Automatically Generating ID

[Mohini Dhanaskar]

hello All,

i want to generate RegistrationID in the Registration form.

how to do this?

[Prashant Chindhade]

put this is Regestration servlet. and call it when you want to get id.

public long GenerateId(){
int randomId = 0;
Random rand = new Random(); 
 for (int j=0;j < 10;j++)
 {   
      randomId = rand.nextLong();  
 } 
return randomId; 
}

[Mohini Dhanaskar]

Suppose this is my code for Complaint Registration, then where should i put that code.

public class ComplaintServlet extends HttpServlet {
 Connection con;
	PreparedStatement ps = null;

	public void init(ServletConfig config) throws ServletException {
		con = DatabaseConnection.getConnection();
	}

	public void destroy() {
		try {
			ps.close();
			DatabaseConnection.close(con);
		} catch (SQLException e) {
			e.printStackTrace();
		}
	}
        public void doGet(HttpServletRequest req,HttpServletResponse res)
   throws ServletException
    {

       try{
            doPost(req,res);
            }
            catch(IOException e)
            { 

            }

     }
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {

               try {
               int cid=Integer.parseInt(request.getParameter("cid"));
               System.out.println("cid = " + cid);
              

               int con_id=Integer.parseInt(request.getParameter("con_id"));
               System.out.println("con_id = " + con_id);


               String Complaint_Type=request.getParameter("Complaint_Type");
               System.out.println("Complaint_Type = " + Complaint_Type);

               int nocomp=Integer.parseInt(request.getParameter("nocomp"));
               System.out.println("nocomp = " + nocomp);

               int noprbm=Integer.parseInt(request.getParameter("noprbm"));
               System.out.println("noprbm= " + noprbm);

               

               String btnSubmit=request.getParameter("btnSubmit");
               System.out.println("btnSubmit= " + btnSubmit);

               if(btnSubmit.equals("SUBMIT"))
               {
                   String sql = "Insert into RegisterComplaint Values(?,?,?,?,?)";
				try {
					ps = con.prepareStatement(sql);
					ps.setInt(1, cid);
                                        ps.setInt(2, con_id);
					ps.setString(3, Complaint_Type);
					ps.setInt(4, nocomp);
					ps.setInt(5, noprbm);
					
					ps.executeUpdate();
				    } catch (SQLException e) {

					e.printStackTrace();
				}
                   response.sendRedirect("SuccessfulComplaintRegister.jsp");
               }

        } catch (Exception ex) {
			System.out.println(ex.getMessage());
        }


    }




}

[Prashant Chindhade]

You can put this code anywhere see for your edited servlet.

see for the generateId() method and randomId variable. use randomId variable where you want to use.

public class ComplaintServlet extends HttpServlet {  
    Connection con;  
    PreparedStatement ps = null;  

public int generateId(){
    int randomId = 0;  
    Random rand = new Random();   
    for (int j=0;j < 10;j++)  
   {     
       randomId = rand.nextInt();    
   }   
      return randomId;   
}  

    public void init(ServletConfig config) throws ServletException {  
        con = DatabaseConnection.getConnection();  
    }  
  
    public void destroy() {  
        try {  
            ps.close();  
            DatabaseConnection.close(con);  
        } catch (SQLException e) {  
            e.printStackTrace();  
        }  
    }  
        public void doGet(HttpServletRequest req,HttpServletResponse res)  
   throws ServletException  
    {  
  
       try{  
            doPost(req,res);  
            }  
            catch(IOException e)  
            {   
  
            }  
  
     }  
    protected void doPost(HttpServletRequest request, HttpServletResponse response)  
    throws ServletException, IOException {  
  
               try {  
               int cid=Integer.parseInt(request.getParameter("cid"));  
               System.out.println("cid = " + cid);  
                
  
               int con_id=Integer.parseInt(request.getParameter("con_id"));  
               System.out.println("con_id = " + con_id);  
  
  
               String Complaint_Type=request.getParameter("Complaint_Type");  
               System.out.println("Complaint_Type = " + Complaint_Type);  
  
               int nocomp=Integer.parseInt(request.getParameter("nocomp"));  
               System.out.println("nocomp = " + nocomp);  
  
               int noprbm=Integer.parseInt(request.getParameter("noprbm"));  
               System.out.println("noprbm= " + noprbm);  
  
