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SQL注入攻击
1.sql注入攻击的演示
- 在登录界面，输入一个错误的用户名或密码，也可以登录成功
2.sql注入攻击的原理
- 按照正常道理来说，我们在密码处输入的所有内容，都应该认为是密码的组成
- 但是现在Statement对象在执行sql语句时，将一部分内容当做查询条件来执行了
3.PreparedStatement的介绍
- 预编译sql语句的执行者对象。在执行sql语句之前，将sql语句进行提前编译。明确sql语句的格式后，就不会改变了。剩余的内容都会认为是参数！参数使用?作为占位符
- 为参数赋值的方法：setXxx(参数1,参数2);
- 参数1：?的位置编号(编号从1开始)
- 参数2：?的实际参数
- 执行sql语句的方法
- 执行insert、update、delete语句：int executeUpdate();
- 执行select语句：ResultSet executeQuery();
4.PreparedStatement的使用
/* 使用PreparedStatement的登录方法，解决注入攻击 */ @Override public User findByLoginNameAndPassword(String loginName, String password) { //定义必要信息 Connection conn = null; PreparedStatement pstm = null; ResultSet rs = null; User user = null; try { //1.获取连接 conn = JDBCUtils.getConnection(); //2.创建操作SQL对象 String sql = "SELECT * FROM user WHERE loginname=? AND password=?"; pstm = conn.prepareStatement(sql); //3.设置参数 pstm.setString(1,loginName); pstm.setString(2,password); System.out.println(sql); //4.执行sql语句，获取结果集 rs = pstm.executeQuery(); //5.获取结果集 if (rs.next()) { //6.封装 user = new User(); user.setUid(rs.getString("uid")); user.setUcode(rs.getString("ucode")); user.setUsername(rs.getString("username")); user.setPassword(rs.getString("password")); user.setGender(rs.getString("gender")); user.setDutydate(rs.getDate("dutydate")); user.setBirthday(rs.getDate("birthday")); user.setLoginname(rs.getString("loginname")); } //7.返回 return user; }catch (Exception e){ throw new RuntimeException(e); }finally { JDBCUtils.close(conn,pstm,rs); } }
5.使用PreparedStatement优化student表的CRUD（作业）
public class StudentDaoImpl implements StudentDao { @Override public ArrayList<Student> findAll() { //定义必要信息 Connection conn = null; PreparedStatement pstm = null; ResultSet rs = null; ArrayList<Student> students = null; try { //1.获取连接 conn = JDBCUtils.getConnection(); //2.获取操作对象 pstm = conn.prepareStatement("select * from student"); //3.执行sql语句，获取结果集 rs = pstm.executeQuery(); //4.遍历结果集 students = new ArrayList<Student>(); while (rs.next()) { //5.封装 Student student = new Student(); student.setSid(rs.getInt("sid")); student.setName(rs.getString("name")); student.setAge(rs.getInt("age")); student.setBirthday(rs.getDate("birthday")); //加入到集合中 students.add(student); } //6.返回 return students; }catch (Exception e){ throw new RuntimeException(e); }finally { JDBCUtils.close(conn,pstm,rs); } } @Override public Student findById(Integer sid) { //定义必要信息 Connection conn = null; PreparedStatement pstm = null; ResultSet rs = null; Student student = null; try { //1.获取连接 conn = JDBCUtils.getConnection(); //2.获取操作对象 pstm = conn.prepareStatement("select * from student where sid = ? "); pstm.setInt(1,sid); //3.执行sql语句，获取结果集 rs = pstm.executeQuery(); //4.遍历结果集 if (rs.next()) { //5.封装 student = new Student(); student.setSid(rs.getInt("sid")); student.setName(rs.getString("name")); student.setAge(rs.getInt("age")); student.setBirthday(rs.getDate("birthday")); } //6.返回 return student; }catch (Exception e){ throw new RuntimeException(e); }finally { JDBCUtils.close(conn,pstm,rs); } } @Override public int insert(Student student) { //定义必要信息 Connection conn = null; PreparedStatement pstm = null; int result = 0; try { //1.获取连接 conn = JDBCUtils.getConnection(); //2.获取操作对象 pstm = conn.prepareStatement("insert into student(sid,name,age,birthday)values(null,?,?,?)"); //3.设置参数 //pstm.setInt(1,null); pstm.setString(1,student.getName()); pstm.setInt(2,student.getAge()); pstm.setDate(3,new Date(student.getBirthday().getTime())); //4.执行sql语句 result = pstm.executeUpdate(); }catch (Exception e){ throw new RuntimeException(e); }finally { JDBCUtils.close(conn,pstm); } return result; } @Override public int update(Student student) { //定义必要信息 Connection conn = null; PreparedStatement pstm = null; int result = 0; try { //1.获取连接 conn = JDBCUtils.getConnection(); //2.获取操作对象 pstm = conn.prepareStatement("update student set name=?,age=?,birthday=? where sid=? "); //3.设置参数 pstm.setString(1,student.getName()); pstm.setInt(2,student.getAge()); pstm.setDate(3,new Date(student.getBirthday().getTime())); pstm.setInt(4,student.getSid()); //4.执行sql语句 result = pstm.executeUpdate(); }catch (Exception e){ throw new RuntimeException(e); }finally { JDBCUtils.close(conn,pstm); } return result; } @Override public int delete(Integer sid) { //定义必要信息 Connection conn = null; PreparedStatement pstm = null; int result = 0; try { //1.获取连接 conn = JDBCUtils.getConnection(); //2.获取操作对象 pstm = conn.prepareStatement("delete from student where sid=? "); //3.设置参数 pstm.setInt(1,sid); //4.执行sql语句 result = pstm.executeUpdate(); }catch (Exception e){ throw new RuntimeException(e); }finally { JDBCUtils.close(conn,pstm); } return result; } }
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C笔记
