记录apache-commons-exec使用错误
Healthy Mind Lv3
 2021-05-19 09:52:37  

​ 在我们需要启动一个进程的时候可以使用 java 原始的 ProccessBuilder 或使用apache-commons-exec执行命令的时候，其实commons-exec是对ProcessBuidler的一个封装

例如

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
private static class ShellExecutor{
     private   DefaultExecutor executor ;

       public ShellExecutor() {
           this.executor = new DefaultExecutor();
           ExecuteWatchdog watchdog = new ExecuteWatchdog(COMMAND_EXEC_TIME_OUT);
           this.executor.setWatchdog(watchdog);

       }

       public BufferedReader exec(CommandLine commandLine) throws IOException {
              PipedInputStream pis = new PipedInputStream();
               //设置输出流
              PipedOutputStream pos = new PipedOutputStream(pis);
               //设置标准输出和错误输出
              PumpStreamHandler ps = new PumpStreamHandler(pos,pos);
              //设置handler 表示异步执行
              DefaultExecuteResultHandler handler = new DefaultExecuteResultHandler();
              executor.setStreamHandler(ps);
              executor.execute(commandLine, handler);
               //返回执行的输出流
              return new BufferedReader(new InputStreamReader(pis, Charset.defaultCharset()));
       }

   }

这主要发现的错误是在 CommandLine 的构建上

在 JAVA的 ProcessBudiler中 命令参数是分别放在不同的数组中的，在构建的CommandLine 应该是命令和参数分开放置，不然会报一些奇怪的错误，而且commons-exec没有log,很难排查错误

1
2
3
4
5
6
7
8
9
10
11
private CommandLine createBackupCommand(CommandConfig.BackupRestoreParam param){
       Objects.requireNonNull(param.host,"数据库地址不能为空!");
       String command = getShellDir()+"/pg_dump";
       String commandParam = "--dbname=postgres://%s:%s@%s:%s/%s -v -f %s ";
       commandParam = String.format(commandParam, param.userName, param.password, param.host, param.port, param.dbName, param.backFilePath);
       //命令
       CommandLine commandLine = new CommandLine(command);
      //参数
       commandLine.addArguments(commandParam);
       return commandLine;
   }

commons-exec 执行命令源码如下

org.apache.commons.exec.launcher.Java13CommandLauncher 源码

1
2
3
4
5
6
7
8
9
@Override
    public Process exec(final CommandLine cmd, final Map<String, String> env,
            final File workingDir) throws IOException {

        final String[] envVars = EnvironmentUtils.toStrings(env);
        //这里调用 CommandLine的 toStrings()方法
        return Runtime.getRuntime().exec(cmd.toStrings(),
                envVars, workingDir);
    }

在看看 org.apache.commons.exec.CommandLine toStrings方法

1
2
3
4
5
6
public String[] toStrings() {
      final String[] result = new String[arguments.size() + 1];
      result[0] = this.getExecutable();
      System.arraycopy(getArguments(), 0, result, 1, result.length-1);
      return result;
  }

这里返回的是数组

还有一个奇怪的问题，我使用单点的Java进程执行，其实是可以解析命令和参数一起放置的

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
package com.trs.exec;

import org.apache.commons.exec.*;

import java.io.*;
import java.nio.charset.Charset;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.logging.Logger;

/**
 * @Description
 * @DATE 2021.5.15 17:12
 **/

public class TrsExce {

    public static void main(String[] args) throws IOException {

        BufferedReader reader =  exeCommand(null);
        if (args.length > 1){
            reader =  exeCommand(args[0]);
        }

        String line = null;
        while ((line = reader.readLine())  != null){
            Logger.getGlobal().info(line);
        }

    }

    public static BufferedReader exeCommand(String cmd) throws IOException {
      if(cmd == null){
          cmd = "/opt/apache-tomcat-7.0.81-8085-kg3/webapps/tckg/WEB-INF/classes/shell/pg_dump --dbname=postgres://postgres:postgres@192.168.1.53:5432/trskg3_tc -v -f /home/postgres/trskg3_tc_20210518092525.dump ";

      }
        CommandLine cmdLine = CommandLine.parse(cmd);

        DefaultExecutor executor = new DefaultExecutor();
        PipedOutputStream outputStream = new PipedOutputStream();
        PipedInputStream pis = new PipedInputStream(outputStream);
        PumpStreamHandler pumpStreamHandler = new PumpStreamHandler(outputStream,outputStream);
        //设置输出流
        executor.setStreamHandler(pumpStreamHandler);
        //设置 进程最大执行时间
        ExecuteWatchdog watchdog = new ExecuteWatchdog(1000 * 60 * 30);
        executor.setWatchdog(watchdog);
        executor.execute(cmdLine,new DefaultExecuteResultHandler()); //设置异步
        BufferedReader reader = new BufferedReader(new InputStreamReader(pis, Charset.forName("GBK")));
        return reader;
    }

}

在单独的java进程中以上是可以执行的，但是在tomcat7中就不行，应该是类加载器加载了不同版本的commons-exec.还没找到具体原因，这里记录一下。