Test SAP Business Accelerator Hub APIs with curl

Go to https://api.sap.com and navigate to the Campaign API. The choice of this specific API is fairly arbitrary; there are lots of APIs from which to choose, but for the sake of choosing something, let’s use this one which is an OData V2 API within the SAP Cloud for Customer API package.

Select the API Reference section, and within that choose the GET /CampaignCollection combination of HTTP method and relative endpoint. This is one of the simpler API calls in that it’s read-only and is likely to return an amount of data that is useful for testing.

Note that the parameters (in particular the ones starting with a $ symbol) give us a clue that it’s an OData API that we’re dealing with, and the structure of the response example value, with the d wrapper, tells us that it’s an OData V2 API.

The SAP Business Accelerator Hub provides you with code snippets in a variety of languages and tools for each API. To get to these code snippets, select the Try Out facility, and within that choose the Code Snippet section, where you should see a variety of sources, one of which is for the command line HTTP client curl:

Note that the snippet already contains the relevant inclusion of your own API key, which needs to be provided on requests in an APIKey header; this is done with curl using a --header option as shown.

These notes might help you to better examine and understand the invocation:

• There is a trailing backslash right at the end of the last line (ignoring the comment line #API endpoint for API sandbox); such backslashes are used to escape the newlines that directly follow them, so that such invocations can be presented – and indeed used on the command line – over multiple lines. This last backslash is unnecessary (and you don’t need to include that comment line either, of course).
• The --request GET option is actually unnecessary as curl will use the method appropriate to the rest of the options given; in this case it will automatically use GET.
• The OData system query options have been URL-encoded (this is actually called Percent-encoding). Specifically, the occurrences of %24 are just $ characters, encoded. Knowing this may make reading the URL easier, in that they are the start of normal OData query parameters $inlinecount=allpages and $top=50.
• The DataServiceVersion: 2.0 header is to explicitly signal that the request is for OData V2; this is optional, and arguably unnecessary as the OData API only supports V2 anyway.
• Perhaps the most interesting header here is the Accept: application/json. This forms part of standard HTTP content negotiation and here represents a desire for the resource being requested to be returned in a JSON representation. If the value of this header were to be set to application/xml then the entity set resource would be returned in an XML representation, aligned with what OData supports.

In the SAP Business Application Studio, create a dev space, giving it a name and choosing the ‘Basic’ option as shown:

You can choose any kind of dev space, but to emphasize that the command line tools you’ll be using are available in all of them, we want you to choose this “Basic” kind.

Once the dev space has started up, open up a terminal with the menu path Terminal -> New Terminal (the menu is available via the three horizontal bar icon in the top left). Now you have a shell prompt in which to run the code snippet, specifically invoking curl. At this point you may wish to maximize the terminal with the up arrow (^) button on the right hand side.

Copy the code snippet from the SAP Business Accelerator Hub page and paste it into the terminal. When you run the command, you should see output that looks something like this:

You’ll notice that the output is not formatted and is not easy to read. To address this you can use the command line JSON processor jq. It’s not just a JSON formatter, it’s an entire language for handling, processing, generating and modifying JSON data, but here we’ll just use its most basic feature, which is the identity function .. This just emits what’s received, with no transformations. How is that useful? Well, unless you say otherwise (with the -c and -M options, in case you’re curious), jq will, by default, pretty-print (and colorize) any JSON it emits.

You can also invoke jq just on its own, without specifying the . identity filter; in this case, the identity filter will be used as default anyway.

Try this now, by piping the output from the curl invocation into jq like this:

curl --url 'https://sandbox.api.sap.com/sap/c4c/odata/v1/c4codataapi/CampaignCollection?$inlinecount=allpages&$top=50' \
  --header 'your-API-key-here' \
  --header 'Accept: application/json' \
  --header 'DataServiceVersion: 2.0' \
| jq .

