LP TRNH THEO KIN TRC 3 LP/TNG

(3-TIERS ARCHITECHTURE)

Xy dng phn mm theo kin trc 3 lp:

Trc y, i vi cc phn mm c s dng lin quan n dliu, thng khi lm ngi lp trnh

thng tch hp vic giao tip vi ngi s dng , x l ri ghi xung d liu trn cng mt form (y l m

hnh mt lp). Nhng trong kin trc 3 lp (m hnh 3 lp), phi c vic phn bit rch ri gia cc lp ny.

M hnh 3 lp c th c m t nh sau :

Lp Presentation: Lp giao din (giao tip vi ngi s dng) : ch thun x l vic giao tip vi ngi

s dng, nhp xut, m khng thc hin vic tnh ton, kim tra, x l, hay cc thao tc lin quan

n c s d liu.

Lp Business Logic: Lp x l nghip v, lp ny chuyn thc hin cc x l , kim tra cc rng buc,

cc qui tc ng x ca phn mm , cc chc nng ch yu, Vic thc hin ny c lp vi cch thit

k cng nh ci t giao din. Thng tin cho lp ny thc hin cc x l ca mnh c ly t lp giao

din.

Lp Data Access: Lp d liu, lp ny chuyn thc hin cc cng vic lin quan n lu tr v truy

xut d liu ca ng dng. D liu c th ly t c s d liu (Access, SQL Server ) hoc tp tin

(text, binary, XML ). Lp ny thc hin kt ni trc tip vi c s d liu v thc hin tt c cc

thao tc lin quan n c s d liu m phn mm cn.

Li ch ca lp trnh theo kin trc 3 lp:

Vi m hnh ny, cc cng vic ca tng lp l c lp vi nhau, gim s gn kt gia cc thc th ca

phn mm. Vic thay i mt lp khng lm thay i cc lp cn li, thun tin hn cho qu trnh ti pht

trin v bo tr phn mm.

Minh ha lp trnh theo kin trc 3 lp:

Bc 1: To project mi trong Visual Studio t tn l project DTO (Data Transfer Object)

Bc 2: Xy dng cc lp DanhMuc v lp SanPham.

Danh mc l tn mt nhm cc sn phm gm 2 thuc tnh (m danh mc v tn danh mc). Mt danh mc

s bao gm nhiu sn phm. Lp SanPham cha thng tin ca sn phm.

Lp DanhMuc.cs

Lp SanPham.cs

Bc 3: Build project DTO

Bc 4: To thm mt project mi t tn l DataAcessTier

Bc 5: B sung reference cho project ny bng cch nhp chut phi vo tn project trong ca s Solution

Explorer v chn Add Reference.

Trong hp thoi xut hin chn DTO.

Bc 6: Xy dng lp DBConnection cho vic kt ni c s d liu ( y l Microsoft Access)

Bc 7: Xy dng cc lp DAO

Ch : Cc lp ny k tha t lp DBConnection, v khai bo using DTO.

Lp DanhMucDAO

Lp SanPhamDAO

Bc 8: Build project DataAccessTier

Bc 9: To mt project mi t tn l BusinessLogicTier

Bc 10: Tng t add reference DTO v DataAccessTier

Bc 11: Thm cc lp BUS.

Lp DanhMucBUS.cs

Lp SanPhamBUS.cs

Build project.

Bc 12: Thm mt project t tn PresentaionTier v Add Reference: DTO v BusinessLogicTier

Bc 13: To form MainForm

Bc 14: Vit code cho MainForm nh sau:

Ch : phi khai bo cc s kin ca Form.

Bc 15: To mt from mi t tn l SanPhamForm

DataGridView

Bc 16: Vit code cho form

Bc 17: Copy file c s d liu mu dbSanPham.mdb vo th mc Debug ca poject ny.

Bc 18: Chy v kim tra chng trnh.

Bi tp: Vit thm chc nng cp nht v kim tra cc iu kin thm/xa/cp nht (nu c) ca chng

trnh.