一、前言
Markdown是一种用来书写结构化文档的纯文本格式，吸收了很多在电子邮件中已有的纯文本标记的特性。CommonMark主要让Markdown语法更明确。同时CommonMark还提供了一个测试工具spec_tests.py或者SpecTestCase.java对Markdown程序进行测试。
二、引入依赖
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| <!-- https://mvnrepository.com/artifact/com.atlassian.commonmark/commonmark -->
<dependency>
<groupId>com.atlassian.commonmark</groupId>
<artifactId>commonmark</artifactId>
<version>0.15.2</version>
</dependency>
<!-- https://mvnrepository.com/artifact/com.atlassian.commonmark/commonmark-ext-gfm-tables -->
<dependency>
<groupId>com.atlassian.commonmark</groupId>
<artifactId>commonmark-ext-gfm-tables</artifactId>
<version>0.15.2</version>
</dependency>
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注意：如果需要其他相关插件，可以引入对应的依赖。
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| <!-- https://mvnrepository.com/artifact/com.atlassian.commonmark/commonmark-ext-heading-anchor -->
<dependency>
<groupId>com.atlassian.commonmark</groupId>
<artifactId>commonmark-ext-heading-anchor</artifactId>
<version>0.15.2</version>
</dependency>
<!-- https://mvnrepository.com/artifact/com.atlassian.commonmark/commonmark-ext-gfm-strikethrough -->
<dependency>
<groupId>com.atlassian.commonmark</groupId>
<artifactId>commonmark-ext-gfm-strikethrough</artifactId>
<version>0.15.2</version>
</dependency>
<dependency>
<groupId>com.atlassian.commonmark</groupId>
<artifactId>commonmark-ext-autolink</artifactId>
<version>0.15.2</version>
</dependency>
<!-- https://mvnrepository.com/artifact/com.atlassian.commonmark/commonmark-ext-yaml-front-matter -->
<dependency>
<groupId>com.atlassian.commonmark</groupId>
<artifactId>commonmark-ext-yaml-front-matter</artifactId>
<version>0.15.2</version>
</dependency>
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三、使用
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| public abstract class MarkdownUtil {
public static List<Extension> extensions = Arrays.asList(TablesExtension.create());
private static final Parser parser = Parser.builder().extensions(extensions).build();
/**
* 对已经有的标签进行改造
*
* @param markdown
* @return
*/
private static final HtmlRenderer renderer = HtmlRenderer.builder().extensions(extensions)
.nodeRendererFactory(context -> new NodeRenderer() {
@Override
public Set<Class<? extends Node>> getNodeTypes() {
return Collections.singleton(FencedCodeBlock.class);
}
@Override
public void render(Node node) {
HtmlWriter html = context.getWriter();
FencedCodeBlock codeBlock = (FencedCodeBlock) node;
Map<String, String> attrs = new HashMap<>();
if (!StringUtils.isEmpty(codeBlock.getInfo())) {
attrs.put("class", "language-" + codeBlock.getInfo());
}
html.line();
html.tag("pre");
html.tag("code", attrs);
html.tag("ol");
String data = codeBlock.getLiteral();
String[] split = data.split("\n");
for (String s : split) {
html.tag("li");
html.text(s + "\n");
html.tag("/li");
}
html.tag("/ol");
html.tag("/code");
html.tag("/pre");
html.line();
}
})
.nodeRendererFactory(context -> new NodeRenderer() {
@Override
public Set<Class<? extends Node>> getNodeTypes() {
// TODO Auto-generated method stub
return Collections.singleton(BlockQuote.class);
}
@Override
public void render(Node node) {
// TODO Auto-generated method stub
HtmlWriter html = context.getWriter();
BlockQuote blockQuote = (BlockQuote) node;
Text text = (Text)blockQuote.getFirstChild().getFirstChild();
Map<String, String> attrs = new HashMap<>();
attrs.put("class", "language-json hljs");
Map<String, String> attrs1 = new HashMap<>();
attrs1.put("type", "a");
html.line();
html.tag("pre");
html.tag("code", attrs);
html.tag("ol",attrs1);
getText(html,text);
html.tag("/ol");
html.tag("/code");
html.tag("/pre");
html.line();
}
})
.nodeRendererFactory(context -> new NodeRenderer() {
@Override
public Set<Class<? extends Node>> getNodeTypes() {
return Collections.singleton(Image.class);
}
@Override
public void render(Node node) {
HtmlWriter html = context.getWriter();
Image image = (Image) node;
Map<String, String> attrs = new HashMap<>();
Map<String, String> attrs2 = new HashMap<>();
attrs.put("href", image.getDestination());
attrs2.put("src", image.getDestination());
html.line();
html.tag("a", attrs);
html.tag("image", attrs2);
html.tag("/a");
html.line();
}
})
.attributeProviderFactory(context -> (node, s, map) -> {
if ("p".equals(s) && node.getParent() instanceof ListItem) {
map.put("class", "show-line");
}
})
.softbreak("<br/>") // 这样设置就可以实现回车一次就换行
.build();
/**
** 增加扩展[标题锚点，表格生成] Markdown转换成HTML
*
* @param markdown
* @return
*/
public static String markdownToHtmlExtensions(String markdown) {
// h标题生成id
Set<Extension> headingAnchorExtensions = Collections.singleton(HeadingAnchorExtension.create());
// 转换table的HTML
List<Extension> tableExtension = Arrays.asList(TablesExtension.create());
Parser parser = Parser.builder().extensions(tableExtension).build();
Node document = parser.parse(markdown);
HtmlRenderer renderer = HtmlRenderer.builder().extensions(headingAnchorExtensions).extensions(tableExtension)
.attributeProviderFactory(new AttributeProviderFactory() {
public AttributeProvider create(AttributeProviderContext context) {
return new CustomAttributeProvider();
}
}).build();
return renderer.render(document);
}
/**
* 处理标签的属性
*/
static class CustomAttributeProvider implements AttributeProvider {
@Override
public void setAttributes(Node node, String tagName, Map<String, String> attributes) {
// 改变a标签的target属性为_blank
if (node instanceof Link) {
attributes.put("target", "_blank");
}
if (node instanceof TableBlock) {
attributes.put("class", "ui celled table");
}
if (node instanceof Image) {
attributes.put("style", "width:150px;height:200px;position:relative;left:50%;margin-left:-100px;");
}
}
}
/*
* 通过迭代方式获取某一个节点下所有内容
*/
public static void getText(HtmlWriter html,Text text){
html.tag("li");
html.text(text.getLiteral() + "\n");
html.tag("/li");
if(text.getNext()==null) return;
getText(html,(Text)text.getNext().getNext());
}
/**
* markdown 转 html
*
* @param markdown
* @return
*/
public static String md2html(String markdown) {
Node document = parser.parse(markdown);
String result = renderer.render(document);
return result;
}
}
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使用：调用其方法就可以了
