在AndroidStudio创建java项目
AndroidStudio引入Mysql jar包
6.0正确的DBHelper写法
多次调用失败总结出来的 这里就不吐槽了。 String driver_url="jdbc:mysql://localhost:3306/userdb?serverTimezone=UTC&verifyServerCertificate=false&useSSL=false";完整代码
public class DBHelper { private static Connection con; public DBHelper() { this.con = getConnection(); } private static Connection getConnection(){ String driver_class="com.mysql.cj.jdbc.Driver"; String driver_url="jdbc:mysql://localhost:3306/userdb?serverTimezone=UTC&verifyServerCertificate=false&useSSL=false"; String database_user="root"; String database_password="119486119a"; try { Class.forName(driver_class); con=DriverManager.getConnection(driver_url,database_user,database_password); } catch (ClassNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } return con; } /** * 鎻掑叆鏁版嵁 * @param student * @return */ public static int insert(User student) { Connection conn = getConnection(); int i = 0; String sql = "insert into user (iduser,user_count) values(?,?)"; PreparedStatement pstmt; try { pstmt = (PreparedStatement) conn.prepareStatement(sql); pstmt.setString(1, student.getId()+""); pstmt.setString(2, student.getCout_us()+""); // pstmt.setString(3, student.getAge()); i = pstmt.executeUpdate(); pstmt.close(); conn.close(); } catch (SQLException e) { e.printStackTrace(); } return i; } public static int update(User student) { Connection conn = getConnection(); int i = 0; String sql = "update user set user_count='" + student.getCout_us() + "' where iduser='" + student.getId() + "'"; PreparedStatement pstmt; try { pstmt = (PreparedStatement) conn.prepareStatement(sql); i = pstmt.executeUpdate(); System.out.println("resutl: " + i); pstmt.close(); conn.close(); } catch (SQLException e) { e.printStackTrace(); } return i; } public static Integer getAll() { Connection conn = getConnection(); String sql = "select * from user"; PreparedStatement pstmt; try { pstmt = (PreparedStatement)conn.prepareStatement(sql); ResultSet rs = pstmt.executeQuery(); int col = rs.getMetaData().getColumnCount(); System.out.println("============================"); while (rs.next()) { for (int i = 1; i <= col; i++) { System.out.print(rs.getString(i) + "\t"); if ((i == 2) && (rs.getString(i).length() < 8)) { System.out.print("\t"); } } System.out.println(""); } System.out.println("============================"); } catch (SQLException e) { e.printStackTrace(); } return null; } public static int delete(String name) { Connection conn = getConnection(); int i = 0; String sql = "delete from user where iduser='" + name + "'"; PreparedStatement pstmt; try { pstmt = (PreparedStatement) conn.prepareStatement(sql); i = pstmt.executeUpdate(); System.out.println("resutl: " + i); pstmt.close(); conn.close(); } catch (SQLException e) { e.printStackTrace(); } return i; } }main调用代码
public class MyClass { public static void main(String[] args) { DBHelper.getAll(); DBHelper.insert(new User(7, 20)); DBHelper.getAll(); DBHelper.update(new User(3,10)); DBHelper.getAll(); DBHelper.delete(2+""); DBHelper.getAll(); // UserWindow userWindow = new UserWindow(); // userWindow.showWindow(); System.out.println("测试中文输出"); } }OK结束 博主大多数时间在 自己的博客网站上写 一般深刻点的都在上面 有兴趣的 百度搜 北京ITEBLOG 第一个就是博主的私人博客.
