@QueryParam

The @javax.ws.rs.QueryParam annotation allows you to inject individual URI query parameters into your Java parameters. For example, let’s say we wanted to query a customer database and retrieve a subset of all customers in the database. Our URI might look like this:

GET /customers?start=0&size=10

The start query parameter represents the customer index we want to start with and the size query parameter represents how many customers we want returned. The JAX-RS service that implemented this might look like this:

@Path("/customers")
public class CustomerResource {

   @GET
   @Produces("application/xml")
   public String getCustomers(@QueryParam("start") int start,
                               @QueryParam("size") int size) {
     ...
   }
}

Here, we use the @QueryParam annotation to inject the URI query parameters "start" and "size" into the Java parameters start and size. As with other annotation injection, JAX-RS automatically converts the query parameter’s string into an integer.

Programmatic Query Parameter Information

You may have the need to iterate through all query parameters defined on the request URI. The javax.ws.rs.core.UriInfo interface has a getQueryParameters() method that gives you a map containing all query parameters:

public interface UriInfo {
...
   public MultivaluedMap<String, String> getQueryParameters();
   public MultivaluedMap<String, String> getQueryParameters(boolean decode);
...
}

You can inject instances of UriInfo using the @javax.ws.rs.core.Context annotation. Here’s an example of injecting this class and using it to obtain the value of a few query parameters:

@Path("/customers")
public class CustomerResource {

   @GET
   @Produces("application/xml")
   public String getCustomers(@Context UriInfo info) {
      String start = info.getQueryParameters().getFirst("start");
      String size = info.getQueryParameters().getFirst("size");
     ...
   }
}