org.apache.ibatis.exceptions.PersistenceException: ### Error building SqlSession. ### Cause: org.ap

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问题描述：

org.apache.ibatis.exceptions.PersistenceException: 
### Error building SqlSession.
### Cause: org.apache.ibatis.builder.BuilderException: Error creating document instance.  Cause: org.xml.sax.SAXParseException; lineNumber: 3; columnNumber: 16; 文档根元素 "configuration" 必须匹配 DOCTYPE 根 "null"。

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解决方案：

这个问题在文件头加上

<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">