February 2005
Intermediate to advanced
528 pages
12h 53m
English
Your Action classes must operate correctly in a
multi-threaded environment.
In your custom Action, never use instance
variables to carry per-request state; only use local variables. If
you want to have local methods called from the execute() method, pass values to these methods as arguments instead
of using instance variables. The Action class in
Example 6-3 demonstrates this approach.
Example 6-3. Thread-safe action
package com.oreilly.strutsckbk.ch06;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.struts.action.Action;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;
public class ThreadSafeAction extends Action {
// This variable is not thread-safe
private SecurityUtil securityUtil = new SecurityUtil.instance( );
public ActionForward execute( ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response)
throws Exception {
// the 'user' variable is thread-safe
User user = (User) request.getSession( ).getAttribute("user");
// pass the user to the private method
doSomething(user);
// ...
return mapping.findForward("success");
}
private void doSomething(User user) throws Exception {
// authenticate the user
securityUtil.authenticate(user);
}
}A Struts Action is subject to the same threading issues as a servlet. Internally, Struts maintains and ...