How to move a REST resource?

I'm tryin开发者_JAVA百科g to move a resource from /buckets/1 to /buckets/2 such that:

Initial state

• /buckets/1 = foo
• /buckets/2 = HTTP 404

Final state

• /buckets/1 = HTTP 301 to /buckets/2
• /buckets/2 = foo

What's a RESTful way of asking the server to move a resource in this manner?

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Answering my own question:

• For the sake of this discussion let's assume that we are storing "balls" in buckets
• The first thing to notice is that a ball's life-cycle is not determined by its containing bucket (moving a ball from one bucket to another does not delete the old ball). As such we should promote balls to a top-level resource: /balls
• REST seems to work best in terms of symbolic links as opposed to inline values, so instead of GET /buckets/1 returning the value of the ball in the bucket let's have it return the URI of the ball instead.

We can then move balls as follows:

(examine original state)
GET /buckets/1: "balls = {'/balls/1'}"
GET /buckets/2: "balls = {}"
GET /balls/1: "bucket = /buckets/1"

(move ball into bucket #2)
PUT /balls/1: "bucket = /buckets/2"

(examine new state)
GET /buckets/1: "balls = {}"
GET /buckets/2: "balls = {'/balls/1'}"
GET /balls/1: "bucket = /buckets/2"

End-result: the ball's identity remains consistent as it moves across buckets and (most importantly) this operation is atomic.

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1. GET /buckets/1
2. DELETE /buckets/1
3. PUT /buckets/2 {data returned by #1}

That doesn't make the server 301, though. The alternative would be to use the WebDAV MOVE method, i.e. by creating your own @MOVE annotation using the @HttpMethod annotation:

import ...;

@Target({ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@HttpMethod("MOVE")
public @interface MOVE {}

but doing so breaks REST's architectural principle of using HTTP as a uniform interface (RESTful Java).

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1. Create original resource:

   PUT /bucket/1

2. Call server procedure that responsible for moving resources:

   POST /bucket/1/move-to/2

3. Original resource path now should return Moved status code:

   GET /bucket/1 HTTP 301

4. Resource now should be available on new path:

   GET /bucket/2 HTTP 200