CYBORG'S LAIR: April 2019

As an info junkie, I am interested in a broad range of topics, able to go through hundreds of links each day. Feedly is allowing me to do it via my cell phone and computer easily.

But when you are following a bigger number of RSS channels, you start to notice duplicate links, pointing to the same articles:

And this can be sometimes pretty annoying.

So, I decided, as a software developer, to get rid of such duplications. I decided to implement a Chrome extension for that because it looks like the most straightforward approach. I also wanted to try it, because I never implemented such an extension before. So, this article can serve as a short tutorial on how to make it.

Basic extension structure

The main file here is manifest.json. It contains metadata related to an extension, like name, description, the extension icon (representing the extension in Chrome's extensions panel), or permissions it needs.

Content and background scripts

There is a possibility to display HTML popup in case a user clicks on the extension icon, but we are not going to need it here. We just need to trigger action that detects duplicate links and removes them.

For this purpose, two separate types of scripts are needed. The first one - background script in Chrome extension development terms - handles the icon click event. Background scripts (defined in background.scripts property of manifest.json file) have access to Chrome API (and thus access to the click event), but cannot access the content of a page.

The second type of scripts - content scripts - have access to page content. These are defined in content_scripts property of the manifest. They are injected into the code of every visited page (if you do not specify any restrictions) and interact with the content.

We want to have a script injected to the Feedly page only in our case. This restriction is defined in content_scripts property - in matches array.

These two types of scripts are separating extension logic from access to page content. But to make it work together another piece of functionality is needed - message passing.

We can see how this works on the example of two scripts from Feedly Unique extension. The first one represents background script - handles Feedly Unique icon click event - sends clicked_feedly_unique message:

The message is then handled by event listener on the content script side:

This script also contains the algorithm for duplicates removal.

Loading the extension into your browser

And now, how to use it in your Chrome browser?

The first thing you need to do is to turn on developer mode in your Chrome - just enter Extensions page (chrome://extensions/) and toggle Developer mode switch in the upper-right corner.

Then click the Load unpacked button (upper-left corner) and select your extension code folder on your local machine.

The plugin is then displayed on Extensions page together with other installed plugins:

For each change, you do to your extension code a reload button highlighted above must be clicked.

Background page link enables you to access the Chrome developer tools window of background scripts. So, you can spot errors or see debug logs of the scripts there. This information is not visible in the developer tools window of a page where a plugin functionality should be applied.

Content scripts stuff only should be visible in the developer tools window of a particular page.

You should see and access the plugin in Google Chrome's extensions panel after load into Chrome:

Feedly Unique and future improvements

The Code of extension that I developed is available on GitHub here.

There are some additional features that could be included in the extension, like automatic scrolling down to load all available links, triggering title-only view and sorting from the oldest to newest (both needed for the proper working of the extension).

Now you need to do all these changes manually before you run the extension.

Oracle revealed in a presentation on 21st March that future Java development will focus on improving language and runtime support for big data, machine learning, and cloud-native workloads.

Couple of days ago (19th March) JDK 12 was released.

This release contains (in preview mode) for example really nice simplification of switch statements - switch expressions.

This reminds me one simple lightweight web framework that I discovered recently, Javalin. Look at simple Hello World example:

Javalin app = Javalin.create()

.port(7000)

.start();

app.get("/hello", ctx -> ctx.html("Hello, Javalin!"));

The server starts at port 7000 and call to "/hello" returns the message.

But I am missing raw String literals from recent Java release, hopefully they will be included in JDK 13.

Anyway, there is a nice approach how to deal with long Strings, simply with String.join call:

String.join(System.getProperty("line.separator"),

"Lorem ipsum dolor sit amet, consectetuer adipiscing elit.",

"Nullam at arcu a est sollicitudin euismod.",

"Class aptent taciti sociosqu ad litora torquent per conubia nostra.");

And more interesting things are to come - one really interesting improvement, that could be included in JDK 13 release, are better default messages for the most common Java exception, NullPointerException.

Spring Framework celebrated the 15th anniversary of its first release on 25th March.

27th March - IntelliJ IDEA 2019.1 was released. Adds functionality like Themes customization (I am so far happy with my Darcula theme), and support for already mentioned switch expressions.

Another for me interesting functionality is for example improved Maven Diagrams for dependencies check and ability to cherry-pick only some of the files right from the VCS log.

Monday, April 29, 2019

Sunday, April 28, 2019

Society

Algorithms

Robots

Health

Cars

Hardware

Brains

Tuesday, April 23, 2019

Friday, April 19, 2019

Society

Algorithms

Robots

Health

Cars

Hardware

Brains

Thursday, April 18, 2019

Monday, April 15, 2019

Basic extension structure

Content and background scripts

Loading the extension into your browser

Feedly Unique and future improvements

Saturday, April 13, 2019

Society

Algorithms

Health

Hardware

Robots

Cars

Brains

Wednesday, April 10, 2019

Thursday, April 4, 2019

Society

Algorithms

Health

Hardware

Robots

Cars

Brains

Tuesday, April 2, 2019