Process.getInputStream() and process.waitfor() block in web application

Question

Hi folks,
i am really stuck with a problem which drives me mad.....
What i want:
I want to call the microsoft tool "handle" (see http://www.microsoft.com/technet/sysinternals/ProcessesAndThreads/Handle.mspx) from within my web-application.
Handle is used to assure that no other process accesses a file i want to read in.
A simple test-main does the job perfectly:
public class TestIt {
   public static void main(String[] args){
      String pathToFileHandleTool = "C:\\tmp\\Handle\\handle.exe";
      String pathToFile = "C:\\tmp\\foo.txt";
      String expectedFileHandleSuccessOutput = "(.*)No matching handles found(.*)";
      System.out.println("pathToFileHandleTool:" + pathToFileHandleTool);
      System.out.println("pathToFile: " + pathToFile);
      System.out.println("expectedFileHandleSuccessOutput: " + expectedFileHandleSuccessOutput);
      ProcessBuilder builder = null;
      // check for os
      if(System.getProperty("os.name").matches("(.*)Windows(.*)")) {
         System.out.println("we are on windows..");
      } else {
         System.out.println("we are on linux..");
      builder = new ProcessBuilder( pathToFileHandleTool, pathToFile);
      Process process = null;
      String commandOutput = "";
      String line = null;
      BufferedReader bufferedReader = null;
      try {
         process = builder.start();
         // read command output
         bufferedReader = new BufferedReader(new InputStreamReader(process.getInputStream()));
          while((line = bufferedReader.readLine()) != null) {
             commandOutput += line;
          System.out.println("commandoutput: " + commandOutput);
         // wait till process has finished
         process.waitFor();
      } catch (IOException e) {
         System.out.println(e.getMessage());
         e.printStackTrace();
      }  catch (InterruptedException e) {
         System.out.println(e.getMessage());
         e.printStackTrace();      }
      // check output to assure that no process uses file
      if(commandOutput.matches(expectedFileHandleSuccessOutput))
         System.out.println("no other processes accesses file!");
      else
         System.out.println("one or more other processes access file!");
} So, as you see, a simple handle call looks like
handle foo.txtand the output - if no other process accesses the file - is:
Handle v3.2Copyright (C) 1997-2006 Mark RussinovichSysinternals - www.sysinternals.com
No matching handles found.
no other processes accesses file!(Wether the file exists or not doesnt matter to the program)
If some processes access the file the output looks like this:
commandoutput: Handle v3.2Copyright (C) 1997-2006 Mark RussinovichSysinternals - www.sysinternals.com
WinSCP3.exe        pid: 1108    1AC: C:\tmp\openSUSE-10.2-GM-i386-CD3.iso.filepart
one or more other processes access file!So far, so good.........but now ->
The problem:
If i know use the __exact__ same code (even the paths etc. hardcoded for debugging purposes) within my Servlet-Webapplication, it hangs here:
while((line = bufferedReader.readLine()) != null) {if i comment that part out the application hangs at:
process.waitFor();I am absolutely clueless what to do about this....
Has anybody an idea what causes this behaviour and how i can circumvent it?
Is this a windows problem?
Any help will be greatly appreciated.....
System information:
- OS: Windows 2000 Server
- Java 1.5
- Tomcat 5.5
More information / What i tried:
- No exception / error is thrown, the application simply hangs. Adding
builder.redirectErrorStream(true);had no effect on my logs.
- Tried other readers as well, no effect.
- replaced
while((line = bufferedReader.readLine()) != null)with
int iChar = 0;
              while((iChar = bufferedReader.read()) != -1) {No difference, now the application hangs at read() instead of readline()
- tried to call handle via
runtime = Runtime.getRuntime();               
Process p = runtime.exec("C:\\tmp\\Handle\\handle C:\\tmp\\foo.txt");and
Process process = runtime.exec( "cmd", "/c","C:\\tmp\\Handle\\handle.exe C:\\tmp\\foo.txt");No difference.
- i thought that maybe for security reasons tomcat wont execute external programs, but a "nslookup www.google.de" within the application is executed
- The file permissions on handle.exe seem to be correct. The user under which tomcat runs is NT-AUTORIT-T/SYSTEM. If i take a look at handle.exe permission i notice that user "SYSTEM" has full access to the file
- I dont start tomcat with the "-security" option
- Confusingly enough, the same code works under linux with "lsof", so this does not seem to be a tomcat problem at all
Thx for any help!

