DDevelopment & Design

OSGi Blueprint visualization

What is blueprint?Blueprint is a dependency injection framework for OSGi bundles. It could be written by hand or generated using Blueprint Maven Plugin. Blueprint file is only an XML describing beans, services and references. Each OSGi bundle could hav…

What is blueprint?

Blueprint is a dependency injection framework for OSGi bundles. It could be written by hand or generated using Blueprint Maven Plugin. Blueprint file is only an XML describing beans, services and references. Each OSGi bundle could have one or more blueprint files.

Blueprint files represent architecture of our bundle. Let’s visualize it using groovy script and graphviz available in my github repository and analyze.

Example generation

Pre: All you need is groovy and graphviz installed on your OS

I am working mostly with bundles with generated blueprint, so I will use blueprint file generated from Blueprint Maven Plugin tests as example. All examples are included in github repository.

Generation could be invoked by running run.sh script with given destination file prefix (png extension will be added to it) and path to blueprint file:

mkdir -p target

./run.sh target/fullBlueprint fullBlueprint.xml

Visualization is available here.

Separating domains

First if you look at the image, you see that some beans are grouped. You could easily extract such domains with tree roots: beanWithConfigurationProperties and beanWithCallbackMethods to separate blueprint files and bundles in future and generate images from them:

./run.sh target/beanWithCallbackMethods example/firstCut/beanWithCallbackMethods.xml
./run.sh target/beanWithConfigurationProperties example/firstCut/beanWithConfigurationProperties.xml
./run.sh target/otherStuff example/firstCut/otherStuff.xml

Now we have three, a bit cleaner, images: beanWithConfigurationProperties.png, beanWithCallbackMethods.png and otherStuff.png.

We also could generate image from more than one blueprint:

./run.sh target/joinFirstCut example/firstCut/otherStuff.xml example/firstCut/beanWithConfigurationProperties.xml example/firstCut/beanWithCallbackMethods.xml

And the result is here. The image contains beans grouped by file, but if you do not like it, you could force generation without such separation using option --no-group-by-file:

./run.sh target/joinFirstCutGrouped example/firstCut/otherStuff.xml example/firstCut/beanWithConfigurationProperties.xml example/firstCut/beanWithCallbackMethods.xml --no-group-by-file

It will generate image with all beans from all files.

Exclusion

Sometimes it is difficult to spot and extract other domains. It will be easier to do some experiments on blueprint. For example, bean my1 is a dependency for too many other beans. You could consider converting my1 bean to OSGi service and extracting it to another bundle.

Let’s exclude my1 bean from generation via -e option and see what happens:

./run.sh target/otherStuffWithoutMy example/firstCut/otherStuff.xml -e my1

Result is available here. Now we see, that tree with root bean myFactoryBeanAsService could be separated and my1 could be inject to it as osgi service in another bundle.

You could exclude more than one bean adding -e switch for each of them, e. g. -e my1 -e m2 -e myBean123.

Conclusion

Blueprint is great for dependency injection for OSGi bundles, but it is easy to create quite big context containing many domains. It is much easier to recognize or search for such domains using blueprint visualizer script.

 

YOUR CODE HRER

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DDevelopment & Design

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DDevelopment & Design

Phonegap / Cordova and cross domain ssl request problem on android.

In one app I have participated, there was a use case:
  • User fill up a form.
  • User submit the form.
  • System send data via https to server and show a response.
During development there wasn’t any problem, but when we were going to release production version then some unsuspected situation occurred. I prepare the production version accordingly with standard flow for Android environment:
  • ant release
  • align
  • signing
During conduct tests on that version, every time I try to submit the form, a connection error appear. In that situation, at the first you should check whitelist in cordova settings. Every URL you want to connect to, must be explicit type in: 
res/xml/cordova.xml
If whitelist looks fine, the error is most likely caused by inner implementation of Android System. The Android WebView does not allow by default self-signed SSL certs. When app is debug-signed the SSL error is ignored, but if app is release-signed connection to untrusted services is blocked.



Workaround


You have to remember that secure connection to service with self-signed certificate is risky and unrecommended. But if you know what you are doing there is some workaround of the security problem. Behavior of method 
CordovaWebViewClient.onReceivedSslError
must be changed.


Thus add new class extended CordovaWebViewClient and override ‘onReceivedSslError’. I strongly suggest to implement custom onReceiveSslError as secure as possible. I know that the problem occours when app try connect to example.domain.com and in spite of self signed certificate the domain is trusted, so only for that case the SslError is ignored. 

public class MyWebViewClient extends CordovaWebViewClient {

   private static final String TAG = MyWebViewClient.class.getName();
   private static final String AVAILABLE_SLL_CN 
                               = "example.domain.com";

   public MyWebViewClient(DroidGap ctx) {
       super(ctx);
   }

   @Override
   public void onReceivedSslError(WebView view, 
                                  SslErrorHandler handler, 
                                  android.net.http.SslError error) {

       String errorSourceCName = error.getCertificate().
                                  getIssuedTo().getCName();

       if( AVAILABLE_SLL_CN.equals(errorSourceCName) ) {
           Log.i(TAG, "Detect ssl connection error: " + 
                       error.toString() + 
                       „ so the error is ignored”);

           handler.proceed();
           return;
       }

       super.onReceivedSslError(view, handler, error);
   }
}
Next step is forcing yours app to  use custom implementation of WebViewClient. 

public class Start extends DroidGap
{
   private static final String TAG = Start.class.getName();

   @Override
   public void onCreate(Bundle savedInstanceState)
   {
       super.onCreate(savedInstanceState);
       super.setIntegerProperty("splashscreen", R.drawable.splash);
       super.init();

       MyWebViewClient myWebViewClient = new MyWebViewClient(this);
       myWebViewClient.setWebView(this.appView);

       this.appView.setWebViewClient(myWebViewClient);
       
       // yours code

   }
}
That is all ypu have to do if minSdk of yours app is greater or equals 8. In older version of Android there is no class 
android.net.http.SslError
So in class MyCordovaWebViewClient class there are errors because compliator doesn’t see SslError class. Fortunately Android is(was) open source, so it is easy to find source of the class. There is no inpediments to ‘upgrade’ app and just add the file to project. I suggest to keep original packages. Thus after all operations the source tree looks like:

Class SslError placed in source tree. 
 Now the app created in release mode can connect via https to services with self-signed SSl certificates.