MyBatis in multi-table query --- -----many query operations roles to users

Database table


intermediate tables

foreign key

Create a maven project in IDEA

Overall structure

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.uek</groupId>
    <artifactId>mybatis03-study03-moretableQuery-manyTomany</artifactId>
    <version>1.0-SNAPSHOT</version>

    <!--打包方式-->
    <packaging>jar</packaging>

    <dependencies>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.5</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.6</version>
        </dependency>

        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.12</version>
        </dependency>

        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.10</version>
        </dependency>
    </dependencies>

</project>

MyBatis main configuration file

In the resource directory ------ 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">
<configuration>

    <!--使用typeAliases配置别名，它只能配置到domian中类的别名-->
    <typeAliases>
        <package name="com.uek.domian"/>
    </typeAliases>
    
    <!--配置环境-->
    <environments default="mysql">
        <!--配置mysql的环境-->
        <environment id="mysql">
            <!--配置事务-->
            <transactionManager type="JDBC"></transactionManager>
            <!--配置连接池-->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useUnicode=true&amp;characterEncoding=utf-8&amp;useSSL=false"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>
    <!--配置映射文件的位置-->
    <mappers>
        <package name="com.uek.dao"/>
    </mappers>
</configuration>

Entity class

public class Role implements Serializable {

    private Integer roleId;
    private String  roleName;
    private String  roleDesc;

    //多对多映射：一个角色可以赋予多个用户
    private List<User> users;

    public List<User> getUsers() {
        return users;
    }

    public void setUsers(List<User> users) {
        this.users = users;
    }

    public Integer getRoleId() {
        return roleId;
    }

    public void setRoleId(Integer roleId) {
        this.roleId = roleId;
    }

    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;
    }

    @Override
    public String toString() {
        return "Role{" +
                "roleId=" + roleId +
                ", roleName='" + roleName + '\'' +
                ", roleDesc='" + roleDesc + '\'' +
                '}';
    }
}

public class User implements Serializable {

    private Integer id;
    private String username;
    private String address;
    private String sex;
    private Date birthday;

    public String getUsername() {
        return username;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getUsername(String mybatis_saveuser) {
        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;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", address='" + address + '\'' +
                ", sex='" + sex + '\'' +
                ", birthday=" + birthday +
                '}';
    }
}

dao layer interface

public interface IRoleDao {

    //查询所有角色
    List<Role> findAll();

    //查询所有的角色，同时获取角色所赋予的用户
    //角色到用户
    List<Role> findRoleAll();
}

Interface Configuration IUserDao.xml

Note: the establishment of a level in the resource directory when the new package
must package name and the interface layer is consistent dao

<?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.uek.dao.IRoleDao">

    <!--定义role表的resultMap-->
    <resultMap id="roleMap" type="role">
        <id property="roleId" column="rid"></id>
        <result property="roleName" column="role_name"></result>
        <result property="roleDesc" column="role_desc"></result>
        <collection property="users" ofType="user">
            <id  column="id" property="id" ></id>
            <result column="username" property="username" ></result>
            <result column="address" property="address" ></result>
            <result column="sex" property="sex" ></result>
            <result column="birthday" property="birthday" ></result>
        </collection>
    </resultMap>

    <!--查询所有-->
    <select id="findAll" resultMap="roleMap">
        select * from role
    </select>

    <!--查询所有的角色，同时获取角色所赋予的用户
        角色到用户
    -->
    <select id="findRoleAll" resultMap="roleMap">
        select u.*,r.id as rid,r.role_name,r.role_desc from role r left outer join user_role ur on r.id = ur.rid left outer join user u on u.id = ur.uid
    </select>

</mapper>

Test category

public class RowTest {

    private InputStream in;
    private SqlSession sqlSession;
    private IRoleDao roleDao;

    @Before   //用于在测试方法执行之前执行
    public void init() throws Exception {
        //1.读取配置文件，生成字节输入流
        in = Resources.getResourceAsStream("SqlMapConfig.xml");
        //2.获取SqlSession对象
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(in);
        //3.获取SqlSession对象
        sqlSession = factory.openSession();
        //4.获取dao的代理对象
        roleDao = sqlSession.getMapper(IRoleDao.class);
    }


    @After //用于在测试方法执行之后执行
    public void destroy() throws Exception {
        //提交事务
        sqlSession.commit();

        //6.释放资源
        sqlSession.close();
        in.close();
    }

    //查询所有
    @Test
    public void testFindAll(){
        List<Role> roles = roleDao.findAll();
        for (Role role : roles) {
            System.out.println("--------每个角色的信息--------");
            System.out.println(role);
        }
    }

    //查询所有的角色，同时获取角色所赋予的用户
    //角色到用户
    @Test
    public void testFindRlowAll(){
        List<Role> ro =roleDao.findRoleAll();
        for (Role rol : ro) {
            System.out.println(rol);
            System.out.println(rol.getUsers());
        }
    }
}