Integrating JAX-RS

[Part 3] Websphere Liberty Profile: OSGi, JPA, JAX-RS, and BPM

Part 3 of 4 Part Series:

Integrating JAX-RS service with OSGi JPA data provider

Part 3: Integrating JAX-RS service with OSGi JPA data provider (this article)

Part 4: Integrated BPM and ReST using OSGi bundles [work-in-progress]

Forward:

I almost gave up this exercise using Liberty... The night before I resigned myself to switching back over to Websphere Application Server.

What held up progress was I couldn't find a work-around for service lookup via InitialContext. Websphere had this feature built-in for OSGi bundles. Liberty also... had this feature. However, I didn't see the missing critical "import-package" on the manifest:

javax.naming

With "javax.naming" in the manifest I was finally able to use the following:

(ColorManager) ic.lookup("osgi:service/"+ColorManager.class.getName());

- or -
(ColorManager) ic.lookup("blueprint:comp/colormanagerservice"); <<< recommended approach

Ironically, I happened to also find another elegant workaround to Liberty's JAX-RS implementation (wink)...

Wink created a new service class per each service request - and, consequently, didn't use the blueprint created instance. This lead to a breakage in blueprint reference injection between JAX-RS and JAP bundles:

Solution was to simply use a static property so that property value is at the class level:

private static ColorManager colorManager = null;

The moral of the story is that, if it should work, it probably does...

OSGi and JAX-RS: Integrating JPA

1) Publish a JPA data-service with JAX-RS Service Interface (ReST)

Publish the JPA service created in previous tutorial

- Requires completion of Part 1 (see above: "Resources")

Import Interface from osgi_jpa_03 (refer to previous tutorial: "part 1: OSGI and JPA")

(refer to previous tutorial: "part 1: OSGI and JPA")

Export from JPA and then import into JAX-RS projects

Export from: osgi_jpa_03

import into: osgi_jaxrs_03a

From osgi_jpa_03, exporting the model package

showing manifest.ms source

Manifest-Version: 1.0

Bundle-Blueprint: OSGI-INF/blueprint/*.xml

Bundle-Version: 1.0.0

Bundle-Name: osgi_jpa_03

Bundle-ManifestVersion: 2

Import-Package: javax.persistence;version="1.1.0",

javax.sql;version="0.0.0",

javax.transaction;version="1.1.0",

javax.xml.bind.annotation

Meta-Persistence:

Bundle-SymbolicName: osgi_jpa_03

Bundle-RequiredExecutionEnvironment : JavaSE-1.6

Export-Package: model

Import the model package into the osgi_jaxrs_03a (our JAX-RS project)

NOTE: Also include package javax.naming

manifest.ms for osgi_jaxrs_03a

Manifest-Version: 1.0

Bundle-ManifestVersion: 2

Bundle-Name: osgi_jaxrs_03a

Bundle-SymbolicName: osgi_jaxrs_03a

Bundle-Version: 1.0.0

Bundle-ClassPath: WEB-INF/classes

Bundle-RequiredExecutionEnvironment : JavaSE-1.6

Web-ContextPath: /osgi_jaxrs_03a

Import-Package: com.ibm.websphere.jaxrs.server;version="1.0.0",

javax.el;version="2.0",

javax.naming,

javax.servlet;version="2.5",

javax.servlet.annotation,

javax.servlet.http;version="2.5",

javax.servlet.jsp;version="2.0",

javax.servlet.jsp.el;version="2.0",

javax.servlet.jsp.tagext;version="2.0",

javax.ws.rs;version="1.0.0",

javax.ws.rs.core;version="1.0.0",

javax.ws.rs.ext;version="1.0.0",

javax.xml.bind.annotation,

model

Create the List container to hold results from queries to JPA color model

Source:

import java.util.ArrayList;

import java.util.List;

import javax.xml.bind.annotation.XmlElement;

import javax.xml.bind.annotation.XmlRootElement;

import model.Color;

@XmlRootElement(name="colorlist" )

public class ColorList {

private List<Color> colorlist = new ArrayList<Color>();

@XmlElement(name = "items")

public List<Color> getColorList() {

return colorlist;

}

public void setColorList(List<Color> list) {

this. colorlist = list;

