Roadmap for Groovy Eclipse work

Hello everyone. I know Ed Povazan has not been active, so I will try and step in to fill the void. There has been activity on the Groovy Eclipse development mailing list requesting a roadmap for the future of plugin work. I know that I have been on a soapbox for a while now about how we need full time and paid work to support the plugin, but I think I should take a stab at what I think that the near future of the plugin should be. I think that the current trunk (or what is out on the dev update site) is a viable candidate for a release. I know I have been telling people over the last couple of months to use the updateDev site and not the main release update site. This is not an acceptable circumstance, the dev site is for internal or beta testing only, but the current release version of the plugin leaves me with no option. I know that there may be some refactoring coolness out there and I do not want to discourage progress in any way, but the current version of the plugin on the release site is quite frankly an embarrassment.

So given this state, I propose that we cut a release that includes Groovy 1.5.6 oand represents what is out there on the update development site, so that we can in good conscience tell people to point at the release update site. After the release of Groovy 1.5.7 so that we can accommodate the refactoring, we can include the new stuff and then release it to the development update site for evaluation. This is based on what I understood from the earlier emails that the refactoring work requires Groovy 1.5.7. After a time, a couple of weeks say, if it proves itself stable and ready, then lets push out a version to the main release site. This is relatively standard practice and I see no reason to circumvent it.

This does bring up an interesting point, a couple of years ago it was possible to get new versions of the plugin out quickly because there was a reliable set of beta testers that could give us feedback quickly. Scott Hickey's (the previous Groovy Eclipse lead) team working on a project would download the plugin and put it through its trials and we could find out trouble quickly. It would be interesting to discover if there is anyone out there who could fill this function. As an Eclipse developer, it is amazing how new eyes can find configuration, provisioning, installation and general plugin bugs when you thought everything was fine. This sort of feedback and work is vital.

If we can get regular activity restarted on the plugin (ahem... listening G2One?), I think that releases should occur at regular intervals of between 4 to 6 weeks, in line with common Agile iteration or spring intervals.

If no one has an issue with this, I will go ahead and build a new release and promote it to the main release update site.

As far as a roadmap goes, I had a brief chat with Scott Hickey (the old Groovy Eclipse plugin lead) and I think we came to a simple understanding.

* First, there is some major work that needs to be done under the hood to not have the plugin use the version of the groovy runtime installed in the workbench, but rather use the one that is set for the workspace.

* Second, there needs to be a structure like IJavaElement, or the equivalent, to allow the Groovy Eclipse plugin to support different versions of the Groovy libraries for different projects. The second issue is related to the first issue to some degree.

* Third, there needs to be better integration of the groovy compiler with Eclipse JDT support. I saw an example in the Scala Eclipse plugin where the project has the Eclipse Java nature added to the project, but the Java Builder was not added. This allows the Scala plugin to provide the scala tools to build the class files. I think that something like this should be done for Groovy Eclipse, especially since the groovy compiler will now compile java as well. This will also prevent collisions between the Java builder and the groovy builder.

* Fourth, we need to be chasing the standard that the good folks at IntelliJ have been blazing. The Groovy Eclipse plugin should try and provide most, if not all, the kind of support that IntelliJ is giving to Groovy now. I think what it does for dynamic methods is awesome.

* Fifth, refactoring tools need to be provided that are robust and first class. Hey great job y'all on this one, this kind of work aint easy. I am still intrigued by this notion, because I would love to see good dynamic language refactoring that is more than just grep and replace.

* Sixth, provide at least a basic level of support for Grails development. I know that there has been some work on providing Grails support, but I know it could only be of the very basic sort and there is so much in Grails that screams for IDE support. I mean how cool could it be to get help with writing those GORM domain classes for instance?

* Seventh, enable Eclipse Plugin Development using the Groovy language. This is really more of a personal desire, I think that Grails support or any of the other points I have listed would affect far more people. Still it would be nice to be able to do more and more Groovy Eclipse work in Groovy, right? I think so. As part of this effort we could try to leverage and improve Groovy support for EMF. Heck maybe we could make EMF usable! (*duck*)

* Eighth, as I stated above, if regular work can be restarted on the plugin, there should be regular releases on the order of 4 to 6 weeks apart.

* Ninth, after getting the plugin in a better state, we need to get companies like Genuitech, eBay and other eclipse distribution providers to start including the plugin, if not included by default, at least as an option. I will make a point to get it in to Genuitech's Pulse service.

Most of the points I came up with really were off the cuff, so if you can think of others, please don't keep it to yourself!

Don't call it a static or dynamic language!

