Package org.opennms.core.utils

Class ExecRunner

  • public class ExecRunner
extends java.lang.Object

    Runs external executables, optionally under a watched thread. In addition, probably the most useful feature of ExecRunner is using it to run a command-line program and obtain its stdout and stderr results in two strings. This is done with exec(String) - see that method for an example. With acknowledgements to Michael C. Daconta, author of "Java Pitfalls, Time Saving Solutions, and Workarounds to Improve Programs." and his article in JavaWorld "When Runtime.exec() Won't".

    Author:
    Scott McCrory .

    • Constructor Summary

      Constructors 
      Constructor Description
      ExecRunner()
      Basic ExecRunner constructor.
      ExecRunner​(java.lang.String command)
      ExecRunner constructor which also conveniently runs exec(String).

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      java.lang.Object clone()
      We override the clone method here to prevent cloning of our class.
      int exec​(java.lang.String command)
      The exec(String) method runs a process inside of a watched thread.
      int exec​(java.lang.String command, java.io.OutputStream stdoutStream, java.io.OutputStream stderrStream)
      Convenience method for calling exec with OutputStreams.
      int exec​(java.lang.String command, java.io.PrintWriter stdoutWriter, java.io.PrintWriter stderrWriter)
      The exec(String, PrintWriter, PrintWriter) method runs a process inside of a watched thread.
      java.lang.String getErrString()
      Returns the error string if exec(String) was invoked.
      int getMaxRunTimeSecs()
      Returns the maximum run time in seconds for this object.
      java.lang.String getOutString()
      Returns the output string if exec(String) was invoked.
      boolean isMaxRunTimeExceeded()
      Returns whether the maximum runtime was exceeded or not.
      static void main​(java.lang.String[] args)
      This is for unit testing of the class.
      void setMaxRunTimeSecs​(int max)
      Sets the maximum run time in seconds.

      • Methods inherited from class java.lang.Object

        equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Constructor Detail

      • ExecRunner

        public ExecRunner()
        Basic ExecRunner constructor.

      • ExecRunner

        public ExecRunner​(java.lang.String command)
           throws java.lang.ExceptionInInitializerError
        ExecRunner constructor which also conveniently runs exec(String).
        Parameters:
        command - The program or command to run
        Throws:
        java.lang.ExceptionInInitializerError - thrown if a problem occurs

    • Method Detail

      • clone

        public final java.lang.Object clone()
                             throws java.lang.CloneNotSupportedException
        We override the clone method here to prevent cloning of our class.
        Overrides:
        clone in class java.lang.Object
        Returns:
        Nothing ever really returned since we throw a CloneNotSupportedException
        Throws:
        java.lang.CloneNotSupportedException - To indicate cloning is not allowed

      • exec

        public int exec​(java.lang.String command)
         throws java.io.IOException,
                java.lang.InterruptedException
        The exec(String) method runs a process inside of a watched thread. It returns the client's exit code and feeds its STDOUT and STDERR to ExecRunner's out and err strings, where you then use getOutString() and getErrString() to obtain these values. Example: 
        
 // Execute the program and grab the results
 try {
     ExecRunner er = new ExecRunner();
     er.setMaxRunTimeSecs(5);
     er.exec("ls -l");
     if (!er.getMaxRunTimeExceeded()) {
         out = er.getOutString();
         err = er.getErrString();
     } else {
         System.out.println("Maximum run time exceeded!");
     }
 } catch (Throwable e) {
     System.out.println("Error executing " + program + ": " + e.getMessage());
     continue;
 }
        Parameters:
        command - The program or command to run
        Returns:
        The command's return code
        Throws:
        java.io.IOException - thrown if a problem occurs
        java.lang.InterruptedException - thrown if a problem occurs

      • exec

        public int exec​(java.lang.String command,
                java.io.OutputStream stdoutStream,
                java.io.OutputStream stderrStream)
         throws java.io.IOException,
                java.lang.InterruptedException
        Convenience method for calling exec with OutputStreams.
        Parameters:
        command - The program or command to run
        stdoutStream - java.io.OutputStream
        stderrStream - java.io.OutputStream
        Returns:
        The command's return code
        Throws:
        java.io.IOException - thrown if a problem occurs
        java.lang.InterruptedException - thrown if a problem occurs

      • exec

        public int exec​(java.lang.String command,
                java.io.PrintWriter stdoutWriter,
                java.io.PrintWriter stderrWriter)
         throws java.io.IOException,
                java.lang.InterruptedException
        The exec(String, PrintWriter, PrintWriter) method runs a process inside of a watched thread. It returns the client's exit code and feeds its STDOUT and STDERR to the passed-in streams.
        Parameters:
        command - The program or command to run
        stdoutWriter - java.io.PrintWriter
        stderrWriter - java.io.PrintWriter
        Returns:
        The command's return code
        Throws:
        java.io.IOException - thrown if a problem occurs
        java.lang.InterruptedException - thrown if a problem occurs

      • getErrString

        public java.lang.String getErrString()
        Returns the error string if exec(String) was invoked.
        Returns:
        The error string if exec(String) was invoked.

      • isMaxRunTimeExceeded

        public boolean isMaxRunTimeExceeded()
        Returns whether the maximum runtime was exceeded or not.
        Returns:
        boolean indicating whether the maximum runtime was exceeded or not.

      • getMaxRunTimeSecs

        public int getMaxRunTimeSecs()
        Returns the maximum run time in seconds for this object.
        Returns:
        the maximum run time in seconds for this object.

      • getOutString

        public java.lang.String getOutString()
        Returns the output string if exec(String) was invoked.
        Returns:
        The output string if exec(String) was invoked.

      • main

        public static void main​(java.lang.String[] args)
                 throws java.io.IOException
        This is for unit testing of the class.
        Parameters:
        args - an array of command-line arguments
        Throws:
        java.io.IOException - thrown if a problem occurs

      • setMaxRunTimeSecs

        public void setMaxRunTimeSecs​(int max)
        Sets the maximum run time in seconds. If you do not want to limit the executable's run time, simply pass in a 0 (which is also the default).
        Parameters:
        max - Maximim number of seconds to let program run