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.

