How to form JSON with salesforce field values in apex/Salesforce

Question

I have created SF to SF connection to put standard object cross org, getting error related to JSON response as 400 Bad Request. Error as: Unexpected parameter encountered during deserialization: LastName....' When im uncommenting line 'Commented 1' it works well with hardcoded values in JSON but fails when i put the field names it fails.

String endPoint='https:aaa//';                          
            Commented 1//String jsonstr='{"Lastname":"Testname123","Phone":"5565565","Website":"www.xyz.com","Status":"Open","Company":"1company"}';
           JSONGenerator gen = JSON.createGenerator(true);
            gen.writeStartObject();
            gen.writeStringField('LastName', Lastname);            
            gen.writeStringField('Phone', Phone);
            gen.writeStringField('Website', Website);
            gen.writeStringField('Status', status);
            gen.writeStringField('Company', company);
             gen.writeEndObject();       
        // Get the JSON string.
            String jsonstr = gen.getAsString();
            String str1= jsonstr;
            system.debug(jsonstr); //this line displays proper JSON format(with the field values)
            Http h2= new Http();
            HttpRequest req2= new HttpRequest();             
            req2.setHeader('Content-Type','application/json; charset=utf-8');
            req2.setHeader('Authorization','Bearer ' + accessToken);          
            req2.setBody(gen.getAsString());
            req2.setMethod('POST');
            req2.setEndpoint(endPoint);
            HttpResponse res2=h2.send(req2);

Answer 1

There are multiple ways to do this. The way that I follow is using a wrapper class

 public class RequestJSON{
    public String lastName;
    public String phone;
    public String website;
    public String status;
    public String company;
}

private String genpayload(String lastName, String phone, String website, String status, String company){
   RequestJSON rj = new RequestJSON();
   rj.lastName = lastName;
   rj.phone = phone;
   rj.website = website;
   rj.status = status;
   rj.company = company;

return JSON.serialize(rj);
}

You can then send the JSON in the request body.

Answer 2

'Lastname' != 'LastName'. Map keys in Apex (and in most languages that might be processing the JSON that you send) are case-sensitive. Your generated JSON does not match the hard-coded JSON with respect to case.

As Avinash also pointed out, you should just be using serialization here; there is no reason to use the clumsy generator classes.