How to implement a client for REST web services

Scope

• Jobs can be implemented to access RESTful web services.
• A REST web service client is available for Scripting of Jobs and Monitors that are implemented with Java or JavaScript.
• This feature is provided with  JITL-213 - Getting issue details... STATUS

Implementation

• JITL provides a static Java class that can be used with Java and JavaScript. This class accepts a URL and returns an object in JSON syntax.
• For use with JavaScript the JSON object can be converted to a JavaScript object.

Methods

com.sos.jitl.restclient.JobSchedulerRestClient.executeRestService

http://localhost:44445/jobscheduler/agent/api/

com.sos.jitl.restclient.JobSchedulerRestClient.executeRestServiceCommand

http://localhost:44445/jobscheduler/agent/api/

com.sos.jitl.restclient.JobSchedulerRestClient.getRestService

4445

com.sos.jitl.restclient.JobSchedulerRestClient.postRestService

4445

Adding Header items

• The header "Accept=application/json" will automatically be added.
• You can add header items with
  
  • com.sos.jitl.restclient.JobSchedulerRestClient.headers.put("header","value");

Integration with JavaScript

• Basically a web service call is implemented by executing one of the above methods from the JITL Java class, e.g.:
  • var response = com.sos.jitl.restclient.JobSchedulerRestClient.executeRestService( "http://localhost:44445/jobscheduler/agent/api/" );
  • var response = com.sos.jitl.restclient.JobSchedulerRestClient.executeRestServiceCommand( "get", "http://localhost:44445/jobscheduler/agent/api/" );
• Webservice returns a serialized JSON Object
  • The result object returned by the web service can be converted to a JavaScript JSON object by use of the eval() function:
    • eval ( "var jsonObject = " + response + ";" );
  • Properties of the JSON object can be accessed within the object hierarchy provided by the web service result object like this:
    • jsonObject.system.hostname
• Webservice returns a xml element
  • The result can be parsed using SOSXMLXPath
    • see example below

function spooler_process() { 
  var s = com.sos.jitl.restclient.JobSchedulerRestClient.executeRestService( "http://www.thomas-bayer.com/sqlrest/CUSTOMER/18/" );
  spooler_log.info( s);
  var xmlDOM = new Packages.sos.xml.SOSXMLXPath( new java.lang.StringBuffer( s ) );
   spooler_log.info( "Firstname is " + xmlDOM.selectSingleNodeValue( "//CUSTOMER/FIRSTNAME" ));
 
  return false;
}

Example

• JavaScript example for use with a job: this job requests the status information from the JobScheduler Universal Agent and returns the total number of tasks that have been executed during the Agents' lifetime. This job reads the web service URL from a job parameter.
• Download: rest_client.job.xml 
   

<job  stop_on_error="no" >
    <params >
        <param  name="agent_service" value="localhost:4445/jobscheduler/agent/api/"/>
    </params>

    <script  language="java:javascript">
        <![CDATA[
function spooler_process() {

    var parameters = spooler.create_variable_set();
    parameters.merge( spooler_task.params );

    var agent_service = parameters.value( "agent_service" );
    var response = com.sos.jitl.restclient.JobSchedulerRestClient.executeRestService( agent_service );

//  alternative REST methods
//  var response = com.sos.jitl.restclient.JobSchedulerRestClient.executeRestService( "http://localhost:44445/jobscheduler/agent/api/" );
//  var response = com.sos.jitl.restclient.JobSchedulerRestClient.executeRestServiceCommand("get", "http://localhost:4445/jobscheduler/agent/api/" );
//  var response = com.sos.jitl.restclient.JobSchedulerRestClient.getRestService( "localhost", 4445, "/jobscheduler/agent/api/", "http" );

    if (response) {
        eval ( "var jsonObject = " + response + ";" ); 
        spooler_log.info( jsonObject.totalTaskCount + " tasks on Agent [" + agent_service + "]: " + jsonObject.system.hostname );
    } else {
        spooler_log.error( "no response from Agent web service at: " + agent_service );
    }

    return (response != "");
}
        ]]>
    </script>

    <run_time />
</job>

References

Change Management References

Documentation

• REST (Representational State Transfer)