+="/"+Main_Building;
else source = Main_Building;
if(Other!=null&&Other.length()!=0)
if(source.length()!=0)
source+="/"+Other;
else source = Other;
Date now = new Date();
SimpleDateFormat formatter = new SimpleDateFormat(" hh:mm:ss a zzz");
String user = (String)session.getAttribute("user");
int srno=1;
try {
conn.setAutoCommit(false);
ResultSet rs = stmt.executeQuery("select max(srno) from incommingletters where deleted = 'F'");
if (rs.next())srno=rs.getInt(1);
srno++;
query= "insert into incommingletters values ("+srno+",'"+date+"','"+source+"','"+Roll_No+"','"+Receiver+"','"+subject+"','"+entrytype+"','F')";
stmt.executeUpdate(query);
query="insert into traceuser values ('"+user+"','Insertion','"+now+"','"+formatter.format(now)+"',"+srno+")";
stmt.executeUpdate(query);
conn.commit();
query_result="Entry No. "+srno+" Successfully Saved";
catch (SQLException e)
query_result= e.toString();
try
conn.rollback();
catch (SQLException e1)
out.println(e.toString());
out.println(e.toString());
     session.setAttribute("query_result",query_result);
     //gotojspPage("/resources/Inward.jsp", req, res);
          try
               res.sendRedirect(res.encodeRedirectURL("../resources/Inward.jsp"));
          catch (Exception e)
               out.println(e.toString());
manish

Answer 1

hi declangallagher,
now i am doing the connection in bean it looks like this
servlet code :
public class ControllerServlet extends HttpServlet
    PrintWriter out;
    HttpSession session;
    String  name=null;
    String buttontype=null;
    ManipulationOfData md= new ManipulationOfData();
     * Method which intialises the servlet
     * @throws ServletException
    public void init() throws ServletException
         * Method in servlet
         * @param req HttpServletRequest req
         * @param res HttpServletResponse res
         * @throws java.io.IOException
         * @throws ServletException
        public void doPost(HttpServletRequest req, HttpServletResponse res) throws IOException, ServletException
            doGet(req, res);
     * Method used in servlet
     * @param req HttpServletRequest req
     * @param res HttpServletResponse res
     * @throws IOException
     * @throws ServletException
    public void doGet(HttpServletRequest req, HttpServletResponse res) throws IOException, ServletException
        res.setContentType("text/html");
        out = res.getWriter();
        session = req.getSession(true);
        initialization();
     try
              trafficController(req, res);
        catch (Exception e)
            out.println(e.toString() + " In traffic controller");
         * Method that controls the traffic in Controllerservlet
         * @param req HttpServletRquest req
         * @param res HttpServletResponse res
         * @throws Exception
        private void trafficController(HttpServletRequest req, HttpServletResponse res) throws Exception
         String submit=null;
        submit= req.getParameter("submit");
        if (submit != null)
            submit = submit.trim();
        if (submit!=null)
                if (submit.equalsIgnoreCase("submit"))
                         buttontype =  req.getParameter("buttontype");
                           if(buttontype!=null)session.setAttribute("buttontype",buttontype);
                           insertData(req,res);
               else if (submit.equalsIgnoreCase("Sign in"))
                     removeValiditySession();
                       checkUser(req,res);
               else if (submit.equalsIgnoreCase("inward"))
                      removeInwardSession();
                   res.sendRedirect(res.encodeRedirectURL("../resources/Inward.jsp"));
                    //gotojspPage("/resources/Inward.jsp", req, res);
               else if (submit.equalsIgnoreCase("edit"))
                    removeOkSession();
                   session.setAttribute("updation","edit");
                   res.sendRedirect(res.encodeRedirectURL("../resources/serialno.jsp"));
               else if (submit.equalsIgnoreCase("remove"))
                    removeOkSession();
                   session.setAttribute("updation","delete");
                   res.sendRedirect(res.encodeRedirectURL("../resources/serialno.jsp"));
                else if (submit.equalsIgnoreCase("Ok"))
