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).

The filter interface DCNFilter is located in the com.sybase.sup.dcn package in the onepage.jar file. All classes that implement a DCN filter should implement this interface. The functions available in the interface are:

• String preprocess(String blobDCNRequest, Map<String, String> requestHeaders); – takes the DCN request as a binary large object (blob), converts it into a valid JSON DCN request format and returns the same.
• String postprocess(String jsonDCNResult, Map<String, String> responseHeaders); – takes the DCN result in a valid JSON format, converts it to the EIS-specific format and returns the same.

When specifying filters, a dcn_filter parameter to the base URL, and to the parameters specified in the DCN request section. The dcn_filter parameter specifies the fully classified name of the filter class, which must be in a valid CLASSPATH location so Unwired Server can locate it using its fully qualified name. If the filter class is in Unwired Platform's root folder, it is automatically propogated across a cluster. The complete URL for specifying a DCN request with a filter is:

http://<host>:<port>/onepage/servlet/UWPServlet?
app=uep&cmd=ServerAdmin.dcn&authenticate.user=<username>
&authenticate.password=<password>&dcn_filter=
<fully qualified name of the filter class>&dcn_request=
<dcn request>