Wednesday, November 20, 2013

JBoss 7.2: From Aries to Gemini and back again

I have been using the combination of JBoss 7.2 and Apache Aries for a while now.
Recently, I had to face a problem, which I had been ignoring for quite a while successfully.

When you use Aries blueprint you cannot use setters with non-void return values. Aries expects setters to have "void" as their return type.
Because fluent interfaces are quite popular at the moment that was a problem for me.
The Aries people already have an open issue to fix/improve this and maybe the blueprint specification also wants setters to have that return type. I don't want to start a discussion about this here.

Nevertheless, I wanted to use the setter. I could have written a subclass with a slightly different setter, which just calls the setter I really want to use. But that would've meant to write a new setter for every existing one. So that was not an option.

Another option was to change the Aries source code by myself (what I should have done in the first place). But I didn't know how complex that would be so I chose the third option.

The option I chose was to replace Aries with Gemini. At some point during my research I found a post, which stated that Gemini could handle non void return values for setters.
After I managed to collect all of Gemini's dependencies and place them in JBoss' bundle directory I thought I reached my goal. But when I started the server it didn't go past the registration of my EJBs. The server log just showed a NPE some seconds before when trying to release some lock.

I wasn't sure what to do because the NPE wasn't really helpful and I couldn't imagine what the problem was. My only idea was to remove the Jar containing the EJBs.
After that the server started but the Blueprint-Extender didn't start automatically. That wasn't much of a deal. I opened up the management console and started the bundles all by hand. Everything seemed to be fine. Even dropping the EJB-Jar in the deployment directory worked.
Unfortunately, after stopping and starting the server again I was staring at the same exception and the JBoss refused to do its work.
What followed was some try-and-error with more error than try. I still don't know what the problem is.

This was really disappointing (it still is). I decided to take the option I refused before and to change Aries' code. Fortunately I had the Gemini-Jars in another local JBoss so I could just go back to the one I had used before.
And who could've guessed? I just had to change one line in org.apache.aries.blueprint.utils.ReflectionUtils:

if (name.length() > 3 && name.startsWith("set") && 
resultType == . && argTypes.length == 1)
 
I just had to remove the Void.TYPE and everything worked.
I guess next time I'll try to change the code first ;)

Friday, July 12, 2013

Comparison of different BPMN-modelling tools

Recently, I stumbled upon the problem that the Activiti-engine wouldn't accept a BPMN-XML-file which I modeled with camunda Modeler.
No error message or warning was displayed, but I could see in the log-file that parsing started.
The process just didn't arrive in the repository.

Because of that, I was wondering, how good the interoperability of the different engines and tools is at the moment.
BPMN is standardised and should work on every tool and engine. But as usual, reality shows us, that it's different.

This blog post covers several modelling tools and how good they work together. In a later blog post I'll feed the different BPMN-files to different engines.

I chose the tools for no special reasons.
Activiti and camunda because I work with Activiti (and camunda forked it).
SemTalk because I do have a license for it (it's the only commercial tool I chose).
The rest is more or less randomly in the list and because they are available for free.

I compared:
  • Activiti Modeler 1.0 (Activiti Version 5.13)
  • camunda Modeler 2.0.12
  • Yaoqiang Version 2.2.2
  • Bizagi 2.5.1.1
  • Bonita BPM Studio 6.0.0
  • MS Vision 2010/ SemTalk 4.2.0.4230
  • Activiti Designer  5.12.0
You can find my results in a PDF, which I placed here.

To give a short explanation of the colours used:
  • green -> everything was alright
  • yellow -> it worked with some problem
  • red -> it didn't work or there were some major problems
  • grey -> it couldn't be tested or was unnecessary.
Bizagi is completely grey, because it has no im- or export for BPMN-XML.

This is the example process I used:
I wanted the example process to be very simple. It includes the basics, which I think should be supported.
It was modeled with every tool and opened with every tool. When testing if editing works, I added a task to the second pool.

