java 命令行执行及工具类封装【实用】

梦里梦外; 2023-10-05 23:40 5阅读 0赞

## 引 ##

java 编程中，特别是一些工具开发过程中，经常会调用系统命令行，如 windowns 上的 `CMD` ，linux 操作系统上的 `sh` 等。

## 分析 ##

java 提供了调用 `CMD` 或 `sh` 的 API , 它被封装在 `Runtime` 类中。其 exec 方法示意如下：  
![在这里插入图片描述][f405f9e7c4b84857a5f8df8c9c03d356.png]

简单使用方法如下：

public static void main(String[] args) throws IOException {
        
            Runtime.getRuntime().exec("command");
    	}

更多 Runtime.exec 见 [java Runtime.exec方法详解][java Runtime.exec]

## 问题 ##

简单使用 Runtime.exec 存在如下问题：

*  线程阻塞 – [Runtime.exec 线程阻塞及处理][Runtime.exec]
 *  没有返回正确的输出或错误信息

为此特编写了如下工具类

## 工具类 ##

日常开发中调用命令行后，需要拿到执行结果或错误结果，并且要高效，为此，结合 Java 异步编程经验，封装了如下工具类：

package com.xzbd.common.utils;
    
    
    import java.io.BufferedReader;
    import java.io.IOException;
    import java.io.InputStream;
    import java.io.InputStreamReader;
    import java.util.concurrent.Callable;
    import java.util.concurrent.ExecutionException;
    import java.util.concurrent.ExecutorService;
    import java.util.concurrent.Executors;
    import java.util.concurrent.Future;
    import java.util.concurrent.TimeUnit;
    import java.util.concurrent.TimeoutException;
    
    import org.apache.commons.lang3.SystemUtils;
    
    public class CommandUtil {
        
    
    	public static String LINUX_CMD = "/bin/sh";
    	public static String WIN_CMD = "cmd.exe";
    	// time out
    	private static long TIME_OUT = 20;
    	// time out unit
    	private static TimeUnit TIME_OUT_UNIT = TimeUnit.SECONDS;
    
    	public static void main(String[] args) throws IOException {
        
    		String result = CommandUtil.runCmd("ls /home/", 12, TimeUnit.SECONDS);
    		System.out.println(result);
    
    	}
    
    	public static String runCmd(String command) {
        
    		return runCmd(command, TIME_OUT, TIME_OUT_UNIT);
    	}
    
    	public static String runCmd(String command, long time, TimeUnit unit) {
        
    		String[] cmds = createCmd(command);
    		String cmd = String.join(" ", cmds);
    		System.out.println("CMD: " + cmd);
    		System.out.println(SystemUtils.LINE_SEPARATOR);
    		Process pro = null;
    		try {
        
    			pro = Runtime.getRuntime().exec(cmds);
    		} catch (IOException e) {
        
    			e.printStackTrace();
    			throw new RuntimeException("cmd exec error");
    		}
    		ExecutorService executorService = Executors.newFixedThreadPool(2);
    		Future<String> result = executorService.submit(new ReaderTask(pro.getInputStream()));
    		Future<String> errResult = executorService.submit(new ReaderTask(pro.getErrorStream()));
    		String r1 = resultHandle(result, time, unit);
    		String r2 = resultHandle(errResult, time, unit);
    		executorService.shutdown();
    		if (r2 != null && !r2.isBlank())
    			return r2;
    		return r1;
    	}
    
    	/**
    	 * 创建cmd
    	 */
    	private static String[] createCmd(String command) {
        
    		if (SystemUtils.IS_OS_LINUX) {
        
    			// linux -c
    			return new String[] {
         LINUX_CMD, "-c", command };
    		} else if (SystemUtils.IS_OS_WINDOWS) {
        
    			// win10 /c
    			return new String[] {
         WIN_CMD, "/c", command };
    		} else {
        
    			String systemInfo = SystemUtils.OS_NAME + " " + SystemUtils.OS_ARCH + " " + SystemUtils.OS_VERSION;
    			throw new RuntimeException("OS Not Supported , the current OS is :" + systemInfo);
    		}
    	}
    
    	/**
    	 * 预留显示效果控制，例如日志
    	 */
    	private static String resultHandle(Future<String> result, long time, TimeUnit unit) {
        
    		String tmp = null;
    		try {
        
    			tmp = result.get(time, unit);
    		} catch (InterruptedException e) {
        
    			e.printStackTrace();
    		} catch (ExecutionException e) {
        
    			e.printStackTrace();
    		} catch (TimeoutException e) {
        
    			e.printStackTrace();
    		}
    		return tmp;
    	}
    
    	private static class ReaderTask implements Callable<String> {
        
    		private InputStream inputStream;
    		private StringBuilder queryResult;
    
    		public ReaderTask(InputStream inputStream) {
        
    			this.inputStream = inputStream;
    			queryResult = new StringBuilder();
    		}
    
    		@Override
    		public String call() throws Exception {
        
    			BufferedReader bf = new BufferedReader(new InputStreamReader(inputStream));
    			String line = null;
    			while ((line = bf.readLine()) != null) {
        
    				queryResult.append(line).append(SystemUtils.LINE_SEPARATOR);
    			}
    			bf.close();
    			return queryResult.toString();
    		}
    	}
    }

其中 `SystemUtils` 源自 `commons-lang3` ，其 mvn 依赖如下：

<dependency>
    			<groupId>org.apache.commons</groupId>
    			<artifactId>commons-lang3</artifactId>
    			<version>3.12.0</version>
    		</dependency>

也可以自己实现一个System 工具类，见 java 获取系统信息

[f405f9e7c4b84857a5f8df8c9c03d356.png]: https://img-blog.csdnimg.cn/f405f9e7c4b84857a5f8df8c9c03d356.png
[java Runtime.exec]: https://zhuanlan.zhihu.com/p/33547017
[Runtime.exec]: https://blog.csdn.net/gongli7143/article/details/102945715