I was talking the other day with someone recruiting me for a position. Smart organizations will contact you with someone who can try and sift the wheat from the chaff. In other words, they'll ask you questions in particular computer science or even, *gasp*, Java questions. Well this one guy asked me a standard question, 'what are the advantages and disadvantages of statically typed versus dynamically typed languages?' Now the full debate on that question could not only fill a whole series of blog entries, but could be a book by itself, which I will not get into here. Still as I was giving my answer I prefaced my comments by saying something that I have put a fair bit of thought into, which was: 'I don't like the name static or dynamic typing, I prefer the notion of implicitly typed and explicitly typed languages.'

Definitions
First off let me start with the definitions of explicit and implicit, both of these are horked from Merriam Webster Online. Implicit is defined as "capable of being understood from something else though unexpressed : implied or involved in the nature or essence of something though not revealed, expressed, or developed." Explicit would be defined as "fully revealed or expressed without vagueness, implication, or ambiguity : leaving no question as to meaning or intent" or as "fully developed or formulated ." I think a good way to think about this is to consider the following question, "are details hidden from you or not?"

WTF (What The Friendly) does this have to do with Programming Languages?
I think if you consider it for a while, the language debate between statically and dynamically typed is clearer when it is considered in terms of whether it emphasizes implicitness or explicitness. First off, all languages and programming platforms are implicit to some degree, since there is no way to encapsulate all of the factors that go into programming a software system to a developer. If they did, the resulting interface to the developer would probably be enough to make an airline pilot's jaw drop. Still the point applies if you focus on types. Most of the debate about programming languages focuses on the issues of types, so it is a good area to concern ourselves with. By my reckoning, a strongly/statically typed language, like Java for instance, would be considered 'explicitly typed' in this nomenclature. A dynamically/weakly typed language, like Python or Ruby for instance, would be called an 'implicitly typed' language from now on. An optionally typed language like Groovy would be optionally explicit or optionally implicit, depending on the developers mood that day. ;)

Actually in my opinion, most of the interest in Groovy is due to its 'implicit' capabilities and therefore I would really put in that category. I know you can explicitly type things in Groovy, but that is really an enabling feature. Enabling feature, you say? Yeah, an enabling feature, kinda like (Note: I have no personal experience with the following analogy, really...) how a drug dealer might give out free samples to hook you in and then afterwords start charging. So being able to specify types in Groovy gives Java developers, like myself, a warm fuzzy about trying out the new features and, therefore, try out the Groovy language.

Ok this is awfully pedantic, so what?
So the question that might be formulating in your mind is, "ok so you have a new definition, how does this help anything?" Well for one thing, no matter what you do with software code, the types are there, period. The difference is if they are hidden or not. In the next few sections I am going to compare equivalent sections of code in Java and in Groovy, but I think that the point holds if we were in Ruby, Smalltalk or Python, even though the examples would vary.

I want to show a quick example from groovy and Java, in this I am going to create an instance of ArrayList:

Java(5.0+):
List<> list = new ArrayList<>();

Groovy:
def list = []

So let me ask you a question? What is the difference in this case? Well for one the amount of actual keystrokes to write the examples. Beyond that, there is not much difference, in both cases you have a variable declaration of list that is initialized with a java.util.ArrayList instance. So what is the advantage of the Java version? Well Java's explicitness is key here, you know straight away that list is of type java.util.List and that it is an instance of java.util.ArrayList. Therefore, someone new to the Java platform would probably have an easier time figuring out what is going on in the Java line(at least not including generics, which is another post entirely) than with the Groovy line. To understand the groovy line you need to know that the array notation is shorthand for instantiating a List object and that by default an ArrayList is used, therefore I would term Groovy an "implicit" language in this case.

One other not so small point, if I was looking at this from a tool developer's viewpoint, I prefer the Java version to the Groovy version, in probably just about every case. In general, it is easier to write tools to analyze and provide support to base Java (or other explicitly typed language) than it is to any implicitly (read: dynamic) typed language.

Another example, I am going to do the simple "HelloWorld" application in both Groovy and Java:

Java: HelloWorld.java
public class HelloWorld
{
public static void main( String[] args )
{
System.out.println( "Hello World!" );
}
}

Groovy: HelloWorld.groovy
println "Hello World!"

This is the example that should drive the point home. What is the difference? In the end the bytecode will be functionally the same in both the Groovy and Java cases (Notice I don't say that the bytecode would be exactly the same). The big difference is that the Java version is explicit, not only about types, but also in requiring a class definition and explicit main method. In Groovy, the type is inferred implicitly from the file name and the main method is also implied.

What about the tools man?
The final example I want to consider is the Domain Specific Language (DSL) in the two kinds of languages. Actually, I lied, I am only going to show an example of a builder in Groovy and skip showing the example in Java, because the example for Java would be far too painful to consider. I want to consider the following example because I want to get to the point about what 'explicit' versus 'implicit' means for tool developers.

