apache-comnons系列之commons-exec1.3 学习笔记

概述

• 参考
  
  • http://blog.csdn.net/fd_mas/article/details/50147701
  • http://blog.csdn.net/accountwcx/article/details/46787603

Executor


The main abstraction to start an external process.
* The interface allows to
* <li>set a current working directory for the subprocess</li>
* <li>provide a set of environment variables passed to the subprocess</li>
* <li>capture the subprocess output of stdout and stderr using an ExecuteStreamHandler</li>
* <li>kill long-running processes using an ExecuteWatchdog</li>
* <li>define a set of expected exit values</li>
* <li>terminate any started processes when the main process is terminating using a ProcessDestroyer</li>
* The following example shows the basic usage:
* Executor exec = new DefaultExecutor();
* CommandLine cl = new CommandLine("ls -l");
* int exitvalue = exec.execute(cl);

- execute—->Methods for starting synchronous execution. The child process inherits all environment variables of the parent process
- execute—->Methods for starting asynchronous execution. The child process inherits all environment variables of the parent process. Result provided to callback handler.

DaemonExecutor—->DefaultExecutor

• ExecuteStreamHandler streamHandler—->taking care of output and error stream
• File workingDirectory—->the working directory of the process
• ExecuteWatchdog watchdog—->monitoring of long running processes
• CommandLauncher launcher—->launches the command in a new process
• int[] exitValues—->the exit values considered to be successful
• ProcessDestroyer processDestroyer—->optional cleanup of started processes
• Thread executorThread—->worker thread for asynchronous execution
• org.apache.commons.exec.DefaultExecutor.executeInternal(执行方法内部调用此方法)
  
  • Execute an internal process. If the executing thread is interrupted while waiting for the child process to return the child process will be killed
  • org.apache.commons.exec.DefaultExecutor.launch(利用命令创建器创建进程)
    
    • org.apache.commons.exec.launcher.Java13CommandLauncher.exec
    • Runtime.getRuntime().exec
  • 将进程的输出流、输入流、错误流转向流处理器(委托给org.apache.commons.exec.PumpStreamHandler)
    
    • streams.setProcessInputStream(process.getOutputStream())
    • streams.setProcessOutputStream(process.getInputStream())
    • streams.setProcessErrorStream(process.getErrorStream());
  • 利用看门狗监控进程的信息
    
    • watchdog.start(process)(委托给org.apache.commons.exec.ExecuteWatchdog.start—->org.apache.commons.exec.Watchdog.start)
  • 同步执行—->exitValue = process.waitFor();
  • 或者异步执行—->创建新线程执行进程的创建等操作—->this.executorThread = createThread(runnable, “Exec Default Executor”);

ExecuteStreamHandler


Used by {@code Execute} to handle input and output stream of subprocesses.


PumpStreamHandler—->ExecuteStreamHandler


Copies standard output and error of sub-processes to standard output and error of the parent process. If output or error stream are set to null, any feedback from that stream will be lost.

- Thread outputThread;/Thread errorThread;/Thread inputThread;
- OutputStream out;/OutputStream err;/OutputStream err;

ExecuteWatchdog—->TimeoutObserver


Destroys a process running for too long. For example:
When starting an asynchronous process than 'ExecuteWatchdog' is the keeper of the process handle. In some cases it is useful not to define
a timeout (and pass 'INFINITE_TIMEOUT') and to kill the process explicitly using 'destroyProcess()'.

- Process process
- org.apache.commons.exec.ExecuteWatchdog.start(Watches the given process and terminates it, if it runs for too long. All information from the previous run are reset.)
- this.notifyAll();
- watchdog.start();
- org.apache.commons.exec.ExecuteWatchdog.stop
- watchdog.stop();

Watchdog

• observers = new Vector(1);
• org.apache.commons.exec.Watchdog.run
• org.apache.commons.exec.Watchdog.fireTimeoutOccured(通知超时时间的观察者)

CommandLine


CommandLine objects help handling command lines specifying processes to execute. The class can be used to a command line by an application.

- arguments = new Vector()—->The arguments of the command
- String executable—->The program to execute
- org.apache.commons.exec.CommandLine.parse(解析命令与参数)
- translateCommandline(line);

DefaultExecuteResultHandler—->ExecuteResultHandler


The callback handlers for the result of asynchronous process execution. When a process is started asynchronously the callback provides you with the result of
the executed process, i.e. the exit value or an exception

- org.apache.commons.exec.ExecuteResultHandler.onProcessComplete(在执行器中用新线程创建新进程完成后的回调方法)
- org.apache.commons.exec.DefaultExecuteResultHandler.waitFor
- Causes the current thread to wait, if necessary, until the process has terminated. This method returns immediately if
- the process has already terminated. If the process has not yet terminated, the calling thread will be blocked until the process exits

ShutdownHookProcessDestroyer—->ProcessDestroyer


Destroys all registered {@link java.lang.Process} after a certain event, typically when the VM exits

- processes = new Vector()—->the list of currently running processes
- ProcessDestroyerImpl destroyProcessThread = null—->he thread registered at the JVM to execute the shutdown handler
- org.apache.commons.exec.ShutdownHookProcessDestroyer.run(进程退出时的回调方法)

Java13CommandLauncher—->CommandLauncherImpl—->CommandLauncher


Interface to shield the caller from the various platform-dependent implementations.

- A command launcher for JDK/JRE 1.3 (and higher). Uses the built-in Runtime.exec() command
- org.apache.commons.exec.launcher.Java13CommandLauncher.exec

测试

• org.apache.commons.exec.TutorialTest