Comparing the client to the server

Comparing the code between the RESTful calculator client and server.

The purpose of this side-by-side comparison is to provide a glimpse of how the client code and the server code relate. In some cases, only the initial line of server code has been provided; you can look at the full source for either the client or the server for the complete code.
Table 1. Client versus Server Code Comparison
Calculator client Calculator server 
LET req = 
  com.HttpRequest.Create("http://localhost:8090/add?a="
  || add_in.a || "&b=" || add_in.b)

The client creates the HTTP request, which is a URL consisting of a path and parameters.

 
LET m_reqInfo.path = req.getUrlPath()
CALL req.getUrlQuery(m_reqInfo.items)

The server parses out the path and the query from the HTTP service request.

 
CALL req.setMethod("GET")

The client sets the method with the verb "GET".

 
LET m_reqInfo.method = req.getMethod()

The server parses out the method verb from the HTTP service request. 

 CALL req.setHeader("Content-Type", "application/json")

The client sets the Content-Type header request.

 
LET m_reqInfo.ctype = getHeaderByName(req,"Content-Type")
    IF m_reqInfo.ctype.getIndexOf("/xml",1) THEN
    LET m_reqInfo.informat = "XML"
ELSE 
    LET m_reqInfo.informat = "JSON"
END IF

The server parses out the value of the Content-Type header request.

 
CALL req.setHeader("Accept", "application/json")

The client sets the Accept header request.

 
LET m_reqInfo.caccept = getHeaderByName(req,"Accept")
IF m_reqInfo.caccept.getIndexOf("/xml",1) THEN
    LET m_reqInfo.outformat = "XML"
ELSE 
    LET m_reqInfo.outformat = "JSON"
END IF

The server parses out the value of the Accept header request.

 
CALL req.doRequest()

The client submits the request.

 
LET req = com.WebServiceEngine.getHTTPServiceRequest(-1)

The server receives the HTTP service request.

 
LET resp = req.getResponse()
LET info.response = resp.getTextResponse()
CALL util.JSON.parse(info.response, add_out)
The client:
  • retrieves the HTTP response using a method of the com.HttpRequest class,
  • returns it as a string using methods of the com.HttpResponse class, and
  • parses out the desired value using methods of the util.JSON class.

This example is for JSON; if the data is XML instead, then the methods doXmlRequest() and getXmlResponse() would be used instead of getting a text response and JSON parsing.

 
CALL req.setResponseHeader("Content-Type","application/json")
CALL req.sendTextResponse(200, "OK", util.JSON.stringify(output_variable))

The server returns a response to the client.