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How to do stuff RESTful

 

When should we use PUT and when should we use POST?

The HTTP methods POST and PUT aren't the HTTP equivalent of the CRUD's create and update. They both serve a different purpose. It's quite possible, valid and even preferred in some occasions, to use POST to create resources, or use PUT to update resources.

Use PUT when you can update a resource completely through a specific resource. For instance, if you know that an article resides at http://example.org/article/1234, you can PUT a new resource representation of this article directly through a PUT on this URL.

If you do not know the actual resource location, for instance, when you add a new article, but do not have any idea where to store it, you can POST it to an URL, and let the server decide the actual URL.

PUT /article/1234 HTTP/1.1
<article>
    <title>red stapler</title>
    <price currency="eur">12.50</price>
</article>
POST /articles HTTP/1.1
<article>
    <title>blue stapler</title>
    <price currency="eur">7.50</price>
</article>

HTTP/1.1 201 Created
Location: /articles/63636

As soon as you know the new resource location, you can use PUT again to do updates to the blue stapler article. But as said before: you CAN add new resources through PUT as well. The next example is perfectly valid if your API provides this functionality:

PUT /articles/green-stapler HTTP/1.1
<article>
    <title>green stapler</title>
    <price currency="eur">9.95</price>
</article>

HTTP/1.1 201 Created
Location: /articles/green-stapler

Here, the client decided on the actual resource URL.

Caveats

  • PUT and POST are both unsafe methods. However, PUT is idempotent, while POST is not.

See also




This recipe has been written by joshua thijssen.