mybatis入门篇：Mapper接口/关联查询/新增数据

1、数据准备

2、编写实体类

package com.forest.owl.entity;

import java.util.Date;

public class User {
    private Long id;
    private String userName;
    private String userPassword;
    private String userPhone;
    private String userEmail;
    private byte[] headImg;
    private Date createTime;
    private Date updateTime;

    public Long getId() {
        return id;
    }

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

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getUserPassword() {
        return userPassword;
    }

    public void setUserPassword(String userPassword) {
        this.userPassword = userPassword;
    }

    public String getUserPhone() {
        return userPhone;
    }

    public void setUserPhone(String userPhone) {
        this.userPhone = userPhone;
    }

    public String getUserEmail() {
        return userEmail;
    }

    public void setUserEmail(String userEmail) {
        this.userEmail = userEmail;
    }

    public byte[] getHeadImg() {
        return headImg;
    }

    public void setHeadImg(byte[] headImg) {
        this.headImg = headImg;
    }

    public Date getCreateTime() {
        return createTime;
    }

    public void setCreateTime(Date createTime) {
        this.createTime = createTime;
    }

    public Date getUpdateTime() {
        return updateTime;
    }

    public void setUpdateTime(Date updateTime) {
        this.updateTime = updateTime;
    }

}

3、编写相对应的Mapper接口

package com.forest.owl.mapper;

import com.forest.owl.entity.User;

import java.util.List;

public interface UserMapper {

    User selectUserById(Long id);

    List<User> selectAllUser();

}

4、编写UserMapper.xml

在resources中加入文件夹com/forest/owl/mapper，在此文件夹中添加UserMapper文件

<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.forest.owl.mapper.UserMapper">
    <resultMap id="userMap" type="com.forest.owl.entity.User">
        <id property="id" column="id" />
        <result property="userName" column="user_name" />
        <result property="userPassword" column="user_password" />
        <result property="userPhone" column="user_phone" />
        <result property="userEmail" column="user_email" />
        <result property="headImg" column="head_img" jdbcType="BLOB" />
        <result property="createTime" column="create_time" jdbcType="TIMESTAMP" />
        <result property="updateTime" column="update_time" jdbcType="TIMESTAMP" />
    </resultMap>

    <select id="selectUserById" resultMap="userMap">
        SELECT * FROM user WHERE id=#{id}
    </select>

    <select id="selectAllUser" resultType="com.forest.owl.entity.User">
        SELECT id, user_name, user_password, user_phone, user_email, head_img, create_time, update_time
        FROM user
    </select>
</mapper>

5、修改mybatis-config.xml文件

<?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>
    <settings>
        <setting name="mapUnderscoreToCamelCase" value="true"/>
    </settings>

    <typeAliases>
        <package name="com.forest.owl.entity"/>
    </typeAliases>

    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC">
                <property name="" value=""/>
            </transactionManager>
            <dataSource type="UNPOOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/forest?useSSL=false"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <package name="com.forest.owl.mapper"/>
    </mappers>
</configuration>

6、编写测试代码

package com.forest.owl;

import com.forest.owl.entity.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.BeforeClass;

import java.io.IOException;
import java.io.Reader;

public class BaseMapperTest {
    private static SqlSessionFactory sqlSessionFactory;

    @BeforeClass
    public static void init(){
        try {
            Reader reader = Resources.getResourceAsReader("mybatis.config.xml");
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
            reader.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public SqlSession getSqlSession(){
        SqlSession sqlSession = sqlSessionFactory.openSession();
        return sqlSession;
    }
}

package com.forest.owl;

import com.forest.owl.entity.User;
import com.forest.owl.mapper.UserMapper;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class MapperTest extends BaseMapperTest{

    @Test
    public void UserMapperTest(){
        SqlSession sqlSession = getSqlSession();
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        User user = userMapper.selectUserById((long) 3);
        System.out.println(user.getUserName());

        List<User> userList = userMapper.selectAllUser();
        userList.stream().forEach(i -> System.out.println(i.getUserName()));
    }
}

7、关联查询

假设在用户信息查询的基础上，我还想查询用户的角色与权限，该如何？

首先定义角色与权限的实体类

package com.forest.owl.entity;

import java.util.Date;

public class Role {
    private Long id;
    private String roleName;
    private int enabled;
    private Long createBy;
    private Date createTime;
    private Long updateBy;
    private Date updateTime;

    public Long getId() {
        return id;
    }

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

    public String getRoleName() {
        return roleName;
    }

    public void setRoleName(String roleName) {
        this.roleName = roleName;
    }

    public int getEnabled() {
        return enabled;
    }

    public void setEnabled(int enabled) {
        this.enabled = enabled;
    }

    public Long getCreateBy() {
        return createBy;
    }

    public void setCreateBy(Long createBy) {
        this.createBy = createBy;
    }

    public Date getCreateTime() {
        return createTime;
    }

    public void setCreateTime(Date createTime) {
        this.createTime = createTime;
    }

    public Long getUpdateBy() {
        return updateBy;
    }

    public void setUpdateBy(Long updateBy) {
        this.updateBy = updateBy;
    }

    public Date getUpdateTime() {
        return updateTime;
    }

    public void setUpdateTime(Date updateTime) {
        this.updateTime = updateTime;
    }

