How to Efficiently Parameterize IN Clauses in JDBC?

IN clause parameterization in JDBC: is there a direct method?

In JDBC, it can be challenging to parameterize IN clauses efficiently. A typical query structure is as follows:

<code class="language-sql">SELECT * FROM MYTABLE WHERE MYCOL in (?)</code>

In order to dynamically inject values ​​into clauses like this, we need a straightforward method that works across various databases without changing the SQL.

Unfortunately, JDBC does not provide a native solution for this problem. However, some drivers may support PreparedStatement#setArray() for IN clauses.

Alternative methods

Alternatively, we can use helper methods to create placeholders and set parameter values ​​iteratively. Here is an implementation:

<code class="language-java">public static String preparePlaceHolders(int length) {
    return String.join(",", Collections.nCopies(length, "?"));
}

public static void setValues(PreparedStatement preparedStatement, Object... values) throws SQLException {
    for (int i = 0; i < values.length; i++) {
        preparedStatement.setObject(i + 1, values[i]);
    }
}</code>

Usage example:

```java private static final String SQL_FIND = "SELECT id, name, value FROM entity WHERE id IN (%s)";

public List find(Set ids) throws SQLException { List entities = new ArrayList<>(); String sql = String.format(SQL_FIND, preparePlaceHolders(ids.size()));

<code>try (
    Connection connection = dataSource.getConnection();
    PreparedStatement statement = connection.prepareStatement(sql);
) {
    setValues(statement, ids.toArray());

    try (ResultSet resultSet = statement.executeQuery()) {
        while (resultSet.next()) {
            entities.add(map(resultSet));
        }
    }
}

return entities;</code>

}

<code>
<p><strong>注意事项</strong></p>

- 请注意，某些数据库限制了IN子句中允许的值的数量。
- 此方法利用PreparedStatement接口，确保跨数据库兼容性。
- 还必须考虑数据库特定的优化，例如使用数组或批量更新。</code>

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