topic Re: SAP Developer Challenge - APIs - Task 3 - Have a Northbreeze product selected for you in Application Development and Automation Discussions

SAP Developer Challenge - APIs - Task 3 - Have a Northbreeze product selected for you

qmacro — Fri, 11 Aug 2023 14:21:34 GMT

(Check out the SAP Developer Challenge - APIs blog post for everything you need to know about the challenge to which this task relates!)

In this task you'll learn a bit about actions and functions in OData V4.

Background

While OData V2 did have function imports, the advent of OData V4 brought about enhancements in this area and we now have a clean distinction between different types of orthogonal endpoints that can be presented in an OData service alongside the entity sets, singletons and more. See the Actions and functions sections of the OData V4 and SAP Cloud Application Programming Model talk slides for more info.

With CAP's support for OData V4's actions and functions ready for us to enjoy, it's a good opportunity to try things out here.

In addition to the entity sets we saw in the previous task, the Northbreeze OData V4 service also sports an action. If you check the service's metadata document document you'll see the evidence of this action.

First, it appears alongside the EntitySet elements within the EntityContainer element:

<EntityContainer Name="EntityContainer">
  <EntitySet Name="Products" EntityType="Northbreeze.Products">
    <NavigationPropertyBinding Path="Category" Target="Categories"/>
    <NavigationPropertyBinding Path="Supplier" Target="Suppliers"/>
  </EntitySet>
  <EntitySet Name="Suppliers" EntityType="Northbreeze.Suppliers">
    <NavigationPropertyBinding Path="Products" Target="Products"/>
  </EntitySet>
  <EntitySet Name="Categories" EntityType="Northbreeze.Categories">
    <NavigationPropertyBinding Path="Products" Target="Products"/>
  </EntitySet>
  <EntitySet Name="Summary_of_Sales_by_Years" EntityType="Northbreeze.Summary_of_Sales_by_Years"/>
  <EntitySet Name="TotalProducts" EntityType="Northbreeze.TotalProducts"/>
  <ActionImport Name="selectProduct" Action="Northbreeze.selectProduct"/>
</EntityContainer>

The action itself is described in more detail along with the EntityType elements. Here it is in full:

<Action Name="selectProduct" IsBound="false">
  <Parameter Name="communityid" Type="Edm.String"/>
  <ReturnType Type="Edm.String"/>
</Action>

You can see from this detail that:

it's an unbound action
it expects a single parameter communityid
it returns a result

Basically, this action expects to receive your SAP Community ID as input, and, based on that ID, will choose a product for you.

Actions vs functions: One of the key differences between actions and functions in OData V4 is that while functions may not have side effects, actions may well have side effects. This means that normally functions will be used for read-only operations, while actions can be used for operations that make some sort of change. But they don't have to. And here, we're using an action, rather than a function, mostly because actions require the POST HTTP method (because they may have side effects), rather than GET. And requiring you to use HTTP POST for this task makes things more interesting.

Your task

Your task is to call this unbound action, supplying your SAP Community ID for the communityid parameter. The response you will receive is a JSON representation, containing a value property, the value for which is the product that has been selected for you (based on your SAP Community ID).

This is the value you must hash and then post that hash as a new reply to this discussion thread, as described in Task 0 - Learn to share your task results.

Here's an example. Calling the action with qmacro as the value for communityid causes this to be returned in response (pretty printed for readability):

{
  "@odata.context": "$metadata#Edm.String",
  "value": "Rössle Sauerkraut"
}

The product name Rössle Sauerkraut is what needs to be hashed. Note, in this case, that any value passed in the URL path must be properly URL encoded. So while the value test, for example, needs no specific URL encoding, this value must be URL encoded, in order to be successfully transported in the URL path and accurately received and parsed by the hash service. In other words, the value:

Rössle Sauerkraut

needs to be URL encoded so it looks like this:

R%C3%B6ssle%20Sauerkraut

When inserted into the URL path, it will therefore look like this:

/v1/hash(value='R%C3%B6ssle%20Sauerkraut')

Hints and tips

You may want to peruse the content of the talk OData V4 and SAP Cloud Application Programming Model, in particular the short Actions and functions section.

You may also wish to watch the replay of the Hands-on SAP Dev live stream episode Back to basics: OData - the Open Data Protocol - Part 5 - Actions & functions.

You can find out what URL encoding is all about in the Wikipedia entry for URL encoding. You're likely to find either a built-in or a library function in your favorite language to do that, for example JavaScript has encodeURIComponent and Python has a quote function in urllib.parse.

Finally, you may wish to read this short post OData query operations and URL encoding the system query options with curl, written in part as a response to a great comment on the previous task.

For discussion

What's the difference between the meanings of "bound" and "unbound" in this context? What does the fact that the selectProduct action is "unbound" suggest to us?

Remember, if you're posting your thoughts on these discussion questions, remember to do it in a reply separate from your hash reply!

Re: SAP Developer Challenge - APIs - Task 3 - Have a Northbreeze product selected for you

vladimirs_semikins — Wed, 09 Aug 2023 05:53:25 GMT

4aad13e1746f9d43e995d2d0bbf1185d2bea565ea487d4d8eb72ccd3986684f3

Re: SAP Developer Challenge - APIs - Task 3 - Have a Northbreeze product selected for you

vladimirs_semikins — Wed, 09 Aug 2023 05:56:22 GMT

What a bummer I got the value containing only one word, no JS this time for me 🌞

Re: SAP Developer Challenge - APIs - Task 3 - Have a Northbreeze product selected for you

ajmaradiaga — Wed, 09 Aug 2023 05:59:59 GMT

a051e43183593a227412695eeac769af9977f07e5efb4bd11c40bd52d1a04396

Re: SAP Developer Challenge - APIs - Task 3 - Have a Northbreeze product selected for you

qmacro — Wed, 09 Aug 2023 06:02:30 GMT

Haha, sorry about that 🙂 The algorithm for picking a product for a given community member is quite simple, and as it's fixed (and consistent, hopefully!) a given community member will always get the same product.

