Ambiguous collection type for property 'categories'. You must specify 'javaType'

1.具体报错信息：

Caused by: org.apache.ibatis.builder.BuilderException: Ambiguous collection type for property 'categories'. You must specify 'javaType' or 'resultMap'.
    at org.apache.ibatis.builder.xml.XMLMapperBuilder.validateCollection(XMLMapperBuilder.java:412)
    at org.apache.ibatis.builder.xml.XMLMapperBuilder.processNestedResultMappings(XMLMapperBuilder.java:399)
    at org.apache.ibatis.builder.xml.XMLMapperBuilder.lambda$buildResultMappingFromContext$0(XMLMapperBuilder.java:383)
    at org.apache.ibatis.parsing.XNode.getStringAttribute(XNode.java:200)
    at org.apache.ibatis.builder.xml.XMLMapperBuilder.buildResultMappingFromContext(XMLMapperBuilder.java:382)
    at org.apache.ibatis.builder.xml.XMLMapperBuilder.resultMapElement(XMLMapperBuilder.java:280)
    at org.apache.ibatis.builder.xml.XMLMapperBuilder.processNestedResultMappings(XMLMapperBuilder.java:400)
    at org.apache.ibatis.builder.xml.XMLMapperBuilder.lambda$buildResultMappingFromContext$0(XMLMapperBuilder.java:383)
    at org.apache.ibatis.parsing.XNode.getStringAttribute(XNode.java:200)
    at org.apache.ibatis.builder.xml.XMLMapperBuilder.buildResultMappingFromContext(XMLMapperBuilder.java:382)
    at org.apache.ibatis.builder.xml.XMLMapperBuilder.resultMapElement(XMLMapperBuilder.java:280)
    at org.apache.ibatis.builder.xml.XMLMapperBuilder.resultMapElement(XMLMapperBuilder.java:254)
    at org.apache.ibatis.builder.xml.XMLMapperBuilder.resultMapElements(XMLMapperBuilder.java:246)
    at org.apache.ibatis.builder.xml.XMLMapperBuilder.configurationElement(XMLMapperBuilder.java:119)
    ... 95 more

2.原因

MyBatis升级之后，语法要求有所变化，原来是可以不写 javaType属性的。

3.解决方法：

在collection中添加javaType属性，属性值为collection的内部数据类型。

<collection property="categories" ofType="com.qfedu.fmmall.entity.CategoryVO" javaType="list">

4.参考资料：

https://blog.csdn.net/qq_29384789/article/details/124963014