Passing Connection objects between servlets

Entire cUser class

package annotation;
import java.io.*;
import java.util.zip.*;
import java.util.*;
import java.lang.*;
import java.awt.event.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.*;

import db.*;
import ns.*;
import search.*;
import user.*;

public class Annotation extends HttpServlet
{
    public final static String SESSION_SINGLE_METADATA="search.SingleMetadata";
    public final static String SESSION_SINGLE_METADATA_ARCHIVE="search.SingleMetadataArchive";
    public final static String SESSION_SINGLE_METADATA_NEXT="search.SingleMetadataNext";
    public final static String SESSION_SINGLE_METADATA_PREV="search.SingleMetadataPrev";
    public final static String SESSION_SINGLE_ANNOTATION_METADATA="search.SingleAnnotationMetatdata";
    public final static String SESSION_DBSEARCHER="search.dbsearcher";

    public final static String SESSION_USER_INFO = "user.user_info";
   
    public final static String APP_ANNOTATION_CONN = "annotation_connection";


    private ConnectionPool cpool;
    private static Connection conn;
    private int dbtype;

    private Vector fieldlist;
    private Hashtable fieldhash;
    private Hashtable err;
   
    public final static String SESSION_CONN="annotation.conn";
    public final static String APP_ANNOTATION_FIELDS="annotation.fieldlist";

    //////////////////////////////////////////////////////
    public void doGet (HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException    
    {
        String formname=request.getParameter("formname")!=null?request.getParameter("formname"):"";
        HttpSession session = request.getSession(true);
        response.setContentType("text/html");

        conn=cpool.getConnection();
        SQLParam param = new MySQLParam();


        if (formname.equals("save_annotation")){
            // Annotation is ready to be saved
            System.out.println("Starting Annotation");

            try{                              
                cAnnotation m_annotation = new cAnnotation(request);
   
                m_annotation.Save(conn,param,m_annotation,false);  //we cannot update from this form update is an admin feature and must use a different form

            } catch (Exception e){
                //redirect and display errors
                System.out.println("Error");
                response.sendRedirect(request.getContextPath()+"/error.jsp");
                return;
            }

        } else if (formname.equals("user_annotation")) {
          // user has enter annotation and it is ready for preview
           
            cAnnotation m_annotation = new cAnnotation(request);
           
            //return current values to form
            session.setAttribute("user_id",     m_annotation.getUserIDString());
            session.setAttribute("element",     m_annotation.element);
            session.setAttribute("value",       m_annotation.value);
            session.setAttribute("oai_id",      m_annotation.oai_id);

            //is input valid
            if (!isValid(m_annotation)){
                 session.setAttribute("err", err);
                 response.sendRedirect(request.getContextPath() + "/annotation.jsp");    
            } else {
           
                // get search results for annotated record then display annotation_preview.jsp
                String id=null;
               
                try
                {
                    id=java.net.URLDecoder.decode(request.getParameter("oai_id"));
                    System.out.println("id="+id);
                }
                catch (Exception e)
                {
                    throw new ServletException("annotation preview page");
                }
               
                SearchParam search_param=null;
                search_param = new BookBagParam(request);
   
                DBSearcher os = new DBSearcher(search_param);    
   
                CMetaData metadata=DBSearcher.getMetaData(conn,id);
   
                Vector annotation=DBSearcherAnnotation.getAnnotationMetaData(conn,id);
               
                if (metadata==null)
                {
                    throw new ServletException("annotation preview page");
                }
   
                session.setAttribute(SESSION_SINGLE_METADATA, metadata);
                session.setAttribute(SESSION_SINGLE_ANNOTATION_METADATA, annotation);
   
                int index = os.getIndex (id);
                int hits = os.GetNumHits ();
               
                if (index+1<hits)
                {
                      
                      CMetaData next=os.getMetaData(conn,index+1);
                      session.setAttribute(SESSION_SINGLE_METADATA_NEXT,next.id);
                }
                else
                      session.setAttribute(SESSION_SINGLE_METADATA_NEXT,null);
                      
                if (index-1>=0)
                {
                      
                      CMetaData prev=os.getMetaData(conn,index-1);
                      session.setAttribute(SESSION_SINGLE_METADATA_PREV,prev.id);
                }
                else
                {
                      session.setAttribute(SESSION_SINGLE_METADATA_PREV,null);      
               
                    cpool.close(conn);    
                    response.sendRedirect(request.getContextPath()+"/annotation_preview.jsp");
                }
            }  //end validation
        } else { //formname not set load annotation page for the first time
            //TO DO test for user_id and oai_id

            //get user name
            user.SQLParam user_param = new user.MySQLParam();
            cUser mUser = new cUser(conn, user_param, Long.parseLong(request.getParameter("user_id")));

            session.setAttribute("user_name",   mUser.user_name);
            session.setAttribute("user_id", mUser.getUserIDString());
           
            response.sendRedirect(request.getContextPath()+"/annotation.jsp?oai_id=" + request.getParameter("oai_id"));
        }

    }


    //////////////////////////////////////////////////////
    public void doPost (HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException    
    {
        doGet(request,response);
    }

    //////////////////////////////////////////////////////
    public void init (ServletConfig config) throws ServletException
    {

        //Open DB Connectionafreader
        ServletContext context=config.getServletContext();
        Object o=context.getAttribute(ConnectionServlet.KEY);
        if (o==null){
            throw new ServletException("ConnectionServlet not started");
        }

        cpool=(ConnectionPool)o;
       
        conn =(Connection) cpool.getConnection ();

        dbtype=cpool.getDBType();


        //Get field information for new annotations
        AnnotationFieldReader afreader=new AnnotationFieldReader(cpool, dbtype);
        afreader.init();
      fieldlist=afreader.getFieldList();
        fieldhash=afreader.getHashedFieldlist();

        context.setAttribute(APP_ANNOTATION_CONN, conn);

      context.setAttribute(APP_ANNOTATION_FIELDS,fieldlist);

        System.out.println("Started Annotations");
           
    }

    //////////////////////////////////////////////////////
    public void destroy()
    {
        if (cpool!=null)
            cpool.destroy();
        super.destroy();
    }

    //////////////////////////////////////////////////////
    public String getServletInfo() {
        return "The Annotation Servlet";
    }


    public boolean isValid(cAnnotation m_annotation) {
        if (err==null) err = new Hashtable();
       
        err.clear();  //clear any previous errors
         if (m_annotation.oai_id.equals("")) {
            err.put("oai_id", "Fatal Error: No oai id");
        }
 
        if (m_annotation.element.equals("")) {
            err.put("element", "Please select a field to annotate");
        }

        AFInfo af = (AFInfo)fieldhash.get(m_annotation.element);
        int maxlength = Integer.parseInt(af.field_length); //get maxlength for element

        if (m_annotation.value.equals("") || m_annotation.value.length() > maxlength) {
            err.put("value", "Annotations for " + af.field_label + " must be between 1 and " + maxlength + " characters.");
        }
       
        System.out.println(Boolean.toString(err.isEmpty()));        
        return err.isEmpty();
    }

}