                    editDelete(req,res);
                else if (submit.equalsIgnoreCase("view"))
                       removeShowSession();
                    res.sendRedirect(res.encodeRedirectURL("../resources/viewresult.jsp"));
                         //gotojspPage("/resources/viewresult.jsp", req, res);
                else if (submit.equalsIgnoreCase("Update"))
                    updateRecord(req,res);
                else if (submit.equalsIgnoreCase("Delete"))
                    //out.println("manish");
                      deleteRecord(req,res);
                        //gotojspPage("/resources/delete.jsp", req, res);
                else if (submit.equalsIgnoreCase("Show Data"))
                    removeShowSession();
                       showData(req,res);
                else if (submit.equalsIgnoreCase("signout"))
                    SignOut();
                  res.sendRedirect(res.encodeRedirectURL("../resources/signout.jsp"));
                else if (submit.equalsIgnoreCase("home"))
                    res.sendRedirect(res.encodeRedirectURL("../resources/authentication.jsp"));
                else if (submit.equalsIgnoreCase("back"))
                    removeShowSession();
                    res.sendRedirect(res.encodeRedirectURL("../resources/viewresult.jsp"));
                else if (submit.equalsIgnoreCase("deleteback"))
                    removeInwardSession();
                    res.sendRedirect(res.encodeRedirectURL("../resources/Inward.jsp"));
                  else
                       out.println("No Target");
    private void checkUser(HttpServletRequest req, HttpServletResponse res)
        try
            Authentication auth = new Authentication();
            String user = req.getParameter("userid");
            user = user.trim();
            String password = req.getParameter("password");
            password = password.trim();
            session.setAttribute("password", password);
            String validity = auth.isValid(user, password);
            session.setAttribute("validity", validity);
            session.setAttribute("user",user);
            if(validity.equals("true"))
                  removeInwardSession();
                res.sendRedirect(res.encodeRedirectURL("../resources/Inward.jsp"));
               //gotojspPage("/resources/Inward.jsp", req, res);
            else
                removeInwardSession();
                res.sendRedirect(res.encodeRedirectURL("../resources/authentication.jsp"));
        catch (Exception ex)
            out.println(ex.toString());
        private   void insertData(HttpServletRequest req, HttpServletResponse res)
             String date = req.getParameter("date");
             String department[] = req.getParameterValues("Department");
             String main_Building[] = req.getParameterValues("Main_Building");
             String Other = req.getParameter("Other");
             String Roll_No = req.getParameter("Roll_No");
             String Receiver = req.getParameter("Receiver");
             String subject = req.getParameter("subject");
              String buttontype = req.getParameter("buttontype");
             String entrytype = req.getParameter("type");
             String query="";
             String query_result="";
             String source="";
             String Department="",Main_Building="";
             if(department!=null && !department[0].equals("Select"))Department=department[0];
             if(department!=null)
            for (int i=1;i<department.length;i++)
                    Department+=","+department;
if(!Department.equals("")) source= Department;
if(main_Building!=null && !main_Building[0].equals("Select"))
Main_Building=main_Building[0];
if(main_Building!=null)
for (int i=1;i<main_Building.length;i++)
Main_Building+=","+main_Building[i];
if(!Main_Building.equals(""))
if(source.length()!=0)
source+="/"+Main_Building;
else source = Main_Building;
if(Other!=null&&Other.length()!=0)
if(source.length()!=0)
source+="/"+Other;
else source = Other;
String user = (String)session.getAttribute("user");
query_result=md.InsertData(date,source,Roll_No,Receiver,subject,entrytype,user);
     session.setAttribute("query_result",query_result);
     //gotojspPage("/resources/Inward.jsp", req, res);
          try
