Convert HTML to Markdown Using Java

Markdown (MD) is a simple markup language that uses a plain-text-formatting syntax. It is commonly used for creating documentation and readme files due to its easy-to-read and easy-to-write format. Its design allows it to be easily converted to many output formats, but initially, it was created to convert only to HTML. Aspose.HTML provides a class library that allows you to convert HTML to Markdown format in Java and other Java programming languages, offering a reverse conversion from HTML to Markdown.

In this article, you find information on how to convert HTML to Markdown using convertHTML() methods of the Converter class, and how to apply MarkdownSaveOptions.

HTML to Markdown by a few lines of Java code

You can convert HTML to Markdown format using Java and other Java programming languages. The static methods of the Converter class are primarily used as the easiest way to convert an HTML code into various formats. The following code snippet shows how to convert HTML to Markdown literally with a few lines of code!

    // Prepare HTML code and save it to a file
    String code = StringExtensions.concat("<h1>Convert HTML to Markdown Using Java</h1>", 
                "<h2>How to Convert HTML to MD in Java</h2>", 
                "<p>The Aspose.HTML for Java library allows you to convert HTML to Markdown.</p>");
    com.aspose.html.internal.ms.System.IO.File.writeAllText("conversion.html", code);

    // Call convertHTML() method
    com.aspose.html.converters.Converter.convertHTML("conversion.html", new MarkdownSaveOptions(), Path.combine(getOutputDir(), "conversion.md"));

Save Options

The MarkdownSaveOptions has a number of properties that give you control over the conversion process. The most important option is MarkdownFeatures. This option allows you to enable/disable the conversion of the particular element.

Method	Description
getDefault()	This method returns a set of options that are compatible with default Markdown documentation.
setFeatures(value)	A flag set that controls which HTML elements are converted to Markdown.
setFormatter(value)	This method gets or sets the Markdown formatting style.
getGit()	This method returns a set of options that are compatible with GitLab Flavored Markdown.
getResourceHandlingOptions()	Gets a ResourceHandlingOptions object which is used for configuration of resources handling.

To learn more about MarkdownSaveOptions, please read the Fine-Tuning Converters article.

In the Markdown Syntax article, you will find information on the main Markdown elements, details, and examples of the Markdown syntax.

Convert HTML to Markdown in Java using MarkdownSaveOptions

setFeatures() method

To convert HTML to Markdown with MarkdownSaveOptions specifying, you should follow a few steps:

1. One popular scenario is to load an HTML file using one of the HTMLDocument() constructors of the HTMLDocument class. But in this example, we create an HTML source from scratch by preparing HTML code and saving it to a file.
2. Create a new MarkdownSaveOptions object. The MarkdownSaveOptions object can be customized to specify different settings for the conversion process.
3. Use the convertHTML(sourcePath, options, outputPath) method of the Converter class to save HTML as a Markdown file.

The following example shows how to process only links and paragraphs, other HTML elements remain as is:

    // Prepare a path for converted file saving 
    String outputPath = Path.combine(getOutputDir(), "save-options-output.md");

    // Prepare HTML code and save it to a file
    String code = StringExtensions.concat("<h1>How to Use MarkdownSaveOptions</h1>", 
                "<h2>setFeatures() method</h2>", 
                "<p>Hello, World!!!</p>", 
                "<a href='aspose.com'>Aspose</a>");
    com.aspose.html.internal.ms.System.IO.File.writeAllText(Path.combine(getOutputDir(), "save-options.html"), code);

    // Create an instance of MarkdownSaveOptions and set up the rule:
    // – only <a> and <p> elements will be converted to Markdown
    MarkdownSaveOptions options = new MarkdownSaveOptions();
    options.setFeatures (MarkdownFeatures.Link | MarkdownFeatures.AutomaticParagraph);

    // Convert HTML to MD
    com.aspose.html.converters.Converter.convertHTML(Path.combine(getOutputDir(), "save-options.html"), options, outputPath);

In the Java code above, the options object is created, and two options are set using the setFeatures() method. The Link feature specifies that HTML <a> elements will be converted to Markdown, while the AutomaticParagraph feature determines that HTML <p> elements will be converted to Markdown. Any other elements in the HTML document will not be converted.

getGit() method

GitHub Flavored Markdown is the GitHub.com version of the Markdown syntax that provides an additional set of helpful features that make it easier to work with content on GitHub.com. It is an extension of the standard Markdown syntax and adds many additional features, including code highlighting, task lists, tables, and more.

