Thursday, 30 March 2017

Setting session timeout in Glassfish

People complained that their sessions timed-out too quickly in Glassfish.

I checked and it is set to 30 minutes (default 1800 seconds), just a tad too little.

Increased it to 2 hours (7200 seconds).

Just went to Configurations - Web Container - Session Properties - Session Timeout.

It changes the domain.xml:

<session-properties timeout-in-seconds="7200"></session-properties>

Problem

Of course, this completely and utterly failed to work in my case.

It turns out I already had a session timeout specified in the web.xml.

<session-config>
  <session-timeout>
    30
  </session-timeout>
</session-config>

The session timeout in the web.xml is specified in minutes.

You can also specify it in the glassfish-web.xml file.¹

<session-config>
    <session-properties>
        <property name="timeoutSeconds" value="600"/>
        <property name="enableCookies" value="false"/>
    </session-properties>
</session-config>

Precedence

You do need to check which setting takes precedence in your application. It's not clear from the documentation.

References

[1] Glassfish 4.0 Application Deployment Guide: https://glassfish.java.net/docs/4.0/application-deployment-guide.pdf
iT Geek Help - Glassfish web container tuning settings: http://itgeekhelp.blogspot.nl/2009/03/glassfish-web-container-tuning-settings.html
StackOverflow - How to set session timeout in glassfish-web.xml configuration file?: http://stackoverflow.com/questions/33067985/how-to-set-session-timeout-in-glassfish-web-app-glassfish-web-xml-configurat

Thursday, 23 March 2017

AssertJ vs. Hamcrest

I recently came across a piece of code that used a Stack¹. The Stack seems to inherit from Vector. The JavaDoc indicated (and so did my IDE, I think) that I should be using the Deque² interface instead. To be precise:

“A more complete and consistent set of LIFO stack operations is provided by the Deque interface and its implementations, which should be used in preference to this class.”

Dequeue basically seems to be a specialized Queue³, that supports element insertion and removal at both ends⁴.

In order to get to grips with Deque, I decided to write some simple tests. These are JUnit Tests (version 4.12) and in one I used Hamcrest⁵ and in the other I went for AssertJ⁶.

Let's see what happens.

A simple compare

Hamcrest:

assertThat(actual, equalTo(testdata2));

AssertJ:

assertThat(actual).isEqualTo(testdata2);

Collections

Hamcrest:

assertThat(transmittedTestdata, hasSize(2));

AssertJ:

assertThat(transmittedTestdata).size().isEqualTo(2);

Null Values

Hamcrest:

assertThat(actual, not(nullValue()));

AssertJ:

assertThat(actual).isNotNull();

Exceptions

Hamcrest:

@Test(expected = NoSuchElementException.class)
public void testEmptyDequeueException()
{
Deque<Testdata> transmittedTestdata = new ConcurrentLinkedDeque<>();
Testdata pop = transmittedTestdata.pop();
}

AssertJ:

assertThatThrownBy(transmittedTestdata::pop).isInstanceOf(NoSuchElementException.class);

Imports

A comparison between the required imports of Hamcrest and Assertj is interesting:
Hamcrest:

import java.util.Deque;
import java.util.NoSuchElementException;
import java.util.concurrent.ConcurrentLinkedDeque;
import static org.hamcrest.CoreMatchers.equalTo;
import static org.hamcrest.CoreMatchers.not;
import static org.hamcrest.CoreMatchers.nullValue;
import static org.hamcrest.MatcherAssert.assertThat;
import static org.hamcrest.Matchers.empty;
import static org.hamcrest.Matchers.hasSize;
import org.junit.After;
import org.junit.AfterClass;
import org.junit.Before;
import org.junit.BeforeClass;
import org.junit.Test;

AssertJ:

import java.util.Deque;
import java.util.NoSuchElementException;
import java.util.concurrent.ConcurrentLinkedDeque;
import static org.assertj.core.api.Assertions.assertThat;
import static org.assertj.core.api.Assertions.assertThatThrownBy;
import org.junit.After;
import org.junit.AfterClass;
import org.junit.Before;
import org.junit.BeforeClass;
import org.junit.Test;

Notes

I really like the AssertJ fluent API. It feels more natural to me than the Hamcrest one.
It is way easier to find the appropriate matchers in AssertJ. I get the full benefit of my IDE code completion.
Adding the appropriate import is way easier. Using Hamcrest, I always get a choice of five different imports for the same matcher.
I need fewer imports anyways.

