By Steve Robinson
steve.robinson@themiddlewareshop.com
http://www.themiddlewareshop.com
Contents
Exercise 12 – OSGi 1
Introduction 2
OSGI Technology Overview 2
Project Structure 2
Product Lifecycle 2
Step 1: Creating the business interface 3
Result 8
Step2: Creating the Business Implementations 8
Creating a new package to contain implementations 11
Creating an implementation class 13
Export the bundle 17
Deploy a bundle using WAS console 18
Complete the remaining 2 bundles 21
Example V2 Error 26
Example V3 Error 26
Set the manifests 27
Import in to WAS (Deploy) 30
Result 30
Step 3: Creating the Servlet bundle 30
Creating the OSGICalculatorServlet 35
Modify the doGet() method 39
Step 4: Creating the OSGI Application 41
Result 42
Result of the manifest update 44
Export the application 44
Deploy Assets 45
Create a new BLA 47
Add assets to the BLA 48
Start the aplication 50
Step 5: Testing the OSGi Application 52
Step 6: Rolling back the configuration 53
Move the application to the latest Composition unit 54
Result: 57
Summary 58
Introduction
In this example we look at a simple OSGI application & bundles along with deploying these assets to WAS.
Resources:
OSGi Examples
OSGI Technology Overview
OSGI or Open Services Gateway Initiative is a common way to implement Service Oriented programming inside a single JVM, this form of programming was available for J2SE programming only until the introduction of the OSGI feature pack for WebSphere Application Server 7.5 and is lately fully available in WebSphere 8.0.
This tutorial will not try to explain why OSGI programming model is good or any best practices of how to implement it correctly, what it will explain is how to create your first OSGI “Hello World – Type” application and understand the basic capabilities inside the OSGI implementation.
Project Structure
Let’s first discuss the structure of the application which we want to build for
illustrating capabilities.
Enterprise Assets (BLA’s) :
- OSGICalculatorInterface (symName: OSGICalculatorInterface,version 1.0)
- OSGICalculatorImplV1 (symName: OSGICalculatorImpl, version 1.0)
- OSGICalculatorImplV2 (symName: OSGICalculatorImpl, version 2.0)
- OSGICalculatorImplV3 (symName: OSGICalculatorImpl, version 3.0)
- OSGICalculatorServlet (symName: OSGICalculatorServlet, version 1.0)
Business Level Applications (EBA)
- OSGICalculatorAPP (symName: OSGICalculatorAPP, version 1.0)
Product Lifecycle
OSGI is all about promoting modularity, loose coupling and code reuse, what we will do in this demo project , is to create three different versions of the same OSGI bundle (OSGICalculatorImpl) and we will deploy at as software assets into the internal OSGI registry as assets, then we will develop an application which will consume one of those assets.
Once the application is done and tested we will discover that our implementation was incorrect and we will need to change to some previous version of the implementation prior to the time the defect was introduced. In a non OSGI environment this will need to include rebuilding the application with different code and redeploying the application which will force an application restart. In an OSGI environment things will be quite different.
Step 1: Creating the business interface
Creating a business interface called OSGICalculatorInterface within a new OSGI Bundle Project
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Make sure you uncheck “Application Membership”
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Click Next, Next
Make a note of the following screen and noted own the Symbolic Name Field which is the Bundles ID and also the version qualifier which is the version of the bundle we will want to build.
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Symbolic Name (ID): OSGICalculatorInterface
Version: 1.0.0.qualifier
Click Finish, then using the project explorer create a new package called calc
Create a new interface named as OSGICalculatorInterface
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Click Finish
Open the manifest editor as seen below
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Navigate to the runtime tab and export the interface by clicking add and selecting calc package
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Then select again and add version 1.0 to it’s version as seen below.
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Result
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Step2: Creating the Business Implementations
Create a new OSGI Bundle using the process we just completed with the following properties
Project Name = OSGICalculatorImpl
Application Memebership = unchecked
Symbolic Name = OSGICalculatorImpl
Version = 1.0.0.qualifier
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Finish
Creating a new package to contain implementations
Create a new package called calc.impl
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Edit the manifest as before
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Using the Manifest Editor, add a dependency as an imported package.