Example: AntBuilder (Groovy)
// Going to zip up a file
def ant = new AntBuilder()
ant.zip( destfile:"${zip.location}", basedir:"${project.location}" )

What all is going on here? You have an instance of AntBuilder being created and a method called zip being invoked. There is an example of named parameters, which is a very cool feature for Groovy I think. Finally, you see there two GStrings (Groovy Strings, quite the name no?) with its built in templating. There is a lot going on here, someone wanting to write a tool would probably take a deep breath, but envision that he/she will be able to do it. The trick is what about the zip method. What about the zip method? Lets get to that next.

In the previous examples, the types and their signatures are just below the surface so to speak. The notation '[]' is a shorthand for java.util.List and in the case where the statements are just put into the Groovy file without a class definition, means there is an implicit class definition and static main method. In the above example, there is no such nicety. Why would I say that? I mean the variable ant is an instance of AntBuilder right? Yes, but look at the javadoc for AntBuilder, where is the method definition for zip? There is not one, but if you want to see for yourself go ahead and look, I'll wait.

The AntBuilder class is an example of a Builder in Groovy which does something like what java.lang.reflect.Proxy does. Proxy provides an InvocationHandler, which has a method called invoke() which the Java platform provides as a hook to allow you to provide runtime implementations of arbitrary types. The Groovy Builder support allows for creation of nodes and invocation of methods on those nodes. All of this means that not only is the full type definition for AntBuilder implicit, but that there is really no way at compile time to figure it out. What I mean is that there is no way for a source code tool developer to write general tools to provide the kind of language support that is available in explicitly typed languages for DSLs. In the first two examples, you could easily imagine being able to provide tooling support for those cases, the types and signatures were implicit, but they could be figured out relatively simply, there is no real way to do it in the last case.

Tooling support is an area that is usually skipped in alot of discussions on explicitly typed versus implicitly typed languages. It is dismissed by implicit proponents with, "well tooling will just catch up." I don't consider it trivial and, having dabbled a bit in providing IDE support for Groovy, I don't assume that the tooling will just be there in the future. Implicitly typed language designers and proponents need to give this its full consideration, elsewise the best your language could hope for is to be the next Lisp, praised by some and used by none.

Conclusion
So the difference between the two languages in the above examples is best exemplified by asking three questions. First, which version do you think someone new to your codebase or the Java platform would understand better? Usually an explicitly typed language like Java (or maybe Scala/Haskell) would be favored. Second, which version do you think someone with experience with your codebase or the Java platform would prefer to write? Usually, I would think that an implicit language like Groovy, Ruby or even Python would be preferred. Third, what kind of tool, particularly IDE support do you want or need? If your project thinks that the first question is more important than the second one, then an explicit language like Java should be your choice. If the second question seems more important, then an implicit language like Groovy should be your choice. The third question can only be answered by surveying what is available and trying it out to see if it is good enough.

Using Groovy for Unit Tests inside Eclipse

I have blogged before in the past about using Groovy to write Eclipse Plugins. In fact, I think I am the only person in the world to ever write about the subject ever. This lack of interest in the subject is unfortunate for many reasons, but one reason in particular is the fact that writing in Groovy as opposed to Java can make many plugin related tasks simpler, particularly a lot of the tasks that make writing plugins no fun. For this specific reason, I am considering giving giving Groovy EMF a hard look as part of my ongoing efforts to make sense out of the Eclipse EMF Project. In my opinion, EMF could be like Grails if the generated code were in Groovy instead of Java.

Still I wanted to focus the blog entry on the use of Groovy for Unit Tests inside of Eclipse. This is because, in my opinion, that writing Unit Tests in Groovy is one of the main entry points for a Java developer to get their feet wet with Groovy and to see its benefits (the other two cases, in my opinion once again, are XML document parsing/generation and scripting). So here goes.

Framing the problem
The trouble with using Groovy in your projects is the same for using it for Unit Tests as when using it in production code from within Eclipse. The problem is that you usually have a build process that is run from the command line, often referred to as headless mode that you use for continuous integration or releases, and then you have the incremental build process that runs from within Eclipse. For headless (or batch/command line) builds, there is support from Groovy to assist with this, first there is the groovyc command that is equivalent to javac and second there is the Groovyc Ant Task. To take advantage of Eclipse incremental builds you really need to have an Eclipse plugin supporting that for you. This is where Groovy Eclipse can really be helpful, it provides the needed plugin support for incremental builds for Groovy from within Eclipse. For the next sections we will focus on solutions for utilizing Groovy for Unit tests.

