global class batchUpdateAccountGeoLocation implements Database.Batchable<sObject>,Database.AllowsCallouts{
    
  //Start 
   global Database.QueryLocator start(Database.BatchableContext BC){
       string query = 'SELECT Id, Name, BillingStreet, BillingCity, BillingState,Location__Latitude__s,Location__Longitude__s ' +
                   'FROM Account ' + 
                   'WHERE BillingStreet!=null and  Location__Latitude__s = null ';
      return Database.getQueryLocator(query);
   }

    //Execute
   global void execute(Database.BatchableContext BC,List<Account> scope){
      
      for(Account a : scope){          
          GeoCodeResponse ogc = GeoCodeAddress.getGeoCodeAddress(a.BillingStreet.replace(' ','+') + ',' + a.BillingCity + ',' + a.BillingState);
                     a.Location__Latitude__s = ogc.results[0].geometry.location.lat;
                     a.Location__Longitude__s = ogc.results[0].geometry.location.lng;                  
      }     
       
       try{
           update scope;
       }catch(exception e){
           system.debug('batchUpdateAccountGeoLocation exception:' + e.getMessage());
       }       
   }

    //Finish
   global void finish(Database.BatchableContext BC){

   }
}




public class GeoCodeAddress {    
        
    public static GeoCodeResponse getGeoCodeAddress(String Address) {
        string url ='https://maps.googleapis.com/maps/api/geocode/json?key=<Your Key Here>&address=' + EncodingUtil.urlEncode(Address, 'UTF-8');
        
        // 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();
        req.setEndpoint(url);
        req.setMethod('GET');
        
        // Send the request, and return a response
        HttpResponse res = h.send(req);        
        
        return GeoCodeResponse.parse(res.getBody());         
    }
    
}


public class GeoCodeResponse {

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

  public List<Results> results;
  public String status;

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

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

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

  public class Viewport {
    public Location northeast;
    public Location southwest;
  }
        
  public static GeoCodeResponse parse(String json) {
    return (GeoCodeResponse) System.JSON.deserialize(json, GeoCodeResponse.class);
  }
 }