Mybatis大家都知道吧，对于数据库来说，它可以说是最流行的框架，那你们知道mybatis该如何返回map结果集吗?跟小编一起来了解了解吧。
例：数据库为MySQL 使用mybatis返回map
首先创建好我们的POJO类：
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;
}
}然后是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();
}测试类:
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定义为:
<?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>
这时候结果为：Map的value为map
当Mapper为这样时：
<?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>
结果：这时候的mapper，它的value就是java对象了。
以上就是今天的全部内容了，如果想要了解更多java架构师相关内容的话，就请持续关注我们的网站吧。
推荐阅读：