manwar / catmandu-importer-getjson

Load JSON data via HTTP GET with Catmandu

NAME

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

STATUS

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 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.