Java Reference
In-Depth Information
bookmarkable URIs. So you've decided that your URI scheme will be
...user/{id}
, which
is a template where the part between the curly braces represents the user's ID. So if you create
a user with ID 007, that bookmarkable URI will be
...resources/forms/user/007
.
NOTE
To follow the basic REST style, you need to create this URI now so that you can return in the HTTP
response the
Location
header populated with the value of the unique URL for the user you created.
This provides the client with metadata about the response and also a choice for the client to transition
state (among others). Remember, hypermedia as the engine of application state.
So in order to build your URI, use the
UriBuilder
class in conjunction with the
UriInfo
ob-
ject, which was injected into the method via the
@Context
parameter to this method. Again,
you don't have to do anything special to get that
UriInfo
object; its values are populated by
the runtime.
Using the
UriInfo
instance, you get the value for the path the current request is answering,
and then use the path method to indicate to your template that you need to populate (
"{a}"
).
The value within the template (in this case,
a
) is not special. It gets substituted for the value
passed to the build method (in this case, the ID of the user you created). Note that the
UriBuilder
class follows a standard builder pattern, and works like
StringBuilder
and oth-
er builder classes (
ResponseBuilder
in JAX-RS, for instance).
Once your URI is created, pass it into your response-building process. The
Response
class
actually has
ResponseBuilder
as an inner class. By using the
created
method initially, you
set the HTTP response code to 201 Created. By using the
entity
method and passing it your
user object (the entity you created), you're able to return the representation of the entity along
with the response. The runtime will look for an available
MessageBodyWriter<User>
imple-
mentation in order to create that entity representation. Finally, by using the location method,
you can automatically add the new URI as the value of the
Location
header in the HTTP re-
sponse.
Note that it's enough to simply post the form to itself by specifying
action=''
because you
have different HTTP methods answering. While there are two GETs in the service, they re-
spond to different paths, as the
viewOne
method only responds when an ID is supplied.
The last class in this little service is the
MessageBodyWriter
implementation that returns your
User
representation as requested by your invocation of the
entity
method on the
Response
builder. The writer is shown in
Example 8-22
.
Example8-22.UserHtmlWriter.java creates an HTML representation of the user entity
