Need a write a wrapper around DDS RTI for Java

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Need a write a wrapper around DDS RTI for Java

Hi 

  I need to write a generic wrapper for DDS-RTI Java. The wrapper should be able to handle any datatype I have defined under idl. But the problem is RTi is creating class for each data type e.g. HelloworldSupport. My requirement is based on the datatype passed I should create corrospoding *Support Object

For C++ I can see C++ trait is there to handle this situtation. Can you please give an excample how to handle this in Java. I am newbie in Java

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Last seen: 1 year 1 month ago
Joined: 01/31/2011
Posts: 37

Hi mr_deb,

Unfortunately, there's no equivalent to the C++ traits for Java.  However, there is an alternative that makes use of Java reflection.  Below is the code for registering a type named "Foo":


Class<?> type = resolver.resolveClass("FooTypeSupport");
if (type == null) {
   throw new Exception("Cannot resolve class " + className);
}
Method getInstanceMethod = null;
Method getTypeNameMethod = null;
Method registerTypeMethod = null;
try {
  // retrieve the "get_instance" method (e.g. FooTypeSupport.get_instance())
  getInstanceMethod = type.getMethod("get_instance");
  // retrieve the "get_type_name" method (e.g. FooTypeSupport.get_type_name())
  getTypeNameMethod = type.getMethod("get_type_name");
  // retrieve "register_type" method (e.g. FooTypeSupport.register_type())
  registerTypeMethod = type.getMethod("register_type", DomainParticipant.class, String.class);
} catch (Exception e) {
  throw new Exception("Invalid TypeSupport class " + className);
}
// invoke get_instance method
TypeSupportImpl inst = (TypeSupportImpl)getInstanceMethod.invoke(null);
// invoke get_type_name method
String typeName = (String)getTypeNameMethod.invoke(null);
if (typeName != null && inst != null) {
   // invoke register_type method
   registerTypeMethod.invoke(null, getValue(), typeName);
}

The fully qualified name of the TypeSupportImpl class is com.rti.dds.topic.TypeSupportImpl.  It's the base interface for all TypeSupport classes.

Second, you can use the *_untyped() API when writing or reading data. For example, when you create a DataWriter for a given topic and type, you use the  create_datawriter() call on a com.rti.dds.publication.Publisher. This method returns an object of type com.rti.dds.publication.DataWriter, which is the base interface for all DataWriters.

This DataWriter interface contains a method called " write_untyped()" that takes an object of type "Object" as argument.  Note that you cannot pass an arbitrary object; it still must be an object that is of the same type (class) as for the topic itself. So if you've registered a type Foo with the participant, then created a topic using type Foo, and then created a DataWriter for this topic ... you must pass in a Foo object to the write_untyped() method.

Hope this helps.

-sumeet

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Last seen: 5 years 5 months ago
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Hi Sumeet

  Thanks a lot for your detail answer. I can also see FooDataWriter also at the end calls write_untype method for wrting. I will try it and will bother you if I need help. 

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We followed the above design for writing the wrapper.and we are facing the problem similar to  (http://stackoverflow.com/questions/22905914/java-passing-generic-type-to-an-another-generic-type-class).

 

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Last seen: 1 year 1 month ago
Joined: 01/31/2011
Posts: 37

Hi mr_deb,

Can you provide more details about the specific problem you are seeing? A code sample plus the exception or error would be helpful.

Thanks,

-sumeet

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Last seen: 1 year 6 months ago
Joined: 07/12/2012
Posts: 51

I would be interested to know if this problem, of a generic wrapper can be address with Java generics. If so, an example would be helpful.

Thanks

Nico