résolu: Perl: XML :: LibXML n'analyse pas ce document XML [duplicate]
Nov 15 2020
Je (alerte débutant) rencontre des problèmes pour analyser les informations d'un document XML. J'ai un appareil ( appelé OW-SERVER ) qui lit les valeurs des capteurs à partir d'un réseau de capteurs 1 fil et fournit les lectures dans un document XML. Le XML se présente généralement comme suit:
<?xml version="1.0" encoding="UTF-8"?>
<Devices-Detail-Response xmlns="http://www.embeddeddatasystems.com/schema/owserver" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<PollCount>1069</PollCount>
<DevicesConnected>1</DevicesConnected>
<LoopTime>1.630</LoopTime>
<DevicesConnectedChannel1>1</DevicesConnectedChannel1>
<DevicesConnectedChannel2>0</DevicesConnectedChannel2>
<DevicesConnectedChannel3>0</DevicesConnectedChannel3>
<DataErrorsChannel1>1</DataErrorsChannel1>
<DataErrorsChannel2>0</DataErrorsChannel2>
<DataErrorsChannel3>0</DataErrorsChannel3>
<VoltageChannel1>4.87</VoltageChannel1>
<VoltageChannel2>4.88</VoltageChannel2>
<VoltageChannel3>4.78</VoltageChannel3>
<VoltagePower>5.09</VoltagePower>
<DeviceName>OWServer_v2-Enet</DeviceName>
<HostName>EDSOWSERVER2</HostName>
<MACAddress>00:04:A3:F8:5F:FE</MACAddress>
<DateTime>2020-10-24 19:27:08</DateTime>
<owd_DS18B20 Description="Programmable resolution thermometer">
<Name>DS18B20</Name>
<Family>28</Family>
<ROMId>3E000005A0472628</ROMId>
<Health>0</Health>
<Channel>1</Channel>
<RawData>000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000</RawData>
<PrimaryValue>0.0000 Deg C</PrimaryValue>
<Temperature Units="Centigrade">0.0000</Temperature>
<UserByte1 Writable="True">0</UserByte1>
<UserByte2 Writable="True">0</UserByte2>
<Resolution>9</Resolution>
<PowerSource>0</PowerSource>
</owd_DS18B20>
<owd_DS18B20 Description="Programmable resolution thermometer">
<Name>DS18B20</Name>
<Family>28</Family>
<ROMId>A4000005A0EC8128</ROMId>
<Health>0</Health>
<Channel>1</Channel>
<RawData>000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000</RawData>
<PrimaryValue>0.0000 Deg C</PrimaryValue>
<Temperature Units="Centigrade">0.0000</Temperature>
<UserByte1 Writable="True">0</UserByte1>
<UserByte2 Writable="True">0</UserByte2>
<Resolution>9</Resolution>
<PowerSource>0</PowerSource>
</owd_DS18B20>
<owd_DS18B20 Description="Programmable resolution thermometer">
<Name>DS18B20</Name>
<Family>28</Family>
<ROMId>69000005A0046128</ROMId>
<Health>0</Health>
<Channel>1</Channel>
<RawData>000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000</RawData>
<PrimaryValue>0.0000 Deg C</PrimaryValue>
<Temperature Units="Centigrade">0.0000</Temperature>
<UserByte1 Writable="True">0</UserByte1>
<UserByte2 Writable="True">0</UserByte2>
<Resolution>9</Resolution>
<PowerSource>0</PowerSource>
</owd_DS18B20>
<owd_DS18B20 Description="Programmable resolution thermometer">
<Name>DS18B20</Name>
<Family>28</Family>
<ROMId>B0000005A00F2528</ROMId>
<Health>0</Health>
<Channel>1</Channel>
<RawData>000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000</RawData>
<PrimaryValue>0.0000 Deg C</PrimaryValue>
<Temperature Units="Centigrade">0.0000</Temperature>
<UserByte1 Writable="True">0</UserByte1>
<UserByte2 Writable="True">0</UserByte2>
<Resolution>9</Resolution>
<PowerSource>0</PowerSource>
</owd_DS18B20>
<owd_DS2423 Description="RAM with counters">
<Name>DS2423</Name>
<Family>1D</Family>
<ROMId>D80000000FD6C41D</ROMId>
<Health>0</Health>
<Channel>1</Channel>
<RawData>000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000</RawData>
<PrimaryValue>0, 0</PrimaryValue>
<Counter_A>0</Counter_A>
<Counter_B>0</Counter_B>
</owd_DS2423>
<owd_DS2423 Description="RAM with counters">
