建表sql语句：

CREATE TABLE `constant` (
`id`  bigint(20) NOT NULL AUTO_INCREMENT ,
`key`  varchar(128) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL ,
`value`  varchar(128) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL ,
`type`  int(10) NULL DEFAULT NULL ,
PRIMARY KEY (`id`)
)

表结构：

表名称为：constant

POJO：

public class Constant {
    private Long id;
    private String key;
    private String value;
    private Integer type;
    public Long getId() {
        return id;
    }
    public void setId(Long id) {
        this.id = id;
    }
    public String getKey() {
        return key;
    }
    public void setKey(String key) {
        this.key = key == null ? null : key.trim();
    }
    public String getValue() {
        return value;
    }
    public void setValue(String value) {
        this.value = value == null ? null : value.trim();
    }
    public Integer getType() {
        return type;
    }
    public void setType(Integer type) {
        this.type = type;
    }
}

DAO层：

import java.util.Map;
import org.apache.ibatis.annotations.MapKey;
import org.springframework.stereotype.Repository;
import com.jm.model.Constant;

@Repository
public interface ConstantDao {
    
    /**
     * 注释@MapKey表示表中那个字段作为Map的key
     * @return
     */
    @MapKey("id")
    Map<Long,Constant> loadConstant();
}

junitTest:

import java.util.Map;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

import com.jm.dao.ConstantDao;
import com.jm.model.Constant;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = { "classpath:spring.xml", "classpath:spring-mybatis.xml" })
public class MubatisMapTest {
    @Autowired
    private ConstantDao constantDao;

    @Test
    public void mapTest() {
        Map<Long,Constant> constantMap = constantDao.loadConstant();
        System.out.println(constantMap);
    }
}

当Mapper代码为:

<?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.jm.dao.ConstantDao">
    <resultMap id="BaseResultMap" type="com.jm.model.Constant">
        <result column="id" property="id" jdbcType="BIGINT" />
        <result column="key" property="key" jdbcType="VARCHAR" />
        <result column="value" property="value" jdbcType="VARCHAR" />
        <result column="type" property="type" jdbcType="INTEGER" />
    </resultMap>
    
    <select id="loadConstant" resultType="map">
        select constant.id,constant.key,constant.value,constant.type from constant
    </select>
    
</mapper>

执行结果是：

Paste_Image.png

这时查询出来的map的value是map

当Mapper为：

<?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.jm.dao.ConstantDao">
    <resultMap id="BaseResultMap" type="com.jm.model.Constant">
        <result column="id" property="id" jdbcType="BIGINT" />
        <result column="key" property="key" jdbcType="VARCHAR" />
        <result column="value" property="value" jdbcType="VARCHAR" />
        <result column="type" property="type" jdbcType="INTEGER" />
    </resultMap>
    
    
    <select id="loadConstant" resultMap="BaseResultMap">
        select * from constant
    </select>
</mapper>

执行结果为：

Paste_Image.png

这时查询出来的map的value是java对象