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Save
Creating an implementation class
Create a new class in the calc.impl package
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Call the class OSGICalculator and make sure it implements the OSGIInterface as seen below
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Using Quick Fix import the messing package ie the Interface
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Using Quick fix add the unimplemented methods as declared by the interface, use right-mouse click
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Or use CTRL-1 to see quick-fix
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Ensure your class has the following code:
/**
* Exercise 12 - OSGI
*/
package calc.impl;
import calc.OSGICalculatorInterface;
/**
* @author
Steve Robinson
*
*/
public
class
OSGICalculator
implements OSGICalculatorInterface {
@Override
public
int add(int x, int y) {
// TODO Auto-generated method stub
int result = x + y;
System.out.println(“OSCICalaculator V1 was [Add] invloked!”);
return result;
}
@Override
public
int mult(int x, int y) {
// TODO Auto-generated method stub
int result = x * y;
System.out.println(“OSCICalaculator V1 was [MULTIPLY] invloked!”);
return result;
}
}
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As you can see in the code above, is contains basic implementations of an Add and Multiply operations. This is the only implementation that is correct in this demo, all other examples will be wrong. This will enable us to demo OAGI capabilities for correcting an application.
Open the manifest editor and make sure to add the calculator implementation you have just created, to the exported packages as seen below.
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Save
Export the bundle
Export your bundle to a suitable location is c:\temp or temp etc
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Deploy a bundle using WAS console
Ensure WAS is running and log into the console for example: http://localhost:9061/ibm/console/
Navigate to Environment -> OSGi bundle repositories -> Internal bundle respository
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Click New
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Browse for your JAR file:
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Click OK, then Save
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The result will be that you see the OSGICalculatorImpl V1 bundle
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Complete the remaining 2 bundles
Using the exact same process, create two more Implementation Bundles. Make sure each on has an error, ensure that you set the Version to be 2.0.0.qualifier, 3.0.0.qualifer so we can identify the version 2 and 3 which contains errors.
Also double check that you use the same Implementation name : OASICalculatorImpl.
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Result:
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Set up the classes as required, edit the manifest and exports as per V1 earlier.
Example V2 Error
/**
* Exercise 12 - OSGI
*/
package calc.impl;
import calc.OSGICalculatorInterface;
/**
* @author
Steve Robinson
*
*/
public
class OSGICalculator implements OSGICalculatorInterface {
@Override
public
int add(int x, int y) {
// TODO Auto-generated method stub
int result = x + x;
System.out.println(“OSCICalaculator V1 was [Add] invloked!”);
return result;
}
@Override
public
int mult(int x, int y) {
// TODO Auto-generated method stub
int result = x * x;
System.out.println(“OSCICalaculator V1 was [MULTIPLY] invloked!”);
return result;
}
}
|
Example V3 Error
/**
* Exercise 12 – OSGI
*/
package calc.impl;
import calc.OSGICalculatorInterface;
/**
* @author Steve Robinson
*
*/
public class OSGICalculator implements OSGICalculatorInterface {
@Override
public int add(int x, int y) {
// TODO Auto-generated method stub
int result = y + y;
System.out.println(“OSCICalaculator V1 was [Add] invloked!”);
return result;
}
@Override
public int mult(int x, int y) {
// TODO Auto-generated method stub
int result = y * y;
System.out.println(“OSCICalaculator V1 was [MULTIPLY] invloked!”);
return result;
}
} |
Your project explorer should look like this:
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Set the manifests
Make sure your manifests are set for identifying versions when exported
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Export and import separate JAR files (Bundles) using the process for V1.
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Import in to WAS (Deploy)
Import into WAS as per the version on import process.
Result
Result after imports:
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Tip: When exporting you can add timestamps to further identify versions.
Step 3: Creating the Servlet bundle
Create a new bundle project called OSGICalculatorServlet
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Add an OSGI Dependency as an imported package, but adding the manifest
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Result:
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Note: the calc.impl is used without an explicit version in order to enable accessing the implementation which is currently active (not static with a version). To remove an actual vision, click bundle -> properties to remove the version number.
Creating the OSGICalculatorServlet
Create a new package called servlets in the OSGICalculatorServlet Project.
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Create a new Servlet called OSGICalculatorServlet in the servlets package
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Take note of the mappings for later
/OSGICalculatorSevlet
Generate doGet()
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Modify the doGet() method
Modify the doGet() Method to as seen below.
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Here is the code you need to enter:
protected
void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
OSGICalculator calc = new OSGICalculator();
int result = calc.add(12, 13);
System.out.println(“result=” + result);
} |
Note: There is no mentioning of a specific version! During the call to V1, V2, V3 etc.