Solution 1: GroovyTestSuite
There is a short snippet on using GroovyTestSuite from within Eclipse. There is one strong advantage to this method, since the groovy code is compiled when the AllTests are run, ostensibly this method could be used in both the headless batch build and from within Eclipse without any changes. So why not just use this method? Well there are downsides:

1. You can't use Eclipse's nice 'Recreate Test Suite' operation to keep the AllTests suite in sync. Over time, this is one of those problems that will bite more than once and usually when you least expect it.
2. If you don't have unit test classes compiled to classfiles, it makes running individual test cases difficult. This is something you feel more when you are trying to get a particularly challenging testcase to pass, in addition to the added compilation time, you will have to run the suite again. Of course you could create a new JUnit Testsuite just for the testcase you are trying to run, but then don't forget to delete it when done and don't check it into your source repository.
3. You have to make an assumption as to the current working directory. If you notice in the example code for GroovyTestSuite you have to assume that the unit test runner is being run from the project source directory. This is fine for Eclipse, just remember to check if that assumption holds for your batch/headless build as well.
4. You have to make assumptions as to the testcase's package. Once again refer to the code example for GroovyTestSuite. In the example see that the source directory, the package path is hardcoded, and the groovy file name is hardcoded. This is fine as long as you never change the source directory or refactor your test code into other groovy files or java packages, (*sarcasm alert*) which will never happen right? Now admittedly if you run your unit tests early and often, you will see this and then you will go and fix them immediately. Still better to not have to make those assumptions right?
5. Be careful about making Groovy code dependent on Java code or vice versa from within the same Eclipse Java project. This is a problem shared with the second approach as well. It is something you must consider (I know that groovyc will now compile Java code as well and it should be evaluated for use from within Groovy Eclipse or from your external build processes). There are a couple of ways to deal with the issue as I currently understand it. First, if you write only Groovy or Java code in a test project, there is no problem. This is usually an ok solution for greenfield test writing, but will not hold long term. Secondly, since there are no generated classfiles from groovy code in your project, you cannot allow your Java code to rely on any groovy code in the same test project period.

Solution 2: Groovy Eclipse Plugin
There is another option from within Eclipse, install the Groovy Eclipse Plugin and then add the Groovy builder and nature to your JUnit test project. Why do this? Well Groovy Eclipse will compile your Groovy code to classfiles and place them in a class folder for Eclipse so that Eclipse sees the compiled code as just another set of compiled Java code. This means that GroovyTestSuite is unnecessary and that running tests will not incur the full costs of compilation at start time, a significant advantage for developers. Another advantage is that the unit tests are compiled, so it is possible to easily run one testcase at a time. If setup correctly, using the Groovy Eclipse plugin makes developing/using Unit Tests in Groovy as seamless and invisible as possible. "So", you may ask, "ok Groovy Eclipse fan boy, what are the tradeoffs?" First off, even though I am a Groovy Eclipse committer and supporter, I am very well aware of its shortcomings, so I am not a fan boy. Secondly, well here are the tradeoffs/issues with this approach.

1. You must include Groovy as part of your batch/headless build process to compile the Groovy Unit Tests first, before the Unit tests are run. This is the same trouble you have if you are using Groovy in your production code. I will refer you to the section above titled 'Framing the Problem', for approaches on dealing with this. Using GroovyTestSuite only requires access to the groovy libraries at runtime.
2. Be careful about making Groovy code dependent on Java code or vice versa from within the same Eclipse Java project. This is not a problem unique to Groovy Eclipse or to writing Unit Tests with Groovy, but it is something you must consider (I know that groovyc will now compile Java code as well and it should be evaluated for use from within Groovy Eclipse). There are a couple of ways to deal with the issue as I currently understand it. First, if you write only Groovy or Java code in a test project, there is no problem. This is usually an ok solution for greenfield test writing, but will not hold long term. Secondly, be careful and avoid the following circumstances, A.groovy depends on B.java which depends on C.groovy or A.java depends on B.groovy which depends on C.java. This is an issue that needs to be addressed in Groovy Eclipse generally, either by leveraging groovyc to compile Java code or do an analysis to provide an Error/Warning marker to the user about the above circumstances. A useful heuristic traditionally is to allow groovy code to depend on java code or java code to depend on groovy code but not vice versa in the same project. If you hold to that heuristic, just consider the issue raised by number 3.
3. The order of the builders in the .project file. First off if you have groovy code depending on java code or vice versa in the same project, make sure that the groovy builder is before or after the java builder in the .project file. This can be easily checked by right clicking the project and then bringing up the properties dialog. Just look for the Builders section, you can easily remove, add, or reorder the builders in your .project file. Secondly, there are other occasions to be careful about the build order. In particular, this one bit me yesterday when I was trying to write a couple of unit tests for Eclipse monkey in groovy. I was pulling my hair out and about to give up on groovy unit tests for monkey (I mentioned I am not a Groovy Eclipse fanboy didn't I?), when I remembered to check the builder order. Sure enough, the groovy builder came after the plugin and manifest builders. Reordering the groovy builder to come before the PDE builders then allowed the PDE JUnit to actually run (Note to self: add better PDE support for Groovy Eclipse).

