Package org.apache.commons.launcher

Class Launcher

  • All Implemented Interfaces:
    java.lang.Runnable
    public class Launcher
extends java.lang.Object
implements java.lang.Runnable
    A class that is used to launch a Java process. The primary purpose of this class is to eliminate the need for a batch or shell script to launch a Java process. Some situations where elimination of a batch or shell script may be desirable are:
    • You want to avoid having to determining where certain application paths are e.g. your application's home directory, etc. Determining this dynamically in a Windows batch scripts is very tricky on some versions of Windows or when softlinks are used on Unix platforms.
    • You need to enforce certain properties e.g. java.endorsed.dirs when running with JDK 1.4.
    • You want to allow users to pass in custom JVM arguments or system properties without having to parse and reorder arguments in your script. This can be tricky and/or messy in batch and shell scripts.
    • You want to bootstrap Java properties from a configuration file instead hard-coding them in your batch and shell scripts.
    • You want to provide localized error messages which is very tricky to do in batch and shell scripts.
    Author:
    Patrick Luby

    • Field Summary

      Fields 
      Modifier and Type Field Description
      static java.lang.Object[] SUPPORTED_ANT_TASKS
      List of supported Ant tasks.
      static java.lang.Object[] SUPPORTED_ANT_TYPES
      List of supported Ant types.

    • Constructor Summary

      Constructors 
      Constructor Description
      Launcher()  

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      static void error​(java.lang.String message, boolean usage)
      Print a detailed error message and exit.
      static void error​(java.lang.Throwable t)
      Print a detailed error message and exit.
      static java.io.File getBootstrapDir()
      Get the canonical directory of the class or jar file that this class was loaded.
      static java.io.File getBootstrapFile()
      Get the canonical directory or jar file that this class was loaded from.
      static java.lang.String getJavaCommand()
      Get the full path of the Java command to execute.
      static java.lang.String getJDBCommand()
      Get the full path of the JDB command to execute.
      static java.lang.String getLocalizedString​(java.lang.String key)
      Get a localized property.
      static java.lang.String getLocalizedString​(java.lang.String key, java.lang.String className)
      Get a localized property.
      static java.io.PrintStream getLog()
      Get the PrintStream that all output should printed to.
      static java.lang.String getToolsClasspath()
      Set the classpath to the current JVM's tools classes.
      static boolean isStarted()
      Get the started flag.
      static boolean isStopped()
      Get the stopped flag.
      static void killChildProcesses()
      Iterate through the list of synchronous child process launched by all of the LaunchTask instances.
      void run()
      Wrapper to allow the killChildProcesses() method to be invoked in a shutdown hook.
      static void setLog​(java.io.PrintStream log)
      Set the PrintStream that all output should printed to.
      static void setVerbose​(boolean verbose)
      Set the verbose flag.
      static int start​(java.lang.String[] args)
      Start the launching process.
      static boolean stop()
      Interrupt the start(String[]) method.

      • Methods inherited from class java.lang.Object

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

    • Field Detail

      • SUPPORTED_ANT_TASKS

        public static final java.lang.Object[] SUPPORTED_ANT_TASKS
        List of supported Ant tasks.

      • SUPPORTED_ANT_TYPES

        public static final java.lang.Object[] SUPPORTED_ANT_TYPES
        List of supported Ant types.

    • Constructor Detail

      • Launcher

        public Launcher()

    • Method Detail

      • isStarted

        public static boolean isStarted()
        Get the started flag.
        Returns:
        the value of the started flag

      • isStopped

        public static boolean isStopped()
        Get the stopped flag.
        Returns:
        the value of the stopped flag

      • start

        public static int start​(java.lang.String[] args)
                 throws java.lang.IllegalArgumentException
        Start the launching process. This method is essential the main(String[]) method for this class except that this method never invokes System.exit(int). This method is designed for applications that wish to invoke this class directly from within their application's code.
        Parameters:
        args - command line arguments
        Returns:
        the exit value of the last synchronous child JVM that was launched or 1 if any other error occurs
        Throws:
        java.lang.IllegalArgumentException - if any error parsing the args parameter occurs

