JDBC——数据层DAO

DAO：Data Access Object

　　DAO　　　　数据层

　　Service　　 逻辑业务层

　　View　　　  视图层

　　entity　　   实体层

实现增、删、改、查的数据层

 public class EmpDAO {     public Employee findEmpById(int id) {         Connection conn = null;
         PreparedStatement ps = null;
         ResultSet rs = null;
         Employee emp = null;         conn = DBTool.getInstance().getConnection();
         String sql = "SELECT * FROM Employee WHERE empId = ?";
         try {
             ps = conn.prepareStatement(sql);
             ps.setInt(1, id);
             rs = ps.executeQuery();
             while(rs.next()){
                 emp = new Employee();
                 emp.setEmpNo(rs.getInt("empId"));
                 emp.seteName(rs.getString("empName"));
                 emp.setSalary(rs.getDouble("salary"));
             }
         } catch (SQLException e) {
             // TODO Auto-generated catch block
             e.printStackTrace();
         }
         finally{
             DBTool.closeAll(conn, ps, rs);
         }
         return emp;
     }
     public int addEmp(Employee emp){
         int row = 0;
         Connection conn = null;
         PreparedStatement ps = null;
         conn = DBTool.getInstance().getConnection();
         String sql = "INSERT INTO Employee (empName,salary) values (?,?)";
         try {
             ps = conn.prepareStatement(sql);
             ps.setString(1, emp.geteName());
             ps.setDouble(2, emp.getSalary());
             row = ps.executeUpdate();
         } catch (SQLException e) {
             // TODO Auto-generated catch block
             e.printStackTrace();
         }
         finally{
             DBTool.closeAll(conn, ps, null);
         }
         return row;
     }
     public int updateEmp(Employee emp){
         int row = 0;
         Connection conn = null;
         PreparedStatement ps = null;
         conn = DBTool.getInstance().getConnection();
         String sql = "UPDATE Employee SET empName = ?,Salary = ? WHERE empId = ?";
         try {
             ps = conn.prepareStatement(sql);
             ps.setString(1, emp.geteName());
             ps.setDouble(2, emp.getSalary());
             ps.setInt(3, emp.getEmpNo());
             row = ps.executeUpdate();
         } catch (SQLException e) {
             // TODO Auto-generated catch block
             e.printStackTrace();
         }
         finally{
             DBTool.closeAll(conn, ps, null);
         }
         return row;
     }
     public int deleteEmp(int id){
         int row = 0;
         Connection conn = null;
         PreparedStatement ps = null;
         conn = DBTool.getInstance().getConnection();
         String sql = "delete from employee where empId = ?";
         try {
             ps = conn.prepareStatement(sql);
             ps.setInt(1, id);
             row = ps.executeUpdate();
         } catch (SQLException e) {
             // TODO Auto-generated catch block
             e.printStackTrace();
         }
         finally{
             DBTool.closeAll(conn, ps, null);
         }
         return row;
     }
 }