Retrieving A Datastore Entity With A Key (or Kind Name & ID)

Short code fragment that someone might find useful: retrieve an Entity if you know what the kind and entity ID/name are.

Key key = KeyFactory.createKey("kind", "id/name");
try {
    Entity entity = DatastoreServiceFactory.getDatastoreService().get(key);
} catch (EntityNotFoundException e) {
    //The entity wasn't found. Handle this exception.

Accessing and searching cells on Google Spreadsheet API

Recently I answered a question on how to access the Google Spreadsheet API. The poster was asking how to search the contents of a row/cell for a specific phrase, so I put together a quick example in Java.

The source code is below. Note that you need to replace the find_word variable with the phrase that you’re searching for, and the username and password variables with your Google username/password.

    try {
        String USERNAME = "username";
        String PASSWORD = "password";
        String find_word = "GOOG";
        find_word = find_word.toLowerCase();
        SpreadsheetService service = new SpreadsheetService(
        service.setUserCredentials(USERNAME, PASSWORD);
        // Make a request to the API and get all spreadsheets.
        SpreadsheetFeed feed = service.getFeed(SPREADSHEET_FEED_URL,
        List<SpreadsheetEntry> spreadsheets = feed.getEntries();
        if (spreadsheets.size() == 0) {
                    "There are no spreadsheets to inspect!");
        // Retrieve an iterator over all spreadsheets contained in
        // this user's Google Drive
        Iterator<SpreadsheetEntry> spreadsheet_iterator = spreadsheets
        while (spreadsheet_iterator.hasNext()) {
            SpreadsheetEntry spreadsheet =;
            String spreadsheet_name = spreadsheet.getTitle().getPlainText();
                    "Currently searching spreadsheet " + spreadsheet_name);

            // Search only the first worksheet of the spreadsheet.
            WorksheetFeed worksheetFeed = service.getFeed(
                    spreadsheet.getWorksheetFeedUrl(), WorksheetFeed.class);
            List<WorksheetEntry> worksheets = worksheetFeed.getEntries();
            WorksheetEntry worksheet = worksheets.get(0);

            // Fetch the cell feed of the worksheet.
            URL cellFeedUrl = worksheet.getCellFeedUrl();
            CellFeed cellFeed = service
                    .getFeed(cellFeedUrl, CellFeed.class);

            for (CellEntry cell : cellFeed.getEntries()) {
                // Retrieve the contents of each cell.
                String cell_contents = cell.getCell().getInputValue()

                // Match the word with the cell contents. Ignoring case.
                if (cell_contents.indexOf(find_word) != -1) {
                    // Found the word.
                            "Cell with contents " + cell_contents
                                    + " matches your phrase!");
                    // Find the row
                    Integer row_index = new Integer(cell.getCell().getRow());
                            "<b>Row " + row_index.toString() + "</b> in "
                                    + spreadsheet_name
                                    + " matches your query.");
                    String rowCollect = "";
                    // Print row data
                    URL rowCellFeedUrl = new URI(worksheet.getCellFeedUrl()
                            + "?min-row="
                            + row_index
                            + "&max-row=" + row_index).toURL();
                    CellFeed rowCellFeed = service.getFeed(rowCellFeedUrl,
                    // Iterate through each cell, printing its value.
                    for (CellEntry rowCell : rowCellFeed.getEntries()) {
                        // Print the cell's formula or text value
                        rowCollect += rowCell.getCell().getInputValue()
                                + "\t";
                            "<b>Row Data: </b>" + rowCollect);
            }// end for looping through cells
        }// end while looping through spreadsheets

    } catch (Exception e) {
        resp.getWriter().println("Exception: " + e.getMessage());

Also, don’t put this example into production use until you switch out the authentication service to OAuth (this example uses ClientLogin to authenticate).

Setting Security Constraints (Or, Adding Admin-Only Areas In web.xml)

After having experimented with Go for the past few weeks, returning back to Java is a little bit annoying, especially when configuring web.xml and appengine-web.xml files. Golang has a clean, neat configuration file in app.yaml, and yet Java on App Engine has to deal with relatively heavyweight XML files.

For instance, this is the markup required to create an admin-only folder on J/GAE:

The markup alone is 2-3 times the size of the settings themselves! There needs to be a better way of handling this.

Adding a domain alias

I was trying to add a subdomain off of this domain ( to my Google Apps, but apparently this isn’t allowed:

Google Apps won’t let you put in any domain that contains the word google. Blogger doesn’t allow it either. Amusingly enough, it does allow domains with competitor names in them, such as bing or microsoft.

Google App Engine Startup Time & Uncompressing JARs

About a week ago, I saw this post!topic/google-appengine/GdBqSxqviYk about instances being unable to load and failing initialization. I took one look at the picture provided, saw the line This request started at [time] and was still executing at [time, 1 minute later], and immediately assumed that the application’s init function was taking too long to run.

In most cases, that’s a fair assumption to make. One of the bigger pitfalls of App Engine is that instances have only 60 seconds to start up (load in all files and run the init method of servlets). It’s very common for developers to write in a huge amount of code within the init method, and then have instances fail startup because initialization took too long. In this case I believed init was the problem for one reason alone: the picture of the logging stack trace included references to ZIP I/O streams. Uncompressing and processing large ZIP files within the init function could easily take more than a minute.

However, it turned out that the developer wasn’t uncompressing ZIP files in the init – the answer was that App Engine was having a slow day, and was exceeding the 60 second startup limit just trying to uncompress the JAR. Which is pretty amazing and notable enough to comment on – the application didn’t even get fully extracted before App Engine shut down the instance as a failure.

Golang App Binary is missing

Getting a lot of app binary is missing errors from App Engine. It’s odd, I’ve been deploying Java apps on GAE for years, and never received any of these errors. But on the Go runtime, these errors are cropping up repeatedly.

Your project must be configured to use a JDK in order to use JSPs

Whenever I configure a new Eclipse install, I get a strange error the first time I use JSP files. Eclipse complains that I have to configure it to use a JDK, even though a JDK is obviously installed (Otherwise how could it compile Java class files?).

The fix is to go to Preferences – Java – Installed JREs. Click on the first JRE entry, press Edit, and navigate to the base JDK directory. After you save the setting restart Eclipse, and everything will work.