HTTP Operations

With HTTP Operations we mean: Identify the action (i.e. Create, Read, Update or Delete) that needs to be performed on a resource (i.e. Client, Order, Employee).

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With API Gateway we mean: A collection of RESTful API operations that can be published to the outside world to give them access to applications that are linked to your business process.

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Each HTTP Method represents a certain action on a resource. Of the most frequently used ones we can make a nice comparison to the CRUD operations:

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HTTP Operations: CRUD Operations:

* POST - Create

* GET - Read

* PUT - Update

* DELETE - Delete

So the POST represents a Create action, the GET a read action, etc.

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This also means that when you do a GET (a read action) it should **not** alter the resource you are requesting from your backend operation if you want to adhere to the RESTful principles.

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== 3. HTTP Operations ==

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A crucial part of setting up your (API) Gateway with the help of RESTful services is

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knowing what HTTP Operations are and how you can use them to control what parties can change via your (API) Gateway.

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Each HTTP Method represents a certain action on a resource. Of the most frequently used ones we can make a nice comparison to the CRUD operations:

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HTTP Operations: CRUD Operations:

* POST - Create

* GET - Read

* PUT - Update

* DELETE - Delete

So the POST represents a Create action, the GET a read action, etc.

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This also means that when you do a GET (a read action) it should **not** alter the resource you are requesting from your backend operation if you want to adhere to the RESTful principles.

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=== 3.1 Determining the HTTP Operations in eMagiz ===

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When you look at the conceptual idea of the API Gateway, exposing backend operations via a centralized location to the outside world

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it stands to reason that when you set up your API Gateway (i.e. the front-end facing part) start with the backend operation you want to expose.

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When the backend operation also adheres to the RESTful principles you can simply reuse that HTTP method.

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For example, if they have a GET operation to an HTTP Operation that you want to expose you should also have a GET operation on the API Gateway side.

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To expose a backend operation directly in the API Gateway double click on the backend system and look for the available Endpoint operations

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[[image:Main.Images.Microlearning.WebHome@crashcourse-api-gateway-api-http-operations--endpoint-operations.png]]

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Select one of them and press the button Expose in Gateway. This will lead you to the following pop-up.

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In this pop-up select, the message type (the resource) that you want to link this operation to and press expose.

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[[image:Main.Images.Microlearning.WebHome@crashcourse-api-gateway-api-http-operations--endpoint-operations-message-type.png]]

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The result is that you will see the following pop-up (which is also the main configuration and edit screen in case you want to alter something).

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[[image:Main.Images.Microlearning.WebHome@crashcourse-api-gateway-api-http-operations--api-gateway-exposed-from-backend-edit.png]]

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The moment you are content with this action press Save and let eMagiz configure the exposed operation correctly.

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=== 3.2 Editing the HTTP Operation in eMagiz ===

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You can easily do so in eMagiz by editing the API Gateway integration in Design via the context menu or by double-clicking on it.

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[[image:Main.Images.Microlearning.WebHome@crashcourse-api-gateway-api-http-operations--edit-api-integration.png]]

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In this pop-up, you can select the (backend) System Operation you want to expose via the API Gateway.

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[[image:Main.Images.Microlearning.WebHome@crashcourse-api-gateway-api-http-operations--edit-api-integration-pop-up.png]]

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By pressing the button Select System Operation you will see an overview of all available operations

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[[image:Main.Images.Microlearning.WebHome@crashcourse-api-gateway-api-http-operations--edit-api-integration-pop-up-available-operations.png]]

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Select the GET operation and eMagiz will update your integration. The result of this example will be that external clients can execute a

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GET call to retrieve HTTP methods from the system called Crash Course * API Gateway via the help of the eMagiz API Gateway.

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[[image:Main.Images.Microlearning.WebHome@crashcourse-api-gateway-api-http-operations--edit-api-integration-pop-up-result.png]]

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In this screen, there are also other things you could edit that will come in handy in other scenarios.

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For example, in case the external party does not adhere to the RESTful principle or does not even publish a REST endpoint but a SOAP endpoint or

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something else entirely you need to remember the basic principles when determining the correct HTTP Operation for the job.

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For example, when you need to call a backend operation that hosts a SOAP web service from which you can retrieve data (but not create or update it) you should use the GET operation **without** a body.

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In future microlearnings, we will discuss these scenarios in more detail.

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== 4. Key takeaways ==

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Each HTTP Method represents a certain action on a resource. Of the most frequently used ones we can make a nice comparison to the CRUD operations:

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HTTP Operations: CRUD Operations: