// Jdbc 的增,删, 改流程类似,只是参数不同, 因此可以向上抽取public class Demo{// Jdbc 的增加public void addStu(Stu stu){Connection con = null;PreparedStatement pstmt = null;try{con = JdbcUtils.getConnection();String sql = "INSERT INTO t_stu VALUES(?,?,?,?)";pstmt = con.prepareStatement(sql);pstmt.setInt(1,stu.getSid());pstmt.setString(2,stu.getSname());pstmt.setInt(3,stu.getAge());pstmt.setString(4,stu.getGender());pstmt.executeUpdate();} catch(Exception e){// 处理异常} finally{// 关闭资源}}// jdbc 修改方法public void UpdateStu(Stu stu){Connection con = null;PreparedStatement pstmt = null;try{con = JdbcUtils.getConnection();// 只需要 sql 语句修改String sql = "UPDATE t_stu SET sname=?,age=?,gender=? WHERE sid=?";pstmt = con.prepareStatement(sql);pstmt.setInt(4,stu.getSid());pstmt.setString(1,stu.getSname());pstmt.setInt(2,stu.getAge());pstmt.setString(3,stu.getGender());pstmt.executeUpdate();} catch(Exception e){// 处理异常} finally{// 关闭资源}}// jdbc 删除方法public void UpdateStu(int sid){Connection con = null;PreparedStatement pstmt = null;try{con = JdbcUtils.getConnection();// 只需要 sql 语句修改String sql = "DELETE FROM t_stu WHERE sid=?";pstmt = con.prepareStatement(sql);pstmt.setInt(1,stu.getSid());pstmt.executeUpdate();} catch(Exception e){// 处理异常} finally{// 关闭资源}}// jdbc 的查询方法 (查询一个)public Stu load(int sid){Connection con = null;PreparedStatement pstmt = null;ResultSetHandler rs = null;try{con = JdbcUtils.getConnection();// 只需要 sql 语句修改String sql = "SELECT * FROM t_stu WHERE sid=?";pstmt = con.prepareStatement(sql);pstmt.setInt(1,stu.getSid());// 发送 sql 语句需要变化rs = pstmt.executeQuery();if(!rs.next()) return null;// 需要把 rs 转换成 Stu 对象Stu stu = new Stu();stu.setSid(rs.getInt("sid"));stu.setSname(rs.getString("sname"));stu.setAge(rs.getInt("age"));stu.setGender(rs.getString("gender"));return stu;} catch(Exception e){// 处理异常} finally{// 关闭资源}    }}// 升级public class QR<T>{private DataSource dataSource;// 构造函数public QR(DataSource dataSource){super();this.dataSource = dataSource;}// 无参构造函数public QR(){super();}// 可以实现数据库的 insert,update, deletepublic int update(String sql, Object... params){Connection con = null;PreparedStatement pstmt = null;try{con = dataSource.getConnection();pstmt = con.prepareStatement(sql);initParams(pstmt, params); // 设置参数// 返回影响的行数return pstmt.executeUpdate();} catch(Exception e){throw new RuntimeException(e);} finally{// 关闭资源try{if(pstmt != null) pstmt.close();if(con != null) con.close();} catch(SQLException e){throw new RuntimeException(e);}}}// 私有方法, 专门给 sql 语句的参数赋值private void initParams(PreparedStatement pstmt, Object... params)throws SQLException{// 循环遍历赋值for(int i=0; i<params.length; i++){pstmt.setObject(i+1, params[i]);}}// 查询方法public T query(String sql, RsHandler rh, Object... params){Connection con = null;PreparedStatement pstmt = null;ResultSet rs = null;try{con = dataSource.getConnection();pstmt = con.prepareStatement(sql);initParams(pstmt,params);rs = pstmt.executeQuery();return (T)rh.handle(rs);}catch(Exception e){throw new RuntimeException(e);} finally{try{if(pstmt != null) pstmt.close();if(con != null) con.close();} catch(SQLException e){throw new RuntimeException(e);}}}}// 接口, 将 ResultSet 转换成 JavaBean 实体interface RsHandler<T>{public T handle(ResultSet rs) throws SQLException;}// 使用上述 QR 类操作数据库public class Demo2{public void fun(){Stu stu = new Stu(1001,"lisi",22,"male");addStu(stu);}// 添加操作public void addStu(Stu stu){// 创建对象时, 给出连接池QR qr = new QR(JdbcUtils.getDataSource());// 给出 sql 模板String sql = "INSERT INTO t_stu VALUES(?,?,?,?)";// 给出参数Object[] params = {stu.getSid(),stu.getSname(),stu.getAge(),stu.getGender()};// 调用 QR 类的 update 方法qr.update(sql,params);}// 查询操作public Stu load(int sid){QR qr = new QR(JdbcUtils.getDataSource());String sql = "SELECT * FROM WHERE sid=?";Object[] params = {sid};// 实现 RsHandler 接口,// 可以将 ResultSet 结果集转换为 Stu 对象RsHandler<Stu> rh = new RsHandler<Stu>(){// 实现方法public Stu handle(ResultSet rs) throws SQLException {if(!rs.next()) return null;Stu stu = new Stu();stu.setSid(rs.getInt("sid"));stu.setSname(rs.getString("sname"));stu.setAge(rs.getInt("age"));stu.getGender(rs.getString("gender"));return stu;}};qr.query(sql,rh,params);}}

DBUtils 工具类的使用

public class Demo(){// 数据库添加数据public void fun1() throws SQLException{// 给出连接池参数QueryRunner qr = new QueryRunner(JdbcUtils.getDataSource());// 给出 sql 模板String sql = "INSERT INTO t_stu VALUES(?,?,?,?)";// 给出参数的值Object[] params = {1003,"zhaoliu",24,"male"};qr.update(sql,params);}// 数据库查询public void fun2() throws SQLException{// 给出连接参数QueryRunner qr = new QueryRunner(JdbcUtils.getDataSource());// 给出 sql 模板String sql ="SELECT * FROM t_stu WHERE sid=?";// 传入参数Object[] params = {1003};// 执行query() 方法, 需要给出结果集处理器, 即 ResultSetHandler 的实现类.// ResultHandler 实现类也就是将 ResultSet 结果集转换为 Stu 对象Stu stu = qr.query(sql,new BeanHandler<Stu>(Stu.class),params);System.out.println(stu);}
}

参考资料:

• JavaWeb 视频教程