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我正在使 servlet 与 J2ME 一起工作，但是每当运行这个时，都会出现以下错误消息。

错误：

java.sql.SQLException：[Microsoft][ODBC SQL Server Driver][SQL Server]第 1 行：“密码”附近的语法不正确。）

public class GetNpostServlet extends HttpServlet
{
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse res) 
                     throws ServletException, IOException
{
// Same code appears in doPost()
// Shown both places to emphasize that data is received thru
// different means (environment variable vs stream), 
// yet processed the same inside the servlet
String acct = req.getParameter("account"),
        pwd = req.getParameter("password");    

String balance = accountLookup(acct, pwd);

if (balance == null)
{
  res.sendError(HttpServletResponse.SC_BAD_REQUEST, 
 "Unable to locate  account.");            
  return;
}

res.setContentType("text/plain");    
PrintWriter out = res.getWriter();
out.print(balance);
out.close();
}

@Override
protected void doPost(HttpServletRequest req, HttpServletResponse res) 
                    throws ServletException, IOException
{
// Same code appears in doGet()
// Shown both places to emphasize that data is received thru
// different means (stream vs environment variable), 
// yet processed the same inside the servlet
String acct = req.getParameter("account"),
        pwd = req.getParameter("password");    

String balance = accountLookup(acct, pwd);

if (balance == null)
{
  res.sendError(HttpServletResponse.SC_BAD_REQUEST, 
"Unable to locate account.");            
  return;
}

res.setContentType("text/plain");    
PrintWriter out = res.getWriter();
out.print(balance);
out.close();
}

/*--------------------------------------------------
 * Lookup bank account balance in database
 *-------------------------------------------------*/
private String accountLookup(String acct, String pwd)
{
Connection con = null;
Statement st = null;
StringBuilder msgb = new StringBuilder("");

try
{
  // These will vary depending on your server/database      
  Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");  
  con = DriverManager.getConnection("jdbc:odbc:acctInfo");

  Statement stmt = con.createStatement();
  ResultSet rs = stmt.executeQuery(
                     "Select balance from acctInfo where account = " +
                     acct + "and password = '" + pwd + "'");      

  if (rs.next())
    return rs.getString(1);
  else
    return null;
   }
   catch (Exception e)
   {                  
    return e.toString();
    }
    }

    }
4

1 回答 1

5

最直接的问题：你没有引用字符串，并且它后面acct没有空格，所以你最终会得到类似的东西：

Select balance from acctInfo where account = fredand password = 'bloggs'

更重要的问题：你不应该首先像这样在 SQL 中包含值。您应该使用参数化 SQL。目前您的代码对SQL 注入攻击是开放的。

进一步的安全问题：您的代码表明密码以纯文本形式保存。请不要这样做。

设计问题：

  • 您似乎将帐户余额视为字符串。这很奇怪。BigDecimal将是更自然的表示。
  • 你正在捕捉Exception而不是特定的例外
  • 您正在返回一个异常字符串表示形式，就好像它是一个 account balance 一样。哎呀！您可能实际上应该让SQLException呼叫者冒泡
  • 您永远不会关闭连接、语句或结果集
于 2012-05-08T09:05:06.237 回答