So far, I like AssertJ a lot.

I need to work with AssertJ a lot more, to see some of the interesting stuff.

References

[1] Java 7 JavaDoc - Stack: https://docs.oracle.com/javase/7/docs/api/java/util/Stack.html
[2] Java 7 JavaDoc - Deque: https://docs.oracle.com/javase/7/docs/api/java/util/Deque.html
[3] Java 7 JavaDoc - Queue: https://docs.oracle.com/javase/7/docs/api/java/util/Queue.html
[4] Wikipedia - Double-ended queue: https://en.wikipedia.org/wiki/Double-ended_queue
[5] Hamcrest - Matchers that can be combined to create flexible expressions of intent: http://hamcrest.org/
[6] AssertJ - Quick start: http://joel-costigliola.github.io/assertj/assertj-core-quick-start.html

Thursday, 16 March 2017

reveal.js

Our architect recently put together a presentation regarding our new framework using reveal.js¹.

I had never heard of reveal.js and I was intrigued. It seems to be a presentation framework that runs in your webbrowser, using npm² and grunt³ and javascript and MarkDown⁴ and all that.

I figured I'd give it a try for my next presentation.

I downloaded a release⁶ and used the very clear instructions on how it works on GitHub⁵.

Installing a new release, seems to be nothing more than:

- download
- unzip
- edit index.html
- browse to index.html

Luckily, I had the changes our architect made to bring it into line with the company layout guidelines. It was nothing more than a different css file that is based on the "white"-theme (which is also a css file). The default theme when you get a release is the "black"-theme, similar to the one visible at [1].

You can decide to just browse to the file index.html locally to display the presentation, but if you do a "grunt serve" a small webserver is started that serves the webpage and related resources. The latter option provides more functionality.

MarkDown

As you can see above, you can specify how the sheets are divided. What exactly the sequence is for detecting a division.

Initializing the presentation is done using:

// More info https://github.com/hakimel/reveal.js#configuration
Reveal.initialize({
      width : 1280,
      height : 1024,
      slideNumber: 'c/t',
      showNotes: true,
      history: true,
// More info https://github.com/hakimel/reveal.js#dependencies
      dependencies: [
          { src: 'plugin/markdown/marked.js' },
          { src: 'plugin/markdown/markdown.js' },
          { src: 'plugin/notes/notes.js', async: true },
          { src: 'plugin/zoom-js/zoom.js', async: true } }
          ]
});

I set the "snowNotes" to true, because I wished to print out the sheets including the notes. See Printing below.

CSS

It is easy to add custom CSS to individual slides. For example:

A common one used to change the font of the previous element (useful for source code):

Printing

Printing your sheets seems to be as simple as surfing to the url:

http://localhost:8080/?print-pdf#/

It generated in Chrome browser a PDF file that you can simply print to file in the browser.

Conclusions

It is very nice, if you are a programmer or web guy and you do not wish to fire up Microsoft Powerpoint.

An advantage is of course that MarkDown files can easily be added to your version control system.

Another advantage is that you can refer to images on the Internet/Intranet. I managed to do just that, by referring to images already on our Intranet Confluence pages. At least the images will always be up to date.

(p.s. It also means that in order to view my presentation properly, one has to be logged into Confluence. I found that out rather quickly, when trying my presentation out in one of our conference rooms.)

I don't really like the markdown setting displayed above, as it is too easy to add one line or remove one line to many.

I also had a problem where I must have made a grammatical mistake, and in my FireFox browser the presentation managed to hang and after several seconds I'd get a "Script is running too long. Do something about it?" message.

There are several keyboard shortcuts for navigation through the sheets during the presentation, which is nice, as the mouse isn't all that handy.

