HowTo: Retrieving data from a BC exposed as a Rest service

This documentation is valid for:

This document explains how to retrieve data from a Business Component exposed as a Rest web services in GeneXus.

First, let's see the basic guidelines:

How do I call the Rest service in GeneXus?

Use the HttpClient data type.

Which HTTP method should I use to retrieve the data?

The HTTP method used for retrieving the data is the GET HTTP method.

Which kind of information is exposed by the web service so I can consume it?

You can get a record given its Primary Key.

However, as since GeneXus X Evolution 2 you cannot retrieve all the data of the table (you can't execute a GET of all the records, e.g: <url base>/rest/Products), nor get the data from a given Foreign Key (<url base>/rest/Invoices?ClientId=234), or the data for a given Description Attribute (e.g:<url base>/rest/Products?ProductName=SmartPhone). This restriction on the information provided by the Rest BC is due to security reasons.

Which is the URL format to execute the GET?

Where <param1>,<param2>,..,<paramN> is the compound Primary Key.

Example

The following figure shows the Invoice Business Component transaction that is exposed as a Rest web service:

In this example, we want to get the Invoice whose InvoiceId=5

Example code

&httpclient.Host= &server
&httpclient.Port = &port
&httpclient.BaseUrl = &urlbase
&httpclient.Execute('GET','Invoice/5')

if &httpclient.StatusCode = 200
    &result = &httpclient.ToString()
else
   msg("There was an error retrieving the data: " + &httpclient.StatusCode.ToString())
endif

Download the sample from Sample GET data using a Rest BC

Notes:

If more than one parameter should be passed in the URL, they need to be separated by commas.
If the service URI is "http://localhost/TestRESTFullGX.NetEnvironment/rest/Invoice", the BASE URL is: "/TestRESTFullGX.NetEnvironment/rest/"
Error handling is managed by querying the HTTP Status Code after the invocation. For example, this error can occur if the data doesn't exist: {"error":{"code":"404","message":"Data with the specified key could not be found."}}.