getting servlet context attributes within action

[Jim Newsham <ne...@hotu.com>]

Hi,

I'm trying to set up a global resource as described in the Struts User
Guide (under the heading "An Aside:  Accessing Relational Databases"),
by creating it in a startup servlet and attaching it to the servlet
context as an attribute.  Within my Action class, how do I retrieve the
attribute?  I tried calling Action.getServlet() as shown in the code
snippet below, but this seems to return null.


public class LoginAction extends Action {

  private DB db;

  // constructor sets up db access
  public LoginAction()
    throws ApplicationException {
    super();

    Servlet servlet = getServlet();  // this is returning null !
    ServletConfig config = servlet.getServletConfig();  // this is line
29
    ServletContext context = config.getServletContext();
    this.db = (DB) context.getAttribute("com.hotu.intra.db.DB");
    //this.db = (DB)
getServlet().getServletConfig().getServletContext().getAttribute("com.hotu.intra.db.DB");

    if (db == null) {
      throw new ApplicationException(ApplicationException.DB_INIT_ERR);
    }
  }

....

}

/caucho.com/http/host/: java.lang.NullPointerException
 at com.hotu.intra.LoginAction.<init>(LoginAction.java:29)
  at java.lang.Class.newInstance0(Native Method)
   at java.lang.Class.newInstance(Class.java:237)
    at
org.apache.struts.action.ActionServlet.processActionCreate(ActionServlet.java:1263)

     at
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1232)
      at
org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:435) at
javax.servlet.http.HttpServlet.service(HttpServlet.java:115)
       at javax.servlet.http.HttpServlet.service(HttpServlet.java:83)
        at
com.caucho.server.http.Invocation.service(Invocation.java:236)
         at
com.caucho.server.http.CacheInvocation.service(CacheInvocation.java:142)

          at
com.caucho.server.http.HttpRequest.handleRequest(HttpRequest.java:211)
           at
com.caucho.server.http.HttpRequest.handleConnection(HttpRequest.java:145)

            at
com.caucho.server.TcpConnection.run(TcpConnection.java:139)
             at java.lang.Thread.run(Thread.java:484)




Thanks in advance,

Jim Newsham

Re: getting servlet context attributes within action

[Pierre Métras <ge...@sympatico.ca>]

Hi Jim,

As a general rule, use only locale variables in your Action class as there's
only one instance but numerous threads wanting to access the methods and
properties.