ResultSet 不是用于 INSERT 查询吗?错误消息:类型不匹配:无法从 int 转换为 String [英] ResultSet is not for INSERT query? Error message: Type mismatch: cannot convert from int to String

问题描述

我想我在结果集"上弄错了.我插入数据的代码是:

I think I got it wrong at the 'resultset'. My code for inserting data is :

ResultSet columns = statement.executeUpdate("INSERT INTO Feedback (Username, Feedbacks) VALUES( '" + user + "','"+ msg +"')");

编译错误为:

类型不匹配:无法从 int 转换为 String

Type mismatch: cannot convert from int to String

你能帮我吗?

推荐答案

Statement#executeUpdate() 不返回 ResultSet，而是一个 int 表示受影响的行.修复如下.

Statement#executeUpdate() doesn't return a ResultSet, but an int representing the affected rows. Fix it as follows.

int affectedRows = statement.executeUpdate(sql);

或者，如果您对受影响的行数不感兴趣，请忽略它.

Or if you aren't interested in the amount of affected rows, just ignore it.

statement.executeUpdate(sql);

顺便说一下，编译错误本身很奇怪.你不是看错线了吗?该错误表明您正在尝试将 int 结果分配给 String，但您的代码显示您正在尝试分配 int结果到 ResultSet.

By the way, the compilation error at its own is weird. Aren't you looking at the wrong line? The error tells that you're trying to assign an int result to a String, but your code shows that you're trying to assign int result to a ResultSet.

也就是说，与您当前的问题无关，如果user 和msg 是用户控制输入的一部分，那么这段代码很容易出现SQL 注入 攻击.我强烈建议将 Statement 替换为 PreparedStatement 然后.另请参阅本教程如何使用准备好的语句.

That said and unrelated to your current problem, if user and msg are parts of user-controlled input, then this piece of code is prone to SQL injection attacks. I strongly recommend to replace Statement by PreparedStatement then. See also this tutorial how to use prepared statement.

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