如何使用 JDBC getGeneratedKeys 获取生成的 UUID 类型？

Question

这是特定于 MySQL 和UUID类型的 id，我正在使用 MySQL 本身的uuid()函数。 它给了我 not null resultSet ，但next()值始终为空。

以下是代码：

String insertQuery = "INSERT INTO fixtures "
                        + "(id, whatever1, whatever2, whatever3, whatever4, "
                        ...
                        + "created_at) "
                        + "VALUES(UUID(), ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)";

PreparedStatement preparedStatement = connection.prepareStatement(insertQuery, Statement.RETURN_GENERATED_KEYS);
.
.
.
preparedStatement.setDate(23, sqlDate);
preparedStatement.executeUpdate();
ResultSet keysResultSet = preparedStatement.getGeneratedKeys();
System.out.println(keysResultSet); // com.mysql.cj.jdbc.result.ResultSetImpl@6892b3b6
if(keysResultSet != null && keysResultSet.next()){
     System.out.println("Generated Emp Id: "+keysResultSet.getString("id"));
} else {
     System.out.println("No KEYS GENERATED");
}

Answer 1

没有生成密钥，但实际上提供了：

因此，要么将创建留给数据库：

String insertQuery = "INSERT INTO fixtures "
                        + "(whatever1, whatever2, whatever3, whatever4, "
                        ...
                        + "created_at) "
                        + "VALUES(?, ?, ?, ?, ?, ?, ?, ?, ?, "
                        + "?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)";

由于我不知道如何在 MySQL 端轻松实现 UUID，我建议在 Java 端使用 UUID 的原始解决方案：

String insertQuery = "INSERT INTO fixtures "
                        + "(id, whatever1, whatever2, whatever3, whatever4, "
                        ...
                        + "created_at) "
                        + "VALUES(?, ?, ?, ?, ?, ?, ?, ?, "
                        + "?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)";
 UUID id = UUID.randomUUID();
 preparedStatement.setString(1, id.toString());

然后获取 UUID 变得无关紧要。

Answer 2

对于 SQL Server 2008 及更高版本，您可以使用自动生成的 UUID 定义主键。 要检索由 INSERT 语句生成的 UUID，请在列定义之后添加 OUTPUT 选项，并将 statement.executeUpdate 替换为 statement.executeQuery 并从 ResultSet 中检索值。 这是一个显示如何执行此操作的代码片段：

            sqlStmt.append("INSERT INTO tableName");
            sqlStmt.append(" (column1");
            sqlStmt.append(", column2");
...
            sqlStmt.append(" OUTPUT inserted.columnUUID");
            sqlStmt.append(" VALUES (?, ?, ?, ?) ");
            statement = connection.prepareStatement(sqlStmt.toString());
            statement.clearParameters();
            int index = 0;
            ResultSet resultSet = statement.executeQuery();
            if (resultSet.next())
            {
                result = resultSet.getString(1);
                companyDB.varUUID = result;
            }

Answer 3

Jop Eggan 的回答解决了这个问题。 但是，如果该方法出现任何错误，您也可以执行以下操作：

String insertQuery = "INSERT INTO fixtures "
                        + "(id, whatever1, whatever2, whatever3, whatever4, "
                        ...
                        + "created_at) "
                        + "VALUES(?, ?, ?, ?, ?, ?, ?, ?, "
                        + "?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)";
 UUID id = UUID.randomUUID();
 preparedStatement.setObject(1, id);