Perl舞者错误执行方法未定义

Question

I was trying to make a website using perl dancer, below is my code. It seems to be correct but the page keeps loading and never enters the values in the database. When I cancel the page I get an error stating " request to POST /appform crashed: Can't call method "execute" on an undefined value ". I can't figured out whats wrong in the code. If you have any other code please mention. I am using SQLite for database. There is a database campus.db and I am inserting the value in student table.

post '/appform' => sub {

        my $q = CGI ->new;
        my $name = $q->param ("firstname");
        my $password = $q->param("password");
        my $mobile_no = $q->param("mobile");
        my $gender = $q->param("gender");
        my $email = $q->param("email");
        my $address = $q->param("address");
        my $sslc = $q->param("SSLC");
        my $hsc = $q->param("HSC");
        my $cgpa = $q->param("cgpa");
        my $languages = $q->param("lang");
        my $internships = $q->param("intern");
        my $preferred_loc = $q->param("country");
        my $sql = "insert into student(name,mobile_no,gender,email,address,sslc,hsc,cgpa,languages,internships,preferred_loc,password,applied_job,company_applied) values ('?','?','?','?','?','?','?','?','?','?','?','?','?','?');";
        my $sth = database->prepare($sql); 
        $sth->execute($name,$mobile_no,$gender,$email,$address,$sslc,$hsc,$cgpa,$languages,$internships,$preferred_loc,$password) or die $sth->errstr;
        #$sth->execute();   
        $sth-> finish;
        set_flash('New entry posted!');
            redirect '/';
    };

Answer 1

You're using the database keyword to get a database handle. I'm guessing that's coming from Dancer2::Plugin::Database (it would be useful if you could include information like this in your question).

The error says that you're calling execute() on an undefined value. You're calling execute() on the variable $sth . So $sth is undefined. You get $sth by calling prepare() on the database handle returned from database() . So it looks like the prepare() call is failing. You should check the return value from that call and throw an error if it fails.

The most common reason for prepare() to fail is that you're trying to compile an SQL statement that contains an error. I can't see any obvious error in your SQL, but it's worth checking it by running it manually against your database.

I see you're using bind params in your SQL statement. That's a great idea, but please note that you don't need to quote the question marks in your SQL - the database driver will handle that for you. I don't think that's what is causing your problem though.

I also see that you're using CGI.pm inside your Dancer app to get the request parameters. To be honest, I'm slightly surprised that it works - but it's a terrible idea. Dancer has its own keywords that will give you this information. Look at query_parameters() , body_parameters() and route_parameters() in the Dancer documentation .

Answer 2

除了已经提出的要点之外，您的DBI prepare（）调用可能还失败了（添加错误检查以查看原因，例如， my $sth = database->prepare('...') or die "DB error: " . database->errstr ），并且您使用的是舞者应用程序内CGI.pm（......不这样做，我很惊讶，它会在所有的工作-看舞者文档如何访问PARAMS您的应用已发送），还请查看Dancer :: Plugin :: Database / Dancer2 :: Plugin :: Database提供的quick_insert便捷方法，因此您根本不必编写该SQL INSERT语句。