Next to the result-table in the PDF, I took some notes during the tests, which I want to share:
  • Activiti Modeler can't display pools or lanes
  • Activiti Modeler can't display message flows
  • Activiti Modeler needs a Tomcat server (or similar), because it's part of Activiti Explorer
  • Yaoqiang would work better with some guides
  • camunda Modeler needs Eclipse, because it's a plug-in
  • modelling a flow (arrow) in SemTalk is too complicated
  • Yaoqiang, because of it's page layout, becomes confusing with big diagrams
  • Bizagi, Bonita and Yaoqiang validate the model
  • To show message passing, Bonita forces you to explicitly model sender and receiver
  • for Activiti Modeler, every file hat to be a .bpmn20.xml and not just .bpmn 
  • Activiti Designer can't display message flows

I don't want to name a winner, because I depends on what you're working on.
Some modelling tools are embedded (like Activiti Modeler and Bonita) and some are standalone (like Yaoqiang) and there are different use-cases and environments in which you would prefer one or the other tool.

But I got to admit, that I am a little bit disappointed by Activiti Modeler. It can't work with any of the the BPMN-files the other tools exported.

I hope my results will be helpful for people who have to chose a modelling tool and I hope that some of the tool-developers will try to improve their tools because of my results. Have fun ;)

Update: I added the results for Activiti Designer to the PDF. It works slightly better than the Modeler but could be better.

Tuesday, June 4, 2013

Using the Activiti-Engine as bundle in JBoss AS 7.2

Introduction


I am quite new to OSGi and when trying to deploy and use the Activiti-Engine as OSGi bundle in JBoss (I'll usw "JBoss" as abbreviation for JBoss AS 7.2) I have had some problems. 
The only example about OSGi and Activiti I was able to find was the one from Activiti in Action which uses Apache Karaf. Of course those environments differ a lot.
So I wanna share my knowledge with you.

 

Motivation 

 

Before we start, I'd like explain why I want to use the combination of Activit, OSGi and JBoss. I won't argue about the pros and cons of using OSGi, there is enough literature about that.

The fact that Activiti scans every new bundle if it contains a process definition will become very helpful for future processes.
Also, updating a process definition by replacing a single bundle and not replacing e.g. a whole WAR-file, seems like an advantage.

But, why do I want to use JBoss and not e.g. Karaf?

When JBoss changed to version 7 they restructured their whole server to use OSGi/JBoss modules. So, OSGi is a part of JBoss.
Last time I checked, JBoss was the only fully JEE 6 compliant server with OSGi integration and because I need EJBs for client - server communication I need JBoss. (At this point, I have no idea how to combine EJBs and OSGi but I'll try to figure that out, soon)

Those are my reasons so let's see how we can get those three running.

 

Let's start

 

Environment


To make sure that everyone can easily repeat my steps, I'll start with the environment/versions:
  • JBoss AS 7.2
  • OSGi 4.2 (included in JBoss)
  • Activiti 5.12.1
Please notice, that I use JBoss AS 7.2, which you have to compile yourself at the moment. With version 7.1.1 I have had a problem.
I had the server running locally under Linux Mint 14.1.

 

Bundle dependencies 


The example from Activiti in Activiti uses a feature.xml to resolve all the dependencies and install them from a Maven repository. Unfortunately, this involves some Karaf "magic". That's why I had to download all dependencies manually. (I also tried

mvn org.apache.felix:maven-bundle-plugin:wrap/bundleall
on the activiti-engine and -osgi project, but that didn't work out for me)

We need the following JARs (I added links to make downloading them easier):

Downloading yourself Apache Aries seems a little bit odd because the JBoss documentation states that there is blueprint support. Nevertheless, I couldn't find, nor activate it, so I was forced to include it myself.

Another interesting thing is, that I couldn't start the included h2 database (com.h2database.h2). That's why I downloaded it, too. Please notice, that you will only need the h2-bundle if you want to use a h2-database (makes sense, doesn't it ;) )

We could throw all those bundles into the <<jboss-root>>/standalone/deployments directory (if you're using JBoss in standalone-mode), but I think a better approach is to place the more general JARs in the <<jboss-root>>/module directory. 
    I placed the three aries-bundles, the h2-bundle and the two slf4j-bundles there.
    For every bundle you have to repeat the following steps:
    If the bundle name is e.g. com.a.b.c.jar create in <<jboss-root>>/module the directory com/a/b/main and place the bundle in the main directory. (Don't worry about the <<jboss-root>>/module/system -directory.)

