DataWriter Use Cases

Working with data writers. More...

Working with data writers.

Setting up a data writer

• Set up publisher
• Set up a topic
• Create a data writer, FooDataWriter, of user data type Foo:

  DataWriterQos writer_qos = new DataWriterQos();
  
  // MyWriterListener is user defined and 
  // implements DataWriterListener
  MyWriterListener writer_listener = new MyWriterListener(); // or = null
  
  publisher.get_default_datawriter_qos(writer_qos);
  
  FooDataWriter writer = null;
  try {
      writer = (FooDataWriter) publisher.create_datawriter(topic, writer_qos,
                                                           writer_listener,
                                                     StatusKind.STATUS_MASK_ALL);
  } catch (RETCODE_ERROR err) {
      // handle exception
  }

Managing instances

• Getting an instance "key" value of user data type Foo

  Foo data = ...;     // user data
  
  try {
      writer.get_key_value(data, instance_handle);
  } catch (RETCODE_ERROR err) {
      // ... check for cause of failure
  }    

• Registering an instance of type Foo

  InstanceHandle_t instance_handle = InstanceHandle_t.HANDLE_NIL;
  
  instance_handle = writer->register_instance(data); 

• Unregistering an instance of type Foo

  try {
      writer.unregister_instance(data, instance_handle);
  } catch (RETCODE_ERROR err) {
      // ... check for cause of failure
  }  

• Disposing of an instance of type Foo

  try {
      writer.dispose(data, instance_handle);
  } catch (RETCODE_ERROR err) {
      // ... check for cause of failure
  }  

Sending data

• Set up data writer
• Register instance
• Write instance of type Foo

  Foo data = new Foo();     // user data
  
  InstanceHandle_t instance_handle
      = InstanceHandle_t.HANDLE_NIL; // or a valid registered handle
  
  try {
      writer.write(data, instance_handle);
  } catch (RETCODE_ERR err) {
      // ... check for cause of failure
  }

Tearing down a data writer

• Delete DataWriter:

  try {
      publisher.delete_datawriter(writer);
  } catch (RETCODE_ERR err) {
      // ... check for cause of failure
  }