D.N*_*.N. 7 java concurrency inputstream exec
我别无选择,只能通过多次Runtime.exec()调用VBScript 来检索一些外部数据.我真的很讨厌这种实现,因为我失去了跨平台的灵活性,但我最终可能会开发类似的*nix脚本来至少缓解这个问题.有人问之前,我不能工作,各地要调用外部脚本来收集我的数据.我会忍受导致的问题.
这些exec()进程在扩展的自定义类中运行Runnable.它使用a BufferedReader来读取数据getInputStream().
编辑:更多的代码按要求添加,但我不知道额外的代码是如何相关的:)我希望它有所帮助,因为它需要一段时间来格式化!哦,如果它的丑陋,我的代码风格变得容易,但鼓励建设性的批评......
public class X extends JFrame implements Runnable {
...
static final int THREADS_MAX = 4;
ExecutorService exec;
...
public static void main(String[] args) {
...
SwingUtilities.invokeLater(new X("X"));
} // End main(String[])
public X (String title) {
...
exec = Executors.newFixedThreadPool(THREADS_MAX);
...
// Create all needed instances of Y
for (int i = 0; i < objects.length; i++) {
Y[i] = new Y(i);
} // End for(i)
// Initialization moved here for easy single-thread testing
// Undesired, of course
for (int i = 0; i < objects.length; i++) {
Y[i].initialize(parent);
} // End for(i)
} // End X
class Y implements Runnable {
// Define variables/arrays used to capture data here
String computerName = "";
...
public Y(int rowIndex) {
row = rowIndex;
...
computerName = (String)JTable.getValueAt(row, 0);
...
exec.execute(this);
} // End Y(int)
public void run() {
// Initialize variables/arrays used to capture data here
...
// Initialization should be done here for proper threading
//initialize(parent);
} // End run()
public void initialize(Z obj) {
runTime = Runtime.getRuntime();
...
try {
process = runTime.exec("cscript.exe query.vbs " + computerName);
stdErr = process.getErrorStream();
stdIn = process.getInputStream();
isrErr = new InputStreamReader(stdErr);
isrIn = new InputStreamReader(stdIn);
brErr = new BufferedReader(isrErr);
brIn = new BufferedReader(isrIn);
while ((line = brIn.readLine()) != null) {
// Capture, parse, and store data here
...
} // End while
} catch (IOException e) {
System.out.println("Unable to run script");
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
stdErr.close();
stdIn. close();
isrErr.close();
isrIn. close();
brErr. close();
brIn. close();
} catch (IOException e) {
System.out.println("Unable to close streams.");
} // End try
} // End try
} // End initialize(Z)
...
} // End class Y
} // End class X
如果我单独执行命令,我会按预期收集数据.但是,如果我run()在类的块中执行命令(意味着调用是并发的,正如我所希望的那样),则看起来好像只生成了一个输入流,它们都BufferedReaders同时消耗.
为了调试这个问题,我在控制台上输出每个消耗的行,前面是我的类的哪个实例正在读取输入流.我期待类似下面的内容,理解它们可能在实例到实例之间出现故障,但单个实例的行顺序将完好无损:
exec 0: Line1
exec 1: Line1
exec 2: Line1
exec 0: Line2
exec 1: Line2
exec 2: Line2
exec 0: Line3
exec 1: Line3
exec 2: Line3
...
奇怪的是我获得了output(Microsoft (R) Windows Script Host Version 5.7)第一行的预期实例数,但在此行之后,只有一个进程继续在输入流中生成数据,并且所有读者随机使用这一个流,例如这个例子:
exec 2: Microsoft (R) Windows Script Host Version 5.7
exec 0: Microsoft (R) Windows Script Host Version 5.7
exec 1: Microsoft (R) Windows Script Host Version 5.7
exec 0: line2
exec 1: line3
exec 2: line4
...
更糟糕的是,读者失速并且readLine()永远不会返回null.我读到这种行为可能与缓冲区大小有关,但是当我只运行两个并发线程时,即使输出很短,它仍然表现出相同的行为.没有任何内容stdErr表明存在问题.