               res.sendRedirect(res.encodeRedirectURL("../resources/Inward.jsp"));
          catch (Exception e)
               out.println(e.toString());
private void showData(HttpServletRequest req, HttpServletResponse res)
String exactdate = req.getParameter("date");
String srnostr = req.getParameter("srno");
String fromdate = req.getParameter("from");
String todate = req.getParameter("to");
String Roll_No = req.getParameter("Roll_No");
String Receiver = req.getParameter("Receiver");
String subject = req.getParameter("subject");
String Department = req.getParameter("Department");
String Main_Building = req.getParameter("Main_Building");
String Other = req.getParameter("Other");
String entrytype = req.getParameter("type");
String condition="";
String buttontxt ="",source="";
String date;
// out.println(fromdate);out.println(todate);
subject = subject.trim();
if(!Department.equalsIgnoreCase("Select")) source= Department;
if(!Main_Building.equalsIgnoreCase("Select"))
if(source.length()!=0)
source+="/"+Main_Building;
else source = Main_Building;
if(Other!=null&&Other.length()!=0)
if(source.length()!=0)
source+="/"+Other;
else source = Other;
if (exactdate!=null && exactdate.length()!=0) condition = " date = '"+exactdate+"'";
else if(fromdate!=null &&todate!=null &&fromdate.length()!=0 && todate.length()!=0)
condition = " date between '"+ fromdate+"' and '"+ todate+"'";
if(source!=null&&source.length()!=0)
if(!condition.equals(""))
condition+=" AND source like '%"+source+"%'";
else
condition+=" source like '%"+source+"%'";
if(Roll_No!=null&&Roll_No.length()!=0)
if(!condition.equals(""))
condition+=" AND rollno like '%"+Roll_No+"%'";
else
condition+=" rollno like '%"+Roll_No+"%'";
if(Receiver!=null&&!Receiver.equalsIgnoreCase("Select"))
if(!condition.equals(""))
condition+=" AND reciever like '%"+Receiver+"%'";
else
condition+=" reciever like '%"+Receiver+"%'";
if(subject!=null&&subject.length()!=0)
if(!condition.equals(""))
condition+=" AND subject like '%"+subject+"%'";
else
condition+=" subject like '%"+subject+"%'";
if(entrytype!=null&&entrytype.length()!=0)
if(!condition.equals(""))
condition+=" AND type = '"+entrytype+"'";
else
condition+=" type = '"+entrytype+"'";
if(srnostr!=null&&srnostr.length()!=0)
int srno = Integer.parseInt(srnostr);
if(!condition.equals(""))
condition+=" AND srno = "+srno;
else
condition+=" srno = "+srno;
buttontxt = req.getParameter("buttontxt");
Vector show_data_vec = md.showData(condition);
String queryexception= show_data_vec.elementAt(0).toString();
Vector cols_name_vec = (Vector)show_data_vec.elementAt(1);
Vector resultset_ob_vec = (Vector)show_data_vec.elementAt(2);
if(queryexception.equals("Successful"))
try {
res.sendRedirect(res.encodeRedirectURL("../resources/result.jsp"));
catch (IOException e)
out.println(e.toString());
else
try
res.sendRedirect(res.encodeRedirectURL("../resources/viewresult.jsp"));
          catch (Exception e)
               out.println(e.toString());
session.setAttribute("queryexception",queryexception);
session.setAttribute("buttontxt",buttontxt);
session.setAttribute("resultset_ob_vec",resultset_ob_vec);
session.setAttribute("cols_name_vec",cols_name_vec);
private void updateRecord(HttpServletRequest req, HttpServletResponse res)
String date = req.getParameter("date");
String department[] = req.getParameterValues("Department");
String main_Building[] = req.getParameterValues("Main_Building");
String Other = req.getParameter("Other");
String Roll_No = req.getParameter("Roll_No");
String Receiver = req.getParameter("Receiver");
String subject = req.getParameter("subject");
     String buttonedit = req.getParameter("buttonedit");
String entrytype = req.getParameter("type");
String query="";
String source="";
String serialnostr=(String)session.getAttribute("serialno");
int serialno=Integer.parseInt(serialnostr);
String Department="",Main_Building="";
if(department!=null && !department[0].equals("Select"))Department=department[0];
if(department!=null)
for (int i=1;i<department.length;i++)
Department+=","+department[i];
if(!Department.equals("")) source= Department;
if(main_Building!=null && !main_Building[0].equals("Select"))
Main_Building=main_Building[0];
if(main_Building!=null)
for (int i=1;i<main_Building.length;i++)
Main_Building+=","+main_Building[i];
if(!Main_Building.equals(""))
