Java運行shell指令碼

利用Runtime.execute方法，我們可以在Java程式中運行Linux的Shell指令碼，或者執行其他程式。參考了互連網上的這篇文章：http://lee79.javaeye.com/blog/418549（感謝一下），我重新整理了代碼。
現在通過CommandHelper.execute方法可以執行命令，該類實現代碼如下：
package javaapplication3;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

/**
 *
 * @author chenshu
 */
public class CommandHelper {

    //default time out, in millseconds
    public static int DEFAULT_TIMEOUT;
    public static final int DEFAULT_INTERVAL = 1000;
    public static long START;

    public static CommandResult exec(String command) throws IOException, InterruptedException {
        Process process = Runtime.getRuntime().exec(command);
        CommandResult commandResult = wait(process);
        if (process != null) {
            process.destroy();
        }
        return commandResult;
    }

    private static boolean isOverTime() {
        return System.currentTimeMillis() - START >= DEFAULT_TIMEOUT;
    }

    private static CommandResult wait(Process process) throws InterruptedException, IOException {
        BufferedReader errorStreamReader = null;
        BufferedReader inputStreamReader = null;
        try {
            errorStreamReader = new BufferedReader(new InputStreamReader(process.getErrorStream()));
            inputStreamReader = new BufferedReader(new InputStreamReader(process.getInputStream()));

            //timeout control
            START = System.currentTimeMillis();
            boolean isFinished = false;

            for (;;) {
                if (isOverTime()) {
                    CommandResult result = new CommandResult();
                    result.setExitValue(CommandResult.EXIT_VALUE_TIMEOUT);
                    result.setOutput("Command process timeout");
                    return result;
                }

                if (isFinished) {
                    CommandResult result = new CommandResult();
                    result.setExitValue(process.waitFor());
                    
                    //parse error info
                    if (errorStreamReader.ready()) {
                        StringBuilder buffer = new StringBuilder();
                        String line;
                        while ((line = errorStreamReader.readLine()) != null) {
                            buffer.append(line);
                        }
                        result.setError(buffer.toString());
                    }

                    //parse info
                    if (inputStreamReader.ready()) {
                        StringBuilder buffer = new StringBuilder();
                        String line;
                        while ((line = inputStreamReader.readLine()) != null) {
                            buffer.append(line);
                        }
                        result.setOutput(buffer.toString());
                    }
                    return result;
                }

                try {
                    isFinished = true;
                    process.exitValue();
                } catch (IllegalThreadStateException e) {
                    // process hasn't finished yet
                    isFinished = false;
                    Thread.sleep(DEFAULT_INTERVAL);
                }
            }

        } finally {
            if (errorStreamReader != null) {
                try {
                    errorStreamReader.close();
                } catch (IOException e) {
                }
            }

            if (inputStreamReader != null) {
                try {
                    inputStreamReader.close();
                } catch (IOException e) {
                }
            }
        }
    }
}

CommandHelper類使用了CommandResult對象輸出結果錯誤資訊。該類實現代碼如下：
package javaapplication3;
/**
 *
 * @author chenshu
 */
public class CommandResult {
    public static final int EXIT_VALUE_TIMEOUT=-1;
    
    private String output;

    void setOutput(String error) {
        output=error;
    }

    String getOutput(){
        return output;
    }

    int exitValue;

    void setExitValue(int value) {
        exitValue=value;
    }

    int getExitValue(){
        return exitValue;
    }

    private String error;

    /**
     * @return the error
     */
    public String getError() {
        return error;
    }

    /**
     * @param error the error to set
     */
    public void setError(String error) {
        this.error = error;
    }
}

現在看看調用代碼的示範（main函數接受一個逾時參數）：
    public static void main(String[] args) {
        try {
            int timeout = Integer.parseInt(args[0]);
            CommandHelper.DEFAULT_TIMEOUT = timeout;
            CommandResult result = CommandHelper.exec("mkdir testdir");
            if (result != null) {
                System.out.println("Output:" + result.getOutput());
                System.out.println("Error:" + result.getError());
            }
        } catch (IOException ex) {
            System.out.println("IOException:" + ex.getLocalizedMessage());
        } catch (InterruptedException ex) {
            System.out.println("InterruptedException:" + ex.getLocalizedMessage());
        }
    }

結果會建立一個testdir目錄。

我嘗試用這種方法建立通過ssh登入到遠程機器，遇到兩個問題：
1）如果希望沒有人機對話方式，則需要使用命令sshpass -p password ssh user@targetIP 'command'
2) 在NetBeans上直接運行工程是不行的，因為許可權不夠,需要在終端裡運行java javaapplication3.Main
3) 很多命令不能運行，只有如pwd等命令可以運行，原因還不清楚，最好改用Ganymed SSH-2庫或者其他類似Java庫，我會在下一篇文章中介紹如何使用。