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;
    }
}