Using a web service callout in a trigger

Question

I am trying to use this JSON parsing in a trigger. The purpose of the trigger is to insert latitude and longitude data to custom object "Branch__c" once data like address, city etc. are inserted so geolocation details are inserted automatically after the trigger is fired. The point is to gather address details from Branch__c custom object and construct a String to be put in "endPointString" variable. I am doing this by using a formula field where I want to concatenate all necessary details. In order to test whether the callout works in a trigger at all I chose to make an "in between steps trigger" just to test the functionality, therefore in all newly inserted rows would be put the same longitude and latitude details as these the "endPointString" variable would have a fixed String value for the moment. The thing is that when I use below trigger which uses above "parsing classes" and tries to insert test data, I get a different error :)

Can you please help? Appreciate your help, Milan

The error: Line: 36, Column: 1 System.DmlException: Insert failed. First exception on row 0; first error: CANNOT_INSERT_UPDATE_ACTIVATE_ENTITY, updGPStest: execution of BeforeInsert caused by: System.CalloutException: Callout from triggers are currently not supported. Class.getGPS.getGPSdata: line 23, column 1 Trigger.updGPStest: line 11, column 1: []

Data to insert:

List<Branch__c> brList = new List<Branch__c> {
new Branch__c(Account__c = '0010Y00000EhCbzQAF', City__c='Kladno', Name__c='Kladno_BULK_TEST1', Postal_Code__c='272 01', Street__c='Vrchlického', Street_No1__c='2409', Street_No2__c='9'),
new Branch__c(Account__c = '0010Y00000EhCbzQAF', City__c='Kladno', Name__c='Kladno_BULK_TEST2', Postal_Code__c='272 01', Street__c='Vrchlického', Street_No1__c='2409', Street_No2__c='9'),
new Branch__c(Account__c = '0010Y00000EhCbzQAF', City__c='Kladno', Name__c='Kladno_BULK_TEST3', Postal_Code__c='272 01', Street__c='Vrchlického', Street_No1__c='2409', Street_No2__c='9')};
// Bulk insert all contacts with one DML call
 insert brList;

My current trigger:

List<Branch__c> addrString = new List<Branch__c>();
getGPS gps = new getGPS();

for(Branch__c br1 : Trigger.New) {


    addrString = [SELECT Concatenate_Address__c FROM Branch__c WHERE Id IN :Trigger.New];

    gps.getGPSdata();



    br1.Location_GPS__latitude__s = gps.getLat();
    br1.Location_GPS__longitude__s = gps.getLng();


     //gps.setEndPointStr('&addrString&');
    //gps.setEndPointStr('http://maps.googleapis.com/maps/api/geocode/json?address=Černokostelecká /, Říčany, 251 01');
    //br1.Test_Column__c = br1.Concatenate_Address__c;


  }
}

web callout classes used: class no.1

public class getGPS {

String endPointString = 'https://maps.googleapis.com/maps/api/geocode/json?address=Žerotínova 1664/57, Praha, 130 00&key=AIzaSyDpkHWwId9J1mMCqu9mirXPEwpM3XTs0GU';
double lng;
double lat;

public double getLng() {
    return lng;
    }

public double getLat() {
    return lat;
    }



  public void getGPSdata() {
      Http httpProtocol = new Http();
      HttpRequest request = new HttpRequest();
      String endpoint = endPointString;
      request.setEndPoint(endpoint);
      request.setMethod('GET');
      HttpResponse response = httpProtocol.send(request); 
      String jsonString = response.getBody();
      googleAddress addr = googleAddress.parse(jsonString);

 googleAddress.Location loc = addr.firstLoc;
 double lng = loc.lng;
 double lat = loc.lat;
 this.lng=lng;
 this.lat=lat;
  }                     
}

class no.2

public class googleAddress {

  public class Address_components {
    public String long_name;
    public String short_name;
    public List<String> types;
}

public class Geometry {
    public Location location;
    public String location_type;
    public Viewport viewport;
}

public List<Results> results;
public String status;
public Location firstLoc;

public class Results {
    public List<Address_components> address_components;
    public String formatted_address;
    public Geometry geometry;
    public Boolean partial_match;
    public String place_id;
    public List<String> types;
}

public class Viewport {
    public Location northeast;
    public Location southwest;
}

public class Location {
    public Double lat;
    public Double lng;
}


public static googleAddress parse(String json) {

    googleAddress returnAddr;

    returnAddr = (googleAddress) System.JSON.deserialize(json,  googleAddress.class);
    if (!returnAddr.results.isEmpty()){
        returnAddr.firstLoc = returnAddr.results[0].geometry.location;
    }
    return returnAddr; 


    }
 }

Answer 1

Note from Apex Web Services and Callouts:

An Apex trigger can execute a callout when the callout is invoked within a method defined as asynchronous: that is, defined with the @future keyword. The @future annotation signifies that the Apex method executes asynchronously. For more information on the @future annotation, please read the documentation.

Also worth reading: HTTP Callout from Triggers