MyBatis多表操作查询功能

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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