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EasyMock

EasyMock is an open source library for creating, and defining the behavior of, mock objects as part of your unit tests. This article describes how to use EasyMock (v3.0), including its record/playback approach, after setting the context with an brief introduction to unit testing in general and the associated need for mock objects.
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Hamcrest Matcher

As a follow up to the Hamcrest post I made yesterday, I wanted to post an example of my own Hamcrest matcher implementation. This matcher tests if a string contains a specified number of substrings.
An example usage could be:


    String sql = "select a,b,c from tableA";
    assertThat(sql, hasNumberOfSubstrings(",", 2));

See the source code below. I have been reading up on OSS licenses recently and decided to release this using the same license as Hamcrest – the new BSD license.

I have also attached a jar which includes the associated unit tests, although you will need the hamcrest-unit-test project to compile, which can be downloaded as part of the hamcrest all-in-one jar.
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Hamcrest

Hamcrest is a framework for writing matcher objects. Matchers have a variety of uses, but are particularly useful when writing unit tests. Instead of using JUnit’s assertEquals methods, we use Hamcrest’s assertThat construct with one (or more) of the many Matchers available. For example

    assertTrue(a.equalTo(b));

becomes

    assertThat(a, equalTo(b));

A small change in this example, but Hamcrest’s benefits are many, enabling you to write much more flexible tests that are easier to read and have more meaningful failure messages.
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OSCON Day4: WebSockets

The first talk of the day I attended at Day 4 of OSCON was from Sean Sullivan (Aravo), who gave a talk on “Programming WebSockets“.

Intro

WebSockets is a technology that enables bidirectional communication between web browsers and server side processes. It provides a persistent connection between client & Server, hence enabling ‘push’ abilities where you can push data/notification to browsers from the client. Other client communication options to compare it with would be Ajax
and Comet (basically Ajax with long polling).

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Open Source Convention in Portland, Oregon

I will be attending the week long Open Source Convention (OSCON) next week in Portland, Oregon. Looking forward to it as there is a huge variety of talks, including databases, Android, Scala, Spring, HTML5 and a bunch of Google technologies. Get in touch with me at Shaun at Abram dot com if you happen to be going along…

Selenium talk at SF JUG

I attended another great San Francisco JUG meeting tonight, this time on How to use Selenium with Maven/Ant to automate testing of web apps.

The talk was given by Chris Bedford, from Build Lackey Labs – “Automating the Monkey Work Out and the Quality In!”. Overall, I thought this was a great talk by Chris. He clearly has a huge amount of experience creating automated tests and integrating them with build tools and he gave a well structured, interesting, well delivered presentation. I have posted a copy of Chris’s slides and I think the video will be posted on the SF JUG site at some point, but I have also posted my notes from the presentation below…
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Data binding in Spring MVC

Two of the most important tasks carried out by Spring MVC when you submit a form are Data binding and validation.
The following article discusses data binding, including the use of custom PropertyEditors, and some of the options available for registering such editors. Most of the information discussed applies to Spring in general, but its application in Spring MVC is my primary interest.

In a future article I would like to discuss validation including the use of custom error messages.

Note that these notes relate to version 2.5.6 of Spring, the latest production code at time of writing, and depend heavily on the corresponding Spring reference docs.

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GTUG Campout Demos

Last night saw the end of the Google Technology Campout weekend, with about 25 or 30 groups giving demos of a lot of cool Wave apps. I particularly liked the robot/gadget that analyzed when it was time for a group of wave participants to leave the wave and meet in real life, supplying a list of possible venues to meet based on the participants’ physical location. A vocabulary analyzer from a group of brothers also looked pretty good. I also liked the h3lp application, kind of like an Onstar four your mobile phone, which pushed out alerts to selected contacts in case of an emergency. In the end, the winner was the video sharing team.

The demo for our BlipWiki project (which I blogged about here) unfortunately had technical difficulties so our presentation didn’t go so well. One of our 2 browsers couldn’t seem to connect so we didn’t get to show our Wiki updating in real time in the way we would have liked. Still, I think we had a great application at the end of the weekend, and I certainly learned a lot, met a lot of great people, and got to know Google Wave much better. A great weekend…

There are photos and videos from the weekend posted here and a write up in the San Jose Mercury News.

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GTUG Campout Follow up

I’m currently at the Google Technology User Group Camp out weekend down at Google’s offices in Mountain View. The objective of the weekend is to form a team and develop an application, using Google technologies. The demos are Sunday afternoon.

I joined the Blip Wiki team. A Blip is simply a single message within a ‘Wave’ conversation. A Wiki, of course, is a software tool that allows users to easily create, link and collaborate on documents. So, our goal with the ‘Blip Wiki’ project was to bring the incredible collaboration capabilities of Google Wave (real time updates, autocorrect context sensitive spelling etc) to the easy document setup and linkability of a Wiki.
Although Wave can certainly be used to collaboratively create documents as it is, Wave is inherently conversation focused. We wanted Blip Wiki to be inherently Document focused.