为了查看这是否是脚本主机的限制,我创建了一个同时具有START多个脚本实例的批处理文件. 我应该声明这是在 Java 之外的cmd shell中运行的,并启动了几个自己的shell. 但是,每个并发实例完全返回预期结果并且表现良好.
编辑:作为另一个故障排除的想法,我决定重新启用并发,但通过在我的Y.run()块中插入以下内容来错开我的初始化方法:
try {
Thread.sleep((int)(Math.random() * 1200));
} catch (InterruptedException e) {
System.out.println("Can't sleep!");
} // End try
initialize(monitor);
进入我的代码.我开始看到前几行的多个输出,但很快就会回复到消费同一个生产者的多个消费者,并且一旦第一个完成的流关闭,其余的消费者就会触发异常.下一个消费者开火了IOException: Read error,剩下的火了IOException: Stream closed!
根据maaartinus,有可能运行多个,并发InputStreams,所以现在问题变成了导致不良行为的原因？如何独立获取输入流？我不想写一个临时文件只是为了处理数据,如果我可以避免它.
我认为你需要注意IO变量的范围.这是一个完美的快速代码,具有来自4个子进程的并发输入流......
import java.io.*;
public class MultiExec {
private final static String[] comLines = {
"date",
"ls /var/spool/postfix",
"ls -F /usr/local/bin",
"wc -l /etc/apache2/apache2.conf"};
public void execute() {
for (int i = 0 ; i < comLines.length ; i++) {
ExecutableChild ec = new ExecutableChild (i, comLines[i]);
new Thread (ec).start();
}}
public class ExecutableChild implements Runnable {
private int prIndex;
private String executable;
public ExecutableChild (int k, String cmd) {
prIndex = k;
executable = cmd;
}
public void run () {
try {
Process child = Runtime.getRuntime().exec(executable);
BufferedReader br = new BufferedReader (new InputStreamReader (
child.getInputStream()));
for (String s = br.readLine() ; s != null ; s = br.readLine())
System.out.println ("[" + prIndex + "] " + s);
br.close();
} catch (IOException ioex) {
System.err.println ("IOException for process #"+
prIndex+ ": " + ioex.getMessage());
}}}
public static void main (String[] args) {
new MultiExec().execute();
}
}
上面代码的输出(%javac MultiExec.java; java MultiExec)
[2] tomcat*
[0] Thu Jan 20 18:38:31 CST 2011
[3] 368 /etc/apache2/apache2.conf
[1] active
[1] bounce
[1] corrupt
[1] defer
[1] deferred
[1] etc
[1] flush
[1] hold
[1] incoming
[1] lib
[1] maildrop
[1] pid
[1] private
[1] public
[1] saved
[1] trace
[1] usr
[1] var
如果您向我们提供了您尝试的源代码,我们可以进行讨论.祝福, - MS
================================================== ===========================
编辑:DN:我理解您对1行输出的担忧.让我们有一个小脚本......
#!/usr/bin/perl -w
foreach (1..50) {
print "$_\n";
}
以及上述Java代码的编辑版本... comLines已更改,并且每个println()后添加了Thread.sleep
公共类MultiExec {
private final static String[] comLines = {
"ls /var/spool/postfix",
"perl count50.pl",
"cat MultiExec.java",
"head -40 /etc/apache2/apache2.conf"};
public void execute() {
for (int i = 0 ; i < comLines.length ; i++) {
ExecutableChild ec = new ExecutableChild (i, comLines[i]);
new Thread (ec).start();
}}
public class ExecutableChild implements Runnable {
private int prIndex;
private String executable;
public ExecutableChild (int k, String cmd) {
prIndex = k;
executable = cmd;
}
public void run () {
try {
Process child = Runtime.getRuntime().exec(executable);
BufferedReader br = new BufferedReader (new InputStreamReader (
child.getInputStream()));
for (String s = br.readLine() ; s != null ; s = br.readLine()) {
System.out.println ("[" + prIndex + "] " + s);
try {
Thread.sleep (20);
} catch (InterruptedException intex) {
}}
br.close();
} catch (IOException ioex) {
System.err.println ("IOException for process #"+
prIndex+ ": " + ioex.getMessage());
}}}
public static void main (String[] args) {
new MultiExec().execute();
}}
这是现在的输出(在编译/运行之后)......
