Rules of injection

package test;

import java.util.HashMap;

import javax.ws.rs.DefaultValue;
import javax.ws.rs.GET;
import javax.ws.rs.HeaderParam;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.QueryParam;
import javax.ws.rs.core.Response;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;

@Path("injection/{id}")
public class InjectedResource {
	ObjectMapper mapper = new ObjectMapper();

	// Injection onto field
	@DefaultValue("q")
	@QueryParam("p")
	private String p;
	private int id;
	private String header;

	@GET
	public Response sendResponse() {
		HashMap<String, Object> hm = new HashMap<String, Object>();
		hm.put("p", p);
		hm.put("id", id);
		hm.put("header", header);
		try {
			return Response.status(Response.Status.OK)
					.entity(mapper.writeValueAsString(hm)).build();
		} catch (JsonProcessingException e) {
			e.printStackTrace();
			return Response.status(Response.Status.BAD_REQUEST).entity("Error")
					.build();
		}
	}

	// Injection onto constructor parameter
	public InjectedResource(@PathParam("id") int id) {
		this.id = id;
	}

	//Header Injection using bean setter method
	@HeaderParam("X-header")
	public void setHeader(String header) {
		this.header = header;
	}
}