Scheduling a Task Using a Custom Implementation

When you create a task using the default task implementation of the ESB, the task can inject messages to a proxy service, or to a sequence. If you have a specific task-handling requirement, you can write your own task-handling implementation by creating a custom Java Class that implements the  org.apache.synapse.startup.Task  interface.

For example, the below sections demonstrate how you can create and schedule a task to receive stock quotes by invoking a back-end service, which exposes stock quotes. The scheduled task will read stock order information from a text file, and print the stock quotes.

Starting the Back End Service

Follow the steps below to start the backend service.

1. Download the backend service from Git Hub.

2. Copy the JAR file you downloaded to the <EI_HOME>/wso2.msf4j/deployment/microservices directory.

3. Start the MSF4J profile. For instructions, see Starting the product profiles.

Creating the custom Task implementation

Follow the steps below to create the implementation of the custom Task.

Creating the Maven Project

Deploying the custom Task implementation

For instructions on deploying the custom Task implementation, see  Deploying artifacts of the Maven Project.

Creating the Task

Follow the steps below to create the task and schedule it.

Creating the ESB Project

1. Create a ESB Solution Project using the following information. For instructions, see Creating the ESB Project.

   • Name:   PrintStockQuote

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   Creating the Sequence

2. Create a Sequence using the following information. For instructions, see Creating the Sequence.

   • Name:  PrintStockQuoteSequence
     

     
     

3. Add a Log Mediator and a Drop Mediator to the sequence and configure them. For instructions, see Creating the Sequence.
   

   Creating the Scheduled Task

4. Create a Scheduled Task using the following information. For instructions, see Creating the Scheduled Task.

   • Task Name: PrintStockQuoteScheduledTask

   • Count: 1

   • Interval (in seconds): 5

   Defining the properties of the Task

• In the Project Explorer, double-click on the  PrintStockQuoteScheduledTask.xml  file and replace its source with the below content.  

  <task class="org.apache.synapse.startup.tasks.MessageInjector" group="synapse.simple.quartz" name="PrintStockQuoteScheduledTask" xmlns="http://ws.apache.org/ns/synapse"> <trigger count="1" interval="5" /> <property name="to" value="http://localhost:9000/soap/SimpleStockQuoteService" xmlns:task="http://www.wso2.org/products/wso2commons/tasks" /> <property name="stockFile" value="/Users/praneesha/Desktop/stockfile.txt" xmlns:task="http://www.wso2.org/products/wso2commons/tasks" /> <property name="synapseEnvironment" value="" xmlns:task="http://www.wso2.org/products/wso2commons/tasks" /> </task>

  The task properties will change according to the custom implementation. Therefore, you need to enter values for your custom properties. This sets the below properties. 

Deploying the Task

For instructions on deploying the Task, see Deploying the Task.

Creating the text file

Create a text file named  stockfile.txt with the following content and save it to a preferred location on your machine. This will include the information to be read by the scheduled task to pass to the backend service.

stockfile.txt

Viewing the output

You will view the stock quotes sent by the backend service printed every 3 seconds by the scheduled task in the below format.

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