I don't much like the "sheet notes", which are displayed in a separate browser window. I usually have them turned off.

References

[1] Reveal.ks - the HTML Presentation Framework: http://lab.hakim.se/reveal-js/
[2] NPM: https://www.npmjs.com/
[3] Grunt: https://gruntjs.com/
[4] Wikipedia - MarkDown: https://en.wikipedia.org/wiki/Markdown
[5] GitHub - reveal.js: https://github.com/hakimel/reveal.js
[6] reveal.js releases: https://github.com/hakimel/reveal.js/releases
GitHub- Basic Writing and Formatting Syntax: https://help.github.com/articles/basic-writing-and-formatting-syntax/

Thursday, 9 March 2017

Git Stash

This little blog post is just for me to remember my favorite "git stash" commands. It took me a little while to actually use the stash, but that is because IntelliJ provides a similar functionality called "shelving", which I had used all this time.

I use branches a lot when using Git, and the problem there is that Git usually complains if I wish to change branches, while I still have uncommitted changes in my current branch. Therefore the "stash" command is for me very valuable.

Stash your current uncommitted changes:

$ git stash

Get your uncommitted changes back from the stash:

$ git stash apply

Get a list of your current stashes:

$ git stash list
stash@{0}: WIP on master: 049d078 added the index file
stash@{1}: WIP on master: c264051 Revert "added file_size"
stash@{2}: WIP on master: 21d80a5 added number to log

Remove a no longer needed stash:

$ git stash drop stash@{0}
Dropped stash@{0} (364e91f3f268f0900bc3ee613f9f733e82aaed43)

One command I particularly like is this one that does both an apply of your stash and once done automatically removes it from the list of stashes:

git stash pop

The stash has a lot of similarities to your standard Stack implementation (or Dequeue, depending on your point of view.)

I notice that if I do not clean up the place or use the "pop" subcommand, that my list of stashes tends to grow quite long unobtrusively.

View a stash without applying:

git stash show

Actually showing the contents of the stash in diff format is:

git stash show -p

The commands above work on the latest stash in your list.

References

6.3 Git Tools - Stashing: https://git-scm.com/book/en/v1/Git-Tools-Stashing
Atlassian Tutorials - Git Stash: https://www.atlassian.com/git/tutorials/git-stash
Ariejan De Vroom - GIT: Using the stash: https://ariejan.net/2008/04/23/git-using-the-stash/
Git Stash - Man Page: https://git-scm.com/docs/git-stash

Update: added the showing of stashes without applying.

Thursday, 2 March 2017

Maven and the Dangers of Snapshots

Recently we've been causing problems in the regular builds of branches of our software.

Basically the problem is our own fault and is related to Maven Snapshots.

According to the guide¹, a Snapshot is a library that is still under development, and may change rapidly as new versions of the Snapshot are pushed to the Nexus regularly.

If a dependency on a Snapshot is defined in your pom.xml, then Maven, as it should, always picks the latest Snapshot.

This is fine and dandy if you are currently developing your software, and you want the newest of the new of the libraries that your other software teams are developing.

The Problem

It means that once you create a stable release of your software (and the appropriate Git branch for it to live in as well, of course) it is important to replace the Snapshot in the pom.xml with the appropriate released version.

We neglected to do just that.

The Consequence

Our branch containing the release version of our software suddenly bombed with compile errors in the Deployment Pipeline.

This caused the maintenance people a headache, as the Git revision of the branch had not changed, between the previous build (which compiled just fine) and the new build (which bombed).

Despite the build being pulled from Git with the exact same revision, it was technically different from the previous build.

All because we kept developing the Snapshot and pushing it into the Nexus.

What we should have done

create a proper release of the library
change the pom.xml in the branch to refer to this release.
create a new snapshot of the library
use the new snapshot in the pom.xml of the master branch (which is used for development)

Now the build of both the branch as well as the master should compile again.

References

[1] Apache Maven - Getting Started: https://maven.apache.org/guides/getting-started/
Continuous Releasing of Maven Artifacts: https://dzone.com/articles/continuous-releasing-maven

Update: reference added.