Question

I'm trying to use the Notion API for Java. To build a Notion client one of the parameters required is user id. Getting a page id or a database id is easy ( extracting it from the url shown in the browser.

I need a user_id and a token (to substitute for the ??'s below)

import org.jraf.klibnotion.client.*;

private static final String TOKEN = "??";

// Replace this constant with a user id that exists
private static final String USER_ID = "???";

// Replace this constant with a database id that exists
private static final String DATABASE_ID = "4187ea78084040079c1ce6ea6e605cc1";

// Replace this constant with a page id that exists
private static final String PAGE_ID = "db4f55eb9f6b4fd089562f82ebb6335e?v=b031267784c8464883952c89a11626f0&pvs=4";

private void initClient() {
    NotionClient notionClient = NotionClient.newInstance(
            new ClientConfiguration(
                    new Authentication(TOKEN),
                    new HttpConfiguration(
                            // Uncomment to see more logs
                            // loggingLevel = HttpLoggingLevel.BODY,
                            HttpLoggingLevel.INFO,
                            null,
                            // This is only needed to debug with, e.g., Charles Proxy
                            new HttpProxy("localhost", 8888),
                            true
                    )
            )
    );
    client = BlockingNotionClientUtils.asBlockingNotionClient(notionClient);
}

private void main() {
    initClient();

    // Get user
    System.out.println("User:");
    User user = client.getUsers().getUser(USER_ID);
    System.out.println(user);
}

Answer 1

There is no direct way to get your user_id through UI. However, you can follow these steps to get the user id:
Open Network tab of Developer tools on your browser in the same tab as where Notion is opened.
On the Notion UI, click on Settings & members.
Click on My account and check the Network call authGetLoginConfiguration and in the preview you should see an attribute called userId.