Conclusion
There are advantages and disadvantages to both approaches to writing Unit Tests for your projects from within Eclipse. The first approach, at first, seems more straightforward and simple, in particular no integration with external builds, compilation of groovy code is reduced to a classpath resolution problem. The second approach, using Groovy Eclipse, leaves the developer with the need to integrate Groovy into their external build processes, but in the longer term provides a more seamless and productive experience. So if you are wanting to write Unit Tests in groovy, give Groovy Eclipse a try!

Add Groovy to your Eclipse Plugin Projects

I have begun some basic work on the Grails Eclipse plugin that I outlined in a proposal in a previous post. One of the features I want to highlight will be the fact that I want the plugin to be almost exclusively written in Groovy instead of Java.

As I start work on the plugin, I want to highlight a feature that I will hopefully add to the Groovy Eclipse Plugin in the real near future, Groovy PDE Build support. If you install the Groovy Eclipse Plugin ( I think the version currently in Head/Trunk is better than the one on the update site ), you will find that your development for the most part goes smoothly, except for when you start using Groovy to write your Eclipse Plugins. The issue is that the PDE Builder doesn't know, and probably doesn't want to know, about the Groovy code and its need to be compiled with the Groovy compiler. So how do you deal with this?

One way is to parallel the work of the Eclipse PDE Build team and write your own scripts that can interpret the build.properties file to export your plugin yourself. This can make you proud and think you are a real programmer, except that why in the heck do you want to repeat something that has already been done?

Another way is to generate the build.xml file, click the custom build option on the plugin and maintain the ant build file manually. Do I need to go into the obvious problems and pain with this option? If you like pain, reading ant XML scripts, pain, deciphering the incredibly ( but probably necessary ) complex PDE build process, pain, keeping your Ant XML file synchronized to changes in your project manually, and yet more pain, go ahead. I wont stop you, for the rest of us I am going to cover the next, and I believe, better option.

One side note, I am very familiar with the pain that I described above, I wrote a series of Groovy scripts to build our products, as per the first option. Pretty cool and better than the second option, but it really was a source of pain and, as I will now show you, unnecessary work.

The final option I give you, with an example, is what I think to be the best option. In fact, I wish I knew of it before on previous Eclipse based projects. As of Eclipse 3.2, you have the ability to specify a custom callbacks XML file.

To add Groovy PDE Build support to your plugin project, first you must install the Groovy Eclipse plugin and enable the groovy nature for your project. Deployment of the groovy libraries into your plugin for installation is another topic for another time.

Afterwards goto your Eclipse installation directory and open up the plugins directory. Goto the org.eclipse.pde.build plugin installation directory and look in the templates/plugins subdirectory. You will see there a template called customBuildCallbacks.xml, import this into your project.

Now open up your build.properties file and add a property called customBuildCallbacks like the following example:

customBuildCallbacks = customBuildCallbacks.xml

This means that the build will now reference a callback Ant Build script in my project called customBuildCallbacks.xml in the root of my project. You could prepend a project relative path to the file name to place the file somewhere else if you choose.

The next step I like to do is to right click the manifest.mf(plugin.xml) file and ask the PDE to generate a build.xml file. Now I am not going to keep the build.xml file around very long nor its javaCompiler args file. I am going to use it to extract the targets that will be called in the callback ant script and to find out the name of the classpath reference that will be used.

Below is an example file from the plugin I am currently working on.

