CREATE TABLE `country` (`cid` int(4) NOT NULL AUTO_INCREMENT COMMENT '国家id',`cname` varchar(20) COLLATE utf8_unicode_ci NOT NULL,PRIMARY KEY (`cid`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci；CREATE TABLE `provincial` (`pid` int(4) NOT NULL AUTO_INCREMENT,`pname` varchar(20) COLLATE utf8_unicode_ci NOT NULL,`countryid` int(4) NOT NULL,PRIMARY KEY (`pid`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci；

package cn.bdqn.bean;/***国家的实体类*/
public class Country {private Integer cId; // 国家的编号private String cName; // 国家的名称public Integer getcId() {return cId;}public void setcId(Integer cId) {this.cId = cId;}public String getcName() {return cName;}public void setcName(String cName) {this.cName = cName;}public Country(Integer cId, String cName) {super();this.cId = cId;this.cName = cName;}public Country() {super();}@Overridepublic String toString() {return "Country [cId=" + cId + ", cName=" + cName;}}

package cn.bdqn.bean;/*** *省会对应的实体类*/
public class Provincial {private Integer pId; // 省会的编号private String pName; // 省会名称// 关联的国家属性private Country country;public Country getCountry() {return country;}public void setCountry(Country country) {this.country = country;}public Integer getpId() {return pId;}public void setpId(Integer pId) {this.pId = pId;}public String getpName() {return pName;}public void setpName(String pName) {this.pName = pName;}public Provincial(Integer pId, String pName) {super();this.pId = pId;this.pName = pName;}public Provincial() {super();}/*@Overridepublic String toString() {return "Provincial [pId=" + pId + ", pName=" + pName + ", country="+ country + "]";}*/}

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration><!-- 通过properties文件配置连接数据库的四要素 --><properties resource="jdbc.properties" /><settings><!-- 打开延迟加载的开关 -->  <setting name="lazyLoadingEnabled" value="true" />  <!-- 将积极加载改为消息加载即按需加载 -->  <setting name="aggressiveLazyLoading" value="false"/></settings><!-- 设置别名 两种方式 --><typeAliases><!--  01.这种方式别名可以随意取  但是如果有多个 类 就需要配置多个typeAlias <typeAlias type="cn.bdqn.bean.Student" alias="student"/> --><package name="cn.bdqn.bean"/><!-- 02.这种方式要求别名必须使用简写的类名  --></typeAliases><!-- 配置运行环境 可以有多个 environment --><environments default="mysql"><!-- 默认采用的环境 --><environment id="mysql"> <!-- 环境的名称 --><!--配置事务管理 采用jdbc默认的事务管理 之后整合的时候 肯定是交给了 spring来处理了 --><transactionManager type="JDBC" /><!-- 数据源采用的是连接池技术 POOLED:mybatis自带的数据源，JNDI:基于tomcat的数据源 --><dataSource type="POOLED"><property name="driver" value="${jdbc.driver}" /><property name="url" value="${jdbc.url}" /><property name="username" value="${jdbc.username}" /><property name="password" value="${jdbc.password}" /></dataSource></environment></environments><!-- 加载映射文件信息 --><mappers><mapper resource="cn/bdqn/dao/StduentMapper.xml" /><!-- <mapper resource="cn/bdqn/dao/CountryMapper.xml" /> --><mapper resource="cn/bdqn/dao/ProvincialMapper.xml" /></mappers>
</configuration>

package cn.bdqn.dao;import cn.bdqn.bean.Provincial;public interface ProvincialDao {/*** 根据省会的id查询出省会和对应国家的信息  */Provincial selectProvincialById(Integer pId);
}

<?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="cn.bdqn.dao.ProvincialDao"><select id="selectCountryByProvincialId" resultType="country">select cid,cname from country where cid = #{countryid} </select><resultMap type="provincial" id="provincialMap"><id column="pid" property="pId"/><result column="pname" property="pName"/><association property="country" javaType="Country"select="selectCountryByProvincialId" column="countryid" ></association></resultMap><select id="selectProvincialById" resultMap="provincialMap">select pid,pname,countryid from provincialwhere pid = #{pid}</select></mapper>

package cn.bdqn.test;import org.apache.ibatis.session.SqlSession;
import org.apache.log4j.Logger;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;import cn.bdqn.bean.Provincial;
import cn.bdqn.dao.ProvincialDao;
import cn.bdqn.util.MybatisUtil;public class Test1 {private Logger logger = Logger.getLogger(Test1.class);SqlSession session;ProvincialDao dao;@Beforepublic void before() {// 因为需要关闭session 需要把session提取出去session = MybatisUtil.getSqlSession();dao = session.getMapper(ProvincialDao.class);}@Afterpublic void after() {if (session != null) {session.close();}}@Testpublic void test1() {Provincial provincial = dao.selectProvincialById(1);/*logger.debug("provincialId=1======>provincial:" + provincial);*//*logger.debug("provincialId=1======>country:" + provincial.getCountry());*/}
}