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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
   
     qr = new QR
    
     (comboPooledDataSource);		String sql = "select * from users where username = ?";		Object[] para = {username};		User user = (User) qr.quary(new QRHandler
     
      () {  //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
   
     {	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 block				e.printStackTrace();			}			try {				con.close();			} catch (SQLException e) {				// TODO Auto-generated catch block				e.printStackTrace();			}		}	}	/*	 * QRHandler
    
     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
     
       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 handler(ResultSet rs) ;}
   

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
   
     rsh = new BeanHandler
    
     (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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