<subant antfile="${customBuildCallbacks}" target="pre.@dot" failonerror="false" buildpath=".">
 <property name="source.folder1" value="src/"/>
 <property name="target.folder" value="${temp.folder}/@dot.bin"/>
 <reference refid="@dot.classpath"/>
</subant>
<!-- compile the source code -->
<javac destdir="${temp.folder}/@dot.bin" failonerror="${javacFailOnError}" verbose="${javacVerbose}" debug="${javacDebugInfo}" includeAntRuntime="no" bootclasspath="${bundleBootClasspath}" source="${bundleJavacSource}" target="${bundleJavacTarget}"  >
 <compilerarg line="${compilerArg}" compiler="${build.compiler}"/>
 <classpath refid="@dot.classpath" />
 <src path="src/"   />
 <compilerarg value="@${basedir}/javaCompiler...args" compiler="org.eclipse.jdt.core.JDTCompilerAdapter"/>
 <compilerarg line="-log '${temp.folder}/@dot.bin${logExtension}'" compiler="org.eclipse.jdt.core.JDTCompilerAdapter"/>
</javac>
<!-- Copy necessary resources -->
<copy todir="${temp.folder}/@dot.bin" failonerror="true" overwrite="false">
 <fileset dir="src/" excludes="**/*.java, **/package.htm*"   />
</copy>
<subant antfile="${customBuildCallbacks}" target="post.compile.@dot" failonerror="false" buildpath=".">
 <property name="source.folder1" value="src/"/>
 <property name="target.folder" value="${temp.folder}/@dot.bin"/>
 <reference refid="@dot.classpath"/>
</subant>

There are two subant tasks that are of interest one before the javac task and one after. You can overload one or both in your callbacks ant script to allow the groovy builder to run before, after or before and after the java compiler. The important thing here is that the target name and classpath reference in your callbacks script must match.

Here below is an example from my current plugin project.

<target name="pre.@dot">
</target>

<!-- ===================================================================== -->
<!-- Steps to do during the compilation target <name>, after the compile   -->
<!-- but before jaring.  Substitute "name" with the name of the compilation-->
<!-- target, eg @dot                                                       -->
<!-- Available parameters :                                                -->
<!--   source.foldern : n = 1 ... N, the source folders                    -->
<!--   target.folder  : where the results of the compilation go            -->
<!--   <name>.classpath : name = name of the compilation target. A         -->
<!--                      reference to the classpath structure.            -->
<!-- ===================================================================== -->
<target name="post.compile.@dot">
 <path id="org.codehaus.groovy.eclipse.libs">
  <fileset dir="../org.codehaus.grails.eclipse/grails-home/lib">
   <include name="**/*.jar"/>
  </fileset>
 </path>
 <taskdef name="groovy"
          classname="org.codehaus.groovy.ant.Groovy"
          classpathref="org.codehaus.groovy.eclipse.libs"/>
 <taskdef name="groovyc"
             classname="org.codehaus.groovy.ant.Groovyc"
    classpathref="org.codehaus.groovy.eclipse.libs"/>
 <delete>
  <fileset dir="${target.folder}" includes="**/*.groovy"/>
 </delete>
 <groovy classpathref="@dot.classpath">
  def classpathString = task.classpath.list().toList().findAll{ new File( "$it" ).exists() }.join( File.pathSeparator )
  ant.groovyc( srcdir: properties.'source.folder1', 
      destdir: properties.'target.folder', 
      stacktrace:'true',
      classpath: classpathString )
 </groovy>
</target>

The important things to notice are that the targets are called pre.@dot and post.compile.@dot which were derived from the generated ant build script and could be derived from your build.properties file. The next thing to notice is the classpath called 'org.codehaus.groovy.eclipse.libs' that points to a directory and slurps in all available jar files. This is done to locate the groovy library and therefore the groovy and groovyc ant tasks. You must set the path, either relative to the workspace or hardcoded from your file system. The last thing to notice is the use of the sourceN.folder properties, if you have more than one source folder that is being compiled into your plugin, then you must make allowance for it. If you are not sure, go back to the generated build.xml, it will tell you since it will set those properties before making the subant call to your customBuildCallbacks.xml script.

Conclusion

What is the point of all this? Well simply put, once you have made these modifications, you can write groovy code in your plugin and have the Eclipse PDE Builder/Exporter compile your groovy code along with your bundle with no muss or fuss. This functionality works if you are exporting a plugin, or as part of a feature or as part of an update site. Cool eh?

One last point, since most of this is rather rote cut and paste, I am looking to enhance the Groovy Eclipse Plugin to handle this for you. Hopefully it should be part of the next official release on the update site.

Grails Eclipse IDE Support

I knew that the idea of an IDE plugin to support Grails could not be new. So I am going to post the contents a nice little "IDE Integration Wish List" from the grails wiki site. I am then going to make a proposal for what I see the path of a Grails Eclipse plugin would take. Comments are more than welcome.