<Name>DS2423</Name>
<Family>1D</Family>
<ROMId>ED0000000FC5741D</ROMId>
<Health>0</Health>
<Channel>1</Channel>
<RawData>000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000</RawData>
<PrimaryValue>0, 0</PrimaryValue>
<Counter_A>0</Counter_A>
<Counter_B>0</Counter_B>
</owd_DS2423>
<owd_DS2423 Description="RAM with counters">
<Name>DS2423</Name>
<Family>1D</Family>
<ROMId>B90000001013E31D</ROMId>
<Health>0</Health>
<Channel>1</Channel>
<RawData>000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000</RawData>
<PrimaryValue>0, 0</PrimaryValue>
<Counter_A>0</Counter_A>
<Counter_B>0</Counter_B>
</owd_DS2423>
<owd_DS2423 Description="RAM with counters">
<Name>DS2423</Name>
<Family>1D</Family>
<ROMId>830000000F97DB1D</ROMId>
<Health>0</Health>
<Channel>1</Channel>
<RawData>000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000</RawData>
<PrimaryValue>0, 0</PrimaryValue>
<Counter_A>0</Counter_A>
<Counter_B>0</Counter_B>
</owd_DS2423>
<owd_DS18B20 Description="Programmable resolution thermometer">
<Name>DS18B20</Name>
<Family>28</Family>
<ROMId>0004175171AFFF28</ROMId>
<Health>7</Health>
<Channel>1</Channel>
<RawData>57014B467FFF0C1038FF0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000</RawData>
<PrimaryValue>21.4375 Deg C</PrimaryValue>
<Temperature Units="Centigrade">21.4375</Temperature>
<UserByte1 Writable="True">75</UserByte1>
<UserByte2 Writable="True">70</UserByte2>
<Resolution>12</Resolution>
<PowerSource>255</PowerSource>
</owd_DS18B20>
</Devices-Detail-Response>
Je veux utiliser XML :: LibXML afin de lire les valeurs de chaque capteur indvidual. Cependant, le script Perl suivant n'a pas réussi:
#!/usr/perl/bin
use warnings;
use strict;
use autodie;
use feature 'say';
use XML::LibXML;
my $file = 'doc.xml'; my $dom = eval {
XML::LibXML->load_xml(location => $file); }; if($@) {
# Log failure and exit
say "Error parsing $url"; say "$@";
say 'I will exit now.';
exit 0;
}
say 'XML::LibXML has read the following:';
say $dom; say ''; say 'Looking for Sensors:'; foreach my $sensor ($dom->findnodes('//owd_DS18B20')) { say 'found one!'; say $sensor->to_literal();
}
Toute aide serait appréciée. Daniel
Réponses
1 Shawn Nov 15 2020 at 11:46
Le problème est d'utiliser un espace de noms par défaut sans lui donner un nom à utiliser dans les requêtes.
Depuis la documentation XML :: LibXML :: Node pour findnodes:
Une erreur courante à propos de XPath est de supposer que les tests de nœuds consistant en un nom d'élément sans préfixe correspondent aux éléments dans l'espace de noms par défaut. Cette hypothèse est erronée - selon la spécification XPath, de tels tests de nœuds ne peuvent correspondre qu'à des éléments qui ne sont pas (c'est-à-dire null) d'espace de noms.
Les espaces de noms, en particulier celui par défaut, et XPath ne fonctionnent tout simplement pas bien sans travail.
L'utilisation de XML :: LibXML :: XPathContext et l'attribution d'un nom à l'espace de noms est l'une des approches suggérées. Ainsi:
#!/usr/bin/env perl
use warnings;
use strict;
use autodie;
use feature 'say';
use XML::LibXML;
use XML::LibXML::XPathContext;
my $file = 'doc.xml'; my $dom = eval {
XML::LibXML->load_xml(location => $file); }; if($@) {
# Log failure and exit
say "Error parsing $file"; say "$@";
say 'I will exit now.';
exit 0;
}
say 'XML::LibXML has read the following:';
say $dom; say ''; say 'Looking for Sensors:'; my $xpath = XML::LibXML::XPathContext->new($dom); $xpath->registerNs("ow", "http://www.embeddeddatasystems.com/schema/owserver");
foreach my $sensor ($xpath->findnodes('//ow:owd_DS18B20')) {
say 'found one!';
say $sensor->to_literal();
}