XML::Twig - 识别不包含元素的 blob

Question

我正在使用 XML::Twig 解析 Azure list-blob REST API.

的输出

特别是，我正在寻找识别和删除未提交的孤立 blob，但我不确定如何最好地使用 XML::Twig 有效地完成这项工作。我什至不知道从哪里开始。

最终我需要检索孤立 blob 的 <Name> 元素。

Azure documentation 状态：

Uncommitted Blobs in the Response

Uncommitted blobs are listed in the response only if the include=uncommittedblobs parameter was specified on the URI. Uncommitted blobs listed in the response do not include any of the following elements:

Last-Modified
Etag
Content-Type
Content-Encoding
Content-Language
Content-MD5
Cache-Control
Metadata

因此，在下面的简化示例中，您可以看到一个名为 "test" 的孤立 blob，因为 <Blob></Blob> 块不包含上述任何元素。

<?xml version="1.0" encoding="utf-8"?>
<EnumerationResults ServiceEndpoint="https://my**account.blob.core.windows.net/"
  ContainerName="testonly">
  <Blobs>
    <Blob>
      <Name>test</Name>
      <Properties>
        <Content-Length>0</Content-Length>
        <BlobType>BlockBlob</BlobType>
        <LeaseStatus>unlocked</LeaseStatus>
        <LeaseState>available</LeaseState>
      </Properties>
    </Blob>
  </Blobs>
  <NextMarker/>
</EnumerationResults>

更新：

实际上，我可能过于简单化了。接受的答案似乎不适用于以下内容，它会打印所有内容：

<?xml version="1.0" encoding="utf-8"?>
<EnumerationResults ServiceEndpoint="https://my**account.blob.core.windows.net/" ContainerName="testonly">
<Blobs>
    <Blob>
        <Name>data/users/docx</Name>
        <Properties>
            <Last-Modified>Wed, 10 May 2017 20:21:25 GMT</Last-Modified>
            <Etag>0x8D497E221E7A5AF</Etag>
            <Content-Length>125632</Content-Length>
            <Content-Type>application/octet-stream</Content-Type>
            <Content-Encoding/>
            <Content-Language/>
            <Content-MD5/>
            <Cache-Control/>
            <Content-Disposition/>
            <BlobType>BlockBlob</BlobType>
            <LeaseStatus>unlocked</LeaseStatus>
            <LeaseState>available</LeaseState>
        </Properties>
    </Blob>
    <Blob>
        <Name>test</Name>
        <Properties>
            <Content-Length>0</Content-Length>
            <BlobType>BlockBlob</BlobType>
            <LeaseStatus>unlocked</LeaseStatus>
            <LeaseState>available</LeaseState>
        </Properties>
    </Blob>
</Blobs>
<NextMarker/>
</EnumerationResults>

我的代码：

sub blob_parse {
        my $blob = $_;
        $blob->first_child($_) and return
        for qw( Last-Modified Etag Content-Type Content-Encoding
                Content-Language Content-MD5 Cache-Control Metadata);
        say "orph: ".$blob->first_child('Name')->text;
}

sub parseAndDelete {
        ### ORPHAN
        $twig_handlers = {'Blobs/Blob' => \&blob_parse};
        $twig = new XML::Twig(twig_handlers=>$twig_handlers);
        $twig->parse($message);
}

Answer 1

更新

没有理由使用 XML::Twig 提供的回调系统，除非你的 XML 数据非常庞大，相应的数据结构消耗太多内存，这对于从互联网上获取的数据来说是不可能的留言

我会这样实现

use strict;
use warnings;
use feature 'say';

use XML::Twig;
use List::Util 'none';

my @unwanted = qw/
    Last-Modified Etag Content-Type Content-Encoding
    Content-Language Content-MD5 Cache-Control Metadata
/;

my $twig = 'XML::Twig'->new;

$twig->parsefile('blob.xml');

for my $blob ( $twig->find_nodes('Blobs/Blob') ) {

    if ( none { $blob->find_nodes("Properties/$_") } @unwanted ) {
        say $_->text for $blob->find_nodes('Name');
    }
}

产出

test

---

如果您的 XML 实际上格式正确并且您的示例数据是错误的，那么打印所有 Name 元素的文本内容很简单

我用过这个数据

<?xml version="1.0" encoding="utf-8"?>
<EnumerationResults ServiceEndpoint="https://my**account.blob.core.windows.net/"
  ContainerName="testonly">
  <Blobs>
    <Blob>
      <Name>test</Name>
      <Properties>
        <Content-Length>0</Content-Length>
        <BlobType>BlockBlob</BlobType>
        <LeaseStatus>unlocked</LeaseStatus>
        <LeaseState>available</LeaseState>
      </Properties>
    </Blob>
  </Blobs>
  <NextMarker/>
</EnumerationResults>

Perl

use strict;
use warnings 'all';
use feature 'say';

use XML::Twig;

my $t = XML::Twig->new;
$t->parsefile( 'blob.xml');

say $_->text for $t->find_nodes('Blobs/Blob/Name');

产出

test

Answer 2

只需为 Blob 创建一个处理程序，如果存在任何元素则不执行任何操作，否则打印名称。使用 first_child 方法检查 blob 的内部结构。

#! /usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

use XML::Twig;

my $xml = '...';

my $twig = 'XML::Twig'->new(twig_handlers => {
    Blob => sub {
        my $properties = $_->first_child('Properties');
        $properties->first_child($_) and return
            for qw( Last-Modified Etag Content-Type Content-Encoding
                    Content-Language Content-MD5 Cache-Control Metadata
                  );
        say $_->first_child('Name')->text;
    },
});
$twig->parse($xml);