To do this however, we needed to use our own instance of a Wave server i.e. use the Google Wave Federation Prototype Server rather than the regular Wave server hosted by Google. We also needed to come up with a new client (something like tiddlywiki) and, most importantly, ensure our client can communicate with the server. Our project won the award for the most ambitious pitch at the start of the weekend!

Federation Prototype Server and example client

We got off to a good start by getting the Wave Prototype Server downloaded, building and running (it runs on top of OpenFire, a real time collaboration server that uses XMPP/Jabber). We then got the demo wave client running and talking to our server. We managed this by late Friday evening.

Client/Server protocol

Next, we created our own demo client and tried to get it interacting with our Wave server. That is when we started running into problems. First, the client/server protocol has not yet been formalized, and there don’t seem to be any definite plans to do that yet either. For example, although this Client Server Protocol White paper describes a protocol and data model, it does not give any details on the format that should be used, or suggestions on how to use it. There is a lengthy discussion in the Wave Protocol Google Group about this. For example, someone suggests that the client server protocol is just protocol buffers ‘over the wire’. But a protobuf is really just a simple data format, and while I assume ‘over the wire’ means RPC, it is all a bit vague.

Submitting changes

The client/server protocol used in the example client (a “toy’ text client) is for “illustrative purposes only”, according to this doc. We couldn’t seem to find much documentation for it, perhaps because it is not supposed to serve as a standardized example. As a result, we found it difficult to reverse engineer. So, we ended up resorting to using the Client example code to marshal our data to and from the server. The example client code in effect became a sort of interface to the server for us. A client side stub, if you will. (We had this running in the web tier servlet layer).

Receiving updates

So, after we had used the Client example code to submit changes (blip updates) to the server, our next hurdle was understanding the data that gets returned. Ideally, we would like a ‘delta’ of the data. That is, after the server has done it Operational Transformation magic, we would just like the latest and greatest version of the data to display on the client. However, this proved difficult to get from the server. Instead all I could seem to get was a non-delimited complete history of the blip. I admit that this was done using pretty hacky code. I am sure there must be another, better way!

So, we ended up taking a similar approach to the example client, and just displaying the latest submissions.

Demo ready – almost…

Right now, we have a working client and server with updates made on one user’s WikiBlip automatically showing up in another users.

It would have been really nice to be able to deploy our local Wave Server to app engine, but apparently this isn’t possible since the OpenFire jars required aren’t on the whitelist of allowed jars.
It also would have been nice to experiment with our local Wave server talking to the real Google Wave server (e.g. to have a regular wave client user be able to interact with a blip wiki), but apparently this is not possible due to authentication issues.

So, we chose a very difficult task for the weekend! But, we have a working version ready to demo and it has been a great weekend all in all.

Thank you’s

A big thank you to

  • Sriram and Sreejith, my BlipWiki teammates
  • Kevin and Van from the GTUG
  • Stephanie, Brian, Fred and all the all Googlers who made the weekend possible and great!

I will post again later with the results of the demo…

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Google Technology User Group Campout

I have signed up for the Google Technology User Group (GTUG) Campout. It is a weekend (August 7-9, 2009) of designing and coding an application, as part of a team, using Google technologies. As far as I know, Google ‘technologies’ can include things like GWT, Android, OpenSocial etc, but there will be a particular emphasis on Google Wave (due to members of the Wave team being out and about to help), and hence Google App Engine.

I am not too familiar with Wave yet, so this should be a great opportunity to get to know it better, meet a bunch of fellow techs, and hopefully produce something cool by the end of the weekend. Looking forward to it…

Registration is free, so if you are interested you can sign up at here.

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SF JUG: Android UIs

There was another great San Francisco JUG meeting tonight down at the Google offices. It was all very well organized as usual by Sasa. The speaker was Romain Guy from Google’s Android UI team. He gave his talk from Google IO: Turbo-charge your UI: How to Make your Android UI Fast and Efficient.

The presentation slides can be found here.

I thought Romain was an excellent presenter and did a top job of talking on his area of expertise: Android UI development. He covered the issues you need to be aware of when developing Android UIs if you want them to be performant, best practices and work-arounds for the gotchas, as well as useful tools that can be used for development. Personally, I would have benefited from more of a broad overview and introduction to Android, but that is more a reflection of my own lack of knowledge on Android! Maybe the newly created Android User Group will provide an ‘Intro To’ type talk at some point…

First, Romain covered the Andriod UI terminology (like Canvas, Drawable, Surfaces and Views) before covering the architecture.

The bulk of his talk covered how to make sure you UI runs fast, including:

  • Avoiding runtime scaling of background images
  • Avoiding invalidating (i.e. redrawing) the entire screen and instead only invalidate the small part of the screen that has actually changed.
  • Minimizing the number of views you use (ideally have <100, which seems pretty reasonable for a tiny phone screen!) and talked about some techniques to help with this including using ViewStubs and recycling views
  • Avoid allocating memory (apparently the Garbage Collector is slow and pretty much stops the world when it is running)
  • Use SoftReferences (objects that only have soft references to them will be kicked out of memory if the Garbage Collector needs more memory) and WeakReferences (which can help to avoid memory leaks) when possible

He also talked about some neat dev and debug tools including Allocation Tracker (which monitors objects being created, memory being allocated etc) and Hierarchy Viewer (which shows you all the devices/windows/views you have how long things are taking to render).
He also mentioned the Android emulator that can be used for testing your apps.

