有一个 mySQL 错误，未知列 where 子句 [英] Having a mySQL error, unknown column where clause

问题描述

我目前在从 mySQL 数据库中选择某个项目时遇到问题.我的程序旨在将参数从 android 应用程序传递到 servlet，然后该 servlet 查询数据库.

I am currently having a problem selecting a certain item from a mySQL database. My program is designed to pass a parameter from an android application to a servlet which then queries the database.

但是控制台窗口出现错误:where 子句"中的未知列0102310c24"

However an error appears on the console window: Unknown column '0102310c24' in 'where clause'

只有当我要选择的值包含字母时才会出现错误.

There is only an error when the value I want to select contains a letter.

当我查询这个号码0106172459时，我想要的数据没有问题返回.

When I query this number 0106172459, the data I want is returned without a problem.

下面是我的 servlet.

Below is my servlet.

import java.io.*;
import java.util.*;
import javax.sql.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class DBServlet extends HttpServlet {
public void service(HttpServletRequest request,HttpServletResponse response)
throws IOException, ServletException{
response.setContentType("text/html");
PrintWriter out = response.getWriter();
String x=request.getParameter("item");
Connection con = null;
Statement stmt = null;
ResultSet rs = null;
try {
Class.forName("com.mysql.jdbc.Driver");
con =DriverManager.getConnection ("jdbc:mysql://IP/databasename", "username", "password");
stmt = con.createStatement();
rs = stmt.executeQuery("SELECT * FROM items WHERE item="+x);
// displaying records
while(rs.next()){
out.print(rs.getObject(1).toString());
out.print(",");
out.print(rs.getObject(2).toString());
out.print(",");
out.print(rs.getObject(3).toString());
out.print(",");
out.print(rs.getObject(4).toString());
out.print(",");
out.print(rs.getObject(5).toString());
out.print(",");
out.print(rs.getObject(6).toString());
out.print(",");
out.print(rs.getObject(7).toString());
out.print(",");
out.print(rs.getObject(8).toString());
out.print(",");
out.print("\n");
}
} catch (SQLException e) {
throw new ServletException("Servlet Could not display records.", e);
} catch (ClassNotFoundException e) {
throw new ServletException("JDBC Driver not found.", e);
} finally {
try {
if(rs != null) {
rs.close();
rs = null;
}
if(stmt != null) {
stmt.close();
stmt = null;
}
if(con != null) {
con.close();
con = null;
}
} catch (SQLException e) {}
}
out.close();
}
}

我用它来将值发送到 servlet.

and I use this to send the value to the servlet.

List<NameValuePair> nameValuePair = new ArrayList<NameValuePair>();
nameValuePair.add(new BasicNameValuePair("item","List<NameValuePair> nameValuePair = new ArrayList<NameValuePair>();
nameValuePair.add(new BasicNameValuePair("item","010238a2cc"));"));

如果有人能帮忙，我将不胜感激

I will be thankful if anyone could help

推荐答案

值 x 应该用引号引起来，否则一个非数字值将被假定为引用一个列而不是一个字符串文字.

The value x should be enclosed in quotes, or a non-numeric value would be assumed to refer to a column rather than a string literal.

rs = stmt.executeQuery("SELECT * FROM items WHERE item='"+x + "'");

请注意，您的脚本似乎容易受到 SQL 注入的攻击，因为值 x 尚未转义，而是从 Request 中收到的.这里最好使用准备好的语句.

Note that your script appears to be vulnerable to SQL injection, as the value x has not been escaped but was received from the Request. It would be better to use a prepared statement here.

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