Question

我正在尝试使用Perl DBI将记录插入MySQL数据库。我没有收到任何错误，但插入不起作用。但是，我能够使用DBI从数据库中成功获取记录。

以下是执行插入的代码：

#!"C:\xampp\perl\bin\perl.exe"

use diagnostics;
use DBI;
use strict;
use warnings;

my $driver = "mysql"; 
my $database = "mysql";
my $dsn = "DBI:$driver:database=$database";
my $userid = "root";
my $password = "password";

my $buffer;
my @pairs;
my $pair;
my $name;
my $value;
my %FORM;

# Read in text
my $ENV;
$ENV{'REQUEST_METHOD'} =~ tr/a-z/A-Z/;
if ($ENV{'REQUEST_METHOD'} eq "GET")
{
    $buffer = $ENV{'QUERY_STRING'};
}

# Split information into name/value pairs
@pairs = split(/&/, $buffer);
foreach $pair (@pairs)
{
    ($name, $value) = split(/=/, $pair);
    $value =~ tr/+/ /;
    $value =~ s/%(..)/pack("C", hex($1))/eg;
    $FORM{$name} = $value;
}

my $first_name= $FORM{name};
my $address = $FORM{address};
my $city  = $FORM{city};
my $occupation  = $FORM{occupation};
my $age  = $FORM{age};

my $dbh = DBI->connect("dbi:mysql:dbname=mysql", "root", "password",{ AutoCommit =>  0,RaiseError => 1}, ) or die ("Couldn't connect to database: ") , $DBI::errstr;

# my $sth = $dbh->prepare("INSERT INTO persons
                        # (FirstName, LastName,Address,City)
                        # values
                        # ($first_name, $last_name,$address,$city)");
my $query = "insert into userrecords(Address,Age,City,Name,Occupation)
             values (?, ?, ?, ?, ?) ";

my $statement = $dbh->prepare($query) or die ("Couldn't connect to database: "), $DBI::errstr;
$statement->execute($address,$age,$city,$name,$occupation) or die ("Couldn't connect to database: "), $DBI::errstr;

$dbh->disconnect();

my $URL = "http://.....:81/cgi-bin/showdata.cgi";
print "Location: $URL\n\n";

exit(0);

当我在Padre IDE中运行我的代码时，出现以下错误：

****Error*********
Useless use of a variable in void context at InsertRecord.cgi line 50 (#1)
    (W void) You did something without a side effect in a context that does
    nothing with the return value, such as a statement that doesn't return a
    value from a block, or the left side of a scalar comma operator.  Very
    often this points not to stupidity on your part, but a failure of Perl
    to parse your program the way you thought it would.  For example, you'd
    get this if you mixed up your C precedence with Python precedence and
    said

        $one, $two = 1, 2;

    when you meant to say

        ($one, $two) = (1, 2);

    Another common error is to use ordinary parentheses to construct a list
    reference when you should be using square or curly brackets, for
    example, if you say

        $array = (1,2);

    when you should have said

        $array = [1,2];

    The square brackets explicitly turn a list value into a scalar value,
    while parentheses do not.  So when a parenthesized list is evaluated in
    a scalar context, the comma is treated like C's comma operator, which
    throws away the left argument, which is not what you want.  See
    perlref for more on this.

    This warning will not be issued for numerical constants equal to 0 or 1
    since they are often used in statements like

        1 while sub_with_side_effects();

    String constants that would normally evaluate to 0 or 1 are warned
    about.

Useless use of a variable in void context at InsertRecord.cgi line 59 (#1)
Useless use of a variable in void context at InsertRecord.cgi line 60 (#1)

Use of uninitialized value in transliteration (tr///) at InsertRecord.cgi line
        23 (#2)
    (W uninitialized) An undefined value was used as if it were already
    defined.  It was interpreted as a "" or a 0, but maybe it was a mistake.
    To suppress this warning assign a defined value to your variables.

    To help you figure out what was undefined, perl will try to tell you the
    name of the variable (if any) that was undefined. In some cases it cannot
    do this, so it also tells you what operation you used the undefined value
    in.  Note, however, that perl optimizes your program and the operation
    displayed in the warning may not necessarily appear literally in your
    program.  For example, "that $foo" is usually optimized into "that "
    . $foo, and the warning will refer to the concatenation (.) operator,
    even though there is no . in your program.

Use of uninitialized value $ENV{"REQUEST_METHOD"} in string eq at
        InsertRecord.cgi line 24 (#2)
Use of uninitialized value $buffer in split at InsertRecord.cgi line 29 (#2)
Location: http://.......:81/cgi-bin/showdata.cgi

Press any key to continue . . .