Re: SAP Developer Challenge - APIs - Task 3 - Have a Northbreeze product selected for you

qmacro — Wed, 09 Aug 2023 06:03:57 GMT

Here's an extra sub-task for you, then, @vladimirs_semikins ... as you were pretty quick, you could help out on this thread and give hints to any of those who need them as to how to call an OData V4 action with an HTTP POST request. Not too many hints, just enough to give them an idea 👍 🙂

Re: SAP Developer Challenge - APIs - Task 3 - Have a Northbreeze product selected for you

kumarniti4 — Wed, 09 Aug 2023 06:09:43 GMT

9ded87220fcf379da1b79b71b1f4b92fb34eb6013ba17afd98be56e5a2111181

Re: SAP Developer Challenge - APIs - Task 3 - Have a Northbreeze product selected for you

prachetas — Wed, 09 Aug 2023 06:21:04 GMT

1663ab8519dc065f9daf05f3f223c8317eb916685d1133a792bbd3edee1c7578

Re: SAP Developer Challenge - APIs - Task 3 - Have a Northbreeze product selected for you

ceedee666 — Mon, 04 Sep 2023 09:20:32 GMT

cee733d6f01eead517dec302cd5b83bf2b852a47e4a07abf31efe6f4b1947fdb

Corrected my sollution.

Re: SAP Developer Challenge - APIs - Task 3 - Have a Northbreeze product selected for you

ceedee666 — Wed, 09 Aug 2023 06:26:47 GMT

Had to look up how to send JSON data with the request library and how to perform URL encoding. Two nice little learnings for a Wednesday morning. Thanks @qmacro! 👏

https://github.com/ceedee666/sap-dev-challenge-apis-in-python

Re: SAP Developer Challenge - APIs - Task 3 - Have a Northbreeze product selected for you

SandipAgarwalla — Wed, 09 Aug 2023 07:23:52 GMT

62ba810562db9972a928b5a817437f80f62b12c759f7953efdfdbdf61b3aca33

Re: SAP Developer Challenge - APIs - Task 3 - Have a Northbreeze product selected for you

vladimirs_semikins — Wed, 09 Aug 2023 07:42:41 GMT

Create a correct URL to properly access the `/selectProduct` action, you can find an example at https://github.com/qmacro/odata-v4-and-cap/blob/main/slides.md#action-examples-post.
Next, use any REST client (curl, postman, insomania, etc.)
Make a POST request with a JSON body type, including the number of attribute(s) defined in the metadata - see EntityType elements inside <Action Name="selectProduct" IsBound="false"> ... </Action>
Encode if required using JS as mentioned
Create Hash as defined in Task 0
Post message here 😉

Re: SAP Developer Challenge - APIs - Task 3 - Have a Northbreeze product selected for you

eakucuk — Wed, 09 Aug 2023 08:09:55 GMT

00e93c286b4316a2fb58bfbb8ddd274703e8059a39e21314eb373b0340d9330e

Re: SAP Developer Challenge - APIs - Task 3 - Have a Northbreeze product selected for you

UweFetzer_se38 — Wed, 09 Aug 2023 08:13:54 GMT

fe09f888ade21a2b8e21ba691918cd1d074e99b3b2cbfbf58bc851e1bdaabf3b

Re: SAP Developer Challenge - APIs - Task 3 - Have a Northbreeze product selected for you

UweFetzer_se38 — Wed, 09 Aug 2023 08:16:41 GMT

Had to Google my product, looks tasty.

Re: SAP Developer Challenge - APIs - Task 3 - Have a Northbreeze product selected for you

huseyindereli — Wed, 09 Aug 2023 08:27:33 GMT

d0cd8095643dde270642afc54c8821748e4c9672aa550c5d38b4542874a99567

Re: SAP Developer Challenge - APIs - Task 3 - Have a Northbreeze product selected for you

choujiacheng — Wed, 09 Aug 2023 08:28:53 GMT

15e994e0614b367768215e40e4b204b37dd2779ffdc6933bf910508265cb58b1

Re: SAP Developer Challenge - APIs - Task 3 - Have a Northbreeze product selected for you

choujiacheng — Wed, 09 Aug 2023 08:48:07 GMT

A bound action is attached to an entity type and can be overloaded. An unbound action is not bounded to an entity and cannot be overloaded. As selectProducts is an unbound action, the URL does not need to call the entity Products, for example, to receive the answer, but rather be called on its own.

Re: SAP Developer Challenge - APIs - Task 3 - Have a Northbreeze product selected for you

Ella — Wed, 09 Aug 2023 08:51:52 GMT

8beb73847eab0a613c8a5b21f15f49976d1e06a52e33e027350f5c8855513c5c

Re: SAP Developer Challenge - APIs - Task 3 - Have a Northbreeze product selected for you

nicoschoenteich — Wed, 09 Aug 2023 09:01:04 GMT

4684f9e47770606d1de40da018df043fd82403ecb48fca2fbf3b6f29f9b263ef