java 在 myBatis <association> 中传递多列
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Passing multiple columns in myBatis <assoctiation>
提问by linuxeasy
I want to know, how do we pass multiple columns in a myBatis association tag.
我想知道，我们如何在一个 myBatis 关联标签中传递多个列。
For example, I have the following xml snippet in one my mapper.xml file:
例如，我的 mapper.xml 文件中有以下 xml 片段：
<resultMap type="com.mysite.domain.CourseBuilderCourses" id="ResultMapWithAssmnts" extends="BaseResultMap">
<association property="totalAssignmentCnt" column="course_id" select="selectTotalAssgnmentsCnt"/>
<association property="totalAssessmentCnt" column="course_id" select="selectTotalAssesmentsCnt"/>
<!-- see this association >> --> <association property="subscription" column="course_id" select="com.mysite.persistence.mybatis.CourseSubscriptionMapper.selectByUsercId"/>
</resultMap>
As you can see, the <association>with propertysubscription has only one column, course_id
如您所见，<association>with propertysubscription 只有一列，course_id
I want to pass 2 columns to it, and therefore the resultant code, how do we do that?
我想将 2 列传递给它，因此生成的代码，我们该怎么做？
I tried the following combinations, none worked:
我尝试了以下组合，均无效：
column="{course_id,user_id}" // null,null are passed as parameters
column="course_id,user_id" // null,null are passed as parameters
column="{COURSE_ID=course_id,USER_ID=user_id}" // null,null are passed as parameters
but if I pass single, column="{course_id}" or column="course_id"
但如果我通过单， column="{course_id}" 或 column="course_id"
works without any issues.
工作没有任何问题。
Any idea guys?
有什么想法吗？
回答by Jarandinor
You should use the following syntax for composite keys:
您应该对复合键使用以下语法：
column="{prop1=col1,prop2=col2}".
Where prop1, prop2are parameters of the associated query and col1, col2are sql columns passed to that query.
prop1, prop2关联查询的参数在哪里以及col1, col2传递给该查询的 sql 列在哪里。
In your case:
在你的情况下：
CourseMapper.xml:
CourseMapper.xml:
column="{courseId=id,userId=user_id}"
...
select id, user_id, ... from course ...
CourseSubscriptionMapper.xml:
CourseSubscriptionMapper.xml：
<select id="selectByUsercId" ...>
select ... where course_id=#{courseId} and user_id=#{userId}
</select>
I just checked it worked fine for me. If you have any questions, please feel free to ask.
我只是检查它对我来说工作正常。如果您有任何问题，请随时提问。
回答by hemantvsn
Multiple column names can be passed as key value pairs
多个列名可以作为键值对传递
@Results(value = { @Result(property = "CourseSubscription", column = "{courseId=id,userId=user_id}
For more info, you can refer the
有关更多信息，您可以参考
org.apache.ibatis.builder.MapperBuilderAssistant.parseCompositeColumnName(String).columnName -- API which parses the meta-data of @Result.column()
org.apache.ibatis.builder.MapperBuilderAssistant.parseCompositeColumnName(String).columnName -- 解析@Result.column()元数据的API
private List<ResultMapping> parseCompositeColumnName(String columnName) {
List<ResultMapping> composites = new ArrayList<ResultMapping>();
if (columnName != null && (columnName.indexOf('=') > -1 || columnName.indexOf(',') > -1)) {
StringTokenizer parser = new StringTokenizer(columnName, "{}=, ", false);
while (parser.hasMoreTokens()) {
String property = parser.nextToken();
String column = parser.nextToken();
ResultMapping.Builder complexBuilder = new ResultMapping.Builder(configuration, property, column, configuration.getTypeHandlerRegistry().getUnknownTypeHandler());
composites.add(complexBuilder.build());
}
}
return composites;
}
