Data Change Notification Requests

The consolidated database (or cache) can be updated by changed data at the enterprise information system (EIS) level using a data change notification (DCN) request. DCN requests can invoke arbitrary MBO operations, including alternate read operations. DCN requests are typically initiated by the EIS back end.

A DCN request is primarily meant to supply the changed data (at the back end) to Unwired Server as payload to enable updating of Unwired Server cache. The payload can contain inserts, updates, and deletions from the back end.

Unwired Server expects a DCN request via HTTP or HTTPS. The base URL for the request is:

http://<host>:<port>/onepage/servlet/UWPServlet

The mandatory parameters for this URL are:

app=uep
cmd=ServerAdmin.dcn
authenticate.user=<username>
authenticate.password=<password>
dcn_request=<dcn request>

Though the authenticate.user. authenticate.password and dcn_request parameters can be provided as URL parameters, Sybase recommends that, for security purposes, you instead embed them in the POST body.

DCN requests must be in a specified in a JavaScript Object Notation (JSON) format, which must include:

Package name (pkg)
A list of messages (messages), where each message includes:
- A message ID (id) used to report back the status.
- Mobile business object name (mbo).
- Operation name (op): ":upsert", ":delete", or an operation name of the specified MBO. ":upsert" and ":delete" are special operation names to specify payload data.
- Bindings (cols): a list of name/value pairs covering at least all primary key attributes of the MBO. For payload data, the bindings contain the payload specified as MBO attribute/parameter names and their values. For an MBO operation, bindings contain operation parameter names and values.

The format of non-string data is same as the one used in providing default values of parameters in tooling. For example, specify timestamp values in a format similar to 2009-03-04T17:03:00+05:30. Base binding names on MBO names rather than EIS names.

For MBO operations that are executed using DCN, any explicit value specified in the DCN request takes precedence over a personalized value. To use a personalized value in DCN processing, do not include the personalized parameter name and its value in the DCN request. The personalized value is then inferred by the server and added to the supplied bindings. Similarly, omit parameters with default values if the intent is to use previously specified default values.

This sample DCN includes new lines and indentation only for clarity; you need not include them in an actual request:

dcn_request=
 {"pkg":"Mobile Studio",
"messages":[
{
"id":"1",
"mbo":"company",
"op":":upsert",
"cols":
 {
"company_id":"6",
"name":"Sonia",
"so_user":"cjobson"
}
},

{
"id":"2",
"mbo":"contact",
"op":":upsert",
"cols":
 {
"company_id":"7",
"first_name":"Diana",
"contact_id":"5"
}
}
]
}

For providing null values to parameters, the special value null 
should be user, note the absence of quotes -  

"cols":
 {
"company_id":"6",
"name":null,
"so_user":"cjobson"
}
 

The old value parameters can be provided in the DCN request by 
prepending the parameter name with "old:" as follows (marked in
italics) - 
"cols":
 {
"company_id":"6",
"name":"Changed",
"old:name":"Diana"
"so_user":"cjobson"
}

Data Change Notification Results
Each binding in a data change notification (DCN) request is associated with an ID. The result status of the DCN request is returned in JavaScript Object Notation (JSON) format. Basically it is a list of IDs followed by a Boolean success field and status message, in case of error.
Data Change Notification Filters
Data change notification (DCN) requests need not always be in the format Unwired Server expects. You can deploy a DCN filter to Unwired Server and reference it in the DCN request. Unwired Server allows the filter to preprocess the submitted DCN. The filter converts raw data in the DCN request to the required JavaScript Object Notation (JSON) format. The filter can also postprocess the JSON response returned by the Unwired Server into the format preferred by the back end (which is governed by the implementation in the filter class).
Data Change Notification, Push Notification, and Filter by Partitioning Examples
User scenarios illustrate how Data Change Notification (DCN) and Unwired Server Push Notifications work together to playback and filter data.

Parent topic: New Features