                 
  
               String btnSubmit=request.getParameter("btnSubmit");  
               System.out.println("btnSubmit= " + btnSubmit);  

               int randomId = generateId();//you can use this randmId anywhere you want to.

               if(btnSubmit.equals("SUBMIT"))  
               {  
                   String sql = "Insert into RegisterComplaint Values(?,?,?,?,?)";  
                try {  
                    ps = con.prepareStatement(sql);  
                    ps.setInt(1, cid);  
                                        ps.setInt(2, con_id);  
                    ps.setString(3, Complaint_Type);  
                    ps.setInt(4, nocomp);  
                    ps.setInt(5, noprbm);  
                      
                    ps.executeUpdate();  
                    } catch (SQLException e) {  
  
                    e.printStackTrace();  
                }  
                   response.sendRedirect("SuccessfulComplaintRegister.jsp");  
               }  
  
        } catch (Exception ex) {  
            System.out.println(ex.getMessage());  
        }  
  
  
    }  
  
  
  
  
}  

[Mohini Dhanaskar]

Sir, after running the same code.

Getting an error.

SEVERE: Servlet ComplaintServlet threw unload() exception
javax.servlet.ServletException: Servlet.destroy() for servlet ComplaintServlet threw exception
        at org.apache.catalina.core.StandardWrapper.unload(StandardWrapper.java:1413)
        at org.apache.catalina.core.StandardWrapper.stop(StandardWrapper.java:1739)
        at org.apache.catalina.core.StandardContext.stop(StandardContext.java:4601)
        at org.apache.catalina.core.StandardContext.reload(StandardContext.java:3222)
        at org.apache.catalina.manager.ManagerServlet.reload(ManagerServlet.java:943)
        at org.apache.catalina.manager.ManagerServlet.doGet(ManagerServlet.java:361)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
        at org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:199)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
        at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:558)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
        at org.apache.coyote.http11.Http11AprProcessor.process(Http11AprProcessor.java:859)
        at org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:579)
        at org.apache.tomcat.util.net.AprEndpoint$Worker.run(AprEndpoint.java:1555)
        at java.lang.Thread.run(Thread.java:662)
Caused by: java.lang.NullPointerException
        at ComplaintServlet.destroy(ComplaintServlet.java:42)
        at org.apache.catalina.core.StandardWrapper.unload(StandardWrapper.java:1394)
        ... 23 more

[Prashant Chindhade]

Mohini Dhanaskar wrote:Sir, after running the same code.

Getting an error.

SEVERE: Servlet ComplaintServlet threw unload() exception
javax.servlet.ServletException: Servlet.destroy() for servlet ComplaintServlet threw exception
        at org.apache.catalina.core.StandardWrapper.unload(StandardWrapper.java:1413)
        at org.apache.catalina.core.StandardWrapper.stop(StandardWrapper.java:1739)
        at org.apache.catalina.core.StandardContext.stop(StandardContext.java:4601)
        at org.apache.catalina.core.StandardContext.reload(StandardContext.java:3222)
        at org.apache.catalina.manager.ManagerServlet.reload(ManagerServlet.java:943)
        at org.apache.catalina.manager.ManagerServlet.doGet(ManagerServlet.java:361)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
        at org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:199)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
        at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:558)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
        at org.apache.coyote.http11.Http11AprProcessor.process(Http11AprProcessor.java:859)
        at org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:579)
        at org.apache.tomcat.util.net.AprEndpoint$Worker.run(AprEndpoint.java:1555)
        at java.lang.Thread.run(Thread.java:662)
Caused by: java.lang.NullPointerException
        at ComplaintServlet.destroy(ComplaintServlet.java:42)
        at org.apache.catalina.core.StandardWrapper.unload(StandardWrapper.java:1394)
        ... 23 more

write throw ServletException after destroy method.

[Mohini Dhanaskar]

Still showing an compile time error.

[Mohini Dhanaskar]

Sir, Should i make any change in the coding also or what?

[Prashant Chindhade]

Mohini Dhanaskar wrote:Sir, Should i make any change in the coding also or what?

Is it showing this error after appending my code?

