Content Handler Module Design

The Content Handler module receives data from Interface modules along with the content type of that data. Using this information it is expected to forward data to an appropriate Processor module that can handle that data. It is also required to have functionality to allow Processor modules to be able to dynamically register and de-register their interest to data of particular content types.

Implementation

The Content Handler module is [going to be] very light-weight. It's purpose, at an implementation level, is to:

• Provide generic interfaces to Interface modules for abstracting the operations that can be performed by Processor modules
• Provide functionality for Processor modules to register/deregister content handlers for specific content (MIME) types at runtime.

See the below interfaces; Processor modules can register handlers for specific content types during module startup (or whenever deemed appropriate by the module). The content handlers need to provide functionality to save and retrieve content. Interface handlers can simply then retrieve a registered instance based on the content type of the data they need to handle. In the event that there are no handlers registered for a specific type, the module can use a handler registered for the "application/*" type or throw an exception if this fall-back doesn't exist either. The module follows the prototype pattern for content handler instantiation. When registering a handler, a Processor module provides an instance of a handler. Then whenever the getContentHandler method is called, the Content Handler module will clone an instance of the handler for use by the caller.

Interfaces

public interface ContentHandlerService extends OpenMRSService {
 
	/** To be called by interface modules */
	ContentHandler getContentHandler(String contentType) throws NoHandlerForContentTypeException;
 
	/** To be called by processor modules on startup */
	void RegisterContentHandler(String contentType, ContentHandler prototype) throws AlreadyRegisteredException;
	/** To be called by processor modules on shutdown */
	void DeregisterContentHandler(String contentType);
}

public interface ContentHandler {
 
	void saveContent(Patient patient, String content);
	void saveContent(Patient patient, String documentId, String content);
 
	String fetchDocument(String documentId);
	String queryEncounters(Patient patient, Date from, Date to);
 
	ContentHandler cloneHandler();
}