记录一次：Ambiguous collection type for property ‘ adds‘. You must specify ‘javaType‘ or ‘resultMap‘.错误；

           最近在学mybatis,在学习高级映射时，自己的xml配置基本和老师的一样，但就是因为collection property=" adds"这句多了一个空格就报了这个错，找半天。真无语

<!-- 以下是一对多的完整代码-->
   <resultMap type="com.bxit.entity.User" id="userMap">
    <id column="num" property="num"/>
     <result column="name" property="name"/> 
     <result column="age" property="age"/>
           <!-- 映射一对多的关系：ofType属性必须要指定 -->
         <collection property=" adds" ofType="com.bxit.entity.Address" >
             <!-- 映射主键 -->
                <id column="a_num" property="aid"/>
                <!-- 映射普通属性 -->
                <result column="a_city" property="city"/>
                <result column="a_street" property="street"/>

 <!-- 一对多 -->
    
   <select id="getUserAddress" resultMap="userMap" >
    select s.*,u.* from t10 s left join t11 u on u.a_umun=s.num 
    where s.name=#{name}
   </select>  

    

<!-- 一对多 -->
   <resultMap type="com.bxit.entity.User" id="userMap">
    <id column="num" property="num"/>
     <result column="name" property="name"/> 
     <result column="age" property="age"/>
           <!-- 映射一对多的关系：ofType属性必须要指定 -->
         
错误出现位置：<collection property=" adds" ofType="com.bxit.entity.Address" >
             <!-- 映射主键 -->
		        <id column="a_num" property="aid"/>
		        <!-- 映射普通属性 -->
		        <result column="a_city" property="city"/>
		        <result column="a_street" property="street"/>



后台报错结果：​
Caused by: org.apache.ibatis.builder.BuilderException: Error parsing Mapper XML. The XML location is 'com/bxit/mapper/UserMapper.xml'. Cause: org.apache.ibatis.builder.BuilderException: Ambiguous collection type for property ' adds'. You must specify 'javaType' or 'resultMap'.
	at org.apache.ibatis.builder.xml.XMLMapperBuilder.configurationElement(XMLMapperBuilder.java:123)
	at org.apache.ibatis.builder.xml.XMLMapperBuilder.parse(XMLMapperBuilder.java:95)
	at org.apache.ibatis.builder.xml.XMLConfigBuilder.mapperElement(XMLConfigBuilder.java:378)
	at org.apache.ibatis.builder.xml.XMLConfigBuilder.parseConfiguration(XMLConfigBuilder.java:120)
	... 4 more
Caused by: org.apache.ibatis.builder.BuilderException: Ambiguous collection type for property ' adds'. 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.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)
	... 7 more

​

改正后：

<resultMap type="com.bxit.entity.User" id="userMap">
    <id column="num" property="num"/>
     <result column="name" property="name"/> 
     <result column="age" property="age"/>
           <!-- 映射一对多的关系：ofType属性必须要指定 -->
         <collection property="adds" ofType="com.bxit.entity.Address" >
             <!-- 映射主键 -->
		        <id column="a_num" property="aid"/>
		        <!-- 映射普通属性 -->
		        <result column="a_city" property="city"/>
		        <result column="a_street" property="street"/>
           </collection>
     </resultMap>  
   

后台：
User [num=1, name=小明, age=15, adds=[Address [aid=1, city=上海, street=龙, user=null], Address [aid=2, city=上海, street=龙田, user=null]]]
Address [aid=1, city=上海, street=龙, user=null]
Address [aid=2, city=上海, street=龙田, user=null]

而且配置文档对于标签的顺序也有要求，一不小心就会报错，得万分小心！