    After that, alter the standalone.xml and add a new capability under the OSGi-Subsystem, e.g.:

    <subsystem xmlns="urn:jboss:domain:osgi:1.2" activation="eager">
       <properties>

        ...
       </properties>
       <capabilities>
          <capability name="com.a.b.c" startlevel="1"/>
       </capabilities>

    </subsystem>

    Pick whichever startlevel you think is appropriate.

    In fact, you can pick any directory-structure you want to, as long as the path in the standalone.xml is correct. That means you could place the h2-bundle e.g. in <<jboss-root>>/module/org/foo/bar/main and JBoss would still be able to find it. Only the last directory has to be named "main".

    After you've done that, take the other bundles an put them into  
    <<jboss-root>>/standalone/deplyoments

    An that's all. These steps should get Activiti running as OSGi-bundle.
    My whole osgi-subsystem configuration looks like this:

    <subsystem xmlns="urn:jboss:domain:osgi:1.2" activation="eager">
                <properties>
                    <property name="org.osgi.framework.startlevel.beginning">
                        2
                    </property>
                </properties>
                <capabilities>
                    <capability name="javax.servlet.api:v25" startlevel="1"/>
                    <capability name="javax.transaction.api" startlevel="1"/>
                    <capability name="org.osgi.core" startlevel="1"/>
                    <capability name="org.osgi.enterprise" startlevel="1"/>
                    <capability name="org.slf4j" startlevel="1"/>
                    <capability name="org.slf4j.impl" startlevel="1"/>
                    <capability name="org.apache.aries.util" startlevel="1"/>
                    <capability name="org.apache.aries.proxy" startlevel="1"/>
                    <capability name="org.apache.aries.blueprint" startlevel="1"/>
                    <capability name="org.h2" startlevel="1"/>
                    <capability name="org.apache.felix.log" startlevel="2"/>
                    <capability name="org.jboss.osgi.logging" startlevel="2"/>
                    <capability name="org.apache.felix.configadmin" startlevel="2"/>
                </capabilities>
            </subsystem> 


    And in my deployments-directory you can find those jars:
    • activiti-bpmn-converter-5.12.1.jar
    • activiti-bpmn-model-5.12.1.jar
    • activiti-engine-5.12.1.jar
    • activiti-osgi-5.12.1.jar
    • com.springsource.javax.transaction-1.1.0.jar
    • com.springsource.org.apache.commons.lang-2.4.0.jar
    • joda-time_2.1.0.jar
    • org.mybatis.mybatis_3.1.1.jar

     

    Blueprint activation

     

    The Activiti-OSGi bundle contains the basic classes Blueprint needs. But we have to register all those services. That's why we need a Blueprint content.xml.

    Thanks to Tijs Rademakers we can copy that from here. It's the example code from/for Activiti in Action.
    We can also use the book-osgi-app in JBoss.
    Just run mvn package on the book-engine, book-process and book-task projects.

    After packaging those three, I had to make a minor change in the MANIFEST.MF and content.xml of the book-engine-project.
    In the content.xml you have to replace the jdbc-url with whatever fits to your database.
    In the MANIFEST.MF I had to remove the Import-Package versions for everything related to activiti, because the generated MANIFEST requires version [5.9, 6) and my activiti-bundles don't contain any version information.

    Now place those three bundles into the deployment-directory and everything should work as expected.
    To test the deployment, I wrote a simple bundle with an activator to look up the Deployment-Service and see, if a process defnition could be found. 

    Summary 

     

    Get all the bundles, place some in the modules-directory and some in the deployment-directory, copy some content.xmls and everything should work. Sounds easy, but it took
    me a while to figure it out ;)

    So have fun with Activiti, OSGi and JBoss!
    In case you find any mistake, feel free to point them out.

     

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