如何在 Java 中将变量作为字符串插入 MySQL [英] How to insert variable as a string into MySQL in Java

问题描述

假设我有两个变量并且我知道它们的值:

Suppose I have two variables and I know their values:

v1=11.1f
v2=22.2f

我可以通过这种方式在字段中插入一串"11.1,22.2".

I can insert a string of "11.1,22.2" into a field in this way.

PreparedStatement pstmt = null;
pstmt = conn.prepareStatement(insertQuery);
pstmt.setString(1, "11.1,22.2");

但是如果我不知道他们的价值观怎么办.如果我按照以下方式进行，

but what should I do if I do not know their values. If I do it in the following way,

pstmt.setString(1, "v1,v2");

它也是一个字符串，但是 v1 和 v2 只是字符而不是变量.

it is also a string, however, v1 and v2 are just characters but not variables any more.

那么如何将变量而不是它们的值放入字符串中，然后在需要时检索它们的值.

So how to put variables instead of their values into a String and then I retrieve their values when I need them.

我问这个问题的原因是我想在 MySQL 中将一个 ArrayList 放在一行中.如果是这样，我想我需要将 float[] 作为一个字符串放在一个字段中.请告诉我会有另一种方法来做到这一点.

That reason why I asked this question is because I want to put an ArrayList in one row in MySQL. If so I thought I need to put float[] as a string in one field. Please tell me there will be another way to do it.

推荐答案

通常，您可以使用以下方法创建带有占位符的字符串:

In general you can create strings with placeholders using:

String result = String.format("%s,%s", v1, v2);

如果您使用的是 JDBC，则可以使用 PreparedStatement，例如:

If you are using JDBC, you can use a PreparedStatement, for example:

PreparedStatement statement = connection.prepareStatement("UPDATE table1 SET column1 = ? WHERE column2 = ?");
int i = 1;
statement.setInt(i++, v1);
statement.setInt(i++, v2);
statement.executeUpdate();

对于创建 JDBC 查询，PreparedStatement 更可取，因为它可以防止输入和字符转义问题.

For creating JDBC queries the PreparedStatement is preferable because it guards you against typing and character escaping problems.

根据请求，另一种方式(虽然不知道它是否更好):

Per request, an alternative way (don't know if it's better though):

MessageFormat form = new MessageFormat("{0},{1}");
Object[] args = new Object[] {v1, v2}; // achtung, auto-boxing
String result = form.format(args)

(这个在房子里，但未经测试)

(this one is on the house, but untested)

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