mybatis的mapper中的sql涉及嵌套且外部引用导致的问题：XML fragments parsed from previous mappers does not contain value for xxx

假设xxx.xml中有类似下方的sql嵌套：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.xxx">
  <!-- 片段1 -->
  <sql id="sql1">
    some sql
  </sql>

  <!-- 片段2 -->
  <sql id="sql2">
    some sql2
  </sql>

  <!-- 片段3 -->
  <sql id="sql3">
    <include refid="sql1" />
    <include refid="sql2" />
  </sql>
</mapper>

当你在yyy.xml中引入他的时候，可能会报错：

XML fragments parsed from previous mappers does not contain value for xxx

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.yyy">
  <select id="searchList">
    some sql
    <include refid="sql3" />
  </select>
</mapper>

本人测试，把xxx.xml改为如下即可解决问题：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.xxx">
  <!-- 片段1 -->
  <sql id="sql1">
    some sql
  </sql>

  <!-- 片段2 -->
  <sql id="sql2">
    some sql2
  </sql>

  <!-- 片段3 -->
  <sql id="sql3">
    <include refid="com.xxx.sql1" />
    <include refid="com.xxx.sql2" />
  </sql>
</mapper>

也就是在内部嵌套的时候，需要填写完整的引用id。
如果只是内部嵌套，那没问题。如果涉及到外部引用就会报错。