Thread: Extending a Servlet and sharing HttpServletRequest

So far I can pass values back to the template which loads up on the extended class, the problem I am currently having is trying to get the HttpServletRequest to be sent back to my extended class

I am not quite sure what you are asking...if you pass an object to a method as a parameter, and change the variables within said object, when that method exits the object has been changed...if the method changes the object itself (eg creates a new reference), you can define that method to return the new object.

Been doing some more testing - it appears that HttpServletRequest req is returning a null value.

What I am trying to achieve is to let the 2nd extended class query the output of http request values from the template which is the master class.

I will send the code base and hopefully it will make more sense.

import java.io.*;
import java.net.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.net.URL;
 
public class Template extends HttpServlet  {
 public Template () {}
        public String op="";
        public String title="";
        public String page="";
        //These 3 work and are values passed from the extended class
        public void setTitle(String tit) { title = tit; }
        public void setOP(String oo) { op = oo; }
        public void setPage(String pg) { page = pg; }
 
        //Could not get it to return request.getParameter("a")
        public static String act="";
        public static void setAct(String aa) { act=aa; }
        public String getAct() { return act; }
 
        Nor any attempts to return entire request to extended class
        //public HttpServletRequest req=null;
        //public void setReq(HttpServletRequest r) { req=r;}
        //public static HttpServletRequest getReq() { return req; }
 
 
        public void doPost(HttpServletRequest req,HttpServletResponse response) throws ServletException,IOException {
                doit (req,response);
 
        }
        public void doGet(HttpServletRequest req, HttpServletResponse response) throws ServletException, IOException {
                doit (req,response);
 
        }
 
        public HttpServletRequest doit (HttpServletRequest req,HttpServletResponse response) throws ServletException,IOException{
        response.setContentType("text/html");
        String output="";
        PrintWriter out = response.getWriter();
        HttpSession session = req.getSession(true);
        String loggedin=(String)session.getValue("LOGGEDIN");
        if (loggedin==null) { loggedin="";}
        String luser=(String)session.getValue("LUSER");
        if (luser==null) { luser=""; }
        String userlevel=(String)session.getValue("ULEV");
        if (userlevel==null) { userlevel="0"; }
        int ulev=Integer.parseInt(userlevel);
        String ipadd=(String)session.getValue("IPADD");
        if (ipadd==null) { ipadd="0.0.0.0";}
        act=(String)req.getParameter("a");
        setAct(act);
        if (act==null) { act="menu"; }
        GetURL gu = new GetURL();
        gu.dothis(req);
        String fullurl=gu.Result();
        String spath=gu.ret_path();
        String scr=gu.ret_url();
        ServletConfig sg=getServletConfig();
        String sname=(String)sg.getServletName();
        String level=(String)req.getParameter("level");
        if (level==null) { level=""; }
        String query=(String)req.getParameter("query");
        String qtype=(String)req.getParameter("qtype");
        if (query==null) { query="";}
        if (qtype==null) { qtype="";}
        //if (loggedin.equals("")) {
          //      response.sendRedirect(spath+"/Login?source="+fullurl+"");
        //}
 
        //This was working so when I sent a page value from extended class it would load up
        // if (!page.equals("")) {
        //        LoadPage lp=new LoadPage();
        //        lp.dothis(req,page);
        //        op=lp.Result();
        //}
 
        //This loads in the page content (header/footer)
        //LoadContent lca=new LoadContent();
        //lca.dothis(req,title,sname,op);
        //output +=lca.Result();
 
        //My attempts to try to set the request
        //setReq(req);
        //getReq(req);
 
        out.println(output);
 
        return req;
  }
}

So this code above is my master template file

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
//import com.ual.Template.*;
 
 
public class Contact extends Template {
        String output="";
        //Contact tm=new Contact();
        //Template tm=new Template();
        //   HttpServletRequest  re=(HttpServletRequest)tm.getReq();
        public String RunThis() {
                try {
                //String mact=(String)re.getParameter("a");
                if (mact==null) { mact=""; }
                String act=(String)Template.getAct();
                if (act==null) { act=""; }
                String title="NOT SET";
                String op="NOT SET";
                String page="";
                if (act.equals("2")) {
                        title=act+"__page2";
                        op="page2";
                        page="login";
 
                }else{
                        title="Contact Web support team";
                        op="Contact us here";
                        page=" page: contact <>"+act+" @ "+mact+" <br>";
                }
                setOP(op);
                setPage(page);
                setTitle(act+"--"+title);
                } catch (Exception e) { output +="Error "+e; }
                return output;
      }
    String done=(String)RunThis();
}

Within web.xml I am referring to the extended Contact Class

<servlet>
<servlet-name>Contact</servlet-name>
<servlet-class>Contact</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>Contact</servlet-name>
<url-pattern>/Contact</url-pattern>
</servlet-mapping>

This works as far as the extended class Contact sending Template values - which it receives and does things accordingly.

This version of Template doit was my attempt to try to get back the httprequest from the Template from within Contact

HttpServletRequest rq=doit(reqs,resp);
String act=(String)rq.getParameter("a");

This has not worked either


So in summary if I define
//public static HttpServletRequest req;

Above doPost/doGet - this then gets recognised in the extended Contact servlet but the value is always null.

The issue I seem to be having is I can send values to the master Template.java which gets processed and viewed via Contact.java (which is the mapped servlet)

But I can not seem to get the values from Template.java to be shown within Contact.java

So within Contact.java I would be looking to get hold of request.getParameter and request.getSession etc

For future reference, please wrap your code within the [highlight=java][/highlight] tags. I have edited your post for you.

I have read your post a few times - but I still don't understand. I was hoping your code would help, but it is jammed packed with tons of variables, methods, and objects which don't directly relate to the problem at hand and makes it very hard to wade through. I recommend cleaning it up on the form of an SSCCE that demonstrates the issue at hand.

So if I understand correctly (again, still a bit fuzzy), the following might be a possibility: declare the Template as abstract, and define an abstract method that is implemented in the child class - this can then be accessed from within the parent class doGet method

public abstract class Template extends HttpServlet{
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //do stuff
        String myString = runAbstract();
        //do something with myString
    }
 
    protected abstract String runAbstract();
 
}

public class Contact extends Template{
       @Override
        protected String runAbstract(){
            return "my string";
        }
}