Invoking Apex Callouts through Visual Flows

Few weeks back I was attending a Webinar on Advanced Flow From SFDCBill(Product Manager Flows Salesforce.com) .I was quite surprised to discover flows are very powerful feature provided by the platform for the administrator to configure the business logic .

My friend Rakesh has been blogging lot of use cases of flows for Salesforce 1 and using chatter objects .You can refer his blog for more details on the work he has done .I have learned lot from those and I am thankful to him for sharing his experience with visual flows through his blog

http://rakeshistom.wordpress.com/category/workflow-rule/visual-workflow-flow/

One of the things that came was invoking callouts or webservices through flows and SFDCBill was able to communicate the design that one needs apex and process plugin for invoking callouts directly from the flow .I did a quick online search to see if this has been demonstrated  and was not able to get some good resource so i thought of sharing a sample tutorial on how to invoke callouts from flows directly.

The more information on the process plugin can be obtained from below URLs ,

https://www.salesforce.com/us/developer/docs/apexcode/Content/apex_process_plugin.htm
https://www.salesforce.com/us/developer/docs/apexcode/Content/apex_process_plugin_example_lead_convert.htm

The Process plugin is an apex Interface and that needs to be implemented in order to pass request into the apex class from the flow input or screen and the apex interface returns the response back to the flow.

Lets discuss how we can make a web service or apex callouts from flow directly .

1)Our first step will be to write the apex plugin class that makes a webservice callout to external website and process and makes the data ready for passing back to the flow.

For webservice part I have taken a sample REST service provided for free for learning purpose from the website http://api.wunderground.com/weather/api/

The web-service takes input of state and city of US and outputs current weather condition in the form of JSON objects .Note that you need to sign up and generate an API key for your use .

The input of state and city can be taken from flow screen and it can be passed directly as request parameter to the apex class .

Here is the complete apex class for the flow plugin

	global class WeatherApp implements Process.Plugin {
	// The main method to be implemented. The Flow calls this at runtime.
	global Process.PluginResult invoke(Process.PluginRequest request) {
	// Get the State and City From Flow
	String State = (String) request.inputParameters.get('state');
	String City = (String) request.inputParameters.get('city');
	// Use the API to call and fetch Weather Info
	WeatherInfo weatherinformation=new WeatherInfo();
	// Instantiate a new http object
	Http h = new Http();
	// Instantiate a new HTTP request, specify the method (GET) as well as the endpoint
	HttpRequest req = new HttpRequest();
	String requestURL='http://api.wunderground.com/api/551013da52923e43/conditions/q/';//One needs to generate the API Key From the http://api.wunderground.com
	requestURL=requestURL+state+'/'+city+'.json';
	req.setEndpoint(requestURL);
	req.setMethod('GET');
	// Send the request, and return a response
	HttpResponse res = h.send(req);
	weatherinformation=(WeatherInfo)JSON.deserialize(res.getBody(), WeatherInfo.class);
	// return to Flow
	Map<String,Object> result = new Map<String,Object>();
	result.put('temperature',weatherinformation.Current_observation.temp_c);
	result.put('faherneit',weatherinformation.Current_observation.temp_f);
	result.put('dewpoint_f',weatherinformation.Current_observation.dewpoint_f);
	return new Process.PluginResult(result);
	}
	// Returns the describe information for the interface
	global Process.PluginDescribeResult describe() {
	Process.PluginDescribeResult result = new Process.PluginDescribeResult();
	result.Name = 'weatherappplugin';
	result.Tag = 'weatherapp';
	result.inputParameters = new
	List<Process.PluginDescribeResult.InputParameter>{
	new Process.PluginDescribeResult.InputParameter('state',
	Process.PluginDescribeResult.ParameterType.STRING, true) ,
	new Process.PluginDescribeResult.InputParameter('city',
	Process.PluginDescribeResult.ParameterType.STRING, true)
	};
	result.outputParameters = new
	List<Process.PluginDescribeResult.OutputParameter>{
	// Temperature obtained From The webservice
	new Process.PluginDescribeResult.OutputParameter(
	'temperature',
	Process.PluginDescribeResult.ParameterType.Double),
	new Process.PluginDescribeResult.OutputParameter(
	'faherneit',
	Process.PluginDescribeResult.ParameterType.Double),
	new Process.PluginDescribeResult.OutputParameter(
	'dewpoint_f',
	Process.PluginDescribeResult.ParameterType.Integer)
	};
	return result;
	}
	}

view raw WeatherApp hosted with ❤ by GitHub

2)For JSON parsing ,I have used another class shown below ,which handles parsing of the data .This can be easily generated using https://json2apex.herokuapp.com/ by providing sample response JSON.

