Catmandu::Importer::getJSON(3pm)

NAME
Catmandu::Importer::getJSON - load JSON-encoded data from a server using a GET HTTP request

SYNOPSIS
The following three examples are equivalent:

    Catmandu::Importer::getJSON->new(
        file => \"http://example.org/alice.json\nhttp://example.org/bob.json"
    )->each(sub { my ($record) = @_; ... );

    Catmandu::Importer::getJSON->new(
        url  => "http://example.org",
        file => \"/alice.json\n/bob.json"
    )->each(sub { my ($record) = @_; ... );

    Catmandu::Importer::getJSON->new(
        url  => "http://example.org/{name}.json",
        file => \"{\"name\":\"alice\"}\n{\"name\":\"bob\"}"
    )->each(sub { my ($record) = @_; ... );

For more convenience the catmandu command line client can be used:

    echo http://example.org/alice.json | catmandu convert getJSON to YAML
    catmandu convert getJSON --from http://example.org/alice.json to YAML
    catmandu convert getJSON --dry 1 --url http://{domain}/robots.txt < domains

DESCRIPTION
This Catmandu::Importer performs a HTTP GET request to load JSON-encoded data from a server. The importer expects a line-separated input. Each line corresponds to a HTTP request that is mapped to a JSON-record on success. The following input formats are accepted:

plain URL
    A line that starts with ""http://"" or ""https://"" is used as plain URL.

URL path
    A line that starts with ""/"" is appended to the configured url parameter.

variables
    A JSON object with variables to be used with an URL template or as HTTP query parameters. For instance the input line "{"name":"Karl Marx"}" with URL "http://api.lobid.org/person" or the input line "{"entity":"person","name":"Karl Marx"}" with URL template "http://api.lobid.org/{entity}{?id}{?name}{?q}" are both expanded to <http://api.lobid.org/person?name=Karl+Marx>.

If the JSON data returned in a HTTP response is a JSON array, its elements are imported as multiple items. If a JSON object is returned, it is imported as one item.

CONFIGURATION

url An URI or an URI templates (URI::Template) as defined by RFC 6570 <http://tools.ietf.org/html/rfc6570> to load JSON from. If no url is configured, plain URLs must be provided as input or option "from" must be used instead.

from
    A plain URL to load JSON without reading any input lines.

timeout / agent / proxy / headers
    Optional HTTP client settings.

client
    Instance of a Furl HTTP client to perform requests with.

dry Don't do any HTTP requests but return URLs that data would be queried from.

file / fh
    Input to read lines from (see Catmandu::Importer). Defaults to STDIN.

fix An optional fix to be applied on every item (see Catmandu::Fix).

wait
    Number of seconds to wait between requests.

cache
    Cache JSON response of URLs to not request the same URL twice. HTTP error codes in the 4xx range (e.g. 404) are also cached but 5xx errors are not.

    The value of this option can be any objects that implements method "get" and "set" (e.g. "CHI"), an existing directory for file caching, a true value to enable global in-memory-caching, or a false value to disable caching (default).

    File caching uses file names based on MD5 of an URL so for instance "http://example.org/" is cached as "4389382917e51695b759543fdfd5f690.json".

warn
    Show error messages on the standard error.

METHODS

  time
Returns the UNIX timestamp right before the last request. This can be used for instance to add timestamps or the measure how fast requests were responded.

  construct_url( [ $base_url, ] $vars_url_or_path )
Returns an URL given a hash reference with variables, a plain URL or an URL path. The optional first argument can be used to override option "url".

    $importer->construct_url( %query_vars )
    $importer->construct_url( $importer->url, %query_vars ) # equivalent

  request($url)
Perform a HTTP GET request of a given URL including logging, caching, request hook etc. Returns a hash/array reference or "undef".

EXTENDING
This importer provides two methods to filter requests and responses, respectively. See Catmandu::Importer::Wikidata for an example.

  request_hook
Gets a whitespace-trimmed input line and is expected to return an unblessed hash reference, an URL, or undef. Errors are catched and treated equal to undef.

  response_hook
Gets the queried response object and is expected to return an object.

LOGGING
URLs are emitted before each request on DEBUG log level.

LIMITATIONS
Future versions of this module may also support asynchronous HTTP fetching modules such as HTTP::Async, for retrieving multiple URLs at the same time.

SEE ALSO
Catmandu::Fix::get_json provides this importer as fix function.

COPYRIGHT AND LICENSE
Copyright Jakob Voß, 2014-

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.