Rafael Santos Blog

A collection of tech articles I have been writting over the years for my own future reference.

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How to Create Many-to-Many Resources with REST

Imagine a classic Many-to-Many relationship where a User can subscribe to many Groups and a Group can have many subscribers. During subscription we need to indicate what is the *role* for that User. Possible *roles* are: owner, collaborator or member.

In relational land, this is a classic User Many-to-Tany Group which results in a join table plus a field to represent the *role* of the User in the Group.

In REST land, we could represent it as a relationship resource:

Create a User

--- Request ---
POST /users
{name: "Jack"}
--- Response ---
{userId: 11, name: "Jack"}

Create a Group

--- Request ---
POST /groups
{description: "Java Programming Language"}
--- Response ---
{groupId: 21, description: "Java Programming Language"}

Now let’s subscribe the User “Jack” to the Group “Java Programming Language” as “collaborator”.

--- Request ---
POST /subscriptions
{userId: 11, groupId: 21, role: "collaborator"}
--- Response ---
{subscriptionId: 31, userId: 11, groupId: 21, role: "collaborator"}

Get all “Jack”’s (userId=11) subscriptions

--- Request ---
GET /subscriptions?userId=11
--- Response ---
[ {subscriptionId: 31, userId: 11, groupId: 21, role: "collaborator"} ]

Delete the subscription

--- Request ---
DELETE /subscriptions/31
--- Response ---
Status 200 OK

Note: subscriptions could be named as users-to-groups or anything else you can think of. I just find subscriptions more meaningful for this scenario.