Is it mandatory to put inner try-with-resources or everything inside one of the try-with-resources will be autoclosed?

Question

Is it mandatory to put inner try-with-resources or everything inside one of the try-with-resources will be autoclosed?

    try (BasicDataSource ds = BasicDataSourceFactory.createDataSource(dsProperties)) {

        // still necessary for Connection to close if inside
        // try-with-resources?
        try (Connection conn = ds.getConnection()) {

            String sql = "SELECT * FROM users";
            try (PreparedStatement stmt = conn.prepareStatement(sql)) {

                try (ResultSet rs = stmt.executeQuery()) {

                    while (rs.next()) {
                        System.out.println(rs.getString("email"));
                        System.out.println(rs.getString("password"));
                    }

                }
            }

        }

    } catch (SQLException e) {

        e.printStackTrace();
    } catch (Exception e) {

        e.printStackTrace();
    }

Answer 1

In a try-with-resources block, only the resources in the try statement will be closed automatically by the try-with-resources construct. Other resources within the block are unrelated, and must be managed^(*).

However, you can put multiple resources in the try statement, instead of using multiple try-with-resources (one for each resource) for example:

try (PreparedStatement stmt = conn.prepareStatement(sql);
     ResultSet rs = stmt.executeQuery()) {
    while (rs.next()) {
        System.out.println(rs.getString("email"));
        System.out.println(rs.getString("password"));
    }
}

^(*)As @alexander-farber pointed out in a comment, there are also some resources that get closed automatically by other mechanism, for example a ResultSet gets closed when the Statement that generated it gets closed. Although you don't manage those resources explicitly, they are managed by their implementation.