解析邮件文本内容； Mime文本解析； MimeStreamParser； multipart解析

原始文本

------=_Part_46705_715015081.1699589700255
Content-Type: text/html;charset=UTF-8
Content-Transfer-Encoding: base64PGh0bWw+CiAgICA8aGVhZD4KICAgICAgICA8bWV0YSBodHRwLW
VxdWl2PSJDb250ZW50LVR5cGUiIGNvbnRlbnQ9InRleHQvaHRt
bDsgY2hhcnNldD1VVEYtOCI+CiAgICAgICAgPHRpdGxlPkpTUC
BQYWdlPC90aXRsZT4KICAgIDwvaGVhZD4KICAgIDxib2R5Pgog
ICAgICAgIDxoMT5IZWxsbyBXb3JsZCE8L2gxPgogICAgPC9ib2
R5Pgo8L2h0bWw+
------=_Part_46705_715015081.1699589700255--

Maven

 <dependency><groupId>org.apache.james</groupId><artifactId>apache-mime4j-core</artifactId><version>0.8.9</version></dependency>

解析方法

String data = "------=_Part_46705_715015081.1699589700255\n" +"Content-Type: text/html;charset=UTF-8\n" +"Content-Transfer-Encoding: base64\n" +"\n" +"PGh0bWw+CiAgICA8aGVhZD4KICAgICAgICA8bWV0YSBodHRwLW\n" +"VxdWl2PSJDb250ZW50LVR5cGUiIGNvbnRlbnQ9InRleHQvaHRt\n" +"bDsgY2hhcnNldD1VVEYtOCI+CiAgICAgICAgPHRpdGxlPkpTUC\n" +"BQYWdlPC90aXRsZT4KICAgIDwvaGVhZD4KICAgIDxib2R5Pgog\n" +"ICAgICAgIDxoMT5IZWxsbyBXb3JsZCE8L2gxPgogICAgPC9ib2\n" +"R5Pgo8L2h0bWw+\n" +"------=_Part_46705_715015081.1699589700255--";
System.out.println(data);
HtmContentHandler contentHandler = new HtmContentHandler();
MimeConfig mime4jParserConfig = MimeConfig.DEFAULT;
BodyDescriptorBuilder bodyDescriptorBuilder = new DefaultBodyDescriptorBuilder();
MimeStreamParser mime4jParser = new MimeStreamParser(mime4jParserConfig, DecodeMonitor.SILENT, bodyDescriptorBuilder);
mime4jParser.setContentDecoding(true);
mime4jParser.setContentHandler(contentHandler);
mime4jParser.parse(new ByteArrayInputStream(data.getBytes(UTF_8)));
System.out.println(contentHandler.getData());

HtmContentHandler

import org.apache.commons.io.IOUtils;
import org.apache.james.mime4j.MimeException;
import org.apache.james.mime4j.dom.Header;
import org.apache.james.mime4j.field.ContentTypeFieldImpl;
import org.apache.james.mime4j.message.SimpleContentHandler;
import org.apache.james.mime4j.stream.BodyDescriptor;
import org.apache.james.mime4j.stream.Field;import java.io.IOException;
import java.io.InputStream;
import java.util.Optional;/*** @author zengrenyuan* @date 2023/11/10**/
public class HtmContentHandler extends SimpleContentHandler {private String data;private String charset;private String contentType;@Overridepublic void body(BodyDescriptor bd, InputStream is) throws MimeException, IOException {this.data = IOUtils.toString(is, Optional.ofNullable(charset).orElse("UTF-8"));//这里可以处理文本内容}@Overridepublic void headers(Header header) {//在这里解析头信息Field contentType = header.getField("Content-Type");if (contentType != null) {if (contentType instanceof ContentTypeFieldImpl) {this.contentType = ((ContentTypeFieldImpl) contentType).getMimeType();charset = ((ContentTypeFieldImpl) contentType).getParameter("charset");}}}public String getData() {return data;}public String getCharset() {return charset;}public String getContentType() {return contentType;}
}

参考资料

https://james.apache.org/mime4j/index.html
https://github.com/apache/james-mime4j

如果想解析一段Email数据也可以参考
https://github.com/ram-sharma-6453/email-mime-parser