在Java中使Servlet线程安全

Question

I have working code as follows

public class receive_meter_to_store extends HttpServlet {

    WSEMAMSTS EMAMService = new WSEMAMSTS();
    ItronEMAMStsBinding itronEMAM = EMAMService.getItronEMAMStsBinding();


    ItronAuthCredit lItronAuthCredit = new ItronAuthCredit();


    EANDeviceID lTerminalID = new EANDeviceID();


    EANDeviceID lClientID = new EANDeviceID();


    SimpleDateFormat itronDF = new SimpleDateFormat("yyyyMMddHHmmss");
    Date current_datetime = new Date();
    String s_current_datetime = itronDF.format(current_datetime);

    MsgID lMsgID = new MsgID();
    reuse_func gc_reuse_func = new reuse_func();
    curr_time gs_current_datetime = new curr_time("");

    protected void processRequest(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        String retdata = "Failure";

        try {
            retdata = add_meter_to_store(request, response);
        }
        finally {
            out.println(retdata);
            out.close();
        }
    } 

I want to make it thread safe, as in to make it run faster. First I am to remove all the global variables, but when i do so, I get error

"An unhandled program error has occured. Please contact the Support services and report the issue"

I have moved them so they can be local as follows

public class receive_meter_to_store extends HttpServlet {

    protected void processRequest(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        String retdata = "Failure";

        reuse_func lc_reuse_func = new reuse_func();

        try {

            WSECMPublic EMAMService = lc_reuse_func.getMeterWebService();

            ItronEMAMStsBinding itronEMAM = EMAMService.getItronEMAMStsBinding();
        }
        catch (Exception ex)
        {

            String ErrorMsg = ex.getMessage();

           out.println("Error" + ErrorMsg);
        }
        finally {
            out.close();
        }

        try {
            retdata = add_meter_to_store(request, response);
        }
        finally {
            out.println(retdata);
            out.close();
        }
    } 

Am I doing something wrong here?

the class i am calling add_meter

public String add_meter_to_store(HttpServletRequest request, HttpServletResponse response)
    { 
        reuse_func lc_reuse_func = new reuse_func();

        try
        {

            WSECMPublic EMAMService = lc_reuse_func.getMeterWebService();

            ItronEMAMStsBinding itronEMAM = EMAMService.getItronEMAMStsBinding();


            ItronAuthCredit lItronAuthCredit = new ItronAuthCredit();

            EANDeviceID lTerminalID = new EANDeviceID();


            EANDeviceID lClientID = new EANDeviceID();


            SimpleDateFormat itronDF = new SimpleDateFormat("yyyyMMddHHmmss");
            Date current_datetime = new Date();
            String s_current_datetime = itronDF.format(current_datetime);


            MsgID lMsgID = new MsgID();

            curr_time ls_current_datetime = new curr_time("");

            // Declare MeterImportResponse Variable
            ItronMeterStsImportResp stsImportResp = new ItronMeterStsImportResp();

            // Call meterStsImport WebMethod
            stsImportResp = itronEMAM.meterStsImport(stsImportReq);



        }
        catch (Exception ex) {
            // TODO handle custom exceptions here
            String ErrorMsg = ex.getMessage();
            retdata = "Error : " + ErrorMsg;
        }

        return retdata;
    }

Note: i have removed the global variables in first part and put them in the class

Answer 1

The problem (or one problem, at least) is that in the first finally block, you close out , but then try to use it again later.

This means that your out.println(retdata) statement is always operating on a closed stream.