MyBatis多表查詢

MyBatis的多表查詢只須要DAO接口和sql語句便可，主要的是mapper裏的返回字段要正確

如今有4張表

SELECT * FROM mybatis.user; select * from mybatis.role; select * from mybatis.account; select * from mybatis.user_role;

user

role

account

user_role

 

 

工程結構

DAO層

import com.jinke.domain.Account; import java.util.List; public interface AccountDao { List<Account> findAll(); }

import com.jinke.domain.Role; import java.util.List; public interface RoleDao { List<Role> findAll(); }

import com.jinke.domain.User; import java.util.List; public interface UserDao { List<User> findAll(); }

 實體類

import java.io.Serializable; public class Account implements Serializable { private Integer id; private Integer uid; private Double money; private User user; public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public Integer getUid() { return uid; } public void setUid(Integer uid) { this.uid = uid; } public Double getMoney() { return money; } public void setMoney(Double money) { this.money = money; } public User getUser() { return user; } public void setUser(User user) { this.user = user; } @Override public String toString() { return "Account{" +
                "id=" + id +
                ", uid=" + uid +
                ", money=" + money +
                '}'; } }

import java.io.Serializable; import java.util.List; public class Role implements Serializable { private Integer id; private String rolename; private String roledesc; private List<User> users; public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public String getRolename() { return rolename; } public void setRolename(String rolename) { this.rolename = rolename; } public String getRoledesc() { return roledesc; } public void setRoledesc(String roledesc) { this.roledesc = roledesc; } public List<User> getUsers() { return users; } public void setUsers(List<User> users) { this.users = users; } @Override public String toString() { return "Role{" +
                "id=" + id +
                ", rolename='" + rolename + '\'' +
                ", roledesc='" + roledesc + '\'' +
                '}'; } }

import java.io.Serializable; import java.util.Date; import java.util.List; public class User implements Serializable { private Integer id; private String username; private String address; private String sex; private Date birthday; private List<Role> roles; public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public String getAddress() { return address; } public void setAddress(String address) { this.address = address; } public String getSex() { return sex; } public void setSex(String sex) { this.sex = sex; } public Date getBirthday() { return birthday; } public void setBirthday(Date birthday) { this.birthday = birthday; } public List<Role> getRoles() { return roles; } public void setRoles(List<Role> roles) { this.roles = roles; } @Override public String toString() { return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", address='" + address + '\'' +
                ", sex='" + sex + '\'' +
                ", birthday=" + birthday +
                '}'; } }

 sql配置文件

AccountDao.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.jinke.dao.AccountDao">

    <resultMap id="accountUserMap" type="account">
        <id property="id" column="aid"/>
        <result property="uid" column="uid"/>
        <result property="money" column="money"/>
        <!--一對一的關係映射，配置封裝user的內容-->
        <association property="user" column="uid" javaType="user">
            <id property="id" column="id"/>
            <result column="username" property="username"/>
            <result column="address" property="address"/>
            <result column="sex" property="sex"/>
            <result column="birthday" property="birthday"/>
        </association>
    </resultMap>

    <select id="findAll" resultMap="accountUserMap"> select * from user a,account b where a.id = b.uid </select>
</mapper>

RoleDao.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.jinke.dao.RoleDao">

    <resultMap id="roleMap" type="role">
        <id property="id" column="rid"/>
        <result property="rolename" column="rolename"/>
        <result property="roledesc" column="roledesc"/>
        <collection property="users" ofType="user">
            <id property="id" column="id"/>
            <result property="username" column="username"/>
            <result property="sex" column="sex"/>
            <result property="address" column="address"/>
            <result property="birthday" column="birthday"/>
        </collection>
    </resultMap>

    <select id="findAll" resultMap="roleMap"> select u.*,r.id as rid,r.rolename,r.roledesc from mybatis.role as r left outer join mybatis.user_role as ur on r.id = ur.rid left outer join mybatis.user as u on u.id = ur.uid </select>
</mapper>

UserDao.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.jinke.dao.UserDao">

    <resultMap id="userAccountMap" type="user">
        <id property="id" column="id"/>
        <result property="username" column="username"/>
        <result property="address" column="address"/>
        <result property="sex" column="sex"/>
        <result property="birthday" column="birthday"/>
        <collection property="roles" ofType="role">
            <id property="id" column="rid"/>
            <result property="rolename" column="rolename"/>
            <result property="roledesc" column="roledesc"/>
        </collection>
    </resultMap>

    <select id="findAll" resultMap="userAccountMap"> select u.*,r.id as rid,r.rolename,r.roledesc from mybatis.user as u left outer join mybatis.user_role as ur on u.id = ur.uid left outer join mybatis.role as r on r.id = ur.rid </select>

    <select id="findById" parameterType="Integer" resultType="user"> select * from user where id = #{uid}; </select>
</mapper>

 測試類

import com.jinke.dao.AccountDao; import com.jinke.dao.RoleDao; import com.jinke.dao.UserDao; import com.jinke.domain.Account; import com.jinke.domain.Role; import com.jinke.domain.User; import org.apache.ibatis.io.Resources; import org.apache.ibatis.session.SqlSession; import org.apache.ibatis.session.SqlSessionFactory; import org.apache.ibatis.session.SqlSessionFactoryBuilder; import org.junit.After; import org.junit.Before; import org.junit.Test; import java.io.InputStream; import java.util.List; public class MyBatisTest { private InputStream in; private SqlSession sqlSession; private UserDao userDao; private AccountDao accountDao; private RoleDao roleDao; @Before public void init() throws Exception { in = Resources.getResourceAsStream("SqlMapConfig.xml"); SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder(); SqlSessionFactory factory = builder.build(in); sqlSession = factory.openSession(); userDao = sqlSession.getMapper(UserDao.class); accountDao = sqlSession.getMapper(AccountDao.class); roleDao = sqlSession.getMapper(RoleDao.class); } @After public void destroy() throws Exception { sqlSession.commit(); sqlSession.close(); in.close(); } @Test public void testFindAccount() { List<Account> accounts = accountDao.findAll(); for (Account account : accounts) { System.out.println(account + " " + account.getUser()); } } @Test public void testFindUser() { List<User> users = userDao.findAll(); for (User user : users) { System.out.println(user + " " + user.getRoles()); } } @Test public void testFindRole() { List<Role> roles = roleDao.findAll(); for (Role role : roles) { System.out.println(role + " " + role.getUsers()); } } }

測試結果

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