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 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 constantMap = constantDao.loadConstant();

System.out.println(constantMap);

}

}

当Mapper代码为:

select constant.id,constant.key,constant.value,constant.type from constant

执行结果是：

Paste_Image.png

这时查询出来的map的value是map

当Mapper为：

select * from constant

执行结果为：

Paste_Image.png

这时查询出来的map的value是java对象