Category Archives: Java/Java EE

GWT 2.2 Breaks Most Plug-ins

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Google Web Toolkit I often comment that the GWT API is extremely unstable, more so than most other open source projects, due to the vast number of changes in each release. When Google released GWT 2.2 a few weeks ago, the release notes implied this was a relatively minor release. After attempted to update a fairly large GWT project to 2.2, I discovered a major issue: all of the referenced GWT plugins broke and required a new version that was GWT 2.2-compatible.

The API Change – Small and Subtle

In GWT 2.2, Google changed the class library JClassType from an abstract class to an interface. On the surface, this may seem like a minor change that would not affect most developers. Java compiler experts may be aware, though, that changing the class type alters the byte code of classes that compile against this class. In other words, any JAR or library compiled prior to GWT 2.2 that references this class will be unable to be used in GWT 2.2.

The error often manifests during a GWT Production mode compilation as:

[ERROR]  Internal compiler error
java.lang.IncompatibleClassChangeError: Found interface com.google.gwt.core.ext.typeinfo.JClassType, but class was expected

The Fallout

Because of this API change, most GWT plug-in libraries must be recompiled to GWT 2.2, and the resulting JAR will not be compatible with versions of GWT older than 2.2. In my case, this affected all the plug-ins I was using.

On the plus side, many GWT plug-in developers have already noticed the issue and begun issuing new versions. For example, if you are using Ext GWT, Sencha just released a new version this morning that is compatible with GWT 2.2. Bst-player, a plug-in I have contributed to, has also been updated for GWT 2.2.

Unfortunately, Google Maps, one of the most commonly used plug-ins, has not yet been updated and is therefore not currently compatible with GWT 2.2, as described in this bug report (please “Star” this issue if you have a G-mail/Google account!). If you rely on Google Maps in your GWT application, I strongly recommend you hold off upgrading to GWT 2.2. If you refer to the ticket, a user has posted their own GWT 2.2-compiled JAR, but this is not an official release.

All or Nothing

The major problem with this update is that it forces developers to update GWT and all plug-ins at the same time. If you upgrade to GWT 2.2, you are required to update all of your plug-in libraries and if, as in the case of Google Maps, there is no such update available, then you cannot upgrade at this time. Alternatively, if you keep the older version of GWT, then you cannot upgrade any of your plug-ins since the new versions will not be compatible with versions of GWT older than 2.2.

Conclusion

When I upgraded from GWT 1 to 2.0, a much more significant process, most plug-ins still worked, albeit with some issues. The fact that the GWT 2.2 upgrade completely breaks existing plug-ins is a serious issue, one I hope Google does not repeat in the future. With any luck, this is not a sign of things to come, and Google will consider supporting existing software in the future.

I'm Speaking at TheServerSide Java Symposium Reminder: Jeanne and I are both presenting at TheServerSide Java Symposium next week. My lecture is entitled “GWT Roundup: An Overview of Google’s Web Toolkit and Hybrid Integration” and Jeanne’s presentation is called “Throw Away All The Rules. Now What Process Do You Follow?.” The conference is being held in Las Vegas and it’s not too late to register to attend.

a sql quiz + is a lower hourly rate cheaper?

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Suppose you have a task to write some JDBC code and you need to do so in the cheapest way possible.  Having your people grow should not be considered here, just the rate.

Person A

Charges 3X per hour and can write working code on the first shot, test it and complete it within an hour

Person B

Charges X per hour, but needs to multiple cycles to fix once the code is typed.  (This includes the time to identify what the problem is for each, build cycles and fix time.) For the SQL quiz , see how many errors you can find in the following code. I’ll post the answers as a comment. See if you can spot any I didn’t insert on purpose.

PreparedStatement stmt = null;
ResultSet rs = null;
try {
  String sql = "select count(*) from table" + "where column = ?";
  stmt = conn.prepareStatement(sql);
  stmt.setString(1, "test");
  rs = stmt.executeQuery();
  System.out.println(rs.getInt(1));
  sql = "select count(*) from table2" + "where column = ?";
  stmt = conn.prepareStatement(sql2);
  stmt.setString(1, "test");
  rs = stmt.executeQuery();
  System.out.println(rs.getInt(1));
} finally {
  stmt.close();
  rs.close();
}

Which is better

In today’s economy, driving down costs is a hot topic.  One phrase service providers consider is “how can we lower the rate.”  This is the wrong question.  The question should be how to lower costs overall.  Person A is going to be cheaper overall even though the hourly rate is three times as high.  We’ve all heard the comment that a good developer is many times more productive than an average one.

Granted, my example is extreme.  It shows the difference between an experienced person and an someone new to JDBC.  The point is to use the extreme to emphasize that it’s not all about the hourly rate.  In the real world, training the entry level person has value too of course.

Another view

This reminds me of the methodologies that ask you to estimate how many hours/days/weeks a task will take without saying who will do the work.  Well, if I do it, the work will take a week.  If an entry level person is doing it, it may take four.  If someone experienced is doing it who doesn’t know the system, it may take two.  How do we balance the differences in people when estimating?

TSS Symposium Preview – GWT Roundup

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I'm Speaking at TheServerSide Java Symposium Google Web Toolkit As previously mentioned, Jeanne and I will both be presenting talks at TheServerSide Java Symposium exactly one month from now. Here is a preview of two of the topics I will be discussing at my talk “GWT Roundup: An Overview of Google’s Web Toolkit and Hybrid Integration” : GWT Image Bundles and Speed Tracer.

1. GWT Image Bundles

One of the more interesting features that GWT offers, beyond what most developers using indirect Ajax frameworks could build on their own, is the concept of Image Bundles. Even GWT developers who use Image Bundles may not have any notion of what is going on under the covers because the implementation details are so well abstracted. The idea is to take a large group of images and combine them into a single image with an interface for accessing each image. This may sound like a strange notion, but the performance advantages of doing so are manyfold:

  • More responsive UI since all images are downloaded together
  • Faster than downloading them individually since they are not downloaded in serial (HTTP 1.1 limits number of outgoing connections to 2 per domain)
  • Bundles use less bandwidth than separate images since multiple image headers are reduced to a single header

2. Speed Tracer

New to GWT 2.0 is the ability to validate such non-functional requirements as user interface performance, using the Speed Tracer tool, a Google Chrome extension. For example, if a particular asynchronous RPC call is causing delays in the user experience, Speed Tracer will help you identify it. Speed Tracer provides two graphs that show user response information and offers “hints” of spikes in response time that could be causing problems in your application.

  • Sluggishness Graph: Shows UI responsiveness
    GWT Speed Tracer - Sluggishness Graph
  • Network Graph: Network activity and latency
    GWT Speed Tracer - Network Graph

See you in Las Vegas!

I hope you enjoyed this preview of the talk I will giving next month. I will also be taking part in a panel hosted by Cameron McKenzie called “Client Side Development Smackdown” . Oh, and it’s not too late to register for TheServerSide Java Symposium 2011. We hope to see you there!