how to write congacomposer endpoint url in apex class

Question

I am trying to write callout to connect congacomposer, didn't get any error but it showing url not specified properly in debug logs.

The same url I used in generate button click. it is worked. please advice me. From one youtube link I got this link. https://composer.congamerge.com?serverUrl={!API.Partner_Server_URL_370}&id={!EDMAForm__c.Id}

EDMAForm is our custom object.

Http http = new Http();
HttpRequest req = new HttpRequest();
req.setEndpoint('https://composer.congamerge.com?serverUrl={!API.Partner_Server_URL_370}&id={!EDMAForm__c.Id}  '+id);
req.setMethod('GET');

HttpResponse res = http.send(req);
String strresp='';
System.debug('response <<<<<<<<<<'+res.getStatusCode());
System.debug('response<<<<<<<<<<'+res.getBody());

Answer 1

The {!fieldname} syntax that you're using is called a merge expression (or a merge field), and is not going to do anything when included in a string in Apex (like what you have). Those are only for use in Visualforce, workflow, formula fields, etc...

You could create a formula field to get you the value of the partner server URL (or hardcode it), and you'll need to insert or query EDMAForm__c to be able to get an Id for one of those records.