Tuesday, 16 July 2013

Running our JavaEE course on Glassfish 4

We've had a few requests asking if our JavaEE course can be run on Glassfish 4 (at the time of writing, the latest version).

The quick answer is: yes, but be careful. You will be able to run all the way up to chapter 16 before you see any problems, and they are very minor. However, Glassfish 4 is not as good as version 3 at reporting errors, and you don't gain any features that you will need to follow the course.

As the important thing is learning the fundamentals of JavaEE (and these haven't changed in JavaEE 7), my advice is to install a Java 6 JDK, and then use the Glassfish 3.0 that we ship with the course. Glassfish 3.0 is more stable, and seems to run faster. You can always upgrade to a later version once you've finished the course and understand the concepts.

(Glassfish 3.0 uses JDK6, although I've blogged here about how you can use it with JDK7. You *can* use Glassfish 3.2 with JDK7, but there was a horrible bug in 3.2 that prevented redeployments - I blogged about that here).

However, some of you will want to use Glassfish 4 - perhaps you need an advanced feature, or your company/project are using. In that case, you can do the course just fine, but there are a few things to be aware of.

1: Spurious warnings and swallowed errors

You will notice as soon as you deploy an application that uses a database on the server (Chapter 10), you will get the following:
Command succeeded with Warning. Cannot create tables for application. The expected DDL file EmployeeManagement_employeeDb_createDDL.jdbc is not available. Cannot create tables for application EmployeeManagement. The expected DDL file EmployeeManagement_employeeDb_createDDL.jdbc is not available.
In fact, all this is saying is "we looked to see if you have a custom create tables script in a file, and you don't". But that's not a problem, because we are using automatic creation of tables, and that will happen in the background. So don't worry, it probably COULD create the tables.

So, it is a very annoying warning. But it gets worse. If you DO have an error in your application (for example, I forgot to annotate one of my injected EJBs), you will get exactly the same warning - but this time as an error. But it will give no further clue as to the real cause of the problem. For that, you need to check in the log (by default, this version logs directly to the console that you started the application server in). So don't forget that your real problem is probably unrelated to creating tables. Check the console log, although you will have a lot of useless information to wade through.

For this reason, I advise avoiding using this version for the training - but if you decide to go ahead, budget for some extra debugging time.

2: Glassfish Libraries

On the course, I advise you to add external references to a large collection of jar files. This was due to a bug in the Glassfish 3, you now just need to add an external reference to gf-client.jar in the early chapters (you'll need a few more later).
Note: gf-client.jar is now located in GLASSFISH_HOME/glassfish/lib
For the JSF chapters, you will need an external link to the GLASSFISH_HOME/glassfish/modules/javax.faces.jar

3: Differences in the UI

There are some minor changes to the UI. Thankfully the UI is hardly changed. But you may have to hunt around for a few menu items.

4: Chapter 16, SOAP Webservices

All chapters upto and including the SOAP webservice chapter should run as on the video. However, in Chapter 16 you must write a new class to represent your webservice. I blogged about this here - although you could get away with not doing so in earlier versions, you need to be careful to do this in Glassfish 4. It's better engineering anyway!

5: Chapter 18, REST Webservices

In the video, we ask you to configure a servlet in your application. This servlet is provided by Glassfish, and it does the work of providing the web service to clients. This isn't part of the JavaEE standard, and it is therefore subject to change. And it has. It was previously a Sun class, I guess for political reasons they've renamed it.

You will need to change your web.xml file. Substitute this for the corresponding XML that you add in this chapter:

     Jersey Web Application

     Jersey Web Application
Edit to add: our Blogging platform seems to add some odd characters in the extract above: if you see XML errors you can download my working web.xml from here.

6: Chapter 19, REST Client

In the training course, we use Jersey-Client version 1, this allows us to call REST based webservices from Java. Your Glassfish 4 is using Jersey version 2. You can continue to use exactly the same client, because the client doesn't know or care that you have upgraded your server. (All the client is doing is issuing HTTP requests - there's no problem with the version mismatch).

If you need to keep up to date on the client as well, you can download Jersey version 2 from here. If you do this, you will need the JAR files from their lib directory, plus all of the JARs in the ext directory.

Unfortunately, Jersey (client) version 2 uses a much altered API, and your client code will break. The changes aren't that radical, but there are too many to list here (for example: all of the packages are renamed, and instead of calling web.get(), you have to call web.request().get()).

You can download the modified REST client here, and a new version of the class we wrote to test delete requests from here - compare these with the ones we used on the course.

However, to reiterate, you don't have to use Jersey version 2 for the client. Version 1 will interoperate perfectly well with your new server.
Edit to add: I accidentally deleted the Client Application from our server, many apologies if you've tried to download this without success. It's now been re-added.

7: Chapter 20, Security

These are the biggest changes because authentication isn't specified in the JavaEE standard. Here are the changes:

* EJB Client: You need to change your external library to point to GLASSFISH_HOME/glassfish/modules/security-ee.jar (and change the reference to this file in your build.xml script). You will now import com.sun.enterprise.security.ee.auth.login.ProgrammaticLogin instead.

  When you add the user and password to the file security realm, be sure to use the "Server Config". This didn't exist on Glassfish 3.

  When you now call pl.login(username, password), you will find this method is now deprecated. You can still call it, but to avoid the deprecation warning, you can call pl.login(username, password.toCharArray());

* REST Client: You will now need to call:
Client client = ClientBuilder.newClient();
client.register(new HttpBasicAuthFilter("rac", "secret"));

Anything else?

A long post, but actually very few real changes. That's as it should be - JavaEE usually introduces new features and avoids breaking changes. If I have missed anything, do contact me and I'll update this blog post as and when things change!