Question

在我的代码的第70行中，Perl 5.30.x中出现“ NOT HASH reference”错误，我在其中尝试测试$ xml的类型：

由于我离开Perl已有相当一段时间了，因此我不知道如何解决该问题，并且希望获得所有建议。

代码遵循（希望如此）。

#!/usr/bin/perl
use strict;
use URI;
use LWP::Simple;
use Net::Amazon;
use XML::Simple;
use constant AMAZON_TOKEN => 'amazon token deleted';
use constant DEBUG => 0;

# get our arguments. the first argument is the
# URL to fetch, and the second is the output.
my $url = shift || die "$0 <url> [<output>]\n";
my $output = shift || '/www/htdocs/cloud.html';

# we'll need to fetch the Alexa XML at some point, and
# we'll do it a few different times, so we create a 
# subroutine for it. Using the URI module, we can
# correctly encode a URL with a query. In fact, you'll
# notice the majority of this function is involved with
# this, and at the end we use LWP::Simple to actually
# download and return the XML.
#####################################################
sub fetch_xml {
    my $url = shift;
    $url = "http://$url" unless $url =~ m[^http://];
    warn "Fetching Alexa data for $url\n" if DEBUG;

    my @args = (
        cli => 10,     dat => 'snba',
        ver => '7.0',  url => $url,
    );

    my $base = 'http://data.alexa.com/data';
    my $uri = URI->new( $base );
    $uri->query_form( @args );
    $uri = $uri->as_string;

    return get( $uri );
}

# raw XML is no good for us, though, as we want to extract
# particular items of interest. we use XML::Simple to turn
# the XML into Perl data structures, because it's easier
# than fiddling with event handling (as with XML::Parser
# or XML::SAX), and we know there's only a small amount of
# data. we want the list of related sites and the list of
# related products. we extract and return both.
#####################################################
sub handle_xml {
    my $page = shift;
    my $xml = XMLin( $page );
    my @related = map {
        {
            asin => $_->{ASIN},
            title => $_->{TITLE},
            href => $xml->{RLS}{PREFIX}.$_->{HREF},
        }
    } @{ $xml->{RLS}{RL} };

    my @products;
    if (ref $xml->{SD}{AMZN}{PRODUCT} eq 'ARRAY') {
        @products = map { $_->{ASIN} } @{ $xml->{SD}{AMZN}{PRODUCT} };
    } else { @products = $xml->{SD}{AMZN}{PRODUCT}{ASIN}; }

    return ( \@related, \@products );
}

# Functions done; now for the program:
warn "Start URL is $url\n" if DEBUG;
my @products; # running accumulation of product ASINs

{
    my $page = fetch_xml( $url );
    my ($related, $new_products) = handle_xml( $page );
    @products = @$new_products; # running list

    for (@$related) {
        my $xml = fetch_xml( $_->{href} );
        my ($related, $new_products) = handle_xml( $page );
        push @products, @$new_products;
    }
}

# We now have a list of products in @products, so
# we'd best do something with them. Let's look
# them up on Amazon and see what their titles are.
my $amazon = Net::Amazon->new( token => AMAZON_TOKEN );
my %products = map { $_ => undef } @products;

for my $asin ( sort keys %products ) {
    warn "Searching for $asin...\n" if DEBUG;
    my $response = $amazon->search( asin => $asin );
    my @products = $response->properties;
    die "ASIN is not unique!?" unless @products == 1;
    my $product = $products[0];
    $products{$asin} = {
        name => $product->ProductName,
        price => $product->OurPrice,
        asin => $asin,
    };
}

# Right. We now have name, price, and
# ASIN. Let's output an HTML report:
{
    umask 022;
    warn "Writing to $output\n" if DEBUG;
    open my $fh, '>', $output or die $!;
    print $fh "<html><head><title>Cloud around $url</title></head><body>";
    if (keys %products) {
        print $fh "<table>";
        for my $asin (sort keys %products) {
            my $data = $products{$asin};
            printf $fh "<tr><td>".
                       "<a href=\"http://amazon.com/exec/obidos/ASIN/%s\">".
                       "%s</a></td> <td>%s</td></tr>",
                       @{$data}{qw( asin name price )};
        }
        print $fh "</table>";
    }
    else { print $fh "No related products found.\n"; }
    print $fh "</body></html>\n";
}

Answer 1

您正在使用XML::Simple。那是一个错误。甚至该模块的文档也与我一致：

此模块的状态

强烈建议在新代码中使用此模块   泄气。其他模块可提供更多   简单，一致的界面。特别是XML::LibXML   强烈建议使用，您可以参考Perl XML::LibXML by Example   以获得教程简介。

XML::Twig是另一个很好的选择。

此模块的主要问题是选项众多   （其中一些不幸的默认值）以及任意方式   这些选项相互影响-通常会产生意想不到的结果。

欢迎提供具有错误修复和文档修复的补丁程序，但它们是新的   功能不太可能添加。

没有看到您的XML很难确定，但这是我认为已经发生的事情。 XML :: Simple在返回的数据结构中众所周知不一致。输入文档中的少量更改会对返回的数据结构产生重大影响。在一个非常相似的文档上，什么是哈希引用变成数组引用是很常见的。

我的建议是停止使用XML :: Simple。就个人而言，我将其替换为XML :: LibXML。

不是哈希参考

1 个答案: