At the Forge - Google Web Services

#!/usr/bin/perl

use strict;
use diagnostics;
use warnings;

use SOAP::Lite;

# ------------------------------------------------------------
# Get the Google key from ~/.google_key
my $google_key_file = "/Users/reuven/.google_key";
open GOOGLE_KEY, $google_key_file or die "Cannot read
'$google_key_file': $! ";

my ($google_key) = <GOOGLE_KEY>;
chomp $google_key;

close GOOGLE_KEY;

# ------------------------------------------------------------
# Get the command-line argument
if ($#ARGV != 0)
{
    print "$0: Invoke with a single argument, your Google search term.\n";
    exit;
}

my $query_string = shift @ARGV;

# ------------------------------------------------------------
# Get the WSDL file
my $google_wsdl = "http://api.google.com/GoogleSearch.wsdl";
my $query = SOAP::Lite->service($google_wsdl);

# ------------------------------------------------------------
# Use the WSDL to make the query
my $starting_page = 1;
my $max_results = 10;
my $filter = 'false';
my $geographic_restriction = '';
my $safe_search = 'false';
my $language_restriction = '';

my $results =
    $query->doGoogleSearch($google_key,
               $query_string,
               $starting_page,
               $max_results,
               $filter,
               $geographic_restriction,
               $safe_search,
               $language_restriction, 'utf-8', 'utf-8');

my @results = @{$results->{resultElements}};

if (@results)
{
    # Iterate through each result we got
    my $counter = 1;
    foreach my $result (@results)
    {
    print "Result $counter of ", $#results + 1, ":\n";

    foreach my $key (sort keys %{$result})
    {
        my $value = $result->{$key};

        # Is this a hash value?  If so, display it accordingly
        if (UNIVERSAL::isa($value, 'HASH'))
        {
        print "\t'$key':\n";

        foreach my $subkey (sort keys %{$value})
        {
            print "\t\t'$subkey' => '$value->{$subkey}'\n";
        }
        }

        # Display the value as a simple string

        else
        {
        print "\t'$key' => '$value'\n";
        }
    }

    $counter++;
    }
}
else
{
    print "There were no results for your query of '$query_string'.\n";
}

Most people, including myself, typically want to query the widest possible number of Web pages with our queries; however, there are times when it is more appropriate to retrieve data only from servers in a particular geography or in a certain language. The fact that Google's API makes this possible and straightforward opens the door for many different interesting applications.

Just as we send a query to Google via SOAP-encoded XML, we receive a result in SOAP-encoded XML. But as SOAP::Lite shielded us from having to write even a tiny bit of XML for the query, we similarly will be insulated when it comes to the response. The $results variable provides a Perl interface to the data that we received in response.

And exactly what data will we receive? To know that, we can look at the WSDL file once again. It indicates (among other things) that we will receive responses as a set of results, each of which looks like this:

<xsd:complexType name="ResultElement">
<xsd:all>
    <xsd:element name="summary" type="xsd:string"/>
    <xsd:element name="URL" type="xsd:string"/>
    <xsd:element name="snippet" type="xsd:string"/>
    <xsd:element name="title" type="xsd:string"/>
    <xsd:element name="cachedSize" type="xsd:string"/>
    <xsd:element name="relatedInformationPresent" type="xsd:boolean"/>
    <xsd:element name="hostName" type="xsd:string"/>
    <xsd:element name="directoryCategory" type="typens:DirectoryCategory"/>
    <xsd:element name="directoryTitle" type="xsd:string"/>
</xsd:all>
</xsd:complexType>

In other words, each search result we receive back from Google (up to a maximum of ten) will provide all of the information we need to create a results page that looks just like Google's. Moreover, we can pick and choose the elements we want to display, showing (for example) only the title and the dmoz directory category and title. Or we can show a short snippet from the searched page. Or all of these. Or none of these.

doGoogleSearch is not the only method described in the WSDL file. There also are other methods, such as working with Google's cached pages and checking the spelling of individual words. When Web services were first unveiled to the public, a common example was that a word processor would now be able to call a remote Web service for spell-checking, rather than coming with a built-in system. That day is still far off in the future, but you can imagine using Google's API for an experimental version of such a service.

Moreover, we can use these outputs as inputs into another Web service call, either locally or remotely. Combining data from multiple sites is an increasingly popular thing to do, especially when combined with Google's maps API. It's amazing to see what can happen when you combine services in this way—something that we will explore in the coming months.