How do I satisfy void return warning in a restful java service

Question

Java Code:

      @GET
      @Path("/stop/{id}")
      public void stop(
      @PathParam("id") String id,
      @Context HttpServletRequest request,
      @Context HttpServletResponse response) throws ServletException,
      IOException
      {
        server.stop(id);
      }

Java Warning's being thrown to console:

WARNING: A HTTP GET method, public void com.myPackage.stop(java.lang.String,javax.servlet.http.HttpServletRequest,javax.servlet.http.HttpServletResponse) throws javax.servlet.ServletException,java.io.IOException, MUST return a non-void type.

No. just performs a method call that does internal computations — stackoverflow, Jun 30 '11 at 14:59
this guy above gets hit from a button click. @Michael Krussel. What would be the better approach? A POST doesn't seem appropriate but then again I'm not a restful expert — stackoverflow, Jun 30 '11 at 15:05
POST would be better than GET, and if it's from a web form, then I believe POST and GET are the only options. The answers provided give a good explanation. — Michael Krussel, Jun 30 '11 at 17:11

Daniel Canas · Answer 1 · 2014-07-28T05:10:57.503

You really shouldn't be using a GET operation.

I would use a POST operation and return a 201 Created with a link to a resource which describes the new state of the system.

For example, I would redirect to a shutdown status resource:

POST /stop/123
...
201 CREATED
Location:
  http://acme.com/shutdownstatus/123

The the client can poll the resource to check on the status

GET /shutdownstatus/123
...
<shutdown xmlns="http://schemas.serverapp.com/shutdown">
  <status>pending</status>
  <message>Looks good so far</message>
</shutdown>

This new GET operation will always return the state of the server for that id. That way you know if it was shutdown correctly or not. If server shutdown takes a long time, the client could poll that resource to check on different shutdown statuses until it is complete. This way you can return from the original server shutdown request quickly.

If an exception was thrown in your process, I wouldn't return it to the client, I would have a status for the exception in the server status resource. I always avoid making a client handle an exceptional case when I can represent it as a resource. This allows you to change the resource freely, such as when the exception causing method is changed or fixed, without changing the external API.

score 4 · Answer 2 · answered Jun 30 '11 at 15:14

4

The warning is correct. A GET operation should be idempotent, so shouldn't affect server state. If you're not returning anything, the method can't be doing anything useful. You should change it to POST or some other appropriate HTTP operation.

answered Jun 30 '11 at 15:14

artbristol

32,010
5
70
103

score -2 · Answer 3 · answered May 15 '17 at 17:07

url must be as follows. {servername}:{port}/{applicationname}/{standardname}/{your service name}/{your operation name}

ex: http://localhost:8080/restful/jersy/user/service/getUserDets

restful - applicationname
jersy - standardname {optional}
user/service - service name
getuserdets - operation name

score -3 · Accepted Answer · answered Jun 30 '11 at 15:13

-3

Try to define it as *V*oid and return null.

  @GET
  @Path("/stop/{id}")
  public void stop(
  @PathParam("id") String id,
  @Context HttpServletRequest request,
  @Context HttpServletResponse response) throws ServletException,
  IOException
  {
    server.stop(id);
    return null;
  }

answered Jun 30 '11 at 15:13

AlexR

114,158
16
130
208

Seems like a hack job. Is this 'THE' solution or 'A'solution? I've been battling this question for a while now. Thanks for the response AlexR – stackoverflow Jun 30 '11 at 15:15

How do I satisfy void return warning in a restful java service

4 Answers4