Some of the questions from the Q&A session included:

Q: Will Android support languages other than Java?
A: Romain mentioned that there is a version of Scala and python that work on Android, but currently all APIs are in Java.

Q: Does Flash work on Android?
A: Development is on-going and the Android team is working with Adobe.
(I found more on the web about this topic here: http://gizmodo.com/5300800/flash-for-android-webos-landing-in-october)

Q: Can JavaFX be used on Android?
A: Code might be hard to run on the phone and may not be performant.

Q: Apparently, Sony Ericsson are also building an Android phone. How do you plan to avoid fragmentation as other companies start shipping Android phones?
A: CTS – Compatibility Test Suite
You cant ship a phone as ‘Android’ if it doesn’t pass the CTS.

Other links:
http://d.andriod.com
source.android.com
android.git.kernel.org
code.google.com/p/apps-for-andriod
http://android-developers.blogspot.com/
http://forum.xda-developers.com/

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Spring and EJB 3 Integration

I attended another excellent SF JUG meeting earlier this month. It was a double billing with Talip Ozturk talking about Hazelcast, an opensource clustering and data distribution platform, and Reza Rehman speaking about EJB3 and Spring Integration.

Reza is the author of EJB3 in Action and an accomplished speaker whom I had the chance to meet at The Server Side Symposium earlier this year, so I was particularly interested in his talk.

Reza gave some background on EJBs and how they have been completely reinvented as part of the latest (EJB3) release, including using 100% annotations (no xml) and making heavy use intelligent defaulting. He also talked about how Spring became popular as an alternative to the heavyweigth approach of the older EJB releases and has thrived through its focus on integration with standards like JPA, JMS, JDBC and JAX-WS.

He then went on to his main point, which was that EJB3 and Spring can now be viewed as complimentary, rather than competing, technologies and he went on to back this up by discussing the integration strategies that can be used, including

  • Embedding Spring inside a Java EE app server
  • Embedding an EJB3 embeddable container withing Tomcat with Spring
  • Enabling Spring @Autowired annotation in EJBs via Interceptors
  • Using EJB3 natively inside Spring using Spring Pitchfork

Reza finished by reiterating the benefits of using Spring and EJBs together to increase ease of coding and vendor neutrality.

Overall, I thought it was an insightful presentation from Reza. I had studied EJBs back in the v2 release as part of the my SCEA certification, and have used Spring in several projects, but this was the first time I had a chance to hear how they can be used together.

I have made Reza’s presentation notes available here, as well as his demo source code available here. You can also follow him on his web site and blog at: www.rahmannet.net.

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TheServerSide Java Symposium – Day 2

Day 2 at TSS Java Symposium.

The highlights of the second day at TSSJS2009 were a couple of interesting talks from Rod Johnson (Mr Spring) and a talk on Groovy from Scott Davis (Groovy.com).

I have included links to some of my (limited) notes below, which includes links to the actual presentation slides (PDFs) where available.

Keynote: How Spring Fits into the Java Landscape – Rod Johnson

Spring for the advanced developer – Rod Johnson

The Amazing Grrovy Weight Loss Plan – Scott Davis

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TheServerSide Java Symposium – Day 1

Today I’m at the first day of the TheServerSide Java Symposium in Las Vegas. There are about 400 attendees and a dozen or so companies exhibiting. I will try to post some notes about the talks as the day goes on…

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JavaFX Plugin for Eclipse – too buggy?

After attending a meetup on JavaFX last month, I have been trying to get more familiar with the technology. I know that NetBeans is the ‘recommended‘ IDE for JavaFX, but I am an Eclipse devotee and thought that surely anything NetBeans can do Eclipse can do. Not in this case it seems.

Some simple JavaFX script just don’t seem to work with the Eclipse plugin. For example, the following snippet:

Stage {
    title: "Nodes"
    scene: Scene {
        fill: Color.LIGHTBLUE
        width: 220
        height: 170
    }
}

Causes the following error:

incompatible types found: integer required: com.sun.javafx.runtime.location.FloatVariable

The same snippet compiled and ran straight off when I tried it before in NetBeans.

The only posting on it I could find is here. I took the advice and downgraded to JavaFX 1.0, which seems to have done the trick for now. If anyone out there has any suggestions on better solutions/fixes, I would love to hear them.

This isn’t the first time I’ve spotted some better GUI related functionality in NetBeans than in Eclipse (e.g. I briefly mentioned the NetBeans GUI Builder tool a while ago). There is no chance of me stopping using Eclipse completely, but maybe I will start using both…

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