Create result to Map or Grouping in Mybatis

README.md

Create result to Map or Grouping in Mybatis

BO.java

@Slf4j
@Service
public class TestBO {
	@Autowired
	private Mapper mapper;
  
	public static void main(String[] args) {
    final List<Integer> ids = new ArrayList<>();
    // init ids...

		final Map<Integer, String> map1 = MappingHelper.toMap(mapper.get1(ids));
		final Map<Long, List<Long>> map2 = MappingHelper.toMapWithListGroupedByKey(mapper.get2(ids));
		final Map<Long, Set<Long>> map3 = MappingHelper.toMapWithSetGroupedByKey(mapper.get3(ids));
	}
}

Mapper.java

@Repository
public interface Mapper {
  List<MappingHelper<Integer, String>> get1(@Param("ids") List<Integer> ids);
	List<MappingHelper<Integer, String>> get2(@Param("ids") List<Integer> ids);
	List<MappingHelper<Integer, String>> get3(@Param("ids") List<Integer> ids);
}

Mapper.xml

<?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">
<!-- @formatter:off -->

<mapper namespace="me.wickso.dao.DomainMapper">
	<resultMap id="nameMap" type="me.wickso.model.MappingHelper">
		<id     property="key"   column="dmn_id"/>
		<result property="value" column="entp_nm"/>
	</resultMap>

	<resultMap id="domainTypeMap" type="me.wickso.model.MappingHelper">
		<id     property="key"   column="dmn_id"/>
		<result property="value" column="dmn_tp_cd" javaType="me.wickso.model.mapping.DomainType"/>
	</resultMap>
  
  	<resultMap id="contactInfoMappingHelper" type="me.wickso.model.MappingHelper">
		<association property="key" javaType="me.wickso.model.key.ObjectKey">
			<constructor>
				<arg column="no"   javaType="_int"/>
				<arg column="uuid" javaType="_int"/>
				<arg column="id"   javaType="java.lang.Long"/>
			</constructor>
			<result property="num"  column="no"/>
			<result property="uuid" column="uuid"/>
			<result property="id"   column="id"/>
		</association>
		<association property="value" javaType="me.wickso.model.ContactInfo">
			<result property="num"    column="no"/>
			<result property="uuid"   column="uuid"/>
			<result property="id"     column="id"/>
			<result property="search" column="sch_attr"/>
			<result property="attr1"  column="attr1"/>
			<result property="attr2"  column="attr2"/>
			<result property="attr3"  column="attr3"/>
			<result property="attr4"  column="attr4"/>
			<result property="attr5"  column="attr5"/>
			<result property="attr6"  column="attr6"/>
			<result property="attr7"  column="attr7"/>
			<result property="attr8"  column="attr8"/>
			<result property="attr9"  column="attr9"/>
			<result property="attr10" column="attr10"/>
		</association>
	</resultMap>

	<select id="get1" resultMap="nameMap">
    ...
	</select>
</mapper>

MappingHelper.java

import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.stream.Collectors;

import lombok.Getter;
import lombok.Setter;
import lombok.extern.slf4j.Slf4j;

/**
 * Helper converting list to map.
 * @param <K> key
 * @param <V> value
 */
@Slf4j
@Getter
@Setter
public class MappingHelper<K, V> {
	private K key;
	private V value;

	/**
	 * Return map from {@link MappingHelper} list.
	 * @param list DTO list
	 * @param <K> key
	 * @param <V> value
	 * @return map
	 */
	public static <K, V> Map<K, V> toMap(List<MappingHelper<K, V>> list) {
		if (list == null) {
			return Collections.emptyMap();
		}
		return list.parallelStream().unordered().collect(Collectors.toMap(MappingHelper::getKey, MappingHelper::getValue));
	}

	/**
	 * Return {@link Map} with {@link List} element grouped by key.
	 */
	public static <K, V> Map<K, List<V>> toMapWithListGroupedByKey(List<MappingHelper<K, V>> list) {
		if (list == null) {
			return Collections.emptyMap();
		}
		return list.parallelStream()
			.unordered()
			.collect(Collectors.groupingBy(MappingHelper::getKey, Collectors.mapping(MappingHelper::getValue, Collectors.toList())));
	}

	/**
	 * Return {@link Map} with {@link Set} element grouped by key.
	 */
	public static <K, V> Map<K, Set<V>> toMapWithSetGroupedByKey(List<MappingHelper<K, V>> list) {
		if (list == null) {
			return Collections.emptyMap();
		}
		return list.parallelStream()
			.unordered()
			.collect(Collectors.groupingBy(MappingHelper::getKey, Collectors.mapping(MappingHelper::getValue, Collectors.toSet())));
	}

}

wip