It's nice that Eclipse uses service oriented architecture more and more, but am I only the developer who sees the lack of knowledge of by what plug-in and at what stage service is registered as a problem?
Consider example:
IServiceLocator someServiceLocator = ...
SomeService someService = (SomeService)someServiceLocator.getService(SomeService.class);
// oops, someService is null
Possible reasons to why someService is null are:
Some plug-in that registers this service doesn't present or not loaded
Service wasn't registered yet
How should one resolve this? Are there any tools?
Thanks.
The short answer: there are no tools available.
For the complete list of services and where they are registered do "Call Hierarchy" on ServiceLocator.registerService(Class api, Object service).
For a good list of the available global services, look at Workbench.initializeDefaultServices(). There are some additional services that are only available at the window or workbench part level.
If you want to know what plugins are installed and started, you can use the OSGI console and see the state of the plugins.
So if you are looking for a service "XService", find the plugin which contains the service and look for the plugin state on the OSGI console.
Start you application with -console option and type ss on the osgi console. This is not straight forward but works.
Related
I am new in liferay want to perform crud operation using service builder so i want to understand need & use of apache felix web console bundle in liferay 7.1 so that i use it in order to check json/webservice api.
I would say you are not looking at the right tool for the job.
The console enables you to interact with the OSGi framework, a good place to start is not on the console but on the file systems if you are looking into understanding how Liferay uses the framework. The framework is embedded into the web app in order to provide the environment where bundles can live and provide services collectively.
Gogo is an auxiliary tool that enables interaction, you can query if bundles are installed, check the dependencies that you missed and who is providing a certain service or exposing a package.
Most of day-to-day of this kind of information you can also find in the app manager and/or logs.
About testing you api, I assume you are looking for seeing if it was installed and if it was resolved and activated. The app managers can provide the first clue for this, but gogo is an adequate tool as well, you will need to learn its commands and syntax. Do not worry they are trivial, you can find a description on the Apache's project page an on Liferay's dev guide.
Now, if you are looking to test the API for correctives or availability, using gogo will demand custom commands and lots of extra logic other tools provide for you.
I am new to Distributed Tracing / Hawkular. And would like to experiment tracing for my distributed cxf rest services using hawkular.
Will it be possible to trace cxf servcies using hawkular and if any one has doc or reference sample app, that will be great.
Also, is there any other tracing tool which can solve this requirement(tracing java cxf rest services). Zipkin-brave has a feature for this which I am looking at also.
I'd recommend instrumenting your application using the OpenTracing API, and later choose a concrete implementation. Under the Hawkular project, there's the Hawkular APM module which provides a solution for capturing, visualizing and making sense of the data. However, we (Hawkular APM) recently decided to join the Jaeger project, to have a better support for the OpenTracing case. We expect to have similar features from Hawkular APM ported to Jaeger "soon".
For OpenTracing, there are quite a few "framework integrations" under the OpenTracing Contrib organization, including JAX-RS, which might serve as base or reference for a CXF-specific implementation. If nothing suits you, I'm certain we'd welcome a contribution.
If you are just looking to learn OpenTracing, I'd suggest taking a look at the Hawkular APM's example directory, including a vertx-opentracing example.
i have osgi services service-1.0.0.jar and service-1.1.0.jar they are implementation of service-api-1.0.0.jar
both these service-1.0.0.jar and service-1.1.0.jar have same service name and packages.
service are registered by bundle-activator
lets assume bundle activator is com.abc.xyz.MyActivator - 1.0.0 and 1.1.0
issue I am facing is when I deploy these services and lookup using service tracker and filter on version I want, I always get same implementation regardless of what version chosen.
this makes me believe that what i am trying to achieve is not doable.
I need multiple implementation of service packaged in separate bundles with difference of version and be able to choose dynamically at runtime.
I am trying this in jboss-6.1.1 eap
if i keep different package name in versions looks like it is able to understand that these are 2 different services but when package names are same i get same service implementation.
am i doing something wrong? has anybody tried this?
is it correct that OSGI allow you to deploy multiple versions of service?
UPDATE After using unique package names for MyActivator in 1.0.0 and 1.1.0 looks like the services are able to maintain the uniqueness.
Does that mean Activators has to unique across bundles?
I assume that service-api-1.0.0.jar exports the package which defines the service interface. In that case, it sounds like you have two implementations of the same version of the service. Not different implementations of different versions of the service. So from a service user point of view, the services are that same: they are from the same service api package version.
