LagartoParser

Fast event-based HTML parser

LagartoParser is an event-based HTML parser. It processes the input and emits events as they are parsed; using a visitor pattern. This makes parsing very fast and memory-usage is minimal. However, sometimes event-based parsing can be tedious; in that case, try LagartoDom parser instead.

Let's see it in action:

LagartoParser lagartoParser = new LagartoParser("<html><h1>Hello</h1></html>");

TagVisitor tagVisitor = new EmptyTagVisitor() {
    @Override
    public void tag(final Tag tag) {
        if (tag.nameEquals("h1")) {
            System.out.println(tag.getName());
        }
    }
	
    @Override
    public void text(final CharSequence text) {
        System.out.println(text);
    }
};

lagartoParser.parse(tagVisitor);

As the input content is parsed, the callback methods in the visitor get invoked. In this case, the result is:

h1
Hello
h1

Note that the tag() event was emitted twice: first for the open tag, and then for the close tag. In other words, LagartoParser performs the tokenization of the input HTML.

Parsing specification

HTML parsing (i.e. tokenization) is done strictly by the official HTML5 specification. Note the following:

the text is emitted as a single block of text and not one by one character.
the case of a tag name (and other tokens) is not changed when emitted.
LagartoParser does only tokenization. The DOM tree is not created, neither validated.
the script tag is emitted separately.
Internet Explorer conditional comments are supported.
XML is supported too.

LagartoParser only performs tokenization and it does not verify if tags make sense. For example, if your HTML has a non-closed tag, LagartoParser will not consider this as an error. LagartoDom, on the other hand, will handle these cases.

Input types

LagartoParser accepts both char[] and CharSequence. This allows the usage of various implementations of inputs, including String, or even a Reader.

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Last updated 3 years ago

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