> Hi,
> Still getting the NPE.
> After adding more debugging log messages, I
> have been able to pinpoint the line throwing
> the NPE but can't figure out why it does.
> It's the srvOut.println() call in printW() that's
> the trouble spot.
> Advice please ! Error and code below.
> Also, Craig, could you please elaborate on how to
> fix the multiple-users-will-make-it-crash problem,
> using method variables as you said in your earlier reply.
> Vasudev
> Error :
> ======================================================
> Host : atlas
> id To1010mC676918158975596At
> created Sat Nov 20 16:50:39 GMT+05:30 1999
> lastaccessed Sat Nov 20 16:50:55 GMT+05:30 1999
> uptime output:
> 4:51pm up 40 days, 1:08, 24 users, load average: 3.63, 3.15, 2.63
> who output:
> Error: 500
> Internal Servlet Error:
> java.lang.NullPointerException
> at SrvStat.printW(SrvStat.java:199)
> at SrvStat.doGet(SrvStat.java:87)
> at javax.servlet.http.HttpServlet.service(HttpServlet.java:715)
...
> Code :
> import java.io.*;
> import java.text.*;
> import java.util.*;
> import javax.servlet.*;
> import javax.servlet.http.*;
> public class SrvStat extends HttpServlet {
> PrintWriter srvOut; // servlet output stream
> PrintWriter prcOut; // output stream to process input
> PrintWriter logOut; // output stream for log file for program
> File logFile; // log file for program
> BufferedReader prcIn; // input stream from process output
> Runtime runtime; // to start the process
> Process process; // a process
> String command; // command to run and write/read to/from
> String result;
> public void doGet(HttpServletRequest request, HttpServletResponse
> response)
> throws IOException, ServletException
> {
> logFile = new File("/tmp/SrvStat.log");
> logOut = new PrintWriter( new FileWriter(logFile), true);
> response.setContentType("text/html");
> PrintWriter srvOut = response.getWriter();
> runtime = Runtime.getRuntime();
> srvOut.println("<html>");
> srvOut.println("<body bgcolor=\"white\">");
> srvOut.println("<head>");
> String title = "Server Status";
> srvOut.println("<title>" + title + "</title>");
> srvOut.println("</head>");
> srvOut.println("<body>");
> srvOut.println("<h2>Host : " + getHostName() + "</h2>");
> srvOut.println("<br><hr>");
> HttpSession session = request.getSession();
> srvOut.println("<P><hr>");
> String uptimeOn = request.getParameter("uptime");
> if (uptimeOn != null) {
> if (uptimeOn.equals("on")) {
> srvOut.println("uptime output: <br>" +
> getUptime() + "<br><hr>");
> }
> }
> String wOn = request.getParameter("w");
> if (wOn != null) {
> if (wOn.equals("on")) {
> logOut.println("Before calling printW");
> srvOut.println("who output: <br>");
> printW();
> srvOut.println("<br><hr>");
> }
> }
> srvOut.println("<P>");
> srvOut.print("<form action=\"");
> srvOut.print("SrvStat\" ");
> srvOut.println("method=GET>");
> srvOut.println("<input type=checkbox name=uptime>");
> srvOut.println("uptime");
> srvOut.println("<br>"); srvOut.println("<input
> type=checkbox name=w>");
> srvOut.println("w"); srvOut.println("<br>");
> srvOut.println("<input type=submit>");
> srvOut.println("</form>");
> srvOut.println("</body>"); srvOut.println("</html>");
> srvOut.close();
> }
>
> String getHostName() throws IOException {
> try {
> command = "hostname"; process =
> runtime.exec(command);
> prcOut = new PrintWriter( new OutputStreamWriter (
> process.getOutputStream() ) );
> prcIn = new BufferedReader( new InputStreamReader (
> process.getInputStream() ) );
> result = prcIn.readLine();
> }
> catch(Exception e) {
> result = "Error executing " + command + ": " +
> e.getMessage();
> }
> return result;
> }
> String getUptime() throws IOException {
> try {
> command = "sh -c \"who | sed 1q\"";
> process = runtime.exec(command);
> prcOut = new PrintWriter( new OutputStreamWriter (
> process.getOutputStream() ) );
> prcIn = new BufferedReader( new InputStreamReader (
> process.getInputStream() ) );
> result = prcIn.readLine();
> }
> catch(Exception e) {
> result = "Error executing " + command +
> ": " + e.getMessage();
> }
> finally {
> prcOut.close();
> prcIn.close();
> return result;
> }
> }
> void printW() throws IOException {
> try {
> command = "date";
> process = runtime.exec(command);
> logOut.println("Before calling getOutputStream");
> prcOut = new PrintWriter( new OutputStreamWriter (
> process.getOutputStream() ) );
> logOut.println("Before calling getInputStream");
> prcIn = new BufferedReader( new InputStreamReader (
> process.getInputStream() ) );
> result = ""; String line = "";
> line = prcIn.readLine();
> srvOut.println("<br>" + line);
> while (line != null) {
> srvOut.println("<br>"); // + line);
> line = prcIn.readLine();
> }
> }
> catch(Exception e) {
> srvOut.println("Error executing " + command +
> ": " + e.getMessage());
> logOut.println("Leaving catch clause");
> }
> finally {
> try {
> prcOut.close();
> prcIn.close();
> }
> catch(Exception e) {
> e.getMessage());
> }
> }
> }
> }
>
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