	public class WeatherInfo {
	public class Current_observation {
	public Image image;
	public Display_location display_location;
	public Observation_location observation_location;
	public Estimated estimated;
	public String station_id;
	public String observation_time;
	public String observation_time_rfc822;
	public String observation_epoch;
	public String local_time_rfc822;
	public String local_epoch;
	public String local_tz_short;
	public String local_tz_long;
	public String local_tz_offset;
	public String weather;
	public String temperature_string;
	public Double temp_f{get;set;}
	public Double temp_c{get;set;}
	public String relative_humidity{get;set;}
	public String wind_string{get;set;}
	public String wind_dir{get;set;}
	public Integer wind_degrees{get;set;}
	public Double wind_mph{get;set;}
	public Integer wind_gust_mph{get;set;}
	public Double wind_kph{get;set;}
	public Integer wind_gust_kph{get;set;}
	public String pressure_mb{get;set;}
	public String pressure_in{get;set;}
	public String pressure_trend{get;set;}
	public String dewpoint_string{get;set;}
	public Integer dewpoint_f{get;set;}
	public Integer dewpoint_c{get;set;}
	public String heat_index_string{get;set;}
	public String heat_index_f{get;set;}
	public String heat_index_c{get;set;}
	public String windchill_string{get;set;}
	public String windchill_f{get;set;}
	public String windchill_c{get;set;}
	public String feelslike_string{get;set;}
	public String feelslike_f{get;set;}
	public String feelslike_c{get;set;}
	public String visibility_mi{get;set;}
	public String visibility_km{get;set;}
	public String solarradiation{get;set;}
	public String UV{get;set;}
	public String precip_1hr_string;
	public String precip_1hr_in;
	public String precip_1hr_metric;
	public String precip_today_string;
	public String precip_today_in;
	public String precip_today_metric;
	public String icon;
	public String icon_url;
	public String forecast_url;
	public String history_url;
	public String ob_url;
	public String nowcast;
	}
	public class Estimated {
	}
	public Response response;
	public Current_observation current_observation;
	public class Image {
	public String url;
	public String title;
	public String link;
	}
	public class Response {
	public String version;
	public String termsofService;
	public Features features;
	}
	public class Display_location {
	public String full;
	public String city;
	public String state;
	public String state_name;
	public String country;
	public String country_iso3166;
	public String zip;
	public String magic;
	public String wmo;
	public String latitude;
	public String longitude;
	public String elevation;
	}
	public class Observation_location {
	public String full;
	public String city;
	public String state;
	public String country;
	public String country_iso3166;
	public String latitude;
	public String longitude;
	public String elevation;
	}
	public class Features {
	public Integer conditions;
	}
	}

view raw WeatherInfo hosted with ❤ by GitHub

Lets dig into the creation of flows ,

Visual workflow basics can be studied from following resources 

http://help.salesforce.com/help/pdfs/en/salesforce_vpm_implementation_guide.pdf
http://www.salesforce.com/us/developer/docs/workbook_vf/workbook_vf.pdf

3)We will need below three components 

i))Input Screen to take data of city and state from User need as input for our webservice
ii)WeatherAppApex Plugin we have just developed using apex
iii)Output Screen to display the result

The input screen will have two fields to capture input 

The Apex Plugin will have a mapping for both input and output from result.The below screen shots show the input and output mappings .Note for output mapping for further usage of output  parameters flow variables are created

The output Screen is last piece to display the results .

Now lets see the outcome of this work in below video

I hope you enjoyed this tutorial and looking forward to your comments below .

Please note error handling in code and Test classes are left as it was just a POC code .Be careful to take care of all these when implementing for client code .

Happy Coding !!!