Package org.apache.commons.launcher
Class Launcher
- java.lang.Object
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- org.apache.commons.launcher.Launcher
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- 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
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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.
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Constructor Summary
Constructors Constructor Description Launcher()
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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 theLaunchTask
instances.void
run()
Wrapper to allow thekillChildProcesses()
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 thestart(String[])
method.
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Method Detail
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isStarted
public static boolean isStarted()
Get the started flag.- Returns:
- the value of the started flag
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isStopped
public static boolean isStopped()
Get the stopped flag.- Returns:
- the value of the stopped flag
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start
public static int start(java.lang.String[] args) throws java.lang.IllegalArgumentException
Start the launching process. This method is essential themain(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
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stop
public static boolean stop()
Interrupt thestart(String[])
method. This is done by forcing the current or next scheduled invocation of theLaunchTask.execute()
method to throw an exception. In addition, this method will terminate any synchronous child processes that any instances of theLaunchTask
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 thestart(String[])
method.- Returns:
- true if this method completed without error and false if an error occurred or the launch process is already stopped
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error
public static void error(java.lang.String message, boolean usage)
Print a detailed error message and exit.- Parameters:
message
- the message to be printedusage
- if true, print a usage statement after the message
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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.
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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
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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
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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
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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
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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
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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
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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
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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 retrieveclassName
- the name of the class to retrieve the property for- Returns:
- the localized and resolved property value
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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
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setVerbose
public static void setVerbose(boolean verbose)
Set the verbose flag.- Parameters:
verbose
- the value of the verbose flag
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killChildProcesses
public static void killChildProcesses()
Iterate through the list of synchronous child process launched by all of theLaunchTask
instances.
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run
public void run()
Wrapper to allow thekillChildProcesses()
method to be invoked in a shutdown hook.- Specified by:
run
in interfacejava.lang.Runnable
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