Unresolved constraint error when installing bundles in Fuse

When installing a bundle in Fuse, it quite common  to encounter the Unresolved constraint error: missing requirement: osgi.wiring.package error.

This error is thrown when the packages imported using Felix plugin are in conflict or if the dependent bundles are not installed. 

The article in this link provides a detailed explanation on the cause and fixes for this error 

But for those looking for quick fix ,the following steps would be handy.

• Use osgi:headers <> to list the manifest details of the bundle.
• In the manifest details,check for packages are marked in Red in Import-Package Listing. These are the  candidates which potentially cause this error.
• Verify if the bundle corresponding to the erroneous package is installed and started 

These  steps should help to resolve most of the unresolved constraint exception when installing a bundle.

IllegalArgumentException when invoking a webservice from a Camel Route

If a service exposes more than one operation then the operation name and namespace should be set in the header before invoking the call from the Route.

The IllegalArgumentException or BindingOperationInfo Exception is thrown when the framework is not able to find the matching operation to invoke.To fix this ,verify the operation name and namespace from the service class defined in the CXF EndPoint Bean.If the operation name or namespace is different,the binding would fail and IllegalArgumentException would be thrown.To fix this error,ensure that  the operation name and namespace match with the details given the SEI class.

  

<route>

     <from uri="timer:foo?period=5000" />

     <setHeader headerName="operationName">

            <constant>generateText</constant>

    </setHeader>

    <setHeader headerName="operationNamespace">

       <constant>http://com.test/generateservice</constant>

   </setHeader>             

  <to uri="cxf:bean:generateService" />

 <log message="The message contains ${body}" />

</route>

In-Memory Components

Camel provides in-memory components like  Direct, Direct VM,SEDA and VM .These components route  messages without using external broker.They should be used when performance or speed takes precedence over reliability requirements.

Direct/Direct VM :

The Direct component allows to make direct synchronous call between a producer and a consumer. This is the simplest component as it requires no additional configuration. It is mainly used to link routes within a Camel Context  and  to expose a route as a synchronous service.

Direct VM is similar to Direct ,only difference is that it supports communication across multiple Camel Context instances within the same JVM.

SEDA :

The SEDA component  is used for asynchronous messaging and is considered as low overhead replacement for JMS .SEDA allows messaging  within a single  Camel Context. It supports concurrent users  in which the configured end points will be triggered and run in separate thread.

VM is similar to SEDA except that it supports communication across multiple Camel Context instances within the same JVM.

Component	Pros	Cons
Direct/Direct VM	Simple to use Allows to reuse route Minimal Overhead	Used only when Producer and Consumer are up at the same time, this may not be viable for all use cases. Works on Single thread only
SEDA /VM	Faster than JMS as it is in memory Supports concurrent users	Message Persistence not supported so there is a risk of losing message if event of   crash. Transactions are not supported as each call is invoked  on a different thread.

Kick-start Guide for JBoss Fuse Development

Hit many roadblocks when I started off  with JBoss Fuse development.Though the framework is great had to face a lot of impediments due to incompatible jars and outdated install documents.This post is to put forward  what worked for me and hope would be helpful for those out there who are yet to start their Fuse Journey.

JBoss Fuse is an open source Enterprise Service Bus (ESB). It is a robust SOA solution designed with build-in fail-over, load balancing and delayed message redelivery. It combines several technologies like core Enterprise Service Bus capabilities (based on Apache Camel, Apache CXF, Apache ActiveMQ), Apache Karaf and Fabric8 in a single integrated distribution.

Red Hat acquired FuseSource and JBoss Fuse was built upon FuseSource’s product, FuseESB.

Ref : http://www.jboss.org/products/fuse/overview/

Prerequisite
JBoss Fuse is based on Apache Camel so it is better to have an understanding on Camel before exploring Fuse.

Requirements
Hardware 

Ø  400 MB free disk space

Ø  2 GB RAM

Software 

Ø   Fuse runtime platforms need Java 6, JRE 1.6.0_18 or later.

JBoss Fuse provides 3 types of Installation

·           Ø    Minimal—installs Apache Karaf, Apache Camel core, and selected Apache Camel components

·          Ø     Medium—installs Apache Karaf, Apache Camel;, and Apache ActiveMQ

       Ø     Full—installs Apache Karaf, Apache Camel, Apache ActiveMQ Apache CXF, and the JBI components

I        I chose Full install for my environment but based on the components required the appropriate install can be selected.

Installation Steps:

1. Download JBoss Fuse 6.1.0.GA Full Zip (latest as of Apr/2015).
2. Need to be a registered user of JBoss Developer to have access to download the file.
3. Extract the downloaded file into a local folder. It is preferable to extract the file into a folder which does not have space in its path
4. The Fuse server can be started using the <>/bin/fuse.bat. The following screen shows up if the server is successfully up.

Note:The loading should be 100%,if not check for the logs in <>/data/log folder for details

   The Fuse server is set up,now we need to set up the IDE.The IDE used here is JBoss developer Studio 8.1.0 GA

Prerequisite
Ø  Maven 3.3.1
Ø  JDK 1.6 or 1.7

Development Tools

JBoss Developer Studio  is an Eclipse based IDE which makes setting up and debugging of the Fuse application easier.

JBoss Developer Studio Integration Stack   is a plugin which provides tooling for developing, configuring and deploying Fuse applications.

Installation Steps

The Developer studio needs to be installed first and the Integration Stack can be added  later on.

1. If maven is already installed in your system, then take a backup of the repository and settings.xml and delete these files. The fuse download has issues with the incompatible jars  which are in the repository.
2. In the settings.xml, configure the JBoss EAP Maven repository,JBoss Community Maven repository and  make the repositories active by default.
3. Download the stable jar from http://www.jboss.org/products/devstudio/download/ The stable jar as of  Apr/2015 is Red Hat JBoss Developer Studio 8.1.0.GA jar file (jboss-devstudio-8.1.0.GA-installer-eap) 
4. Install the jar  (java -jar <> <>).
5. Follow the instructions in the wizard. The installation may take 10 to 15 minutes.
6. After this step Integration Stack can be updated.
7. Select Software/Update from the JBoss Splash screen and choose the options as shown in the snapshot below.
8. For the IDE version 8.1.0,the updates are available on Early access basis, so ensure to select the Enable Early access Check box.

   

   Once the Development Studio is set up, the Fuse project can be created using the Fuse Project Wizard.   Refer to this  tutorial for creating fuse project.