if(source.length()!=0)
source+="/"+Main_Building;
else source = Main_Building;
if(Other!=null&&Other.length()!=0)
if(source.length()!=0)
source+="/"+Other;
else source = Other;
String user = (String)session.getAttribute("user");
String editqrexception=null;
ResultsetData rsdata = new ResultsetData();
editqrexception=md.UpdateData(rsdata,date,source,Roll_No,Receiver,subject,serialno,entrytype,user);
session.setAttribute("rsdata",rsdata);
session.setAttribute("buttonedit",buttonedit);
session.setAttribute("editqrexception",editqrexception);
try
res.sendRedirect(res.encodeRedirectURL("../resources/edit.jsp"));
catch (Exception e)
out.println(e.toString());
private void deleteRecord(HttpServletRequest req, HttpServletResponse res)
          String serialnostr = (String) session.getAttribute("serialno");
int serialno = Integer.parseInt(serialnostr);
          out.println(serialno);
          String deleteqrexception=null,buttondelete=null;
ResultsetData rsdata = new ResultsetData();
String user = (String)session.getAttribute("user");
deleteqrexception=md.DeleteData(rsdata,serialno,user);
          if(!deleteqrexception.equals("Successful"))
session.setAttribute("rsdata",rsdata);
session.setAttribute("buttondelete",buttondelete);
session.setAttribute("deleteqrexception",deleteqrexception);
try
res.sendRedirect("../resources/delete.jsp");
catch (Exception e)
out.println(e.toString());
else
try
res.sendRedirect(res.encodeRedirectURL("../resources/deletemessage.html"));
catch (Exception e)
out.println(e.toString());
private void editDelete(HttpServletRequest req, HttpServletResponse res)
String buttonok=null;
String updation=(String)session.getAttribute("updation");
String serialnostr = req.getParameter("serialno");
buttonok = req.getParameter("buttonok");
session.setAttribute("buttonok",buttonok);
int rowcount = 0;
ResultsetData rsdata = new ResultsetData();
String query_result =null;
int serialno = Integer.parseInt(serialnostr);
query_result = md.editDelete(serialno,rsdata);
session.setAttribute("serialno",serialnostr);
session.setAttribute("rsdata",rsdata);
if(query_result.equals("Successful"))
if (updation!=null)
if(updation.equals("edit"))
try
removeEditSession();
res.sendRedirect(res.encodeRedirectURL("../resources/edit.jsp"));
catch (IOException e)
out.println(e.toString());
else if (updation.equals("delete"))
try {
removeDeleteSession();
res.sendRedirect(res.encodeRedirectURL("../resources/delete.jsp"));
catch (IOException e)
out.println(e.toString());
else
try
res.sendRedirect(res.encodeRedirectURL("../resources/serialno.jsp"));
          catch (Exception e)
               out.println(e.toString());
private void initialization()
Vector initial_vec = new Vector();
Vector departments_vec = new Vector();
Vector mainbuild_vec = new Vector();
Vector receiver_vec = new Vector();
initial_vec = md.Initialization();
departments_vec = (Vector)initial_vec.elementAt(0);
mainbuild_vec = (Vector)initial_vec.elementAt(1);
receiver_vec = (Vector)initial_vec.elementAt(2);
session.setAttribute("departments_vec",departments_vec);
session.setAttribute("mainbuild_vec",mainbuild_vec);
session.setAttribute("receiver_vec",receiver_vec);
private void removeInwardSession()
          String serialno ="";
          String buttontype = (String)session.getAttribute("buttontype");
serialno = (String) session.getAttribute("serialno");
          if(serialno!=null)
                    serialno=null;
                    session.setAttribute("serialno",serialno);
          if(buttontype!=null)
                    buttontype=null;
                    session.setAttribute("buttontype",buttontype);
private void removeShowSession()
          String buttontxt ="";String queryexception ="";
          buttontxt = (String) session.getAttribute("buttontxt");
          if(buttontxt!=null)
                    buttontxt=null;
                    session.setAttribute("buttontxt",buttontxt);
queryexception = (String) session.getAttribute("buttontxt");
          if(queryexception!=null)
                    queryexception=null;
                    session.setAttribute("queryexception",queryexception);
private void removeEditSession()
          String buttonedit ="";
          buttonedit = (String) session.getAttribute("buttonedit");
          if(buttonedit!=null)
