perl 3.01 用JSON/XML 格式导入导出数据

>**JSON.pm 和 XML/Sample.pm是常用的perl解析JSON/XML格式的模块，这篇笔记就是介绍这两种模块的。**

# JSON.pm
##官方文档：
http://search.cpan.org/~makamaka/JSON-2.90/lib/JSON.pm  
##直接上code：
```perl
#!/usr/bin/perl
use warnings;
use strict;
use Data::Dumper;
use JSON;
my $hash = { "aa" => "11","bb" => { "cc" => "22", "dd" => "33" } , "ee" => "44" };
#my $result_json = encode_json $hash;
#面向方法的写法
my $result_json = JSON->new->encode($hash);
#面向对象的写法
#my $result_json = JSON->new->utf8(1)->encode($hash);
#utf8 的格式？
#my $result_json = JSON->new->pretty(1)->encode($hash);
#输出可读的json 字符串
print Dumper $result_json;
#my $result_hash = decode_json $result_json;
my $result_hash = JSON->new->decode($result_json);
print Dumper $result_hash;
```
运行结果：
```bash
[root@test perl]# ./json.pl
$VAR1 = '{"bb":{"cc":"22","dd":"33"},"aa":"11","ee":"44"}';
$VAR1 = {
          'bb' => {
                    'cc' => '22',
                    'dd' => '33'
                  },
          'aa' => '11',
          'ee' => '44'
        };
```
##命令行上解析JSON：
```bash
[root@test perl]# echo '{"aa":{"bb":2}}' | perl -MJSON -MData::Dumper -lne 'print Dumper decode_json($_);'
$VAR1 = {
          'aa' => {
                    'bb' => 2
                  }
        };
```
##其他小技巧:
有时候我们想把配置文件写成JSON格式，还需要给配置写一些注释，但是JSON格式里当然不能插入注释，这时候我们可以用JSON模块的relaxed功能，它会忽略‘#’后的内容:
配置文件
```bash
[root@test perl]# cat config.js
{
   "host_config" : {       #host config
      "ip" : "0.0.0.0",    #ip
      "hostname" : "localhost"  #hostname
   },
   "user" : "admin",  #user
   "limit" : 2        #other config
}
```
code:
```perl
#!/usr/bin/perl
use warnings;
use strict;
use Data::Dumper;
use JSON;
chomp(my $string=`cat $ARGV[0]`);
my $result_hash = JSON->new->relaxed(1)->decode($string);
print Dumper $result_hash;
```
运行结果：
```bash
[root@test perl]# ./read_js.pl config.js
$VAR1 = {
          'host_config' => {
                             'ip' => '0.0.0.0',
                             'hostname' => 'localhost'
                           },
          'user' => 'admin',
          'limit' => 2
        };
```
***
#XML::Simple.pm
>**写这篇笔记时发现官网已经建议新code不要用这个模块，原因是这个模块太老太臃肿，很多默认选项不合理。官网建议用XML::LibXML（http://search.cpan.org/~shlomif/XML-LibXML-2.0123/LibXML.pod）代替。所以这里只是简单介绍这个模块，以后再补充XML::LibXML的介绍。(¬_¬)**
##官方文档:
http://search.cpan.org/~grantm/XML-Simple-2.22/lib/XML/Simple.pm
##直接上code:
```perl
#!/usr/bin/perl
use warnings;
use strict;
use Data::Dumper;
use XML::Simple;
my $hash = { "aa" => "11","bb" => { "cc" => "22", "dd" => "33" } , "ee" => "rr" };
my $xml = XMLout($hash);  #把hash 转成xml
print $xml;
my $new_hash = XMLin("$ARGV[0]"); #也可以是变量，把变量或文件里的字符串(xml格式)转成hash
print Dumper $new_hash;
```
运行成果
```bash
[root@test perl]# cat ./config.xml
<host hostname="localhost" ip="127.0.0.1">
  <disk space="90%" inode="1%" />
  <memory mem="100" swap="20" />
</host>
[root@test perl]# ./xml.pl ./config.xml
<opt aa="11" ee="rr">
  <bb cc="22" dd="33" />
</opt>
$VAR1 = {
          'memory' => {
                      'swap' => '20',
                      'mem' => '100'
                    },
          'disk' => {
                    'inode' => '1%',
                    'space' => '90%'
                  },
          'ip' => '127.0.0.1',
          'hostname' => 'localhost'
        };
```

乱读天书， 不求甚解

乱读天书，不求甚解