[Mohini Dhanaskar]

yes,Sir

[Prashant Chindhade]

try this.

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.*;
import java.sql.*;
import java.io.*;
import java.util.*;


public class ComplaintServlet extends HttpServlet {    

  Connection con;    
    PreparedStatement ps = null;    
  
public int generateId(){  
    int randomId = 0;    
    Random rand = new Random();     
    for (int j=0;j < 10;j++)    
   {       
       randomId = rand.nextInt();      
   }     
      return randomId;     
}    
  
  
    
    
    public void service (HttpServletRequest request, HttpServletResponse response)throws
	IOException{    
    
               try { 
		// Load the drivers   
		Class.forName("drivers class");
		con = DriverManager.getConnection("url+dbName","userName","password");
               int cid=Integer.parseInt(request.getParameter("cid"));    
               System.out.println("cid = " + cid);    
                  
    
               int con_id=Integer.parseInt(request.getParameter("con_id"));    
               System.out.println("con_id = " + con_id);    
    
    
               String Complaint_Type=request.getParameter("Complaint_Type");    
               System.out.println("Complaint_Type = " + Complaint_Type);    
    
               int nocomp=Integer.parseInt(request.getParameter("nocomp"));    
               System.out.println("nocomp = " + nocomp);    
    
               int noprbm=Integer.parseInt(request.getParameter("noprbm"));    
               System.out.println("noprbm= " + noprbm);    
    
                   
    
               String btnSubmit=request.getParameter("btnSubmit");    
               System.out.println("btnSubmit= " + btnSubmit);    
  
               int randomId = generateId();//you can use this randmId anywhere you want to.  
  
               if(btnSubmit.equals("SUBMIT"))    
               {    
                   String sql = "Insert into RegisterComplaint Values(?,?,?,?,?)";    
                try {    
                    ps = con.prepareStatement(sql);    
                    ps.setInt(1, cid);    
                                        ps.setInt(2, con_id);    
                    ps.setString(3, Complaint_Type);    
                    ps.setInt(4, nocomp);    
                    ps.setInt(5, noprbm);    
                        
                    ps.executeUpdate();   
		    ps.close();
		    con.close(); 
                    } catch (SQLException e) {    
    
                    e.printStackTrace();    
                }    
                   response.sendRedirect("SuccessfulComplaintRegister.jsp");    
               }    
    
        } catch (Exception ex) {    
            System.out.println(ex.getMessage());    
	//    ps.close();
	  //  con.close();
        } 
	finally {
//		ps.close();
//		con.close();
	}
	
    
    
    }    
	
    
    
    
}    

[Prashant Chindhade]

which database are you using?

[Mohini Dhanaskar]

Sir, Oracle

[Prashant Chindhade]

Check this Link

it will show you basic steps to connect to database. read full article and than start development.

[Prashant Chindhade]

Also check this.

[Winston Gutkowski]

prashant chindhade wrote:put this is Regestration servlet. and call it when you want to get id.

Prashant, I'm sure you're trying to be helpful, but please DontBeACodeMill (←click).

Also, your method (even corrected) mystifies me:
1. Why create a new Random object for each invocation? Completely unnecessary.
2. Why loop 10 times?

@Mohini:
1. If this ID is related to a database table, then I would strongly urge you to use a sequence number obtained from the DB itself.
2. If not, there are a couple of Java classes for obtaining unique (or near-unique) IDs: java.rmi.server.UID and java.util.UUID. I suggest you also look at them before ploughing ahead too soon.

Winston

[Kunal Lakhani]

prashant chindhade, you should provide the hint to the logic and let others try to figure out the logic. So, don't provide the full implementations

con = DatabaseConnection.getConnection();

is it ok?

I have always used

DriverManager.getConnection

or DatabaseConnection is a separate class created by you?

1. If this ID is related to a database table, then I would strongly urge you to use a sequence number obtained from the DB itself

I agree with Winston Gutkowski

[Prashant Chindhade]

@Kunal and @Winston: Actually i didn't notice the error at first.
but next time i will take care of everything.
thanks for noticing my error.

[Winston Gutkowski]

prashant chindhade wrote:...but next time i will take care of everything...

As I said before: next time, provide help, not code.

Winston