Updating Android SDK using Eclipse on Windows 7

Recently I was trying to get my head around few errors related to Android SDK updates. I wanted to upgrade the API and install few updates related to SDK tools.

When you open Android SDK Manager, you expect to load all updates and other packages automatically. But this is not the case when you start your Android SDK Manager in Eclipse (Pretty bad).

By default, download cache is enabled and Android SDK Manager uses cache to load the data.

By disabling cache you can see the available updates.

• Click Tools > Options. 
• Uncheck Use download Cache checkbox.
• Hit Clear Cache button.
• Restart Android SDK Manager.

Now you should see available updates.

IE 8 and Ajax Support

Recently I came across few bugs related to IE 8, Ajax and JSF.
The main issue was a delay in firing ajax events in IE 8. For example, when user clicked on a radio button, the event did not fire immediately. The event did not get fired on first click. User had to click on radio button and then somewhere else on web page to see the expected result. After spending some time, I found the solution. The solution is using Javascript blur() function,

The blur function is used to remove the focus from the object that it belongs to. Before applying this solution, user had to click somewhere else on webpage to remove the focus from the current object.

Here is the code sample. Write simple Javascript function to blur the object.

Then in html/jsp/xhtml code we call function blurAction on the onclick attribute.

The clicked object becomes non-current immediately and we can fire ajax events.

Using Exception Handlers in CXF

I was developing a web application and used Apache CXF for developing RESTful web-services. During the development we often come across scenarios where the expected entity does not exist in database. In RESTful web-services we form our own URLs to access the web-service and get the response. It is a common test scenario where one can try to access some data using such urls and that data may not be present in database at all.
For Example, lets see I am accessing company information using its name via webservice.

Say the URL looks like http://localhost:8080/resource/company/developmentCompany.


Lets say but the database does not contain any row for developmentCompany. Obviously the query will fail and end up throwing exception.


We can always handle such exceptions using null checks but it is more accurate to handle such exceptions using some ExceptionMappers which will show some User friendly message. In CXF, we can create our own ExceptionMappers to handle such scenarios in following way.


    Create your own Mapper class which will implement
     javax.ws.rs.ext.ExceptionMapper interface and use the actual exception  
    class as a parameter class to javax.ws.rs.ext.ExceptionMapper. Now your 
    mapper class needs to implement the method toResponse(E exception).

public class NoResultMapper implements ExceptionMapper<javax.persistence.noresultexception>{
  private static Logger logger = Logger.getLogger(NoResultMapper.class.getName());
  @Override
  public Response toResponse(NoResultException exception) {
  logger.warn("Result not found.. The entity does not exist in database." + exception.getCause() + ": " +                   
                                 exception.getMessage());
  return Response.serverError().entity(new GenericError("Result not found.. The entity does not exist in database.",   
  exception.getCause() + ": " + exception.getMessage())).build();
}

After creating your own mapper, you need to declare your mapper in your service beans xml file.

<bean id="noResultMapper" class="exceptionMappers.NoResultMapper" /> 

Enables/Disable CXF Logging (payload)

I was using Apache CXF web-service framework. Its usually good to have logging enabled in applications. But with cxf I observed that cxf keeps logging the payload of every response received from a web-service. The web service was returning images which massively affected the size of log files. I used log4j logger to log the messages and removed the cxf logging.


To remove cxf logging just comment out or remove code the following code from your cxf configuration xml file.
   

          

                            

EclipseLink: Null primary key encountered in unit of work clone

I came across this weird issue while using EclipseLink 2.0 with JPA 2.0. It isn't actually that complicated as it looks. Though I spent lot of time figuring out whether any objects have null id or negative id. Finally figured out that, The database had rows with id as '0'. By default EclipseLink treats zero ids as null. I don't


Simple fix is to tell EclipseLink to treat '0' as a valid id and not null. It can be done by specifying the property in persistence.xml 


In persistence.xml add the following property to get rid of this exception. 


     <property name="eclipselink.allow-zero-id" value="true"/>


This property simply tells EclipseLink to treat '0' as a valid primary key instead of null.