IDE Wish List (from grails.org)
Below are the features that would be great to have from a Grails IDE:

• Wizards to create Grails artifacts like controllers/domain objects and so on. Unlike Rails, Grails doesn't do any background configuration with its command line tools so these can merely be simple wizards
• Running a Grails server embedded in the IDE and being able to step debug the application. Groovy provides all the information in the classes necessary to enable step debugging of Groovy code
• Code navigation with keyboard shotcuts and CTRL+click between Grails artifacts like controllers domain classes etc.
• Code completion for things like dynamic finders and persistent methods like save/delete/findAll/findBy* on domain classes
• Auto-completion of Grails tags in GSPs
• Integration of an embedded Grails console to be able to execute arbitrary scripts against a running application
• Being able to right-click execute Grails unit tests and get green/red bars etc.
• Being able to right-click on a Grails project and execute all unit tests
• Being able to right-click on a domain class and click generate to generate a controller and views for CRUD
• Better editor support for groovy files. This means autocompletion and so on.
• Special outline views for Domain-Classes, Controllers and Views
  Graphical editor for Domain Classes, with a UML-like or ER-like view
• The IDE should hook into Grails' upcoming plug-in architecture to be able to do things like auto-find new executable scripts, download and install new plug-ins etc.
• Integration of every Servlet-Container to test the Grails-App. The best solution were intergration into webtools
• XP Refactor support (e.g. rename methods/groovy file names and cascade changes to all dependencies)

Proposal
I would like to start by taking the Grails application and embedding it within a set of Eclipse plugins and then have Eclipse plugins to be able to run directly from the workbench ( via right click options ) the command line commands directly. This would mean that you would not have to install Grails seperately, kinda like Eclipse handles ant.

After that I would like to begin integrating the Groovy Eclipse plugin into the mix. I think that the Groovy Eclipse plugin should be included seperately from the Grails plugin to avoid issues of differing Groovy versions ( that Grails could require different versions from the main Groovy distribution ) and to avoid the overhead of installing all the Grails libraries along with the Groovy Eclipse plugin. Of course, there would be lots and lots of overlap and we should be able to leverage any new improvements in the Groovy plugin quickly. The Groovy Eclipse plugin with its editor and outline view would be the basis for adding more support for Grails.

After the Groovy Eclipse plugin functionality is added, the fun can really begin. As I mentioned in a previous post, convention over configuration would allow us to inject suggestions to method completion. A first target would be the Data Source configuration files, a second would be the Domain classes, and so forth.

A related issue would be to find an open source JSP Editor project that would be willing to partner with us to help develop the GSP Editor. If an acceptable one is not found, then one will have to be fabricated, probably based on a previously existing XML editor.

I think this could be very useful ( i.e. cool ) and since we could leverage already existing tools, we could have something to show rather quickly and have a nice evolutionary path to add new features and functions a little bit at a time.

I would love comments on this proposal.

Convention over Configuration == Eclipse IDE completion support for Grails?

As I am going through the "Definitive Guide to Grails", I can definitely say that for the most part things are going well. I wish that the dynamic update feature would work, but other than that things are going well.

One thing that has been hitting me like a pile of bricks, is Grails' use of injection to put properties and methods onto an object without it needing to extend a base class. This is all fine and dandy, but who can remember all those extensions easily for like a domain class? I know the IDE can.

As work has been progressing on method completion on the Groovy Eclipse plugin ( great work Ed ), it occured to me that adding additional completion options based on the fact that the project is a grails project should not be very hard, not hard at all. In fact, I did something similar in Groovy Monkey to add autocompletion and elements in the outline view based on what the script's binding was. How cool would that be, to not have to remember the domain's class' get, what actions are injected automatically into a controller, to perhaps provide some assistance to using the findBy* methods?

In fact, the way I think about it, using conventions is a bit like having static type information around. And if you have some equivalent of static type information, don't autocompletion and other IDE goodies follow?

Why dig into Grails?

During my time as a C/C++ then Java developer, somehow I have avoided the need to write J2EE web applications. Not web enabled or web services applications, no I have somehow avoided the beast that is J2EE ( not to mention *gasp* EJB ). However the current Web 2.0 ( I read AJAX ) wave has forced me from my comfort zone ( replace 'comfort zone' with Happy Gillmore's 'Happy Place' if you like ).

*Note: when I read AJAX I read, browser based client side UI programming and not alot of buzzword happy nonsense.

I have to admit that the current wave of browser based web applications are pretty cool. I love GMail, blogger.com's interface, Google Reader, Google Calendar etc... I don't think of myself as a google fan boy, but that is another topic ( hmm... maybe I should try out 37 signals stuff like backpack ). Another reason that has forced me from my comfort zone is that fact that I have recently been evaluating technologies for my current job and taking a cursory look at the Job market again and I have come to a conclusions of sorts. People out there like these browser based applications. Something about avoid the problems of upgrades, deployment, configuration, licensing, etc... Personally I don't see their point ;) I actually like to ram my head into walls, tables, floors, etc... So I have begun a journey to acquire some of these skills and acquaint myself with those technologies that can enable them.

