How to model parent-child entities via REST and JAX-RS
 I am working on a REST based API, and having some trouble figuring out what the canonical way is to represent parent / child relationships.  (I am writing beans in CXF and using JAX-RS and JAXB.  I started from the basic example provided by CXF)

My problem is let's say you have a Foo and a Bar.  There is a 1-N relationship with Foo and Bar, that is 1 Foo has many Bars.  My question is, what's the canonical way to find out what Bars a Foo has?  And what's the canonical way to access Bar resources owned by the Foo?

I have figured out that for example I might list Foos at:

GET http://xxx/fooservice/foos

And operate on a single foo at:

PUT/UPDATE/DELETE http://xxx/fooservice/foo/{fooid}

But how do I list Bars that Foo 121 has?  And how do I access them?  I've noticed that it seems the default JAXB marshaller doesn't output Collections just attributes for a bean, so if a Foo is:

<pre>
Foo
  - String id
  - String name
  - Collection<Bar> bars
</pre>

JAXB outputs something like:

&lt;foo&gt;&lt;id&gt;123&gt;/id&gt;&lt;name&gt;foo name&lt;/name&gt;&lt;/foo&gt; &lt;-- note the absence of the bars attribute

Which is problematic, as there is no way for the client to reasonably be expected to know that Foo has Bars, unless it "just knows" (which seems bad to me).  So while I can imagine to get a list of bars using:

GET http://xxx/fooservice/foo/121/bars

How does a client know that Foo has Bars if the output of the entity doesn't say anything about it?  Now presuming the client does get the list, then it seems entity operations would be something like:

GET/DELETE/UPDATE http://xxx/fooservice/foo/121/bar/435

which would access Bar 435 owned by Foo 121.  
How to model parent-child entities via REST and JAX-RS
===

 I am working on a REST based API, and having some trouble figuring out what the canonical way is to represent parent / child relationships.  (I am writing beans in CXF and using JAX-RS and JAXB.  I started from the basic example provided by CXF)

My problem is let's say you have a Foo and a Bar.  There is a 1-N relationship with Foo and Bar, that is 1 Foo has many Bars.  My question is, what's the canonical way to find out what Bars a Foo has?  And what's the canonical way to access Bar resources owned by the Foo?

I have figured out that for example I might list Foos at:

GET http://xxx/fooservice/foos

And operate on a single foo at:

PUT/UPDATE/DELETE http://xxx/fooservice/foo/{fooid}

But how do I list Bars that Foo 121 has?  And how do I access them?  I've noticed that it seems the default JAXB marshaller doesn't output Collections just attributes for a bean, so if a Foo is:

<pre>
Foo
  - String id
  - String name
  - Collection<Bar> bars
</pre>

JAXB outputs something like:

&lt;foo&gt;&lt;id&gt;123&gt;/id&gt;&lt;name&gt;foo name&lt;/name&gt;&lt;/foo&gt; &lt;-- note the absence of the bars attribute

Which is problematic, as there is no way for the client to reasonably be expected to know that Foo has Bars, unless it "just knows" (which seems bad to me).  So while I can imagine to get a list of bars using:

GET http://xxx/fooservice/foo/121/bars

How does a client know that Foo has Bars if the output of the entity doesn't say anything about it?  Now presuming the client does get the list, then it seems entity operations would be something like:

GET/DELETE/UPDATE http://xxx/fooservice/foo/121/bar/435

which would access Bar 435 owned by Foo 121.  