Using Registry Resources for Output Mapping

WSO2 CEP allows you to map custom content from registry for the XML, JSON and Text mapping  types. Custom mapping is stored as a registry resource to be used by the publisher instead of being specified as inline input. WSO2 CEP caches this resource at runtime, and the cache is updated after every cache timeout specified in minutes. If caching is not required, specify the cache timeout as 0.

The following tutorial illustrates how to carry out custom mapping using a registry resource.

1. Log into the WSO2 CEP Management Console.
2. Define an event stream as follows. For detailed instructions to create event streams, see Understanding Event Streams.
   
   

   1. Enter basic information for the stream as follows.

      Parameter	Value
      Event Stream Name	sensorsteam
      Event Stream Version	1.0.0

      Add attributes as follows.

      Attribute Category	Attribute Name	Attribute Type
      Meta Data	sensorId	int
      	sensorName	string
      	language	string
      Correlation Data	longitude	double
      	latitude	double
      Payload Data	sensorValue	double

3. Add an output mapping template as a registry resource as follows. For more information about the registry, see Registry.
   
   1. In the Main tab expand the Registry section and click Browse.
   2. Under Tree View, navigate to /_system/config directory and click Detail View. Click Add Collection. In the Name field, enter Template and click Add. This creates a new sub directory named template in the /_system/config directory.

   3. Navigate to the /_system/config/template sub directory and click Add Resource. Then enter information as shown in the table below, and click Add.
      

      Field	Value
      Method	Create Text Content
      Name	message
      Media Type	text/plain
      Content	Welcome Sensor {{meta_sensorName}} reports {{sensorValue}} from {{correlation_longitude}}:{{correlation_latitude}}

4. Create a new publisher as follows. For more information, see Configuring CEP to Create Alerts - Creating event publishers.

   Field	Value
   Event Publisher Name	samplelogger
   Event Source	sensorstream
   Output Event Adapter Type	logger

5. Under Mapping Configuration, select Text for the Message Format field. Then click Advanced. This expands the Create a New Event Publisher page to display the Text Mapping section. Select the Pick from Registry option. In the Registry Path field, navigate to the registry location where you saved the registry resource created in step 3.

   

   In this example, the default value of 15 is left unchanged for the Cache Timeout (in minutes) field. Therefore, this resource will be cached every 15 minutes.

6. Click Add Event Publisher.

7. In the Tools tab, click Event Simulator. In the Event Stream Name field, select sensorstream. Enter the following values for the parameters displayed, and then click Send to simulate a single event.
   

   Parameter	Value
   sensorid	10
   sensorName	Temperature
   language	en
   longitude	79.861256
   latitude	6.927131
   sensorValue	23.0

    

   The output for this event is logged in the terminal as follows. 
   

Using custom registry paths

The registry resource path itself can be parameterized using runtime attribute values. e.g., If the event stream to which the logger publisher in the example above is connected has an attribute named meta_language, a different registry source is selected depending on the runtime value of the meta_language attribute.

The following tutorial illustrates how to change the registry resource path from which a custom output mapping is picked based on the value of an attribute.

1. Log into the CEP Management Console.

2. Create two sub directories in the Template directory you created in the previous tutorial, and add a resource to each of these sub directories as described below. For more information about the registry, see Registry.
   1. In the Main tab expand the Registry section and click Browse.
   2. Under Tree View, navigate to the  /_system/config/template sub directory. Create two more sub directories in it named en and fr.

   3. Navigate to the /_system/config/template/en sub directory and click Add Resource. Then enter information as shown in the table below, and click Add.

      Field	Value
      Method	Create Text content
      Name	message
      Media Type	text/plain
      Content	Welcome Sensor {{meta_sensorName}} reports {{sensorValue}} from {{correlation_longitude}}:{{correlation_latitude}}

   4. Navigate to the /_system/config/template/fr sub directory and click Add Resource. Then enter information as shown in the table below, and click Add.

      Field	Value
      Method	Create Text content
      Name	message
      Media Type	text/plain
      Content	Bienvenue Sensor {{meta_sensorName}} reports {{sensorValue}} from {{correlation_longitude}}:{{correlation_latitude}}

   After adding both the resources, the registry tree view should look as follows.
   

3. Delete the publisher named sample logger and redefine it as follows. For more information, see Configuring CEP to Create Alerts - Creating event publishers.
   

   Field	Value
   Event Publisher Name	samplelogger
   Event Source	sensorstream
   Output Event Adapter Type	logger

    

4. Under Mapping Configuration, select Text for the Message Format field. Then click Advanced. This expands the Create a New Event Publisher page to display the Text Mapping section. Select the Pick from Registry option. Then enter information as follows.

   Field	Value
   Registry Path	conf:/template/{{meta_language}}/message
   Cache Timeout (in minutes)	15

5. Log into the CEP Management Console.

6. In the Tools tab, click Event Simulator. In the Event Stream Name field, select sensorstream. Send three events with the following values.

   Parameter	Value for Event 1	Value for Event 2	Value for Event 3
   sensorid	10	10	10
   sensorName	Temperature	Temperature	Temperature
   language	en	fr	ru
   longitude	79.861256	79.861256	79.861256
   latitude	6.927131	6.927131	6.927131
   sensorValue	23.0	23.0	23.0

   
   The three events are logged as follows. 
   Note that an error is returned for the third event. This is because no output mapping was done for the ru language.