                    buttonedit=null;
                    session.setAttribute("buttonedit",buttonedit);
private void removeDeleteSession()
          String buttondelete ="";
          buttondelete = (String) session.getAttribute("buttondelete");
          if(buttondelete!=null)
                    buttondelete=null;
                    session.setAttribute("buttondelete",buttondelete);
private void removeOkSession()
          String buttonok ="";
          buttonok = (String) session.getAttribute("buttonok");
          if(buttonok!=null)
                    buttonok=null;
                    session.setAttribute("buttonok",buttonok);
private void removeValiditySession()
          String validity ="";
          validity = (String) session.getAttribute("validity");
          if(validity!=null)
                    validity=null;
                    session.setAttribute("validity",validity);
private void SignOut()
removeValiditySession();
public void destroy()
try
ConnectionPool.freeCon(conn);
removeValiditySession();
catch (Exception exp)
out.println(exp.toString());
i know its very lengthy so concentrate on insertData method and doget only
and here is the bean
public class ManipulationOfData
        String url="jdbc:postgresql://10.99.13.203/dispatch";
        String driver="org.postgresql.Driver";
        String username="manish";
        String password="manish";
        Connection conn=null;
        Statement stmt =null;
       String valid="false";
    public void getConnection()
      try
           Class.forName(driver);
           conn = DriverManager.getConnection(url,username,password);
           stmt= conn.createStatement();
        catch(Exception e)
            valid=e.toString();
    public void closeConnection()
      try
           stmt.close();
           conn.close();
        catch(Exception e)
            valid=e.toString();
    public synchronized String InsertData(String date,String source,String Roll_No,String Receiver,String subject,String entrytype,String user)
        getConnection();
        int srno=1;
        String query_result="";
        Date now = new Date();
        SimpleDateFormat formatter = new SimpleDateFormat(" hh:mm:ss a zzz");
            try {
                    conn.setAutoCommit(false);
                    ResultSet rs = stmt.executeQuery("select max(srno) from incommingletters where deleted = 'F'");
                    if (rs.next())srno=rs.getInt(1);
                    srno++;
                    String query= "insert into incommingletters values ("+srno+",'"+date+"','"+source+"','"+Roll_No+"','"+Receiver+"','"+subject+"','"+entrytype+"','F')";
                        stmt.executeUpdate(query);
                        query="insert into traceuser values ('"+user+"','Insertion','"+now+"','"+formatter.format(now)+"',"+srno+")";
                        stmt.executeUpdate(query);
                        conn.commit();
                     query_result="Entry No. "+srno+" Successfully Saved";
            catch (SQLException e)
                    query_result= e.toString();
                    try
                        conn.rollback();
                    catch (SQLException e1)
                        query_result=e.toString();
                  query_result=e.toString();
        closeConnection();
    return query_result;
    public synchronized String UpdateData(ResultsetData rsdata,String date,String source,String Roll_No,String Receiver,String subject,int serialno,String entrytype,String user)
        getConnection();
        String query_result="";
        Date now = new Date();
        SimpleDateFormat formatter = new SimpleDateFormat(" hh:mm:ss a zzz");
        try {
                conn.setAutoCommit(false);
                String query= "update incommingletters set date = '"+date+"',type = '"+entrytype+"',source = '"+source+"',rollno = '"+Roll_No+"',"+
                        "reciever = '"+Receiver+"',subject = '"+subject+"' where srno ="+serialno +" and deleted = 'F'";
                stmt.executeUpdate(query);
                query="insert into traceuser values ('"+user+"','Updation','"+now+"','"+formatter.format(now)+"',"+serialno+")";
                stmt.executeUpdate(query);
               conn.commit();
               ResultSet rs = stmt.executeQuery("select * from incommingletters where srno ="+serialno+
