DAO設(shè)計(jì)模式.doc

DAO設(shè)計(jì)模式 分類： JavaEE學(xué)習(xí)筆記 dao設(shè)計(jì)模式exception數(shù)據(jù)庫stringuserDAO設(shè)計(jì)模式：1、DAO簡介： DAO設(shè)計(jì)模式是屬于J2EE數(shù)據(jù)層的操作，使用DAO設(shè)計(jì)模式可以簡化大量代碼，增強(qiáng)程序的可移植性。 2、DAO各部分詳解：DAO設(shè)計(jì)模式包括以下5個(gè)主要部分：（1）、數(shù)據(jù)庫連接類; 數(shù)據(jù)庫連接類的主要功能是連接數(shù)據(jù)庫并獲得連接對(duì)象，以及關(guān)閉數(shù)據(jù)庫。通過數(shù)據(jù)庫連接類可以大大的簡化開發(fā)，在需要進(jìn)行數(shù)據(jù)庫連接時(shí)，只需常見該類的實(shí)例，并調(diào)用其中的方法就可以獲得數(shù)據(jù)庫連接對(duì)象和關(guān)閉數(shù)據(jù)庫，不必再進(jìn)行重復(fù)操作。例：java view plaincopyprint?Package com.javaweb.dao1 Import java.sql.*; Public class DataBaseConnection Private final String DBDRIVER = “com.mysql.jdbc.Driver”; Private final String DBURL = “jdbc:mysql:/localhost:3306/javaweb”; Private final String DBUSER = “root”; Private final String DBPASSWORD = “585762”; Private Connection conn = null; Public DataBaseConnection() Try Class.forName(DBDRIVER); This.conn = DriverManager.getConnection(DBURL,DBUSER,DBPASSWORD); catch(Exception e) System.out.println(“加載數(shù)據(jù)庫驅(qū)動(dòng)失??！”); Public Connection getConnection() Return conn; Public void close() Try Conn.close(); catch() System.out.println(“數(shù)據(jù)庫連接關(guān)閉失??！”); Package com.javaweb.dao1Import java.sql.*;Public class DataBaseConnection Private final String DBDRIVER = “com.mysql.jdbc.Driver”; Private final String DBURL = “jdbc:mysql:/localhost:3306/javaweb”; Private final String DBUSER = “root”; Private final String DBPASSWORD = “585762”; Private Connection conn = null; Public DataBaseConnection() Try Class.forName(DBDRIVER); This.conn = DriverManager.getConnection(DBURL,DBUSER,DBPASSWORD); catch(Exception e) System.out.println(“加載數(shù)據(jù)庫驅(qū)動(dòng)失敗！”); Public Connection getConnection() Return conn; Public void close() Try Conn.close(); catch() System.out.println(“數(shù)據(jù)庫連接關(guān)閉失??！”); （2）、VO類： VO類是一個(gè)包含屬性和表中字段完全對(duì)應(yīng)的類，并在該類中提供setter和getter方法來設(shè)置并獲取該類中的屬性。例：java view plaincopyprint?Package com.javaweb.dao1 Public classs User Private int userid; Private String username; Private String password; Public int getUserid() Return userid; Public void setUserid(int userid) Return userid; Public String getUsername() Return username; Public void setUsername(String username) Return username; Public String getUserpassword() Return userpassword; Public void setUserid(String userpassword) Return userpassword; Package com.javaweb.dao1Public classs User Private int userid; Private String username; Private String password; Public int getUserid() Return userid; Public void setUserid(int userid) Return userid; Public String getUsername() Return username; Public void setUsername(String username) Return username; Public String getUserpassword() Return userpassword; Public void setUserid(String userpassword) Return userpassword; （3）、DAO接口： DAO接口中定義了所有的用戶操作，如添加記錄、刪除記錄及查詢記錄等。不過因?yàn)槭墙杩冢詢H僅是定義，需要子類實(shí)現(xiàn)。例：java view plaincopyprint?Package com.javaweb.dao1; Import java.util.*; Public class UserDAO public void insert(User user)throw Exception; Public void update(User user)throw Exception; Public void delete(int userid)throw Exception; Public User queryById(int userid)throw Exception; Public List queryAll()throw Exception; Package com.javaweb.dao1;Import java.util.*;Public class UserDAO public void insert(User user)throw Exception; Public void update(User user)throw Exception; Public void delete(int userid)throw Exception; Public User queryById(int userid)throw Exception; Public List queryAll()throw Exception; （4）、DAO實(shí)現(xiàn)類： DAO實(shí)現(xiàn)類實(shí)現(xiàn)了DAO接口，并實(shí)現(xiàn)了接口中定義的所有方法。（5）、DAO工廠類： 在沒有DAO工廠類的情況下，必須通過創(chuàng)建DAO實(shí)現(xiàn)類的實(shí)例才能完成數(shù)據(jù)庫操作。這時(shí)就必須知道具體的子類，對(duì)于后期的修改非常不方便。 使用DAO工廠類，可以比較方便地對(duì)代碼進(jìn)行管理，而且可以很好地解決后期修改的問題，通過該DAO工廠類的一個(gè)靜態(tài)方法來獲取DAO實(shí)現(xiàn)類實(shí)例。這時(shí)如果要替換DAO實(shí)現(xiàn)類，只需要修改該Dao工廠類中的方法代碼，而不必邀修改所有的操作數(shù)據(jù)庫代碼。例：java view plaincopyprint?Package com.javaweb.dao1; Public class DAOFactory Public static UserDAO getUserDAOInstance() Return new