To convert HTML to Markdown you can define your own set of rules or use the predefined templates. For instance, you can use the template based on GitLab Flavored Markdown syntax:

    // Prepare a path for converted file saving 
    String savePath = Path.combine(getOutputDir(), "output-git.md");

    // Prepare HTML code and save it to the file
    String code = StringExtensions.concat("<h1>Header 1</h1>", 
                "<h2>Header 2</h2>", 
                "<p>Hello World!!</p>");
    com.aspose.html.internal.ms.System.IO.File.writeAllText(Path.combine(getOutputDir(), "document.html"), code);

    // Convert HTML to Markdown
    com.aspose.html.converters.Converter.convertHTML(Path.combine(getOutputDir(), "document.html"), MarkdownSaveOptions.getGit(), savePath);

In the java example above, the convertHTML(sourcePath, options, outputPath) method performs the conversion. It takes three arguments: sourcePath, options, and outputPath. The second argument is an instance of the MarkdownSaveOptions. We use the getGit() method in MarkdownSaveOptions that returns an options instance with Git enabled. Enabling Git in MarkdownSaveOptions means that the generated Markdown output file will contain a Git-flavored Markdown, a Markdown syntax that includes Git-specific features.

Limitation

Markdown is a lightweight and easy-to-use syntax. Not all HTML elements are possible to convert to Markdown since there is no equivalent in Markdown syntax. The elements such as STYLE, SCRIPT, LINK, EMBED, etc. will be discarded during conversion.

Inline HTML

Markdown allows you to specify the pure HTML code, which will be rendered as is. The feature, which allows this behaviour, is called “Inline HTML”. In order to use it, you should place one of the specific elements, supported by this feature, at the beginning of new line. Or you can mark one of such elements as “Inline HTML”, by adding the attribute markdown with the value inline to this element. Here is small example, which demonstrate, how to use this attribute:

The “Inline HTML” feature in Markdown enables you to include pure HTML code that will be rendered as-is. To use this feature, you need to place one of the specific elements supported by this feature at the beginning of a new line. Alternatively, you can mark an element as “Inline HTML” by adding the attribute markdown with the value inline to that element. Here is a small example that demonstrates how to use this attribute:

    // Prepare a path for converted file saving 
    String savePath = Path.combine(getOutputDir(), "inline-html.md");

    // Prepare HTML code and save it to the file
    String code = "text<div markdown='inline'><code>text</code></div>";
    com.aspose.html.internal.ms.System.IO.File.writeAllText(Path.combine(getOutputDir(), "inline.html"), code);

    // Call convertHTML method to convert HTML to Markdown.
    com.aspose.html.converters.Converter.convertHTML(Path.combine(getOutputDir(), "inline.html"), new MarkdownSaveOptions(), savePath);

    // Output file will contain: text\r\n<div markdown="inline"><code>text</code></div>

As you can see, content of the <div> element is not converted to Markdown and is treated by Markdown Processor as-is. The list of elements, which support this feature, is different for every Markdown processor.

The original Markdown specification supports these tags: BLOCKQUOTE,H1, H2, H3, H4, H5, H6, P, PRE, OL, UL, DL, DIV, INS, DEL, IFRAME, FIELDSET, NOSCRIPT, FORM, MATH.

The GitLab Flavored Markdown extends this list with the next tags: ARTICLE, FOOTER, NAV, ASIDE, HEADER, ADDRESS, HR, DD, FIGURE, FIGCAPTION, ABBR, VIDEO, AUDIO, OUTPUT, CANVAS, SECTION, DETAILS, HGROUP, SUMMARY.

Features nesting

Although Markdown supports a wide range of features, not all of them can be combined. For example, list elements inside table elements will not be converted. The table below shows which features can be nested. Each feature is a member of the MarkdownFeatures enumeration.

Parent feature	Features which can be processed inside
Header	Link, Emphasis, Strong, InlineCode, Image, Strikethrough, Video
Blockquote	Any
List	AutomaticParagraph, Link, Emphasis, Strong, InlineCode, Image, LineBreak, Strikethrough, Video, TaskList, List
Link	Emphasis, Strong, InlineCode, Image, LineBreak, Strikethrough
AutomaticParagraph	Link, Emphasis, Strong, InlineCode, Image, LineBreak, Strikethrough
Strikethrough	Link, Emphasis, Strong, InlineCode, Image, LineBreak
Table	Video, Strikethrough, Image, InlineCode, Emphasis, Strong, Link
Emphasis	Link, InlineCode, Image, LineBreak, Strikethrough, Video
Strong	Link, InlineCode, Image, LineBreak, Strikethrough, Video

You can download the complete examples and data files from GitHub.

Aspose.HTML offers a free online HTML to Markdown Converter that converts HTML to Markdown with high quality, easy and fast. Just upload, convert your files and get results in a few seconds!