Casse Management

DESCRIPTION
Hi everyone,
This is my first application, it serves
to add, search for articles ...
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Here is a code example:
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import java.sql.*;

import javax.swing.JOptionPane;
import javax.swing.table.DefaultTableModel;
public class ManipDB {
 String query;
 Statement stx;
 ResultSet rset;
 Connection conn;
 public ManipDB(){
  ConnDisc.connect();
  conn=ConnDisc.getConnexion();
  rset=null;
 }
 public ResultSet afficherCaissier(int id){
  try{
   stx=conn.createStatement();
   query="SELECT idCaissier,nomCaissier,passwordCaissier FROM Caissier"+" WHERE idCaissier="+id+"";
   rset=stx.executeQuery(query);

  }
  catch(SQLException ex){
   ex.printStackTrace();


  }
  return rset;
 }
 public DefaultTableModel  afficherStock(){
  DefaultTableModel dt = new DefaultTableModel();
  dt.addColumn("Stock Unitaire");
  dt.addColumn("Stock Lot");
  dt.addColumn("chiffre d'affaire Article");
  dt.addColumn("chiffre d'affaire Lot");
  dt.addColumn("chiffre d'affaire global");
  try{

   stx=conn.createStatement();
   query="SELECT * FROM Stock";
   rset=stx.executeQuery(query);
   while(rset.next()){
    Object []tableau={rset.getInt("stockU"),rset.getInt("stockLot"),rset.getDouble("chiffreArticle"),rset.getDouble("chiffreLot"),
      rset.getDouble("chiffreAffaire")};
    dt.addRow(tableau);
   }
  }
  catch(SQLException ex){
   ex.printStackTrace();
   JOptionPane.showMessageDialog(null,"ERROR","Message d?avertissement",JOptionPane.ERROR_MESSAGE);

  }
  return dt;
 }
 public void acheterArticle(int nb,String nom){
  try{
   double prixarticle=0.0;
   double chiffreaffaire=0.0;
   int stocku=0;

   stx=conn.createStatement();
   query="SELECT prixArticle FROM Article WHERE nomArticle="+nom+" ";
   rset=stx.executeQuery(query);

   while(rset.next()){
    prixarticle=rset.getDouble("prixArticle");
   }

   query="SELECT stockU,chiffreAffaire FROM Stock";
   rset=stx.executeQuery(query);
   while(rset.next()){
    chiffreaffaire=rset.getDouble("chiffreAffaire");
    stocku=rset.getInt("stockU");
   }

   double prixArticle=prixarticle*nb;
   chiffreaffaire+=prixArticle;
   stocku-=nb;

   if(stocku>0){
    query="UPDATE Stock SET chiffreAffaire="+chiffreaffaire+",stockU="+stocku+",chiffreArticle="+prixArticle+"";
    stx.executeUpdate(query);
   }
   else{
    JOptionPane.showMessageDialog(null,"stock n'est plus disponible","Message d?avertissement",JOptionPane.ERROR_MESSAGE);
   }

  }
  catch(SQLException ex){
   ex.printStackTrace();
   JOptionPane.showMessageDialog(null,"ERROR","Message d?avertissement",JOptionPane.ERROR_MESSAGE);
  }
   }


 public void acheterLot(int nb,String nom){
  try{
   double prixlot=0.0;
   double chiffreaffaire=0.0;
   int stocku=0;
   int stocklot = 0;
   stx=conn.createStatement();
   query="SELECT prixLot FROM Lot"+" WHERE nomLot="+nom+"";
   rset=stx.executeQuery(query);
   while(rset.next()){
    prixlot=rset.getDouble("prixLot");
   }
   query="SELECT stockU,stockLot,chiffreAffaire FROM Stock";
   rset=stx.executeQuery(query);
   while(rset.next()){
    chiffreaffaire=rset.getDouble("chiffreAffaire");
    stocku=rset.getInt("stockU");
    stocklot=rset.getInt("stockLot");
   }
   double prixLot=prixlot*nb;
   chiffreaffaire+=prixLot;
   System.out.println(chiffreaffaire);
   //supposons qu'on a un lot de 3 articles.
   stocku-=(nb*3);
   stocklot-=nb;
   if(stocku>0)
   {
    query="UPDATE Stock SET chiffreAffaire="+chiffreaffaire+",stockU="+stocku+",stockLot="+stocklot+",chiffreLot="+prixLot+"";
    stx.executeUpdate(query);
   }
   else{
    JOptionPane.showMessageDialog(null,"stock n'est plus disponible","Message d?avertissement",JOptionPane.ERROR_MESSAGE);
   }
  }
  catch(SQLException ex){
   ex.printStackTrace();
   JOptionPane.showMessageDialog(null,"stock n'est plus disponible","Message d?avertissement",JOptionPane.ERROR_MESSAGE);

  }

 }
 public DefaultTableModel afficherProduit(int code){
  DefaultTableModel dt = new DefaultTableModel();
  dt.addColumn("numero");
  dt.addColumn("Reference");
  dt.addColumn("Designation");
  dt.addColumn("Nom");
  dt.addColumn("Prix");
  try{

   stx=conn.createStatement();
   query="SELECT * FROM Article WHERE codeArticle="+code+" UNION SELECT * FROM Lot WHERE codeLot="+code+"";;
   rset=stx.executeQuery(query);
   while(rset.next()){
    Object []tableau={rset.getInt(1),rset.getString(2),rset.getString(3),rset.getString(4),rset.getDouble(5)};
    dt.addRow(tableau);
   }
  }
  catch(SQLException ex){
   ex.printStackTrace();

  }
  return dt;

 }

 public boolean verifier(int login,String password){
  boolean test=false;
  int log =0;
  String pass=null;
  try{
   stx=conn.createStatement();
   query="SELECT idCaissier,passwordCaissier FROM caissier";
   rset=stx.executeQuery(query);
   while(rset.next()|| (test==true)){
    log=rset.getInt("idCaissier");
    pass=rset.getString("passwordCaissier");
    if((log==login) && (pass.equals(password)))
     test=true;
   }
  }
  catch(SQLException ex){
   ex.printStackTrace();
  }

  return test;

 }

}

Link to download the project complete :http://fit.sh/gEc
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