Request matching

JAX-RS uses the @Path annotation for dispatching requests to corresponding resource or sub-resource methods using the following steps:

Identify a set of candidate root resource classes matching the request.
Obtain a set of candidate resource methods for the request.

Identify the method that will handle the request.
If no matching resource method or sub-resource method can be found, then an appropriate error response is returned.

Now let us illustrate, for the following services, Service1 and Service2, how request dispatching happens when a client requests the target resources:

@Path("/s1")
public class Service1 {
    /**
     * Creates a new instance of Service1     
    */
    public Service1() {
    }

    @GET
    @Path("{name : .+}")
    @Produces(MediaType.APPLICATION_JSON)
    public String get1(@PathParam("name") String name) {
        System.out.println("Service1.get1 Invoked");
        return "Service1.get1."+name;
    }

    @GET
    @Path("{name : .+}/g2")
    @Produces(MediaType.APPLICATION_JSON)
    public String get2(@PathParam("name") String name) {
        System.out.println("Service1.get2 Invoked");
        return "Service1.get2."+name;
    }   
}

Let's see how it works with Service 2 here:

@Path("/{any : .*}")
public class Service2 {
    /**
     * Creates a new instance of Service2
     */
    public Service2() {
    }

    @GET
    @Produces(MediaType.APPLICATION_JSON)
    public String get1() {
        System.out.println("Service2.get1 Invoked");
        return "Service2.get1";
    }

    @PUT
    @Consumes(MediaType.APPLICATION_JSON)
    public void put1(String content) {
        System.out.println("Service2.put1 Invoked");
        System.out.println(content);
    }
}

Now let us look at how the different client requests get resolved to the corresponding target resource:

Client request	Request matching steps
HTTP `GET` request `/s1/g1`	Matching root resource class is `Service1` as `@Path(“/s1”)` best matches the `Service1` class. Candidate resource methods is `get1` as the `@Path` expression resolves to `{name : .+}`. The `.+` is a regular expression that will match any stream of characters after `/s1`. The method that will handle the request is `get1` in this case.
HTTP `GET` request `/s1/x/g2`	Matching root resource class is `Service1` as `@Path(“/s1”)` best matches the `Service1` class. Candidate resource methods is `get2` as the `@Path` expression resolves to `{name : .+}/g2`. The `.+` is a regular expression that will match any stream of characters after `/s1` that ends with `g2`. The method that will handle the request is `get2` in this case.
HTTP `GET` request `/s1/x/g1`	Matching root resource class is `Service1` as `@Path(“/s1”)` best matches the `Service1` class. Candidate resource methods is `get1` as the `@Path` expression resolves to `{name : .+}`. The `.+` is a regular expression that will match any stream of characters after `/s1`. The method that will handle the request is `get1` in this case.
HTTP `GET` request `/s2/g1`	Matching root resource class is `Service2` as `@Path(“{any : .*}”)` best matches the `Service2` class. Candidate resource methods is `get1`, which is the only available `GET` method in this class. The method that will handle the request is `get1` in this case.
HTTP `PUT` request `/s2/g1`	Matching root resource class is `Service2` as `@Path(“{any : .*}”)` best matches the `Service2` class. Candidate resource methods is `put1`, as that is the only available `PUT` method in this class. The method that will handle the request is `put1` in this case.
HTTP `PUT` request `/s1/g1`	Matching root resource class is `Service1` as `@Path(“/s1”)` best matches the `Service1` class. Candidate resource methods is `get1` as the `@Path` expression resolves to `{name : .+}`. The `.+` is a regular expression that will match any stream of characters after `/s1`. As `get1` does not support `PUT` requests, the server responds saying `HTTP Status 405 - Method Not Allowed.`

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Request matching