MyBatis多表操作查询功能
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2022-07-03 22:20:04
一对一查询用户表和订单表的关系为,一个用户多个订单,一个订单只从属一个用户一对一查询的需求:查询一个订单,与此同时查询出该订单所属的用户在只查询order表的时候,也要查询user表,所以需要将所有数...
一对一查询
用户表和订单表的关系为,一个用户多个订单,一个订单只从属一个用户
一对一查询的需求:查询一个订单,与此同时查询出该订单所属的用户
在只查询order表的时候,也要查询user表,所以需要将所有数据全部查出进行封装select *,o.id oid from orders o,user u where o.uid=u.id
创建order和user实体
order
public class order { private int id; private date ordertime; private double total; //表示当前订单属于哪一个用户 private user user;
user
public class user { private int id; private string username; private string password; private date birthday;
创建ordermapper接口
public interface usermapper { //查询全部的方法 public list<order> findall(); }
配置ordermapper.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"> <mapper namespace="com.zg.mapper.ordermapper" > <resultmap id="ordermap" type="order"> <!--手动指定字段与实体的映射关系--> <!--comlumn:数据表的字段名称 property:实体的属性名称--> <id column="oid" property="id"></id> <result column="ordertime" property="ordertime"></result> <result column="total" property="total"></result> <result column="uid" property="user.id"></result> <result column="username" property="user.username"></result> <result column="password" property="user.password"></result> <result column="birthday" property="user.birthday"></result> </resultmap> <!--这里不能使用resulttype=“order”,因为order中没有user中的字段,只有一个user对象--> <select id="findall" resultmap="ordermap"> select *,o.id oid from orders o,user u where o.uid=u.id </select> </mapper>
sqlmapconfig.xml
<?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"> <!--主要配置mybatis的核心配置--> <configuration> <!--通过properties标签加载外部properties文件--> <properties resource="jdbc.properties"></properties> <!--自定义别名--> <typealiases> <typealias type="com.zg.domain.user" alias="user"></typealias> <typealias type="com.zg.domain.order" alias="order"></typealias> </typealiases> <!--配置当前数据源的环境--> <environments default="developement"> <environment id="developement"> <transactionmanager type="jdbc"></transactionmanager> <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--> <mappers> <mapper resource="com.zg.mapper/usermapper.xml"></mapper> <mapper resource="com.zg.mapper/ordermapper.xml"></mapper> </mappers> </configuration>
在一对一配置的时候,在order实体中创建了一个user,所以property属性都使用user.**
的方式进行编写,但是这里还可以使用association
<?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.zg.mapper.ordermapper" > <resultmap id="ordermap" type="order"> <!--手动指定字段与实体的映射关系--> <!--comlumn:数据表的字段名称 property:实体的属性名称--> <id column="oid" property="id"></id> <result column="ordertime" property="ordertime"></result> <result column="total" property="total"></result> <!--<result column="uid" property="user.id"></result> <result column="username" property="user.username"></result> <result column="password" property="user.password"></result> <result column="birthday" property="user.birthday"></result>--> <!--以上被封装到user内的还可以使用association进行配置--> <!--association匹配的意思,在order中有个属性叫user--> <!-- property="user"当前order实体中的属性名称,javatype="user"当前实体order中的属性类型user--> <association property="user" javatype="user"> <id column="uid" property="id"></id> <result column="username" property="username"></result> <result column="password" property="password"></result> <result column="birthday" property="birthday"></result> </association> </resultmap> <!--这里不能使用resulttype=“order”,因为order中没有user中的字段,只有一个user对象--> <select id="findall" resultmap="ordermap"> select *,o.id oid from orders o,user u where o.uid=u.id </select> </mapper>
一对多查询的模型
用户表和订单表的关系为,一个用户有多个订单,一个当但只从属一个用户
一对多查询需求:查询一个用户,与此同时查询出该用户具有的订单
package com.zg.domain; import java.util.date; import java.util.list; public class user { private int id; private string username; private string password; private date birthday; //描述当前用户存在哪些订单 private list<order> orderlist; public list<order> getorderlist() { return orderlist; } public void setorderlist(list<order> orderlist) { this.orderlist = orderlist; } @override public string tostring() { return "user{" + "id=" + id + ", username='" + username + '\'' + ", password='" + password + '\'' + ", birthday=" + birthday + ", orderlist=" + orderlist + '}'; } public int getid() { return id; } public void setid(int id) { this.id = id; } public string getusername() { return username; } public void setusername(string username) { this.username = username; } public string getpassword() { return password; } public void setpassword(string password) { this.password = password; } public date getbirthday() { return birthday; } public void setbirthday(date birthday) { this.birthday = birthday; } }
