Overview

Markdown parsers for Apache Zeppelin. Markdown is a plain text formatting syntax designed so that it can be converted to HTML. Apache Zeppelin uses flexmark, pegdown and markdown4j. Since both pegdown and markdown4j are deprecated but it support for backward compatibility.

Architecture

Current interpreter implementation creates the instance of parser based on the configuration parameter provided, default is flexmark through Markdown and render the text into html.

Technical overview

When interpreter is starting it check which parser has configured in markdown.parser.type, based on this value, it creates the instance of that parser. For each subsequent request, respective parser get the markdown text, parses it and renders into the html.

Flexmark Parser Overview

CommonMark/Markdown Java parser with source level AST.

Flexmark Requirement

• maven dependency to add in pom.xml

<flexmark.all.version>0.50.40</flexmark.all.version>

<dependency>
      <groupId>com.vladsch.flexmark</groupId>
      <artifactId>flexmark-all</artifactId>
      <version>${flexmark.all.version}</version>
</dependency>

Flexmark Technical overview for Custom Extension

To support, YUML and websequnce diagram, need to build the image URL from the respective block and render it into HTML, So it requires to implement some custom classes. UMLExtension is base class which has factory for other classes like UMLBlockQuoteParser and UMLNodeRenderer. UMLBlockQuoteParser which parses the UML block and creates block quote node UMLBlockQuote. UMLNodeRenderer which builds the URL using this block quote node UMLBlockQuote and render it as image into HTML.