Answer 1

Hi,
thx for the links, unfortanutely nothing worked........
What i tried:
1. Reading input and errorstream separately via a thread class called streamgobbler(from the link):
          String pathToFileHandleTool = "C:\\tmp\\Handle\\handle.exe";
          String pathToFile = "C:\\tmp\\foo.txt";
          String expectedFileHandleSuccessOutput = "(.*)No matching handles found(.*)";
          logger.debug("pathToFileHandleTool: " + pathToFileHandleTool);
          logger.debug("pathToFile: " + pathToFile);
          logger.debug("expectedFileHandleSuccessOutput: " + expectedFileHandleSuccessOutput);
          ProcessBuilder builder = new ProcessBuilder( pathToFileHandleTool, pathToFile);
          String commandOutput = "";
          try {
               logger.debug("trying to start builder....");
               Process process = builder.start();
               logger.debug("builder started!");
               logger.debug("trying to initialize error stream gobbler....");
               StreamGobbler errorGobbler = new StreamGobbler(process.getErrorStream(), "ERROR");
               logger.debug("error stream gobbler initialized!");
               logger.debug("trying to initialize output stream gobbler....");
               StreamGobbler outputGobbler = new StreamGobbler(process.getInputStream(), "OUTPUT");
               logger.debug("output stream gobbler initialized!");
               logger.debug("trying to start error stream gobbler....");
               errorGobbler.start();
               logger.debug("error stream gobbler started!");
               logger.debug("trying to start output stream gobbler....");
               outputGobbler.start();
               logger.debug("output stream gobbler started!");
               // wait till process has finished
               logger.debug("waiting for process to exit....");
               int exitVal = process.waitFor();
               logger.debug("process terminated!");
               logger.debug("exit value: " + exitVal);
          } catch (IOException e) {
               logger.debug(e.getMessage());
               logger.debug(e);
          }  catch (InterruptedException e) {
               logger.debug(e.getMessage());
               logger.debug(e);
     class StreamGobbler extends Thread {
          InputStream is;
         String type;
         StreamGobbler(InputStream is, String type) {
             this.is = is;
             this.type = type;
         public void run() {
              try {
                 InputStreamReader isr = new InputStreamReader(is);
                 BufferedReader br = new BufferedReader(isr);
                 String line=null;
                 logger.debug("trying to call readline() .....");
                 while ( (line = br.readline()) != null)
                     logger.debug(type + ">" + line);   
             } catch (IOException ioe) {
                     ioe.printStackTrace(); 
     }Again, the application hangs at the "readline()":
pathToFileHandleTool: C:\tmp\Handle\handle.exe
pathToFile: C:\tmp\openSUSE-10.2-GM-i386-CD3.iso
expectedFileHandleSuccessOutput: (.*)No matching handles found(.*)
trying to start builder....
builder started!
trying to initialize error stream gobbler....
error stream gobbler initialized!
trying to initialize output stream gobbler....
output stream gobbler initialized!
trying to start error stream gobbler....
error stream gobbler started!
trying to start output stream gobbler....
output stream gobbler started!
waiting for process to exit....
trying to call readline().....
trying to call readline().....Then i tried read(), i.e.:
     class StreamGobbler extends Thread {
          InputStream is;
         String type;
         StreamGobbler(InputStream is, String type) {
             this.is = is;
             this.type = type;
         public void run() {
              try {
                 InputStreamReader isr = new InputStreamReader(is);
                 BufferedReader br = new BufferedReader(isr);
                 logger.debug("trying to read in single chars.....");
                 int iChar = 0;
                 while ( (iChar = br.read()) != -1)
                     logger.debug(type + ">" + iChar);   
             } catch (IOException ioe) {
                     ioe.printStackTrace(); 
     }Same result, application hangs at read()......
Then i tried a dirty workaround, but even that didnt suceed:
I wrote a simple batch-file:
C:\tmp\Handle\handle.exe C:\tmp\foo.txt > C:\tmp\handle_output.txtand tried to start it within my application with a simple:
Runtime.getRuntime().exec("C:\\tmp\\call_handle.bat");No process, no reading any streams, no whatever.....
Result:
A file C:\tmp\handle_output.txt exists but it is empty..........
Any more ideas?