<dependency>  
    <groupId>com.vladsch.flexmark</groupId>  
    <artifactId>flexmark-all</artifactId>  
    <version>0.64.8</version>  
</dependency>

Flexmark 可以：

• html <<<--->>> md
• md --->>> PDF
• md --->>> DOCX

md -> html

Document document = Parser.builder().build().parse("md字符串");  
String html = HtmlRenderer.builder().build().render(document);  
System.out.println(html);