      • stop

        public static boolean stop()
        Interrupt the start(String[]) method. This is done by forcing the current or next scheduled invocation of the LaunchTask.execute() method to throw an exception. In addition, this method will terminate any synchronous child processes that any instances of the LaunchTask class have launched. Note, however, that this method will not terminate any asynchronous child processes that have been launched. Accordingly, applications that use this method are encouraged to always set the LaunchTask.TASK_NAME task's "waitForChild" attribute to "true" to ensure that the application that you want to control can be terminated via this method. After this method has been executed, it will not return until is safe to execute the start(String[]) method.
        Returns:
        true if this method completed without error and false if an error occurred or the launch process is already stopped

      • error

        public static void error​(java.lang.String message,
                         boolean usage)
        Print a detailed error message and exit.
        Parameters:
        message - the message to be printed
        usage - if true, print a usage statement after the message

      • error

        public static void error​(java.lang.Throwable t)
        Print a detailed error message and exit.
        Parameters:
        message - the exception whose stack trace is to be printed.

      • getBootstrapDir

        public static java.io.File getBootstrapDir()
                                    throws java.io.IOException
        Get the canonical directory of the class or jar file that this class was loaded. This method can be used to calculate the root directory of an installation.
        Returns:
        the canonical directory of the class or jar file that this class file was loaded from
        Throws:
        java.io.IOException - if the canonical directory or jar file cannot be found

      • getBootstrapFile

        public static java.io.File getBootstrapFile()
                                     throws java.io.IOException
        Get the canonical directory or jar file that this class was loaded from.
        Returns:
        the canonical directory or jar file that this class file was loaded from
        Throws:
        java.io.IOException - if the canonical directory or jar file cannot be found

      • getJavaCommand

        public static java.lang.String getJavaCommand()
        Get the full path of the Java command to execute.
        Returns:
        a string suitable for executing a child JVM

      • getJDBCommand

        public static java.lang.String getJDBCommand()
        Get the full path of the JDB command to execute.
        Returns:
        a string suitable for executing a child JDB debugger

      • getLog

        public static java.io.PrintStream getLog()
        Get the PrintStream that all output should printed to. The default PrintStream returned in System.err.
        Returns:
        the PrintStream instance to print output to

      • getToolsClasspath

        public static java.lang.String getToolsClasspath()
                                          throws java.io.IOException
        Set the classpath to the current JVM's tools classes.
        Returns:
        a string suitable for use as a JVM's -classpath argument
        Throws:
        java.io.IOException - if the tools classes cannot be found

      • getLocalizedString

        public static java.lang.String getLocalizedString​(java.lang.String key)
        Get a localized property. This method will search for localized properties and will resolve ${...} style macros in the localized string.
        Parameters:
        key - the localized property to retrieve
        Returns:
        the localized and resolved property value

      • getLocalizedString

        public static java.lang.String getLocalizedString​(java.lang.String key,
                                                  java.lang.String className)
        Get a localized property. This method will search for localized properties and will resolve ${...} style macros in the localized string.
        Parameters:
        key - the localized property to retrieve
        className - the name of the class to retrieve the property for
        Returns:
        the localized and resolved property value

      • setLog

        public static void setLog​(java.io.PrintStream log)
        Set the PrintStream that all output should printed to.
        Parameters:
        a - PrintStream instance to print output to

      • setVerbose

        public static void setVerbose​(boolean verbose)
        Set the verbose flag.
        Parameters:
        verbose - the value of the verbose flag

      • killChildProcesses

        public static void killChildProcesses()
        Iterate through the list of synchronous child process launched by all of the LaunchTask instances.

      • run

        public void run()
        Wrapper to allow the killChildProcesses() method to be invoked in a shutdown hook.
        Specified by:
        run in interface java.lang.Runnable