How can I grab all query parameters in Jersey JaxRS?

Adding a bit more to the accepted answer. It is also possible to get all the query parameters in the following way without adding an additional parameter to the method which maybe useful when maintaining swagger documentation.

@Context
private UriInfo uriInfo;

@POST
public Response postSomething(@QueryParam("name") String name) {
     MultivaluedMap<String, String> queryParams = uriInfo.getQueryParameters(); 
     String nameParam = queryParams.getFirst("name");
}

ref

You can access a single param via @QueryParam("name") or all of the params via the context:

@POST
public Response postSomething(@QueryParam("name") String name, @Context UriInfo uriInfo, String content) {
     MultivaluedMap<String, String> queryParams = uriInfo.getQueryParameters(); 
     String nameParam = queryParams.getFirst("name");
}

The key is the @Context jax-rs annotation, which can be used to access:

UriInfo, Request, HttpHeaders, SecurityContext, Providers

The unparsed query part of the request URI can be obtained from the UriInfo object:

@GET
public Representation get(@Context UriInfo uriInfo) {
  String query = uriInfo.getRequestUri().getQuery();
  ...
}