}

package com.forest.owl.entity;

import java.util.Date;

public class Privilege {
    private Long id;
    private String privilegeName;
    private String privilegeUrl;
    private Long createBy;
    private Date createTime;
    private Long updateBy;
    private Date updateTime;

    public Long getId() {
        return id;
    }

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

    public String getPrivilegeName() {
        return privilegeName;
    }

    public void setPrivilegeName(String privilegeName) {
        this.privilegeName = privilegeName;
    }

    public String getPrivilegeUrl() {
        return privilegeUrl;
    }

    public void setPrivilegeUrl(String privilegeUrl) {
        this.privilegeUrl = privilegeUrl;
    }

    public Long getCreateBy() {
        return createBy;
    }

    public void setCreateBy(Long createBy) {
        this.createBy = createBy;
    }

    public Date getCreateTime() {
        return createTime;
    }

    public void setCreateTime(Date createTime) {
        this.createTime = createTime;
    }

    public Long getUpdateBy() {
        return updateBy;
    }

    public void setUpdateBy(Long updateBy) {
        this.updateBy = updateBy;
    }

    public Date getUpdateTime() {
        return updateTime;
    }

    public void setUpdateTime(Date updateTime) {
        this.updateTime = updateTime;
    }

}

在User实体类中添加Role与Privilege属性

    private Role role;
    private Privilege privilege;

    public Role getRole() { return role; }
    public void setRole(Role role) { this.role = role; }
    public Privilege getPrivilege() { return privilege; }
    public void setPrivilege(Privilege privilege) { this.privilege = privilege; }

修改UserMapper.xml文件

<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.forest.owl.mapper.UserMapper">
    <resultMap id="userMap" type="com.forest.owl.entity.User">
        <id property="id" column="id" />
        <result property="userName" column="user_name" />
        <result property="userPassword" column="user_password" />
        <result property="userPhone" column="user_phone" />
        <result property="userEmail" column="user_email" />
        <result property="headImg" column="head_img" jdbcType="BLOB" />
        <result property="createTime" column="create_time" jdbcType="TIMESTAMP" />
        <result property="updateTime" column="update_time" jdbcType="TIMESTAMP" />
        <association property="role">
            <result property="roleName" column="role_name" />
        </association>
        <association property="privilege">
            <result property="privilegeName" column="privilege_name" />
            <result property="privilegeUrl" column="privilege_url" />
        </association>
    </resultMap>

    <select id="selectUserById" resultMap="userMap">
        SELECT u.*,
        r.role_name,
        p.privilege_name,
        p.privilege_url
        FROM user u
        INNER JOIN user_role ur on ur.user_id=u.id
        INNER JOIN role r on r.id=ur.role_id
        INNER JOIN role_privilege rp on rp.role_id=r.id
        INNER JOIN privilege p on p.id=rp.privilege_id
        WHERE u.id=#{id}
    </select>

    <select id="selectAllUser" resultType="com.forest.owl.entity.User">
        SELECT u.id,
        u.user_name,
        u.user_password,
        u.user_phone,
        u.user_email,
        u.head_img,
        u.create_time,
        u.update_time,
        r.role_name as "role.roleName",
        p.privilege_name as "privilege.privilegeName",
        p.privilege_url as "privilege.privilegeUrl"
        FROM user u
        INNER JOIN user_role ur on ur.user_id=u.id
        INNER JOIN role r on r.id=ur.role_id
        INNER JOIN role_privilege rp on rp.role_id=r.id
        INNER JOIN privilege p on p.id=rp.privilege_id
    </select>
</mapper>

编写测试类

    @Test
    public void UserMapperTest(){
        SqlSession sqlSession = getSqlSession();
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        User user = userMapper.selectUserById((long) 3);
        System.out.println(user.getUserName());
        System.out.println(user.getRole().getRoleName());
        System.out.println(user.getPrivilege().getPrivilegeName());
        System.out.println(user.getPrivilege().getPrivilegeUrl());

        List<User> userList = userMapper.selectAllUser();
        userList.stream().forEach(i -> {
            System.out.println(i.getUserName());
            System.out.println(i.getRole().getRoleName());
            System.out.println(i.getPrivilege().getPrivilegeName());
            System.out.println(i.getPrivilege().getPrivilegeUrl());
        });
    }

 8、新增数据

在UserMapper接口中新增方法

int insertUser(User user);

UserMapper.xml

<insert id="insertUser">
    INSERT INTO user (user_name, user_password, user_phone, user_email, head_img, create_time, update_time)
    VALUES( #{userName},  #{userPassword}, #{userPhone}, #{userEmail}, #{headImg}, #{createTime}, #{updateTime} )
</insert>

测试代码

    @Test
    public void UserMapperTest(){
        SqlSession sqlSession = getSqlSession();
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);

        User user = new User();
        user.setUserName("新用户名");
        user.setUserPassword("密码");
        user.setUserPhone("手机号");
        user.setUserEmail("邮箱号");

        int result = userMapper.insertUser(user);
        System.out.println(result);
        sqlSession.commit();
    }

因为SqlSessionFactory.openSession()是不自动提交的，故此处需要手动提交，否则无效。

对于想要得到插入数据的主键，可以设置mybatis-config.xml的配置项useGeneratedKeys为true

    <settings>
        <setting name="mapUnderscoreToCamelCase" value="true"/>
        <setting name="useGeneratedKeys" value="true"/>
    </settings>

然后在<insert />配置中添加keyProperty="id"，在数据插入成功后，mybatis会将主键回写至id里，届时使用user.getId()获取即可。

    <insert id="insertUser" keyProperty="id">
        INSERT INTO user (user_name, user_password, user_phone, user_email, head_img, create_time, update_time)
        VALUES( #{userName},  #{userPassword}, #{userPhone}, #{userEmail}, #{headImg}, #{createTime}, #{updateTime} )
    </insert>