Step 4: Creating the OSGI Application
Now we have our modular OSGi bundles, we an create an OSGi application.
Create a new OSGi Application Project called OSGICalculatorApp
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Next
In the Contained OSGi Bundles and Composite Bundles screen select the required bundles. In this example we are including the V3 defect bundle i.e. where we have y+y and y*y which is the wrong implemented business logic.
OSGICalculatorInterface
OSCICalculatorImpl 3.0.0
OSGICalculatorServlet
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Click Finish
Result
Result as seen in Project Explorer
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If you look at the OSGICalulatorApp’s Manifest you can see the following:
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In order for the application to use previous versions of bindles, click the OSGICalculatorImpl – > properties and set the minimum version to match.
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Result of the manifest update
Verify your manifest is updated as required.
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Save
Export the application
Export the OSGi App
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Deploy Assets
Log into the Administrative Console of WAS,
Navigate to Applications -> Application Types -> Assets
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Click Import
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Click Next until end
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Save
Result:
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Create a new BLA
Navigate to Applications -> Business Level Applications – New
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Apply, Save
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Add assets to the BLA
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Click Next, Next, not the Context Root of the application’s servlet
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Click Next, Next then Finish
Click Save
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Start the aplication
Start the application and check SystemOut.log
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Result:
| [07/11/12 13:23:49:952 GMT] 00000059 StepStartBLA A CWWMH0196I: Business-level application “WebSphere:blaname=OSGICalculatorApp” was started successfully. |
Step 5: Testing the OSGi Application
http://localhost:9081/OSGICalculatorServlet/OSGICalculatorServlet
Result:
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Logs:
[07/11/12 13:29:29:389 GMT] 00000033 servlet I com.ibm.ws.webcontainer.servlet.ServletWrapper init SRVE0242I: [AsynchronousServletEAR] [/AsynchronousServletEARWeb] [AsyncServlet]: Initialization successful.
[07/11/12 13:29:29:545 GMT] 00000061 SystemOut O AsyncWorker:Class: ENTER run
[07/11/12 13:29:29:545 GMT] 00000037 SystemOut O Event completed.
[07/11/12 13:30:10:764 GMT] 00000036 servlet I com.ibm.ws.webcontainer.servlet.ServletWrapper init SRVE0242I: [OSGICalculatorApp..1.0.0.201211071302..OSGICalculatorServlet..1.0.0.201211071302.war] [/OSGICalculatorServlet] [sevlets.OSGICalculatorServlet]: Initialization successful.
[07/11/12 13:30:10:764 GMT] 00000036 SystemOut O OSCICalaculator V1 was [Add] invloked!
[07/11/12 13:30:10:764 GMT] 00000036 SystemOut O result=26
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We can see that we are getting the result [26] y=13 + y=13, we want x=12 + y=13 [25]
We need to roll back the application to a previous implementation in order to get the correct intended results.
Step 6: Rolling back the configuration
Navigate to Application -> Application Types -> Assets -> OSGICalculatorApp.eba -> update bundle versions for this application.
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Click Preview, then Create
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Save
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We have only updated the assets.
No changes were made to the running application, until we move the application to the latest composition unit.
Move the application to the latest Composition unit
Navigate to Applications -> Business-level Applications
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Select the OSGICalculatorApp, and locate the EBA.
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Locate and click “Update to latest deployment ..”
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Review, then click OK
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Save changes
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Invoke the Servlet again
Result:
[07/11/12 13:41:29:249 GMT] 00000035 servlet I com.ibm.ws.webcontainer.servlet.ServletWrapper init SRVE0242I: [OSGICalculatorApp..1.0.0.201211071302..OSGICalculatorServlet..1.0.0.201211071302.war] [/OSGICalculatorServlet] [sevlets.OSGICalculatorServlet]: Initialization successful.
[07/11/12 13:41:29:264 GMT] 00000035 SystemOut O OSCICalaculator V1 was [Add] invloked!
[07/11/12 13:41:29:264 GMT] 00000035 SystemOut O result=25 |
Congratulations, you have now completed the basics of OSGi Development, Deployment & Management.
Summary
The tutorial has introduced the concepts of OSGi and the flexibility with the programming model it provides. We have learned that we can modularize our components in to composite units (assets) and use the WebSphere Application Server’s Business Level Application concepts mage assets versions. OSGi also supports roll back in very easy to understand process. We have now harnessed the power of both OSGi and WAS. OSGi offer significant power and flexibility to those who choose to use it.