}

Create the ColorModelService interface

Source:

package colorservice;

import model.ColorManager; // imported from the JPA project

public interface ColorModelService {

public ColorManager getColorManager();

public void setColorManager(ColorManager colorManager);

public ColorList getColorsSTUB();

public ColorList getColors();

}

Create the ColorModelServiceImpl

source:

package colorservice;

import java.util.ArrayList;

import java.util.List;

import javax.naming.InitialContext;

import javax.naming.NamingException;

import javax.ws.rs.GET;

import javax.ws.rs.Path;

import javax.ws.rs.Produces;

import model.Color;

import model.ColorManager;

@Path(value = "/colorservice")

public class ColorModelServiceImpl implements ColorModelService {

// private ColorManager colorManager = null;

// Trying a static property - not sure that I'd use this for a 'real' application.

// see other options below under 'getColoManager()'

private static ColorManager colorManager = null;

public ColorModelServiceImpl() {

System. out.println( "*** ColorModelServiceImpl()");

}

public void startUp() {

System. out.println( "*** ColorModelServiceImpl.startUp CALLED");

}

public void shutdown() {

System. out.println( "*** ColorModelServiceImpl.shutdown CALLED");

System. out.println( "*** setting colorManager to NULL");

ColorModelServiceImpl. colorManager = null;

}

public ColorManager getColorManager() {

if (ColorModelServiceImpl. colorManager == null) {

System. out.println( "*** ColorModelServiceImpl.getColors().colorManager is NULL! ");

}

// ----------------------

if (ColorModelServiceImpl. colorManager == null) {

System. out.println( "*** Setting colorManager with osgi service lookup");

try {

InitialContext ic = new InitialContext();

// this.colorManager = (ColorManager) ic.lookup("osgi:service/model.ColorManager");

// The next two methods of lookup work with Liberty v8.5.0.2

// this.colorManager = (ColorManager) ic.lookup("osgi:service/"+ColorManager.class.getName());

ColorModelServiceImpl. colorManager = (ColorManager) ic.lookup("blueprint:comp/colormanagerservice" );

} catch (NamingException e) {

e.printStackTrace();

} catch (Exception e) {

e.printStackTrace();

}

// ----------------------

return colorManager;

}

public void setColorManager(ColorManager colorManager) {

System. out.println( "*** ColorModelServiceImpl.setColorManager()");

ColorModelServiceImpl. colorManager = colorManager;

}

@Override

@GET

@Path("stub")

@Produces("application/json")

public ColorList getColorsSTUB() {

ColorList colorList = new ColorList();

List<Color> list = new ArrayList<Color>();

list.add( new Color( "blue", "blue"));

list.add( new Color( "green", "green"));

list.add( new Color( "purple", "purple"));

colorList.setColorList(list);

return colorList;

}

@Override

@GET

@Path("getcolors")

@Produces("application/json")

public ColorList getColors() {

ColorManager cMgr = getColorManager();

List<Color> list = cMgr.getColor();

ColorList colorList = new ColorList();

colorList.setColorList(list);

return colorList;

}

---------------------------------------------

ColorModelServiceImpl Review:

NOTE: Only covering the interesting bits

---------------------------------------------

private static ColorManager colorManager = null;

Both CXF and Wink (JAX-RS implementations) create a new ColorModuleServiceImpl per each invocation. Though I've read of a few methods, via blueprint, in guiding proper managed startup... I haven't been able to make them work. I listed three work-arounds in source:

1) use a static colorManager property

2) InitialContext().lookup("osgi:service/model.ColorManager")

3) InitialContext().lookup("blueprint:comp/colormanagerservice")

#3 is the IBM's recommended approach

I choose #1 for simplicity - though, I probably wouldn't go with this approach normally and prefer to pull instances from some sort of a managed pool of ready connections.

------------------------------------------------

public ColorManager getColorManager()

Normally this simply returns the static property colorManager. Earlier however, I was having some trouble getting Wink to use my "officially" blueprint managed ColorModelService instance. The method's details illustrates other methods for working around object lookup.

------------------------------------------------

public void setColorManager(ColorManager colorManager)

Blueprint requires the setter for dependency wiring. As blueprint creates a "managed" bean, this property is automatic set via "property reference" (see below details under "blueprint").