                       " and deleted = 'F'");
               rsdata =  putResClass(rs,rsdata);
                //conn.close();
                //ConnectionPool.freeCon(conn);
                query_result="Successfully Updated";
            catch (SQLException e)
                try
                    conn.rollback();
                    //conn.close();
                    //  ConnectionPool.freeCon(conn);
                } catch (SQLException e1) {
                    query_result=e.toString();
                query_result=e.toString();
        closeConnection();
     return query_result;
    public synchronized String DeleteData(ResultsetData rsdata,int serialno,String user)
        getConnection();
        Date now = new Date();
        SimpleDateFormat formatter = new SimpleDateFormat(" hh:mm:ss a zzz");
        String query_result="";
        try {
                conn.setAutoCommit(false);
                stmt.executeUpdate("update incommingletters set deleted ='T' where srno ="+serialno);
                String query="insert into traceuser values ('"+user+"','Deletion','"+now+"','"+formatter.format(now)+"',"+serialno+")";
                stmt.executeUpdate(query);
                conn.commit();
                query_result = "Successful";
        catch (SQLException e)
            query_result=e.toString();
            try {
                    conn.rollback();
                    ResultSet rs = stmt.executeQuery("select * from incommingletters where srno ="+serialno+" and deleted='F'");
                    rsdata =  putResClass(rs,rsdata);
                    // conn.close();
                    //ConnectionPool.freeCon(conn);
            catch (SQLException e1)
                    query_result=e1.toString();
         closeConnection();
       return query_result;
   public Vector showData(String condition)
       getConnection();
       String query="",query_result="";
       int rowcount=0;
       Vector show_data = new Vector();
       Vector cols_name_vec = new Vector();
       Vector resultset_ob_vec = new Vector();
       ResultSet rs=null;
       try {
                if(!condition.equals(""))
                query = "select COUNT(*) as rowcount from incommingletters where "+condition+" and deleted='F'";
                 else
                query = "select COUNT(*) as rowcount from incommingletters where deleted ='F' ";
                 rs = stmt.executeQuery(query);
                if(rs.next()) rowcount= rs.getInt("rowcount") ;
       catch (SQLException e)
                query_result=e.toString();
       if(rowcount!=0)
                 try
                     if(!condition.equals(""))
                      query = "select * from incommingletters where "+condition+" and deleted='F' order by srno";
                    else
                        query = "select * from incommingletters where deleted = 'F' order by srno";
                        rs = stmt.executeQuery(query);
                     query_result ="Successful";
                     ResultSetMetaData rsmd = rs.getMetaData();
                     int totcols=rsmd.getColumnCount();
                     String col;
                     for(int i=0;i<totcols;i++)
                         if(!rsmd.getColumnName(i+1).equals("type")&&!rsmd.getColumnName(i+1).equals("deleted"))
                         cols_name_vec.addElement(rsmd.getColumnName(i+1));
                        try {
                                while (rs.next())
                                          ResultsetData rsdata = new ResultsetData();
                                          rsdata = new ResultsetData();
                                          rsdata.setSrno(rs.getInt("srno"));
                                          rsdata.setDate(rs.getDate("date"));
                                          rsdata.setRollno(rs.getString("rollno"));
                                          rsdata.setSource(rs.getString("source"));
                                          rsdata.setReciever(rs.getString("reciever"));
                                          rsdata.setSubject(rs.getString("subject"));
                                          resultset_ob_vec.addElement(rsdata);
                        catch (SQLException e)
                     Results