使用perl解析json文件
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parsing json file using perl
提问by UKR
I am trying to parse a json file in perl. I want to extract the key "name" and corresponding value of it. my file looks like this
我正在尝试用 perl 解析一个 json 文件。我想提取键“名称”及其对应的值。我的文件看起来像这样
{
"data":[
{
"name":"ABC",
"id":"123",
},
{
"name":"PQR",
"id":"456",
},
{
"name":"XYZ",
"id":"789",
}
]
}
I am trying with below code:
我正在尝试使用以下代码：
#/usr/lib/perl
use lib qw( ..);
use LWP::Simple;
use JSON;
my $filename = '/file.txt';
my $data;
if (open (my $json_str, $filename))
{
local $/ = undef;
my $json = JSON->new;
$data = $json->decode(<$json_str>);
close($json_stream);
}
print $data->{name};
But I not getting any output.
但我没有得到任何输出。
Can anyone tel me what is wrong ?
谁能告诉我出了什么问题？
回答by average
Your json file is invalid.
您的 json 文件无效。
Lines 5,10,15 should not end with a comma since that is the last key/value pair of those hashes.
第 5、10、15 行不应以逗号结尾，因为这是这些散列的最后一个键/值对。
After you fix that, here is a version of your code that gives you the expected result:
修复此问题后，这里是您的代码版本，可为您提供预期结果：
#/usr/lib/perl
use strict;
use warnings;
use lib qw(..);
use JSON qw( );
my $filename = 'file.txt';
my $json_text = do {
open(my $json_fh, "<:encoding(UTF-8)", $filename)
or die("Can't open $filename\": $!\n");
local $/;
<$json_fh>
};
my $json = JSON->new;
my $data = $json->decode($json_text);
for ( @{$data->{data}} ) {
print $_->{name}."\n";
}
Some of the problems:
一些问题：
- You were using
$json_streamand$json_str. You meant to use$json_streamin all places to denote the filehandle - The
$data->{name}should be applied to all members of the array in the .json file, not to the json itself. So you need to iterate through them first
- 您正在使用
$json_stream和$json_str。您打算$json_stream在所有地方使用来表示文件句柄 - 的
$data->{name}应在上传.json文件被施加到所述阵列的所有成员，而不是到JSON本身。所以你需要先遍历它们
When debugging this, make sure your json is valid. Either through jsonlint.comor the json_xsutility that comes with JSON::XSfrom cpan.
调试时，请确保您的 json 有效。通过jsonlint.com或来自 cpan 的JSON::XS附带的json_xs实用程序。
JSON can describe complicated data structures so when you parse it into Perl you get a complex data structure too. Try to first have a look at the data structure using Data::Dumperor Data::Printeror Data::TreeDumper
JSON 可以描述复杂的数据结构，因此当您将其解析为 Perl 时，您也会得到一个复杂的数据结构。尝试首先使用Data::Dumper或Data::Printer或Data::TreeDumper查看数据结构
回答by TLP
Besides having an extra comma in the JSON string, you do not reference the right values. Always use
除了在 JSON 字符串中有一个额外的逗号之外，您没有引用正确的值。一直使用
use strict;
use warnings;
-- they will tell you what's wrong. In this case, you are printing an undefined value $data->{name}, a variable that has not been assigned a value. If you print your decoded structure in Data::Dumperit looks like this:
——他们会告诉你出了什么问题。在这种情况下，您正在打印一个 undefined value $data->{name}，一个尚未赋值的变量。如果您在Data::Dumper其中打印解码结构，则如下所示：
$VAR1 = {
'data' => [
{
'name' => 'ABC',
'id' => '123'
},
{
'name' => 'PQR',
'id' => '456'
},
{
'name' => 'XYZ',
'id' => '789'
}
]
};
And as you can see, $datais actually a hash reference, where the first and only key is called 'data', whose value is an array with three elements, each containing a hash reference. So, in order to print those elements you would do something like:
正如你所看到的，$data实际上是一个散列引用，其中第一个也是唯一一个键被称为'data'，其值是一个包含三个元素的数组，每个元素包含一个散列引用。因此，为了打印这些元素，您可以执行以下操作：
print $data->{data}[0]{name}; # prints ABC
my $aref = $data->{data};
for my $element (@$aref) {
print $element->{name}; # prints ABC, PQR, XYZ
}