***********END***********************

问题是什么？

Answer 1

当我编辑代码以使其更具可读性时，我偶然发现了我认为的解决方案：

您在插入数据库时使用$name，但在获取值$first_name时使用$FORM{name}。因此，由于您使用了上面的$name，因此它具有所使用的姓氏的值，无论可能是什么。相关代码片段：

($name, $value) = split(/=/, $pair);
...
$FORM{$name} = $value;
...
my $first_name = $FORM{name};
...
$statement->execute($address,$age,$city,$name,$occupation)
#                                       ^^^^^--- should be $first_name

如果您在变量上使用了适当的范围，那么问题就解决了，例如：

 foreach my $pair (@pairs) {
     my ($name, $value) = split(/=/, $pair);
     $value =~ tr/+/ /;
     $value =~ s/%(..)/pack("C", hex($1))/eg;
     $FORM{$name} = $value;
 }

然后，当您稍后尝试使用$name时，您将收到错误

Global variable "$name" requires explicit package name ...

这会提醒您错误，并节省您的调试时间。当您在脚本顶部声明变量时，而不是在尽可能小的范围内，您可以有效地禁用use strict 'vars'提供的保护。所以不要这样做。

此外，您应该使用CGI模块而不是尝试手动处理它。它将使事情变得更容易，更安全。不要忘记对数据执行完整性检查以防止数据库注入攻击。

清理并正确格式化后的脚本看起来像this.

Answer 2

使用此替换代码时会发生什么：

#!"C:\xampp\perl\bin\perl.exe"
use strict;
use warnings;

use diagnostics;
use DBI;
use CGI qw[param redirect];    

my $driver   = "mysql"; 
my $database = "mysql";
my $dsn      = "DBI:$driver:database=$database";
my $userid   = "root";
my $password = "password";

my $dbh = DBI->connect("dbi:mysql:dbname=mysql", "root", "password",
    { AutoCommit =>  0,RaiseError => 1}, )
    or die "Couldn't connect to database: ", $DBI::errstr;

my $query = "insert into userrecords(Address,Age,City,Name,Occupation)
values (?, ?, ?, ?, ?) ";

my $statement = $dbh->prepare($query)
    or die "Couldn't connect to database: " , $DBI::errstr;
$statement->execute(param('address'), param('age'), param('city'),
                    param('name'), param('occupation'))
    or die "Couldn't connect to database: " , $DBI::errstr;    
$dbh->disconnect();

my $URL = "http://.....:81/cgi-bin/showdata.cgi";
print redirect($URL);

我基本上做了两处修改：

使用CGI.pm模块处理CGI交互（获取参数并打印重定向标头）。
通过删除所有对die的调用中放错位置的括号来修正您的“无效上下文”错误。

我没有对代码进行实质性更改，但至少我们现在有一个干净的版本。

更新： D'哦。很明显，现在代码被清理了一下。如果您关闭了“自动提交”，则需要提交更改。在对$dbh->commit和execute()的调用之间添加disconnect()。

Answer 3

警告来自：

or die ("Couldn't connect to database: ") , $DBI::errstr;

, $DBI::errstr位于骰子之外，没有任何处理，因此处于无效环境中。你想要这样的东西：

or die ("Couldn't connect to database:  $DBI::errstr");

此外，您的表单处理代码存在一些问题。如果您正在编写CGI脚本，也可以使用CGI模块。这是对代码的快速清理：

#!"C:\xampp\perl\bin\perl.exe"
use diagnostics;
use CGI ':standard';
use DBI;
use strict;
use warnings;

my $driver   = "mysql";
my $database = "mysql";
my $dsn      = "DBI:$driver:database=$database";
my $userid   = "root";
my $password = "password";

my $name       = param('name');
my $address    = param('address');
my $city       = param('city');
my $occupation = param('occupation');
my $age        = param('age');

my $dbh = DBI->connect( $dsn, $userid, $password,
    { AutoCommit => 1, RaiseError => 1 },
) or die("Couldn't connect to database: $DBI::errstr");

my $query = <<'END';
INSERT INTO userrecords(Address,Age,City,Name,Occupation)
                VALUES (      ?,   ?,  ?,    ?,        ?)
END

my $statement = $dbh->prepare($query);
$statement->execute( $address, $age, $city, $name, $occupation );
$dbh->disconnect();

my $URL = "http://.....:81/cgi-bin/showdata.cgi";
print "Location: $URL\n\n";

请注意，我删除了许多or die语句，因为您已将RaiseError设置为真值。

为了简单起见，我也（不情愿地）开启AutoCommit。

无法使用DBI将记录插入MySQL数据库

3 个答案: