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我一直在努力从 perl 启动一个 java 进程。问题的根源是 java 进程缺少JAVA_HOME导致ClassNotFoundException.

我开始使用IPC::Run3它是因为它相对优雅的 STDIN/STDOUT 重定向。

假设IPC::Run3会使用%ENV，我尝试添加$ENV{JAVA_HOME}.

当那不起作用时，我尝试做system(). 那没有用，所以最后，我让它工作了system("JAVA_HOME=/path/to/java && /path/to/java_program");

我的测试程序如下。自然我会取消注释正确的块来测试适当的调用。

#!/usr/bin/perl -w
use strict;

use IPC::Run3;

use vars qw(%Config $nutch_stdout $nutch_stderr);

%Config = (
  'nutch_binary'       => q[/home/crawl/nutch/runtime/local/bin/nutch],
  'nutch_crawl_dir'    => q[/home/crawl/nutch-crawl/crawl/crawldb/current/part-00000],
  'nutch_seed_dir'     => q[/home/crawl/urls],
  'solr_url'           => q[http://localhost:8080/solr],
);

my @nutch_command = ("$Config{nutch_binary}",
                 "crawl $Config{nutch_seed_dir}",
                 "-solr $Config{solr_url}",
                 "-d    $Config{nutch_crawl_dir}",
                 "-threads 1",
                 "-depth 1");

$ENV{JAVA_HOME}       = '/usr/lib/jvm/java-1.6.0';

while ((my $key,my $value) = each %ENV) {
    print "$key=$value\n";
}

print "Running @nutch_command\n";

# My original code. Next few lines are shown in first batch of output below.
#run3 \@nutch_command, undef, \$nutch_stdout, \$nutch_stderr;
#print "Output from Nutch:\n";
#print $nutch_stdout;
#print "Errors from Nutch:\n";
#print $nutch_stderr;

# Second try. The next line's output is the second batch of output.
#system(@nutch_command);

# Third try. Despite setting and displaying %ENV, this is the only thing I tried that worked
system("JAVA_HOME=/usr/lib/jvm/java-1.6.0 && @nutch_command");

这是运行 run3 的输出：

    -bash-3.2$ ./test.pl 
    ... [snip] ...
    JAVA_HOME=/usr/lib/jvm/java-1.6.0
    ... [snip] ...
    Running /home/crawl/nutch/runtime/local/bin/nutch crawl /home/crawl/urls -solr http://localhost:8080/solr -d    /home/crawl/nutch-crawl/crawl/crawldb/current/part-00000 -threads 1 -depth 1
    Output from Nutch:
    Errors from Nutch:
    Exception in thread "main" java.lang.NoClassDefFoundError: crawl
    Caused by: java.lang.ClassNotFoundException: crawl
at java.net.URLClassLoader$1.run(URLClassLoader.java:217)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
at java.lang.ClassLoader.loadClass(ClassLoader.java:321)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
    Could not find the main class: crawl. Program will exit.

第一个 system() 调用的输出：

    -bash-3.2$ ./test.pl
    ... [snip] ...
    JAVA_HOME=/usr/lib/jvm/java-1.6.0
    ... [snip] ...
    Running /home/crawl/nutch/runtime/local/bin/nutch crawl /home/crawl/urls -solr http://localhost:8080/solr -d    /home/crawl/nutch-crawl/crawl/crawldb/current/part-00000 -threads 1 -depth 1
    Exception in thread "main" java.lang.NoClassDefFoundError: crawl
    Caused by: java.lang.ClassNotFoundException: crawl
at java.net.URLClassLoader$1.run(URLClassLoader.java:217)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
at java.lang.ClassLoader.loadClass(ClassLoader.java:321)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
    Could not find the main class: crawl. Program will exit.

最后，第三个系统调用——唯一有效的！——使用内联设置的环境变量：

    -bash-3.2$ ./test.pl
    ... [snip] ...
    JAVA_HOME=/usr/lib/jvm/java-1.6.0
    ... [snip] ...
    Running /home/crawl/nutch/runtime/local/bin/nutch crawl /home/crawl/urls -solr http://localhost:8080/solr -d    /home/crawl/nutch-crawl/crawl/crawldb/current/part-00000 -threads 1 -depth 1
    crawl started in: crawl-20120216133832
    ... continue success stdout output

最后的问题：除了必须在 system() 调用中设置环境外，将环境变量传递给 IPC::Run3 或 system() 调用的适当方法是什么？

（注意：%ENV 的输出被截断为仅相关的行... PATH、SHELL、_ 等与省略的问题无关的行）

如果它是相关的：

-bash-3.2$ uname -a
Linux hostname 2.6.18-238.el5xen #1 SMP Thu Jan 13 16:41:45 EST 2011 x86_64 x86_64 x86_64 GNU/Linux
-bash-3.2$ perl --version
This is perl, v5.8.8 built for x86_64-linux-thread-multi
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1 回答 1

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问题的根源在于 java 进程缺少 JAVA_HOME 环境变量导致 ClassNotFoundException。

修改

这不是问题的根源。事实上，Java 本身并不需要设置 JAVA_HOME。

问题的直接原因是以下之一：

  • 包装器没有为您尝试执行的应用程序正确 设置类路径。

  • 包装器使用了错误的类名。类名“nutch”不寻常且可疑——没有包名。

真正的根本原因似乎是您错误地组装了参数列表。每个带有空格的参数实际上应该是两个参数；IE

        my @nutch_command = ("$Config{nutch_binary}",
             "crawl", "$Config{nutch_seed_dir}",
             "-solr", "$Config{solr_url}",
             "-d", "$Config{nutch_crawl_dir}",
             "-threads", "1",
             "-depth", "1");

我怀疑这混淆了 nutch 包装脚本，并导致它使用了错误的类名（除其他外）。当您将整个命令作为一个字符串传递并让 shell 解析它时，问题（自然）就消失了。

于 2012-02-16T23:48:59.230 回答