The output should now appear pretty-printed, something like this (all but one of the entities in the results set, and many individual properties, have been removed for brevity here):

{
  "d": {
    "__count": "452",
    "results": [
      {
        "__metadata": {
          "uri": "https://sandbox.api.sap.com/sap/c4c/odata/v1/c4codataapi/CampaignCollection('00163E03A0701ED28B9EB2A63189D226')",
          "type": "c4codata.Campaign",
          "etag": "W/\"datetimeoffset'2012-11-12T18%3A20%3A06.8114710Z'\""
        },
        "ObjectID": "00163E03A0701ED28B9EB2A63189D226",
        "CampaignType": "4",
        "CampaignTypeText": "Phone Call",
        "CampaignID": "1",
        "CampaignName": "Campaign for CN Customers",
        "EntityLastChangedOn": "/Date(1352744406811)/",
        "ETag": "/Date(1352744406811)/",
        "CampaignNotes": {
          "__deferred": {
            "uri": "https://sandbox.api.sap.com/sap/c4c/odata/v1/c4codataapi/CampaignCollection('00163E03A0701ED28B9EB2A63189D226')/CampaignNotes"
          }
        },
        "CampaignOutboundMarketingActivity": {
          "__deferred": {
            "uri": "https://sandbox.api.sap.com/sap/c4c/odata/v1/c4codataapi/CampaignCollection('00163E03A0701ED28B9EB2A63189D226')/CampaignOutboundMarketingActivity"
          }
        }
      }
    ]
  }
}

The formatted output represents the results of a simple call to the Campaign Collection API endpoint - an OData entity set.

Now that you have invoked your first curl request to make a call to an API endpoint, you can start to modify the request to suit your needs or curiosity.

One way of doing that is to edit the invocation on the command line directly.

Another way is to go back to the Try Out facility in the SAP Business Accelerator Hub, modify the request parameter values in the Web-based UI, and then re-copy the code snippet which will have been modified to match your changes.

Try this example:

First, reduce the number of entities requested by setting a low value for the $top parameter:

Next, choose Status and StatusText for the properties to be returned, using the $select parameter:

Then go back to the Code Snippet facility, and note that the URL for the curl invocation has been adjusted accordingly:

Follow the same approach of copying and pasting this into your terminal session, and you should see the effect - a drastic reduction of data returned:

{
  "d": {
    "__count": "452",
    "results": [
      {
        "__metadata": {
          "uri": "https://sandbox.api.sap.com/sap/c4c/odata/v1/c4codataapi/CampaignCollection('00163E03A0701ED28B9EB2A63189D226')",
          "type": "c4codata.Campaign",
          "etag": "W/\"datetimeoffset'2012-11-12T18%3A20%3A06.8114710Z'\""
        },
        "Status": "2",
        "StatusText": "Active"
      },
      {
        "__metadata": {
          "uri": "https://sandbox.api.sap.com/sap/c4c/odata/v1/c4codataapi/CampaignCollection('00163E03A0701ED28B9EB2A63189F226')",
          "type": "c4codata.Campaign",
          "etag": "W/\"datetimeoffset'2012-11-12T18%3A20%3A06.8114710Z'\""
        },
        "Status": "2",
        "StatusText": "Active"
      },
      {
        "__metadata": {
          "uri": "https://sandbox.api.sap.com/sap/c4c/odata/v1/c4codataapi/CampaignCollection('00163E03A0701ED28B9EB2A6318A1226')",
          "type": "c4codata.Campaign",
          "etag": "W/\"datetimeoffset'2012-11-12T18%3A20%3A06.8114710Z'\""
        },
        "Status": "2",
        "StatusText": "Active"
      }
    ]
  }
}

Now you know how to use the SAP API Accelerator Hub code snippet features, and what to do with the curl command line examples.

If you want to find out more about jq, you might find the content of this Community Talk from SAP TechEd 2023 in Bengaluru useful: Handle JSON like a boss with jq.