Databases Reference
In-Depth Information
@Path
(
"/{name1}/{name2}"
)
public
String
getDistance
(
@PathParam
(
"name1"
)
String
name1
,
@PathParam
(
"name2"
)
String
name2
)
{
String
query
=
"START first=node:user(name={name1}),\n"
+
"second=node:user(name={name2})\n"
+
"MATCH p=shortestPath(first-[*..4]-second)\n"
+
"RETURN length(p) AS depth"
;
Map
<
String
,
Object
>
params
=
new
HashMap
<
String
,
Object
>();
params
.
put
(
"name1"
,
name1
);
params
.
put
(
"name2"
,
name2
);
ExecutionResult
result
=
executionEngine
.
execute
(
query
,
params
);
return
String
.
valueOf
(
result
.
columnAs
(
"depth"
).
next
()
);
}
}
Of particular interest here are the various annotations:
•
@Path("/distance")
specifies that this extension will respond to requests directed
to relative URIs beginning
/distance
.
• The
@Path("/{name1}/{name2}")
annotation on
getDistance()
further qualifies
the URI template associated with this extension. The fragment here is concatenated
with
/distance
to produce
/distance/{name1}/{name2}
, where {name1} and {name2}
are placeholders for any characters occurring between the forward slashes. Later
on, in
“Testing server extensions” on page 87
, we'll register this extension under
the
/socnet
relative URI. At that point, these several different parts of the path ensure
that HTTP requests directed to a relative URI beginning
/socnet/distance/{name1}/
{name2}
(for example,
http://<server>/socnet/distance/Ben/Mike
) will be dispatch‐
ed to an instance of this extension.
•
@GET
specifies that
getDistance()
should be invoked only if the request is an HTTP
GET.
@Produces
indicates that the response entity body will be formatted as
text/
plain
.
• The two
@PathParam
annotations prefacing the parameters to
getDistance()
serve
to map the contents of the
{name1}
and
{name2}
path placeholders to the method's
name1
and
name2
parameters. Given the URI
http://<server>/socnet/distance/Ben/
Mike
,
getDistance()
will be invoked with
Ben
for
name1
and
Mike
for
name2
.
• The
@Context
annotation in the constructor causes this extension to be handed a
reference to the embedded graph database inside the server. The server infrastruc‐
ture takes care of creating an extension and injecting it with a graph database in‐
stance, but the very presence of the
GraphDatabaseService
parameter here makes
