DBUtils原理及基本使用

来源：互联网发布：做视频剪辑的软件编辑：程序博客网时间：2024/05/21 04:40

首先我们通过一个基本的演示来了解一下DBUtils的基本原理

public class UseDButils {public static void main(String[] args) {/*addUser(new User("weijinhao","123456"));quary("weijinhao");*/}public static  void addUser(User user) {ComboPooledDataSource comboPooledDataSource = new ComboPooledDataSource();QR qr = new QR(comboPooledDataSource);String sql = "insert into users values(?,?)";Object[] para = {user.getUsername(),user.getPassword()};qr.update(sql, para);}public static void quary(String username) {ComboPooledDataSource comboPooledDataSource = new ComboPooledDataSource();QR<User> qr = new QR<User>(comboPooledDataSource);String sql = "select * from users where username = ?";Object[] para = {username};User user = (User) qr.quary(new QRHandler<User>() {  //我们在这使用的是匿名内部类public User handler(ResultSet rs) {User user = new User();try {rs.next();user.setUsername(rs.getString(1));user.setPassword(rs.getString(2));} catch (SQLException e) {e.printStackTrace();}return user;}}, sql,para);System.out.println(user);}}

/** *  * 我们用这个类来模拟一下DBUtils类的结构，麻雀虽小五脏俱全 *  */public class QR<T> {private DataSource ds;public QR() {super();}public QR(DataSource ds) {   super();this.ds = ds;}/* * 给出sql和object[]来实现增删改查 */public void update(String sql ,Object...objects)   {  Connection con = null;PreparedStatement ps = null;try{con = ds.getConnection();ps = con.prepareStatement(sql);init(ps,objects);  //我们调用该函数来进行prepareStatement的初始化ps.executeUpdate();}catch(SQLException s){s.printStackTrace();}finally{try {ps.close();} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}try {con.close();} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}}}/* * QRHandler<T>用该对象来进行表数据到对像属性的映射,其实在DBUtils中不用我们自己写该接口的实现类，有写好的可以直接使用 * sql为要查询的语句 *  */public T quary(QRHandler<T> hd, String sql ,Object...objects) {Connection con = null;PreparedStatement ps = null;T user = null;try{con = ds.getConnection();ps = con.prepareStatement(sql);init(ps,objects);ResultSet rs = ps.executeQuery();user =  hd.handler(rs);  //用该对象来进行表数据到对像属性的映射}catch (SQLException e) {e.printStackTrace();}finally {try {ps.close();} catch (SQLException e) {e.printStackTrace();}try {con.close();} catch (SQLException e) {e.printStackTrace();}return user;}}void init(PreparedStatement ps,Object...objects) {for(int i = 0;i < objects.length;i++) {try {ps.setObject(i + 1, objects[i]);} catch (SQLException e) {e.printStackTrace();}}}}

public interface QRHandler<T> {T handler(ResultSet rs) ;}

好了，如果看懂了上面的源码，那你就算是基本会了DBUtils的使用了。

让我们来看一下DBUtils类的使用源码：

public class UseDBUtils {public static void main(String[] args) throws SQLException {//update();//query();}public static void query() throws SQLException {ComboPooledDataSource comboPooledDataSource = new ComboPooledDataSource();QueryRunner qr = new QueryRunner(comboPooledDataSource);String sql = "select * from users where username=?";BeanHandler<User> rsh = new BeanHandler<User>(User.class);//关于结构集处理器有好几中，还可以自己实现自己的结构集处理器User user = qr.query(sql, rsh, "zhoufeifei");System.out.println(user);}public static void update() throws SQLException {ComboPooledDataSource comboPooledDataSource = new ComboPooledDataSource();QueryRunner qr = new QueryRunner(comboPooledDataSource);String sql = "insert into users values(?,?)";Object[] params = {"zhoufeifei" , "123456"};int i = qr.update(sql, params);System.out.println(i);}}

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