I think you are using the OSGi services in a strange way. As a client you should not look into the implemention bundles to determine versions or other informations.
Instead you should use the service interface and service properties to distinguish between services.
So for example you can have a property version and publish the first service with version=1 and the second with version=2. Then you can filter for this property to get a specific service.
Using reflection is also a rather unusual thing. Better try to provide classes in the interface package that you use to exchange data between client and service. This will make the client less dependent on the service impl.
If you have multiple implementations of the same service API, and a client queries for an implementation of the service API, it could get any of the implementations. And that's good because the client shouldn't care.
Say for example you have a Greeting interface with multiple implementations registered as services, possibly by multiple bundles. If a client asks OSGi for a Greeting service then OSGi will simply pick one. After all, if you just ask for a Greeting without specifying anything else then you should accept any implementation. Clients certainly shouldn't care which particular bundle the service comes from: this is the nature of decoupling.
Incidentally, when this happens OSGi normally chooses the implementation that was registered first (actually the one with the lowest service.id, which is an ever-incrementing number, so it's effectively the same thing). This is probably why you see OSGi consistently choosing one particular service.
If your client needs to distinguish between service implementations then you can add properties to the published services and filter on those services. For example one bundle could publish a Greeting service with property language=en_US (i.e. US English) and another could publish a Greeting service with language=de. If your client only wants greetings in English then it can use a filter like (language=en*).
I've always used eclipse before, but I'm using Netbeans for the first time because of it's integration with Web Service clients.
However, after following multiple tutorials, the way to add a web service client is to:
https://netbeans.org/kb/docs/websvc/flower_swing.html
Make a new project
Right click on your project, New->Other->Other->Web Service Client
However, I do not have the web service client option available, not sure what I am doing wrong.
Please mention the net beans version you have. You should use newer version of the IDE to use latest features.
For other developers who will face this problem like me, I will leave my answer here.
I'm currently using Apache NetBeans IDE 11.0 and it's in Web Services -> Web Service Client. If you still cannot find it, just use filter feature. I found it with filter.
I have a scenario where during the system install time, a few services were deployed on to the OSGi container and these services will be listening for other bundles that provide data and are dynamically installed and uninstalled at runtime.
These data providers do not expose any services and should not even invoke services; my idea is to enable the pre-deployed services to listen for the event of installation of these data provider bundles and if the pattern matches, then process and persist the data into the data store.
For example I have a WidgetService which will listen for installation or uninstallation event of Widget data provider bundles, ShppingCartService that will listen for the installation/uninstallation events from ShoppableItem data provider bundles, etc.
This helps me to keep the processing and persisting logic be centralized and my data providers need not write any code to make their data processed. All that is expected from the data provider bundles is the Service Name/id, Service Version,PreRequisites, and the data that they need to publish.
I have read several articles on OSGi that explain dynamic pluggability of services and the clients able to discover or discard services based on their availabity; however, those are all talking about scenarios where clients are to be intelligent to discover and execute the services they are interested in.
My intention is to make client completely unaware of any service discovery, for that matter any code. All that the client passes is the info about the service the client is interseted in, the dependencies, and the data; the client should be completely dumb.
Is this possible in OSGi? I'm ready to consider this architecture even at the cost of extending a few of the OSGi core framework classes!
I have found some what, may be, remotely related question on stack overflow at :
Discovering Bundle MetaData with out installing the bundle
However, I want a hook or an event that will call my respective service when one or more data provider bundles have been installed. These data provider bundles can be interested in any of the services that are installed in the system. I'm even ready to write a central bunle repository manager/listener kind of stuff that will listen to any bundle installation and invoke my Service facade that will decide which service to execute based on the meta data provided by the data provider bundle.
I'm just starting OSGi, so need a little direction on how to move forward...
I'll be really thankful to you guys/girls :) if you can help me achieve this!
I have a doubt deep in my mind that this may not be readily available in OSGi, and even if that is true I'm ready to spend time and extend the framework to achieve this. All I need is a few guidelines and a clear direction. Who knows, if OSGi is really lacking this functionality, then it would be a very useful add-on to a future OSGi spec.
You might have a look at section 4.7 (Events) of the OSGi Core spec. The Framework raises BundleEvents when there is a change in the lifecycle of a bundle, e.g. when it is installed or uninstalled. What you need to do is to implement a BundleListener, which then will receive the events, so your service can react on the changes.
I have described a design pattern that I call "OSGi Mediator", which may be a solution to your problem.
The items you want to mediate would only require to register with the service registry; all the dependencies could be managed by your mediator implementation.