Last week I showed you how to increase the performance of multiple java calls by making them asynchronous and parallel. This week we take a look at another potential performance booster, you should always keep in mind - caching.

Let’s imagine a scenario where you call a REST service and you know the returned values don’t change very often. In this case you really need to consider caching the response. We will use Guava’s provided caching capabilities to implement such a cache for this example.

New dev bookmarks added in the 4th calendar week of 2018. Hot topics this week:

• angular
• async
• asynchronous
• debugging
• dev-tools
• jackson
• java
• javaee
• javascript
• json
• package-manager
• postman
• regex
• rest
• turbo
• vim

Some time ago I wrote how elegant and rapid is to make parallel calls in NodeJS with async-await and Promise.all capabilities. Well, it turns out in Java is just as elegant and succinct with the help of CompletableFuture which was introduced in Java 8. To demonstrate that let’s imagine that you need to retrieve a list of ToDos from a REST service, given their Ids. Of course you could iterate through the list of Ids and sequentially call the web service, but it’s much more performant to do it in parallel with asynchronous calls.

New dev bookmarks added this year so far. They were marked with the following keywords:

• clean-code
• debugging
• design-patterns
• expressjs
• git
• http
• mongodb
• mongoose
• nodejs
• npm
• rxjs
• ssh
• testing
• typescript
• unit-testing
• utils
• vscode

I have a use case where I need to retrieve the latest added public dev-bookmarks. They are store in a mongo database, and I use Mongoose as ORM.

I want to have two possibilites to achieve this:

1. specify the number of days to look back
2. specify the timestamp since when to look forward

I think the code is self explanatory

/**
 * Returns the codingmarks added recently.
 * 
 * The since query parameter is a timestamp which specifies the date since we want to look forward to present time.
 * If this parameter is present it has priority. If it is not present, we might specify the number of days to look back via
 * the query parameter numberOfDays. If not present it defaults to 7 days, last week.
 *
 */
router.get('/latest-entries', async (req, res) => {
  try
  {

    if(req.query.since) {
      const bookmarks = await Bookmark.find(
        {
          createdAt: { $gte: new Date(parseFloat(req.query.since,0)) }
        }).sort({createdAt: 'desc'}).lean().exec();

      res.send(bookmarks);
    } else {
      const numberOfDaysToLookBack = req.query.days ? req.query.days : 7;

      const bookmarks = await Bookmark.find(
        {
          createdAt: { $gte: new Date((new Date().getTime() - (numberOfDaysToLookBack * 24 * 60 * 60 * 1000))) }
        }).sort({createdAt: 'desc'}).lean().exec();

      res.send(bookmarks);
    }

  }
  catch (err)
  {
    return res.status(500).send(err);
  }
});