在Mybatis中动态使用HashMap进行参数映射
好的,这是对这个问题的重新发布Inserting HashMap Values to a table using ibatis(但我正在寻找不同的方法-答案对我不起作用)。
DB1GetStudentDataMapper.xml(这查询一个数据库)
<?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.testing.db1.DB1GetStudentDataMapper">
<select id="selectAllStudents" resultType="java.util.Map">
SELECT STUDENT_CD, STUDENT_NM, PARENT_CD, CREATED_DATE
FROM STUDENT
WHERE STD_STATUS='ACT'
</select>
</mapper>
DB2InsertStudentMapper.xml(这查询到不同的数据库)
<?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.testing.db2.DB2InsertStudentMapper">
<insert id="insertStudent" parameterType="java.util.HashMap">
INSERT INTO STUDENT
<!-- dynamically select column names from hashmap -->
(#{stdMap.keySet}) // this is not working - its coming as null
<!-- dynamically select values for the above columns from hashmap -->
VALUES (#{stdMap.values}) // this is not working - its coming as null
</insert>
</mapper>
DB2InsertStudentMapper.java
public interface TMODSBDataRefreshMapper {
void insertStudent(@Param("stdMap") HashMap stdMap);
}
StudentDataProcess.java
public class Student {
// I have defaultExecutorType as BATCH in my mapper config file
private DB1GetStudentDataMapper db1Mapper; // Interface Mapper for first data source
private DB2InsertStudentMapper db2Mapper; // Interface Mapper for second data source
public processStudent() throws Exception {
List<HashMap> rs = db1Mapper.selectAllStudents(); // Gets some 15k+ records
for(int i =0; i < rs.size(); i++) { // so this will loop through 15k+ records
HashMap result = rs.get(i);
System.out.println(result.keySet()); // prints column names from select query [STUDENT_CD, STUDENT_NM, PARENT_CD, CREATED_DATE]
System.out.println(result.values()); // prints above column values of first data set [1001, Mike, 5001, 2021-07-01]
// All I am trying is to insert above 15k records into different database dynamically rather than creating POJO
db2Mapper.insertStudent(result);
}
}
}
注意:仅举个例子,我使用了4列-我有大约150多列要处理..
PS:请记住,此解决方案在使用较少列时效果较好,但如果使用大容量插入则效果不佳,它会影响性能。
解决方案
使用<foreach />
迭代映射时,键和值会分别赋给index
和item
中指定的变量。
因此,您的INSERT语句应该如下所示。
<insert id="insertStudent">
INSERT INTO STUDENT (
<foreach collection="stdMap" index="col" separator=",">
${col}
</foreach>
) VALUES (
<foreach collection="stdMap" item="val" separator=",">
#{val}
</foreach>
)
</insert>
- 必须使用
${}
表示列名,使用#{}
表示值。有关详细信息,请参阅FAQ。 - 若要以相同的顺序迭代映射,应使用
java.util.LinkedHashMap
作为<select />
的结果类型。
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