[0] active
[1] 1
[2] import java.io.*;
[3] #
[2]
[0] bounce
[1] 2
[3] # Based upon the NCSA server configuration files originally by Rob McCool.
[2] public class MultiExec {
[1] 3
[0] corrupt
[3] #
[1] 4
[2]
[0] defer
[3] # This is the main Apache server configuration file. It contains the
[2] private final static String[] comLines = {
[0] deferred
[1] 5
[3] # configuration directives that give the server its instructions.
[2] "ls /var/spool/postfix",
[0] etc
[1] 6
[3] # See http://httpd.apache.org/docs/2.2/ for detailed information about
[2] "perl count50.pl",
[0] flush
[1] 7
[3] # the directives.
[2] "cat MultiExec.java",
[1] 8
[0] hold
[3] #
[1] 9
[2] "head -40 /etc/apache2/apache2.conf"};
[0] incoming
[3] # Do NOT simply read the instructions in here without understanding
[2]
[0] lib
[1] 10
[3] # what they do. They're here only as hints or reminders. If you are unsure
[1] 11
[2] public void execute() {
[0] maildrop
[3] # consult the online docs. You have been warned.
[2] for (int i = 0 ; i < comLines.length ; i++) {
[0] pid
[1] 12
[3] #
[1] 13
[2] ExecutableChild ec = new ExecutableChild (i, comLines[i]);
[0] private
[3] # The configuration directives are grouped into three basic sections:
[1] 14
[2] new Thread (ec).start();
[0] public
[3] # 1. Directives that control the operation of the Apache server process as a
[2] }}
[1] 15
[0] saved
[3] # whole (the 'global environment').
[1] 16
[0] trace
[2]
[3] # 2. Directives that define the parameters of the 'main' or 'default' server,
[0] usr
[2] public class ExecutableChild implements Runnable {
[1] 17
[3] # which responds to requests that aren't handled by a virtual host.
[0] var
[2]
[1] 18
[3] # These directives also provide default values for the settings
[1] 19
[2] private int prIndex;
[3] # of all virtual hosts.
[1] 20
[2] private String executable;
[3] # 3. Settings for virtual hosts, which allow Web requests to be sent to
[2]
[1] 21
[3] # different IP addresses or hostnames and have them handled by the
[1] 22
[2] public ExecutableChild (int k, String cmd) {
[3] # same Apache server process.
[1] 23
[2] prIndex = k;
[3] #
[1] 24
[2] executable = cmd;
[3] # Configuration and logfile names: If the filenames you specify for many
[2] }
[1] 25
[3] # of the server's control files begin with "/" (or "drive:/" for Win32), the
[2]
[1] 26
[3] # server will use that explicit path. If the filenames do *not* begin
[1] 27
[2] public void run () {
[3] # with "/", the value of ServerRoot is prepended -- so "/var/log/apache2/foo.log"
[1] 28
[2] try {
[3] # with ServerRoot set to "" will be interpreted by the
[1] 29
[2] Process child = Runtime.getRuntime().exec(executable);
[3] # server as "//var/log/apache2/foo.log".
[1] 30
[2] BufferedReader br = new BufferedReader (new InputStreamReader (
[3] #
[1] 31
[2] child.getInputStream()));
[3]
[1] 32
[2] for (String s = br.readLine() ; s != null ; s = br.readLine()) {
[3] ### Section 1: Global Environment
[1] 33
[2] System.out.println ("[" + prIndex + "] " + s);
[3] #
[1] 34
[2] try {
[3] # The directives in this section affect the overall operation of Apache,
[1] 35
[2] Thread.sleep (20);
[3] # such as the number of concurrent requests it can handle or where it
......
输入流工作正常,不要认为我在这里有问题.很抱歉回复这么长时间.祝你最好,等着看你的代码, - MS
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