Friday, April 27, 2012

@HeaderParam Implementation in JAX-RS

There are 2 ways to get HTTP request header in JAX-RS :
Inject directly with @HeaderParam
Pragmatically via @Context

Implementation using @HeaderParam :

In this example, it gets the browser “user-agent” from request header.

import javax.ws.rs.GET;
import javax.ws.rs.HeaderParam;
import javax.ws.rs.Path;
import javax.ws.rs.core.Response;

@Path("/users")
public class UserService {

@GET
@Path("/get")
public Response addUser(@HeaderParam("user-agent") String userAgent) {
  return Response.status(200)
.entity("addUser is called, userAgent : " + userAgent)
.build();
}
}

Access via URI pattern “/users/get“, with FireFox, see following result :
addUser is called, userAgent : Mozilla/5.0 (Windows NT 6.1; rv:5.0) Gecko/20100101 Firefox/5.0



Implementation using @Context : 

Alternatively, you can use @Context to get “javax.ws.rs.core.HttpHeaders” directly

import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.core.Context;
import javax.ws.rs.core.HttpHeaders;
import javax.ws.rs.core.Response;

@Path("/users")
public class UserService {

@GET
@Path("/get")
public Response addUser(@Context HttpHeaders headers) {
  String userAgent = headers.getRequestHeader("user-agent").get(0);
  return Response.status(200)
.entity("addUser is called, userAgent : " + userAgent)
.build();
  }
 }
Access via URI pattern “/users/get“, with Google Chrome, see following result :

addUser is called, userAgent : Mozilla/5.0 (Windows NT 6.1) AppleWebKit/534.30 (KHTML, like Gecko) Chrome/12.0.742.112 Safari/534.30

List all request headers 
You can list all available HTTP request headers via following code :

for(String header : headers.getRequestHeaders().keySet()){
System.out.println(header);
}

Wiki link to headers : http://en.wikipedia.org/wiki/List_of_HTTP_header_fields

Author : Anuj Patel
Blog : http://goldenpackagebyanuj.blogspot.in/

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