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A HTML parser for Clojure.

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Octocat-spinner-32 src Add typehints December 17, 2013
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README.md

clj-tagsoup

This is a HTML parser for Clojure, somewhat akin to Common Lisp's cl-html-parse. It is a wrapper around the TagSoup Java SAX parser, but has a DOM interface. It is buildable by Leiningen.

Usage

The two main functions defined by clj-tagsoup are parse and parse-string. The first one can take anything accepted by clojure.java.io's reader function except for a Reader, while the second can parse HTML from a string.

The resulting HTML tree is a vector, consisting of:

  1. a keyword representing the tag name,
  2. a map of tag attributes (mapping keywords to strings),
  3. children nodes (strings or vectors of the same format).

This is the same format as used by hiccup, thus the output of parse is appropriate to pass to hiccup.

There are also utility accessors (tag, attributes, children).

clj-tagsoup will automatically use the correct encoding to parse the file if one is specified in either the HTTP headers (if the argument to parse is an URL object or a string representing one) or a <meta http-equiv="..."> tag.

clj-tagsoup is meant to parse HTML tag soup, but, in practice, nothing prevents you to use it to parse arbitrary (potentially malformed) XML. The :xml keyword argument causes clj-tagsoup to take into consideration the XML header when detecting the encoding.

There are two other options for parsing XML:

  • parse-xml just invokes clojure.xml/parse with TagSoup, so the output format is compatible with clojure.xml and is not the one described above.
  • lazy-parse-xml (introduced in clj-tagsoup 0.3.0) returns a lazy sequence of Event records defined by clojure.data.xml, similarly to the source-seq function from that library.

Example

(use 'pl.danieljanus.tagsoup)
=> nil

(parse "http://example.com")
=> [:html {}
          [:head {}
                 [:title {} "Example Web Page"]]
          [:body {}
                 [:p {} "You have reached this web page by typing \"example.com\",\n\"example.net\",\n  or \"example.org\" into your web browser."]
                 [:p {} "These domain names are reserved for use in documentation and are not available \n  for registration. See "
                     [:a {:shape "rect", :href "http://www.rfc-editor.org/rfc/rfc2606.txt"} "RFC \n  2606"]
                     ", Section 3."]]]

FAQ

  • Why not just use Enlive?

    Truth be told, I wrote clj-tagsoup prior to discovering Enlive, which is an excellent library. That said, I believe clj-tagsoup has its niche. Here is an à la carte list of differences between the two:

    • Enlive is a full-blown templating library; clj-tagsoup just parses HTML (and XML).
    • Unlike Enlive, clj-tagsoup's parse function goes out of its way to return parsed data in a proper encoding. It will detect the <meta http-equiv="..."> tag in your data and reinterpret the input stream to the indicated encoding as needed.
    • clj-tagsoup boasts a way to lazily parse XML with TagSoup.
  • What's with the dependency on stax-utils?

    It's for lazy-parse-xml. It's needed because that function uses clojure.data.xml, which under the hood uses the StAX API. TagSoup is a SAX parser, so a bridge between the two parsing APIs is needed.

    If you don't use lazy-parse-xml, you can optionally exclude stax-utils from your project.clj, like this:

    :dependencies [[clj-tagsoup "0.3.0" :exclusions [net.java.dev.stax-utils/stax-utils]]]
    

Author

clj-tagsoup was written by Daniel Janus.

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