XML Event Formatter

XML event formatter converts the events coming from Siddhi to XML events according to the mapping configurations. You can inject the CEP's back-end runtime event data to the output as XML, by adding the appropriate back-end runtime event attribute names in double curly braces (e.g., {{price}}) into the output XML template.

You can configure through the management console as explained below or by manually adding an XML file as explained in step 5.

1. Start the CEP, log in to its management console, select Event Formatters and click Add Event Formatter.
2. Enter details in the form that appears and click the Add Event Formatter button at the end of the form. For example,
   The fields in the above configuration are as follows:
   
   
   • Event Formatter Name : Property to uniquely identify an event formatter configuration
   • Event Stream (marked as 1 in the screenshot) : Select an event stream (stream name with version) to listen for events.
   • Stream Attributes : Based on the event stream selected earlier, this shows what the attributes available in the stream are. This field is only for reference.
   • Output Event Adaptor Name (marked as 2 in the screenshot) : Select the event adaptor used to publish events from the CEP. This drop-down list shows the output event adaptors already created.
   • Output Mapping Type (marked as 3 the screenshot) : Select xml mapping type. This drop-down list is populated based on the event adaptor selected earlier. It lists only the mapping types supported by a particular event adaptor. Some event adaptors support multiple types of mappings. Also, see XML Mapping section below.
   • Topic : Since you selected ws-event-local type event adaptor, you need a Topic to be used when subscribing the events by the receiver.
     
     

     XML Mapping

     When you select the xml mapping, you see a text area to define an in-line or a registry-based template of the output XML event.

     In-line : XML mapping is enabled for in-line templates by default. You must add the template of the output XML event as shown in the example above. Note that any attribute name must be in double curly braces. E.g., {{symbol}}.

     Registry-based : Follow the steps below to create a registry-based template.

     Step 1: Create a plain text content file (resource) in either the config or the governance directory of the registry. For more information, see For example,

     

     Step 2: Select the resource that you created in registry. First, click on the Pick from registry option, then you can see options (Configuration Registry and Governance Registry) to select the registry resource.

     

     3. Then click on Configuration Registry link, since we have create the resource in config directory, select the specific resource as shown below and click on OK button. 

     

3. After an event formatter is successfully created, you can change its configuration and redeploy it. To do this, click the Edit link associated with it.
4. An XML based editor opens allowing you to edit the event builder configuration from the UI itself, without having to edit the file in the file system. Do your modifications and click Update.

5. Alternatively, you can specify an event formatter configuration using an XML file and save it in <PRODUCT_HOME>/repository/deployment/server/eventformatters directory, which is the event formatter deployment directory. Since hot deployment is enabled, you can simply add/remove files to deploy/undeploy from the server.
   
   Create the XML file with the following XML mapping event formatter configurations. Event formatter implementation must start with <eventformatter> root element as in the example below.

   <eventFormatter name="xmlEventFormatter" xmlns="http://wso2.org/carbon/eventformatter">
     <from streamName="stockStream" version="1.0.0"/>
     <mapping type="xml">
       <inline>
         <quotedata:StockQuoteDataEvent
           xmlns:quotedata="http://ws.cdyne.com/"
           xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
           <quotedata:StockSymbol>{{symbol}}</quotedata:StockSymbol>
           <quotedata:LastTradeAmount>{{price}}</quotedata:LastTradeAmount>
         </quotedata:StockQuoteDataEvent>
       </inline>
     </mapping>
     <to eventAdaptorName="localWsEventSender" eventAdaptorType="ws-event-local">
       <property name="topic">FastMovingStockQuotes</property>
     </to>
   </eventFormatter>