A brief aside, I have not been doing monolithic applications for some time now, but it is just that my container of choice is the OSGi Java container that the Eclipse platform is based on. After learning a bit more about the Spring framework and the new Spring OSGi project, I am even more impressed with OSGi as a container and enterprisey platform architecture, but this is a digression from the current topic.

Before digging into topics like AJAX, I figured I better get more acquainted with the Java Web application world in general. I know that even though frameworks exist to make development easier, but in the end you wind up needing to at least be familiar with what is going on underneath the hood. So I began to get more familiar and see what was out there.

One more point, before I tried to begin this journey, I have been acquainted with Ruby on Rails (RoR) and its convention over configuration paradigm. "Convention over configuration" is something that I had begun to use in my own work and I immediately saw its advantages over doing everything in an XML configuration file. I was suitably impressed with the ability of RoR to generate scaffolding and allow you to have an up and running web application in minutes. I am a "lazy" ( as in the good way ) kind of person and I don't like to have to perform lots of scaffolding to get get something up. Needless to say, this was something I wanted in a web application platform that I wanted to use.

So the next obvious question is, "why not use RoR?" Good question. The answer is I am a Java developer that has been working with Java for sometime now and I don't want to have to give up all my experience just to bet it on something new, if there is a viable alternative. Second part of the answer is something I don't like about Java, lack of native integration support with legacy code (JNI (Java Native Interface) is not on my christmas card list). People out there have alot written for J2EE in Java for the web, as far as I know there is no direct way to be able to leverage this legacy stuff directly in RoR. I know that the JRuby folks are getting closer to being able to run RoR through the JVM, but they are not there yet. Even when they do, the code to interact with other Java code can be awkward. This is normal, since Ruby was developed independently and has its own ideas of what a collection, array, type is and it differs at times significantly from Java. So is there a viable alternative? I think so, the Groovy language with Grails.

Groovy
Groovy (http://groovy.codehaus.org/) is a dynamic scripting language written to be friendly to those of us coming from the statically typed Java world. Just remember that Groovy is Java, just not the Java language. Java is the title of a platform that includes the JVM, libraries and the Java language. Groovy natively sits on top of the JVM and directly uses the Java libraries, so it is a Java platform language. Visit the web site to learn more and I highly recommend the "Groovy In Action" book for you to acquaint yourself with Groovy. Groovy has the great feature of being native to the Java platform and being optionally static. Now what does Grails have to do with Groovy? Simple, Groovy is the language that a Grails application is written in. So you have a choice of learning a new language that has a completely separate syntax than you are used to ( being a Java/C++ developer ) or learn a language that is more of an extension of Java and that has most ( if not all ) the advantages of the other language? Is it really an issue? To me it wasn't, if I could find a web framework like RoR to go with it.

Grails
Groovy is all fine and dandy, but it can only do so much to help with writing Web Applications. Ruby without Rails has much the same problem, that is why the Rails framework was created. Grails is the Groovy ( and indeed Java ) world's equivalent to RoR. I have been reading the "Definitive Guide to Grails" and I find the framework very interesting. You have alot of the same advantages of RoR, namely the quick development of a simple web application, standard project structure, support for writing test suites, delineation of environments ( development, production, testing ), support for switching between databases, support for the Model-View-Controller (MVC) pattern, etc... The nice thing about it all is that in the end you have a Java based web application that can be injected directly into a servlet container like Tomcat and will seamlessly interoperate with the other web applications you have already developed.

For example to create an application in Grails you type, "grails create-app". You enter in the project name and voila, the project and its scaffolding is created for you automatically. Being an Eclipse fanboy (hey if the shoe fits... yup it does...), I like the fact that the grails application scaffolding includes a .project and .classpath file that allows me to directly import the generated grails application directly into Eclipse. The cool thing is that you can type, "grails run-app" from the project directory and you have a Jetty web server up and running your web application. You can open up a web browser and see the results immediately. This is just the sort of thing that got people all excited about RoR. Another great feature is that of dynamic loading. While running your web application in Grails with "grails create-app" you can modify the code of the application and have the results displayed in your browser by just refreshing the page. This is the sort of thing that dynamically typed languages have held over Java all this time. Now Java can have this advantage, enabling quick iterative development. This is the sort of thing that in another context, that of eclipse plugin writing, led me to write the Groovy Monkey tool.

So I have been sold, hook, line and sinker. I am going to try and write some quick blog entries over the next few days as I continue to learn Grails and highlight my progress and issues.

*Btw I have no financial interests in Grails or any of the two publications I recommended ( 'Groovy in Action' and 'The Definitive Guide to Grails' ). So take my recommendations with as much salt as you like, but at least know it is not tied to any 'check in the mail' coming to me. *Sigh*