JAX-RS资源方法签名

Question

I'm using Jersey 2.19 to implement a REST API.

I'd like to know how I find out from the Jersey user guide or other specification how I'm supposed to know what the signature of my JAX-RS resource should be.

Eg for a resource that handles POST requests I've experimented with the following different signatures using examples I've found.

public Response myResource()
public Response myResource(String param)

Both of these are valid in that they compile and run and the method is called under the right conditions.

Can anyone tell me where it is specified what the signatures should be and what the parameters mean? It seems like a straightforward question but I can't find the answer.

Answer 1

As you are saying its a POST request , so it should recieve some data from the Request. So you should expect something in Parameter. public Response myResource(String param) But the type of parameter should depend upon actually @Consumes annotation like :-

@Consumes(MediaType.APPLICATION_JSON) : This expects a JSON input OR @Consumes(MediaType.APPLICATION_XML) : This expects a XML input OR @Consumes(MediaType.TEXT_PLAIN) : This expects a String plain text input

Answer 2

You annotate your Methods like described in the official documentation . Also, do not forget to annotate the service-class with @Path

@Path("MyService")
public class MyService
{
    @GET
    @Produces(MediaType.APPLICATION_JSON)
    @Path("/User")
    public List<User> getUser()
    {
        //Return all users
    }

    //Inserts new User in JSON Format
    @Get
    @Path("/User/UserId/{userid}")
    public User getUserById(@PathParam("userid") String userid)
    {
        //Find User with ID in Database and return it
    }

    @POST
    @Consumes(MediaType.APPLICATION_JSON)
    public User getUserById(User user)
    {
        //add user to your Database or something
    }
}

If you now want to get all users in json format you have to call: http://ip-address/MyService/user

Answer 3

There is an exact answer to your question, but gird your loins. Because if the Jersey docs are overly vague these are in the extreme opposite direction: written by someone showing off their PhD in abstract algebra it looks to me.

The answer to everything is in the JAX-RS spec, of which Jersey is an implementation . You can download it here as PDF (after you sign away your soul)

The specific answer to how one of those methods is selected instead of the other, is too detailed for me to paste in here, but it's under section " 3.7.2 Request Matching "

I won't even try to paste in the mathematical rules used to set up the list of potential methods to match a request, then select from among them. There's no chance of getting them formatted readably in SO.

For your more general questions, the section " 3.3 Resource Methods " is much more accessible. Here are a few choice excerpts:

3.3 Resource Methods

... JAX-RS defines a set of request method designators for the common HTTP methods: @GET, @POST, @PUT, @DELETE, @HEAD and @OPTIONS. ...

3.3.1 Visibility: Only public methods may be exposed as resource methods. ...

3.3.2 Parameters: Resource methods MUST have at most one entity parameter ...

3.3.3 Return Type: Resource methods MAY return void, Response, GenericEntity, or another Java type...

etc, etc.