threads and requests

[Ali Khalfan]

Hi,

I need to set something straight...are requests thread-safe?

let's say i'm in a controller servlet..

request.setAttribute("username", "koba");
 
RequestDispatcher view = request.getRequestDispatcher("result.jsp");

does this mean there is no way at all that concurrency can effect this?

p.s. this thread thing is getting me obsessed

[Musab Al-Rawi]

Yes they are. Request scope attributes and local method variables are thread safe, anything else is not, that includes:
- session attributes (since more than one request can be sent from the same client)
- application attributes (since all servlets share the same application/context and can access them anytime they wish)
- servlet's instance variables those variables defined in the body of the servlet (since any request to that servlet can access them)

[Justin Russo]

Yes.. but why was the request synchronized for the servlet below. This is for servlet generated by tomcat for a JSP.

snippet below copied from tomcat generated servlet

synchronized (request) {
        s= (exam.scwcd5.ELTest) _jspx_page_context.getAttribute("f", PageContext.REQUEST_SCOPE);
        if (s == null){
          throw new java.lang.InstantiationException("bean f not found within scope");
        }
      }

[Ali Khalfan]

just come to think of it...technically the request attributes are not thread-safe are they....i mean no code will lock the request object. it's just that it is not possible (i think) two get something as two concurrent requests

is there?

have i got this right?
[ June 16, 2008: Message edited by: Ali Khalfan ]