修改user实体
package com.zg.domain; import java.util.date; import java.util.list; public class user { private int id; private string username; private string password; private date birthday; //描述当前用户存在哪些订单 private list<order> orderlist; public list<order> getorderlist() { return orderlist; } public void setorderlist(list<order> orderlist) { this.orderlist = orderlist; } @override public string tostring() { return "user{" + "id=" + id + ", username='" + username + '\'' + ", password='" + password + '\'' + ", birthday=" + birthday + ", orderlist=" + orderlist + '}'; } public int getid() { return id; } public void setid(int id) { this.id = id; } public string getusername() { return username; } public void setusername(string username) { this.username = username; } public string getpassword() { return password; } public void setpassword(string password) { this.password = password; } public date getbirthday() { return birthday; } public void setbirthday(date birthday) { this.birthday = birthday; } }
创建usermapper接口
package com.zg.mapper; import com.zg.domain.user; import java.util.list; public interface usermapper { public list<user> findall(); }
配置usermapper.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"> <mapper namespace="com.zg.mapper.usermapper" > <resultmap id="usermap" type="user"> <id column="uid" property="id"></id> <result column="username" property="username"></result> <result column="password" property="password"></result> <result column="birthday" property="birthday"></result> <!--配置集合信息--> <!--property:集合名称 oftype:当前集合中的数据类型--> <collection property="orderlist" oftype="order"> <!--封装order的数据--> <id column="oid" property="id"></id> <result column="ordertime" property="ordertime"></result> <result column="total" property="total"></result> </collection> </resultmap> <select id="findall" resultmap="usermap"> select *,o.id oid from user u,orders o where u.id=o.uid </select> </mapper>
测试
@test//测试一对多 public void test2() throws ioexception { inputstream resourceasstream = resources.getresourceasstream("sqlmapconfig.xml"); sqlsessionfactory sqlsessionfactory = new sqlsessionfactorybuilder().build(resourceasstream); sqlsession sqlsession = sqlsessionfactory.opensession(); usermapper mapper = sqlsession.getmapper(usermapper.class); list<user> userlist = mapper.findall(); for (user user : userlist) { system.out.println(user); } sqlsession.close(); }
多对多查询
用户表和角色表的关系为,一个用户有多个角色,一个角色被多个用户使用
多对多查询的需求:查询用户同时查询该用户的所有角色
select * from user u,sys_user_role ur ,sys_role r where u.id=ur.userid and ur.roleid=r.id
创建role实体,修改user实体
添加usermapper接口
package com.zg.mapper; import com.zg.domain.user; import java.util.list; public interface usermapper { public list<user> findall(); public list<user> finduserandroleall(); }
配置usermapper.xml
<resultmap id="userrolemap" type="user"> <!--user信息的封装--> <id column="userid" property="id"></id> <result column="username" property="username"></result> <result column="password" property="password"></result> <result column="birthday" property="birthday"></result> <!--user内部的rolelist信息--> <collection property="rolelist" oftype="role"> <id column="roleid" property="id"></id> <result column="rolename" property="rolename"></result> <result column="roledesc" property="roledesc"></result> </collection> </resultmap> <select id="finduserandroleall" resultmap="userrolemap"> select * from user u,sys_user_role ur ,sys_role r where u.id=ur.userid and ur.roleid=r.id </select>
测试代码
@test//测试多对多 public void test3() throws ioexception { inputstream resourceasstream = resources.getresourceasstream("sqlmapconfig.xml"); sqlsessionfactory sqlsessionfactory = new sqlsessionfactorybuilder().build(resourceasstream); sqlsession sqlsession = sqlsessionfactory.opensession(); usermapper mapper = sqlsession.getmapper(usermapper.class); list<user> userandroleall = mapper.finduserandroleall(); for (user user : userandroleall) { system.out.println(user); } sqlsession.close(); }
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