Question

I have this code running in a servlet

public void doPost(HttpServletRequest request, HttpServletResponse response) {
    final HttpServletRequest requestF = request;
    Runnable runner  = new Runnable() {
       public void run() {
           String something = requestF.getParameter("anything");
           //do other things...
        }
    };
    Thread thread = new Thread(runner);
    thread.start();

But it throws an Exception when i try to get the parameter from the request object.

Exception in thread "Thread-25" java.lang.NullPointerException
    at org.apache.catalina.connector.Request.parseParameters(Request.java:2560)
    at org.apache.catalina.connector.Request.getParameter(Request.java:1086)
    at org.apache.catalina.connector.RequestFacade.getParameter(RequestFacade.java:355)
    at javax.servlet.ServletRequestWrapper.getParameter(ServletRequestWrapper.java:158)
    at br.com.test.controller.ajax.MyServlet$1.run(MyServlet.java:54)
    at java.lang.Thread.run(Thread.java:619)

The requestF object is not null, I’ve checked.
Does anyone know if i can access the request object inside a new Thread?

Answer 1

Yes, Zaske is right.
You may copy using a new instance of map object, like this:

final Map<String,String> mapParameters = new HashMap<String,String>();
mapParameters.putAll(request.getParameterMap());

and use mapParameters inside your “run” method:

public void doPost(HttpServletRequest request, HttpServletResponse response) {
    final Map<String,String> mapParameters = new HashMap<String,String>();
    mapParameters.putAll(request.getParameterMap());
    Runnable runner  = new Runnable() {
       public void run() {
           String something = mapParameters.get("anything");
           //do other things...
       }
    };
    Thread thread = new Thread(runner);
    thread.start();
}