首先我們通過一個基本的演示來了解一下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>() { //我們在這使用的是匿名內(nèi)部類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);}} /*** * 我們用這個類來模擬一下DBUtils類的結(jié)構(gòu)，麻雀雖小五臟俱全* */ public class QR<T> {private DataSource ds;public QR() {super();}public QR(DataSource ds) { super();this.ds = ds;}/** 給出sql和object[]來實現(xiàn)增刪改查*/public void update(String sql ,Object...objects) { Connection con = null;PreparedStatement ps = null;try{con = ds.getConnection();ps = con.prepareStatement(sql);init(ps,objects); //我們調(diào)用該函數(shù)來進行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>用該對象來進行表數(shù)據(jù)到對像屬性的映射,其實在DBUtils中不用我們自己寫該接口的實現(xiàn)類，有寫好的可以直接使用* sql為要查詢的語句* */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); //用該對象來進行表數(shù)據(jù)到對像屬性的映射}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碼，那你就算是基本會了DBUtils的使用了。
讓我們來看一下DBUtils類的使用源碼：

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);//關于結(jié)構(gòu)集處理器有好幾中，還可以自己實現(xiàn)自己的結(jié)構(gòu)集處理器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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