@RestResource(urlMapping='/ApexCallout/*')
global class ApexCallout {
    
    
    @HttpPost
    global static String doPost(String value1, String value2) {
          String passVal = 'TEST';
        try {
            if(value1 == 'Account') {
                Account a = (Account) JSON.deserialize(value2, Account.class);
                if(a.Id == null)
                    insert a;
              }
          
        return passVal;
    }
    
    public static String dmlCallout(String value1, String value2) {
        
        Http rh = new Http();
        HttpRequest req = new HttpRequest();
        req.setMethod('POST');
        req.setHeader('content-type', 'application/json');
        req.setHeader('Host', 'ap1.salesforce.com');
        req.setEndpoint(Endpoint);

        Map<String, String> body = new Map<String, String>();
        body.put('value1', value1);
        body.put('value2', value2);
        String sbody = JSON.serialize(body);

        req.setHeader('Content-Length', String.valueOf(sbody.length()));
        req.setBody(sbody);

        HTTPResponse res = rh.send(req);
        
        if(res.getStatusCode() == 500) {
            String jsonString = res.getBody();
            jsonString = jsonString.substring(1, jsonString.length() - 1);
            Map<String, String> error = (Map<String, String>)JSON.deserialize(jsonString, Map<String, String>.class);
            String errorMsg = error.get('message');
            errorMsg = (errorMsg == null ? '' : errorMsg);
            throw new Exception('' + eMsg + '');
        }
        
        String passVal = res.getBody();
      
        return passVal;
    }
    
    public static String update(Account a) {
        return dmlCallout('Account', JSON.serialize(a));
    }
    
  
}