Parsing YAML Front matter in Java

Question

I have to parse YAML Front Matter in java like jekyll, So Iooked into the source code, and found this but I can't make much sense of it(I don't know much ruby).

So My Question is, How do I parse YAML Front Matter in java ?

I have snakeyaml in my classpath and I would be parsing YAML Front Matter from a markdown file, for which I use pegdown

Answer 1

void parse(Reader r) throws IOException {
    BufferedReader br = new BufferedReader(r);

    // detect YAML front matter
    String line = br.readLine();
    while (line.isEmpty()) line = br.readLine();
    if (!line.matches("[-]{3,}")) { // use at least three dashes
        throw new IllegalArgumentException("No YAML Front Matter");
    }
    final String delimiter = line;

    // scan YAML front matter
    StringBuilder sb = new StringBuilder();
    line = br.readLine();
    while (!line.equals(delimiter)) {
        sb.append(line);
        sb.append("\n");
        line = br.readLine();
    }

    // parse data
    parseYamlFrontMatter(sb.toString());
    parseMarkdownOrWhatever(br);
}

To get a obtain Reader, you will probably need a FileReader or an InputStreamReader.

Answer 2

Ok, since your comment clarified what your question is:

The yaml front matter is everything that is inside the lines with three dashes (---). YAML Front matter is ALWAYS at the beginning od the file.

So you just have to parse the file and extract the YAML Front Matter from the start of the file. you can either parse it with an automaton or an RegEx. It's really up to you. It is always structured the same way:

---
some YAML here
---
Markdown / textile / HTML contents of file