String sno = request.getParameter("sno"); String cno = request.getParameter("cno"); String sql = "select * from sc where sno = '"+sno+"' and cno='"+ cno +"'"; ResultSet rs = stmt.executeQuery(sql); rs.next(); String grade= rs.getString("grade"); 帮我找出问题
时间: 2024-03-27 08:37:36 浏览: 138
在这段代码中,SQL查询语句的参数值(sno和cno)是从客户端请求中获取的,这可能会导致SQL注入攻击。建议使用参数化查询语句来避免这种情况。此外,如果查询结果集为空,调用`rs.next()`方法可能会抛出异常。应该在调用`rs.next()`方法之前,通过调用`rs.isBeforeFirst()`方法检查结果集是否为空。以下是建议的修改代码:
```java
String sno = request.getParameter("sno");
String cno = request.getParameter("cno");
String sql = "select * from sc where sno = ? and cno = ?";
PreparedStatement ps = conn.prepareStatement(sql);
ps.setString(1, sno);
ps.setString(2, cno);
ResultSet rs = ps.executeQuery();
if (rs.isBeforeFirst()) {
rs.next();
String grade = rs.getString("grade");
// do something with grade
} else {
// handle empty result set
}
```
相关问题
编写程序,实现对数据库StudentInfo中的表student进行插入操作.要求使用预处理语句对象PreparedStatement完成以下数据的插入: insert into student values('001','张三',18,'女') 注:给定数据库登录用户名:sa,密码:123. Input.jsp: 请输入待新增的学生信息 学号: 姓名: 年龄: 性别: addStudent.jsp: <% String url="jdbc:sqlserver://localhost;databaseName=StudentInfo"; request.setCharacterEncoding("utf-8"); String sno = request.getParameter("sno"); String sname = request.getParameter("sname"); int sage = Integer.valueOf(request.getParameter("sage")); String sex = request.getParameter("sex"); try{ //补全此部分代码 } // 捕获异常 catch(SQLException ex) { System.out.println ("\n*** 发生SQL异常 ***\n"+ex.getMessage()); } catch(ClassNotFoundException ex) { System.out.println(ex); }
addStudent.jsp:
```
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Add Student</title>
</head>
<body>
<h1>Add Student</h1>
<form action="insertStudent.jsp" method="post">
<label for="sno">学号:</label>
<input type="text" id="sno" name="sno" /><br>
<label for="sname">姓名:</label>
<input type="text" id="sname" name="sname" /><br>
<label for="sage">年龄:</label>
<input type="text" id="sage" name="sage" /><br>
<label for="sex">性别:</label>
<input type="text" id="sex" name="sex" /><br>
<input type="submit" value="提交" />
</form>
</body>
</html>
```
insertStudent.jsp:
```
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ page import="java.sql.*" %>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert Student</title>
</head>
<body>
<%
String url="jdbc:sqlserver://localhost;databaseName=StudentInfo";
request.setCharacterEncoding("utf-8");
String sno = request.getParameter("sno");
String sname = request.getParameter("sname");
int sage = Integer.valueOf(request.getParameter("sage"));
String sex = request.getParameter("sex");
try{
Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
Connection conn = DriverManager.getConnection(url,"sa","123");
String sql = "insert into student values(?,?,?,?)";
PreparedStatement pstmt = conn.prepareStatement(sql);
pstmt.setString(1, sno);
pstmt.setString(2, sname);
pstmt.setInt(3, sage);
pstmt.setString(4, sex);
int num = pstmt.executeUpdate();
if(num > 0){
out.print("插入成功!");
}
pstmt.close();
conn.close();
}
catch(SQLException ex){
System.out.println ("\n*** 发生SQL异常 ***\n"+ex.getMessage());
}
catch(ClassNotFoundException ex){
System.out.println(ex);
}
%>
</body>
</html>
```
String sno = Mytools.toChinese(request.getParameter("sno")); String cno = Mytools.toChinese(request.getParameter("cno"));帮我找出错误
在这段代码中,Mytools.toChinese() 方法可能会导致编码问题和安全问题,因为它会将 HTTP 请求参数从 ISO-8859-1 编码转换为 UTF-8 编码,但这种转换可能会导致数据损坏或安全问题。建议使用 request.setCharacterEncoding() 方法来设置请求编码,例如:
```
request.setCharacterEncoding("UTF-8");
String sno = request.getParameter("sno");
String cno = request.getParameter("cno");
```
这样可以保证请求参数的编码正确,并且可以避免安全问题。
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