------------------------------------------------

public ColorList getColorsSTUB ()

This test STUB returns a fully constructed color list without needing a JPA connection into our database.

public ColorList getColorsSTUB() {

ColorList colorList = new ColorList();

List<Color> list = new ArrayList<Color>();

list.add( new Color( "blue", "blue"));

list.add( new Color( "green", "green"));

list.add( new Color( "purple", "purple"));

colorList.setColorList(list);

return colorList;

}

------------------------------------------------

public ColorList getColors()

The primary responsibility for this class is to fetch colors from the database via JPA

public ColorList getColors() {

ColorManager cMgr = getColorManager(); // gets a reference to the color manager (JPA entity wrapper)

List<Color> list = cMgr.getColor(); // fetch a list of color entities

ColorList colorList = new ColorList(); // create ColorList wrapper - required for JSON/XML construction

colorList.setColorList(list); // set list into the container

return colorList;

}

1a) Configure Blueprint

Add ColorModelServiceImpl.class to AppService

package colorservice;

import java.util.HashSet;

import java.util.Set;

import javax.ws.rs.core.Application;

public class AppService extends Application {

@Override

public Set<Class<?>> getClasses() {

Set<Class<?>> classes = new HashSet<Class<?>>();

// URL http://babe:9080/osgi_jaxrs_03a/jaxrs/servicetest

classes.add(ServiceTest. class);

// http://babe:9080/osgi_jaxrs_03a/jaxrs/colorservice/stub

// http://babe:9080/osgi_jaxrs_03a/jaxrs/colorservice/getcolors

classes.add(ColorModelServiceImpl.class);

return classes;

}

2) Configure Blueprint

Create blueprint.xml

right-click project -> select "other" -> filter on "bue" -> select Blueprint File"

-> Next

New Blueprint File

Select default location for this OSGi type of project

"osgi_jaxrs_03a/WebContent/OSGI-INF/blueprint"

-> next

Add blueprint namespaces

-> Finish

Create a "Bean"

Select "Blueprint" -> click "add"

Add a Bean

Select "Bean" click "OK"

New Blueprint Bean

click "Browse" -> filter on "colorservice." -> select ColorModelServiceImpl from osgi_jaxrs_03a project

NOTE: Make sure you select the class from the correct project !

Create new blueprint bean

Leave default recommendation for Bean ID

-> OK

Bean Created

Create Reference

Select "blueprint" -> click "add"

Select Reference

Select "Reference" -> click "OK"

Select Interface to Reference

Don't forget we're adding a reference into osgi_jaxrs_03a (JAX-RS) project

-- We're referencing an interface within the osgi_jpa_03 (JPA) project

Click "Browse" -> select ColorManager interface from osgi_jpa_03 project

-> OK

Leave Component name blank!

Bean and Reference created from osgi_jaxrs_03a project

Reviewing references

The bean class points to colorservice.colorModelServiceImpl

The reference interface points to model.ColorManager interface within osgi_jpa_03 project

Property colorManager points to reference ColorModelServiceImplBeanReference

Create a Property for ColorModelServiceImplBean

Select ColorModelServiceImplBean -> click Add

-> Select Property -> click OK

Set Property Details

select the property we just created -> Details Reference Browse ->

-> select Reference: ColorModelServiceImplBeanReference -> OK

Set Property Details (continued)

Set Name -> colorManager

NOTE: "colorManager" the property from class ColorModelServiceImpl (see above code review)

Blueprint property requires a setter to set value (wire) ColorManager to ColorModelService (ReST API)

Create Reference Listener for ColoModelServiceImplBeanReference

Select referecne -> click "add" -> select Reference listener

-> OK

Fill in Reference Listener Details

Click Browse -> select Reference (created above) -> OK

Reference Listener Method References

Fill in method names:

Bind: referenceBind

Unbind: referenceUnBind

Reference Listener methods point to ColorManagerImpl methods (from JPA project)

3) Create OSGi Application and Deploy to Liberty Server

Create OSGi Application Project

Add projects:

- osgi_jpa_03 (jpa project)

- osgi_jaxrs_03a (JAX-RS project)

Deploy project to Liberty Server and Start

Log output: messages.log

Right-click service and copy/paste url into browser

Test Works

==============

DONE

==============