ASP.NET Web API : HTTP status code standard of restful API

While designing the restful API, we need to make sure that API should always return the right and consistence HTTP status Code and without consistent HTTP status codes, customers will not know the difference between success or failure without parsing the response body.

HTTP standard provides almost 70 status codes to describe the response status and you can use below HTTP status code for restful API.

200 – OK

204 – OK – No Content

400 – Bad Request

401 – Unauthorized

404 – Resource Not Found

500 – Internal Server Error

503 – Service is not available

HTTP – GET (Resource Inquiry):

HTTP GET  Sequence Diagram

The above sequence diagram explain how the HTTP request is being processed and returns the HTTP status code.

There are the possible scenarios for processing of the HTTP GET request.

1.    Scenario :   If request resource is found, Returns HTTP – 200 OK with Resource data

2.    Scenario :  If request resource is not available, return HTTP – 404 Resource Not Found  – with message “Resource is not available”

           

3.    Scenario:       Any Validation Error/invalid input – returns HTTP – 400 Bad Request with validation or error message.

             

HTTP – POST (Resource Creation) 

HTTP POST Sequence Diagram

The above sequence diagram explain how the HTTP request is being processed and returns the right HTTP status code.

There are the possible scenarios for processing of the HTTP POST request.

1.    Scenario:   If requested resource is successfully created, Returns HTTP – 201 OK with Newly created Resource data

2.    Scenario:

If request resource is already found or duplicate resource, returns – returns HTTP – 400 Bad Request with validation message

                                                                               OR

·              Any validation or invalid input error - returns HTTP – 400 Bad Request with validation message

  

   HTTP – PUT (Resource Update)

HTTP PUT Sequence Diagram

The above sequence diagram explain how the HTTP request is being processed and returns the right HTTP status code.

There are the possible scenarios for processing of the HTTP PUT request.

1.    Scenario:   Any validation or invalid input error - returns HTTP – 400 Bad Request with validation message

           

2.    Scenario:  If request resource is not available, return HTTP – 404 Resource Not Found  – with message “Resource is not available”

In this scenario, if resource is not available, many architect prefer to create new resource and returns HTTP – 201 OK with newly created resource data

        

3.    Scenario:  If request resource is available and successfully updated, Returns HTTP – 200 OK with updated Resource data

     

HTTP – PATCH (Partially Resource Update)

 

HTTP PATCH Sequence Diagram

The above sequence diagram explain how the HTTP request is being processed and returns the right HTTP status code.

There are the possible scenarios for processing of the HTTP PATCH request.

1.    Scenario : If request resource is available and successfully updated , Returns HTTP – 200 OK with updated Resource data

         

2.    Scenario :  Any validation or invalid input error - returns HTTP – 400 Bad Request with validation message

                                                         

3.    Scenario :  If request resource is not available, return HTTP – 404 Resource Not Found  – with message “Resource is not available”

                

HTTP – DELETE (Delete Resource)

HTTP DELETE Sequence Diagram

The above sequence diagram explain how the HTTP request is being processed and returns the right HTTP status code.

There are the possible scenarios for processing of the HTTP DELETE request.

1.    Scenario : If request resource is available and successfully deleted, Returns HTTP – 200 OK 

2.     Scenario :  Any validation or invalid input error - returns HTTP – 400 Bad Request with validation message

3.    Scenario :  If request resource is not available, return HTTP – 404 Resource Not Found  – with message “Resource is not available”

Note: In some scenario, requested URI is not matching with any API URI., then by default Web API/IIS returns HTTP – 404 - with message “HTTP resource was found that matches the request URI”

References:

·       Principles and Practices of Web API’s

·       API Best Practices: Plan Your API (Part 1)

 
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