个人作业直接连接远程数据库（例子）
package com.example.demo3.utils; import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; //function： 数据库工具类，连接数据库用 public class JDBCUtils { private static String driver = "com.mysql.jdbc.Driver";// MySql驱动 private static String dbName = "db_timing";// 数据库名称 private static String user = "root";// 用户名 private static String password = "123456";// 密码 public static Connection getConn(){ Connection connection = null; try{ Class.forName(driver);// 动态加载类 String ip = "10.99.163.140";// 写成本机地址，不能写成localhost，同时手机和电脑连接的网络必须是同一个 // 尝试建立到给定数据库URL的连接 connection = DriverManager.getConnection("jdbc:mysql://" + ip + ":3306/" + dbName, user, password); }catch (Exception e){ e.printStackTrace(); } return connection; } }
这个是连接数据库 的代码
public class StudentDao { private static final String TAG = "mysql-db_timing-StudentDao"; private static String currentLoggedInUserId; // 添加一个类变量来存储当前登录用户的ID public int login(String id,String password){ HashMap<String,Object> map =new HashMap<>(); //连接数据库 Connection connection = JDBCUtils.getConn(); int msg = 0; try{ //简单的sql查询 String sql = "select * from student where id = ?"; if (connection != null){// connection不为null表示与数据库建立了连接 PreparedStatement ps = connection.prepareStatement(sql); if (ps != null){ Log.e(TAG,"账号：" + id); //根据账号进行查询 ps.setString(1, id); // 执行sql查询语句并返回结果集 ResultSet rs = ps.executeQuery(); int count = rs.getMetaData().getColumnCount(); //将查到的内容储存在map里 while (rs.next()){ // 注意：下标是从1开始的 for (int i = 1;i <= count;i++){ String field = rs.getMetaData().getColumnName(i); map.put(field, rs.getString(field)); } } connection.close(); ps.close(); if (map.size()!=0){ StringBuilder s = new StringBuilder(); //寻找密码是否匹配 for (String key : map.keySet()){ if(key.equals("password")){ if(password.equals(map.get(key))){ msg = 1; //密码正确 currentLoggedInUserId = id; // 设置当前登录用户的ID } else msg = 2; //密码错误 break; } } }else { Log.e(TAG, "查询结果为空"); msg = 3; } }else { msg = 0; } }else { msg = 0; } }catch (Exception e){ e.printStackTrace(); Log.d(TAG, "异常login：" + e.getMessage()); msg = 0; } return msg; } /** * function: 注册 * */ public boolean register(Student student){ HashMap<String, Object> map = new HashMap<>(); // 根据数据库名称，建立连接 Connection connection = JDBCUtils.getConn(); try { String sql = "insert into student(id,name,phone,className,password,setGoal,setRecord) values (?,?,?,?,?,?,?)"; if (connection != null){// connection不为null表示与数据库建立了连接 PreparedStatement ps = connection.prepareStatement(sql); if (ps != null){ //将数据插入数据库 ps.setString(1,student.getId()); ps.setString(2,student.getName()); ps.setString(3,student.getPhone()); ps.setString(4,student.getClassName()); ps.setString(5, student.getPassword()); ps.setInt(6,student.getSetGoal()); ps.setInt(7,student.getSetRecord()); // 执行sql查询语句并返回结果集 int rs = ps.executeUpdate(); if(rs>0) return true; else return false; }else { return false; } }else { return false; } }catch (Exception e){ e.printStackTrace(); Log.e(TAG, "异常register：" + e.getMessage()); return false; } } public Student findStudent(String StudentId) { // 根据数据库名称，建立连接 Connection connection = JDBCUtils.getConn(); Student student = null; try { String sql = "select * from student where id = ?"; if (connection != null){// connection不为null表示与数据库建立了连接 PreparedStatement ps = connection.prepareStatement(sql); if (ps != null) { ps.setString(1, StudentId); ResultSet rs = ps.executeQuery(); while (rs.next()) { //注意：下标是从1开始 String id = rs.getString(1); String name = rs.getString(2); String phone = rs.getString(3); String className = rs.getString(4); String password = rs.getString(5); int setGoal = rs.getInt(6); int setRecord = rs.getInt(7); student = new Student(id, name, phone, className, password, setGoal, setRecord); } } } }catch (Exception e){ e.printStackTrace(); Log.d(TAG, "异常findUser：" + e.getMessage()); return null; } return student; } public static String getCurrentLoggedInUserId() { return currentLoggedInUserId; } /** * 增加 setGoal 字段的值 */ public static boolean incrementSetGoal() { Connection connection = JDBCUtils.getConn(); if (connection != null) { try { String sql = "UPDATE student SET setGoal = setGoal + 1 WHERE id = ?"; PreparedStatement ps = connection.prepareStatement(sql); String studentId = getCurrentLoggedInUserId(); // 获取当前登录用户的ID ps.setString(1, studentId); int rowsAffected = ps.executeUpdate(); ps.close(); connection.close(); return rowsAffected > 0; } catch (Exception e) { e.printStackTrace(); Log.e(TAG, "异常 incrementSetGoal：" + e.getMessage()); return false; } } return false; } /** * 增加 setRecord 字段的值 */ public static boolean incrementSetRecord() { Connection connection = JDBCUtils.getConn(); if (connection != null) { try { String sql = "UPDATE student SET setRecord = setRecord + 1 WHERE id = ?"; PreparedStatement ps = connection.prepareStatement(sql); String studentId = getCurrentLoggedInUserId(); // 获取当前登录用户的ID ps.setString(1, studentId); int rowsAffected = ps.executeUpdate(); ps.close(); connection.close(); return rowsAffected > 0; } catch (Exception e) { e.printStackTrace(); Log.e(TAG, "异常 incrementSetRecord：" + e.getMessage()); return false; } } return false; } public int getSetGoal(String studentId) { StudentDao studentDao = new StudentDao(); Student student = studentDao.findStudent(studentId); if (student != null) { return student.getSetGoal(); } else { // 如果未找到学生，则返回默认值或者抛出异常，这取决于你的需求 return 0; // 默认值为0 } } public int getSetRecord(String studentId){ StudentDao studentDao = new StudentDao(); Student student = studentDao.findStudent(studentId); if (student != null) { return student.getSetRecord(); } else { // 如果未找到学生，则返回默认值或者抛出异常，这取决于你的需求 return 0; // 默认值为0 } }
我们最后需要下面的操作对数据库
https://www.cnblogs.com/heyang78/p/15695063.html
这个是解决的方法的博客
