passing object between applet and servlet

[may Lee]

Applet on Apache web server sends the object with some parameters to servlet,then servlet supported by tomcat passes back the object with changed parameters. The interesting is: in applet side, it is not working if I sending/getting object can not be put in two try{}(see the attached list 1). It is working when I put then in one try{}(see the attached list 2). Don't why?

List 1:

 /***send object to servlet***/
        try{
            URL url=new URL(servletPath);
            URLConnection conn=url.openConnection();
            conn.setDoInput(true);
            conn.setDoOutput(true);
            conn.setUseCaches(false);
            conn.setDefaultUseCaches(false);
            conn.setRequestProperty("Content-Type","application/octet-stream");
            ObjectOutputStream toServlet=new ObjectOutputStream(conn.getOutputStream());
            toServlet.writeObject(dts);
            toServlet.flush();
            toServlet.close();
        }catch(Exception e){
            error1=e.toString();
        }
        /***get object from servlet***/
        try{
            URL url=new URL(servletPath);
            URLConnection conn=url.openConnection();
            /***Applet client-side get a object from servlet***/
            conn.setDoOutput(true);
            conn.setDoOutput(true);
            conn.setUseCaches(false);
            conn.setDefaultUseCaches(false);
            conn.setRequestProperty("Content-Type","application/octet-stream");
            /***read the input from servlet***/
            ObjectInputStream fromServlet=new ObjectInputStream(conn.getInputStream());
            dts1=(dataTransfer)fromServlet.readObject();
            dtsyear=dts1.dyear;
            dtsmonth=dts1.dmonth;
        }catch(Exception e){
            error2=e.toString();
        }

List 2

            try{
                URL url=new URL(servletPath);
                URLConnection conn=url.openConnection();
                conn.setDoInput(true);
                conn.setDoOutput(true);
                conn.setUseCaches(false);
                conn.setDefaultUseCaches(false);
                conn.setRequestProperty("Content-Type","application/octet-stream");
                /***send object to servlet***/
                ObjectOutputStream toServlet=new ObjectOutputStream(conn.getOutputStream());
                toServlet.writeObject(dts);
                toServlet.flush();
                toServlet.close();
                
                ObjectInputStream fromServlet=new ObjectInputStream(conn.getInputStream());
                dataTransfer dts1=(dataTransfer)fromServlet.readObject();
                dtsyear=dts1.dyear;
                dtsmonth=dts1.dmonth;
            }catch(Exception e){
                error1=e.toString();
            }

--Added code tags and formatted for easy reading- Carl
[ June 09, 2004: Message edited by: Carl Trusiak ]

[Carl Trusiak]

Gee, in Listing 1, you have TWO URLConnections, one you write the object to and the other (Which by the way has NOTHING to do with the first) you are trying to read an Object off of. You can do this in 2 try blocks but, you need to use the same connection objecct in both:
List 3

        try{
            url=new URL(servletPath);
            conn=url.openConnection();
            conn.setDoInput(true);
            conn.setDoOutput(true);
            conn.setUseCaches(false);
            conn.setDefaultUseCaches(false);
            conn.setRequestProperty("Content-Type","application/octet-stream");
            ObjectOutputStream toServlet=new ObjectOutputStream(conn.getOutputStream());
            toServlet.writeObject(dts);
            toServlet.flush();
            toServlet.close();
        }catch(Exception e){
            error1=e.toString();
        }
        /***get object from servlet***/
        try{
            /***read the input from servlet***/
            ObjectInputStream fromServlet=new ObjectInputStream(conn.getInputStream());
            dts1=(dataTransfer)fromServlet.readObject();
            dtsyear=dts1.dyear;
            dtsmonth=dts1.dmonth;
        }catch(Exception e){
            error2=e.toString();
        }
        

There really is no reason to split these out like this. What will happen, if you get an exception in the first block, you will also get an exception in the second.

[William Brogden]

Also NEVER close the connection after sending to the servlet, just flush() the stream. Calling toServlet.close(); will close the whole connection so don't do it until the response has been received.
Bill

[may Lee]

Thanks very much!