Question

What’s the difference between the JAX-RS @QueryParam and @MatrixParam?
From the documents.The queryparam and matrixparam both can location one resource in special condition. So what’s the use case difference?

ps:

Queryparam:

url ? key=value;

Matrixparam

url; key=value;

Answer 1

As stated in this Oracle documentation:

The @PathParam and the other parameter-based annotations,
@MatrixParam, @HeaderParam, @CookieParam, @FormParam obey the
same rules as @QueryParam. @MatrixParam extracts information from
URL path segments. @HeaderParam extracts information from the HTTP
headers. @CookieParam extracts information from the cookies declared
in cookie related HTTP headers.

Example (drawn from here):

@Path("/books")
public class BookService {

    @GET
    @Path("{year}")
    public Response getBooks(@PathParam("year") String year,
            @MatrixParam("author") String author,
            @MatrixParam("country") String country) {

        return Response
            .status(200)
            .entity("getBooks is called, year : " + year
                + ", author : " + author + ", country : " + country)
            .build();

    }

}

See following URI patterns and result:

1. URI Pattern : “/books/2012/”

   getBooks is called, year : 2012, author : null, country : null

2. URI Pattern : “/books/2012;author=andih”

   getBooks is called, year : 2012, author : andih, country : null

3. URI Pattern : “/books/2012;author=andih;country=germany”

   getBooks is called, year : 2012, author : andih, country : germany

4. URI Pattern : “/books/2012;country=germany;author=andih”

   getBooks is called, year : 2012, author : andih, country : germany

For an explanation of the difference you may have a look at
URL matrix parameters vs. request parameters