黑马mybatis教程全套视频教程

简介

mybatis 快速入门

create database if not exists mybatis;
use mybatis;

drop table if exists tb_user;

create table tb_user(
    id int primary key auto_increment,
    username varchar(20),
    password varchar(20),
    gender char(1),
    addr varchar(30)
);

insert into tb_user values(1,'zhangsan','123','男','北京');
insert into tb_user values(2,'李四','456','女','天津');
insert into tb_user values(3,'王五','789','男','西安');

<?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>

    <!-- ... -->

    <dependencies>
        <!-- mybatis -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.5</version>
        </dependency>
        <!-- mysql驱动 -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.46</version>
        </dependency>
        <!-- 测试 -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.13</version>
            <scope>test</scope>
        </dependency>
        <!-- slf4j日志 -->
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>1.7.20</version>
        </dependency>
        <!-- logback -->
        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-classic</artifactId>
            <version>1.2.3</version>
        </dependency>
        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-core</artifactId>
            <version>1.2.3</version>
        </dependency>
    </dependencies>
</project>

package org.malred;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

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.malred.entity.User;

public class MybatisDemo {
    public static void main(String[] args) throws IOException {
        // 1. 加载mybatis核心配置文件，获取SqlSessionFactory
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        // 2. 获取SqlSession对象，用它执行sql
        SqlSession sqlSession = sqlSessionFactory.openSession();

        // 3. 执行sql
        List<User> users = sqlSession.selectList("test.selectAll");
        System.out.println(users);

        // 4. 释放资源
        sqlSession.close();
    }
}

package org.malred.entity;

public class User {

    private Integer id;
    private String username;
    private String password;
    private String gender;
    private String addr;

    @Override
    public String toString() {
        return "{" +
                " id='" + getId() + "'" +
                ", username='" + getUsername() + "'" +
                ", password='" + getPassword() + "'" +
                ", gender='" + getGender() + "'" +
                ", addr='" + getAddr() + "'" +
                "}";
    }

    public Integer getId() {
        return this.id;
    }

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

    public String getUsername() {
        return this.username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return this.password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getGender() {
        return this.gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public String getAddr() {
        return this.addr;
    }

    public void setAddr(String addr) {
        this.addr = addr;
    }
}

<!-- mappers/UserMapper.xml -->
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!-- 名称空间 -->
<mapper namespace="test">
    <select id="selectAll" resultType="org.malred.entity.User">
        select * from tb_user;
    </select>
</mapper>

<!-- mybatis-config.xml -->
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "https://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC" />
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver" />
                <property name="url" value="jdbc:mysql://localhost:3307/mybatis?useSSL=false" />
                <property name="username" value="root" />
                <property name="password" value="123456" />
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="mappers/UserMapper.xml" />
    </mappers>
</configuration>

sql 语句警告

Mapper 代理开发

mvn 编译完，resources 里的文件都在一个目录下

如果要让 resources 里的 UserMapper 打包后（编译后）和我们接口类 UserMapper 在一个目录，则需要在 resources 下创建和接口类一样的包结构

<!-- mybatis-config.xml -->
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "https://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <!-- ... -->
    <mappers>
        <mapper resource="org/malred/mappers/UserMapper.xml" />
    </mappers>
</configuration>

<!-- org/malred/mappers/UserMapper.xml -->
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!-- 名称空间 -->
<mapper namespace="org.malred.mappers.UserMapper">
    <select id="selectAll" resultType="org.malred.entity.User">
        select * from tb_user;
    </select>
</mapper>

package org.malred.mappers;

import java.util.List;

import org.malred.entity.User;

public interface UserMapper {
    List<User> selectAll();
}

package org.malred;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

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.malred.entity.User;
import org.malred.mappers.UserMapper;

/**
 * 代理开发
 */
public class MybatisDemo2 {
    public static void main(String[] args) throws IOException {
        // 1. 加载mybatis核心配置文件，获取SqlSessionFactory
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        // 2. 获取SqlSession对象，用它执行sql
        SqlSession sqlSession = sqlSessionFactory.openSession();

        // 3. 执行sql
        // 3.1 获取UserMapper接口的代理对象
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        List<User> users = userMapper.selectAll();

        System.out.println(users);

        // 4. 释放资源
        sqlSession.close();
    }
}

使用 package 批量指定 mapper

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "https://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <!-- ... -->
    <mappers>
        <!-- <mapper resource="org/malred/mappers/UserMapper.xml" /> -->
        <package name="org.malred.mappers" />
    </mappers>
</configuration>

mybatis 核心配置文件

可以配置多数据源

以后整合 ssm 后，一般都是使用 spring 管理事务，所以这个标签没什么用

别名

<!-- UserMapper.xml -->
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!-- 名称空间 -->
<mapper namespace="org.malred.mappers.UserMapper">
    <!-- <select id="selectAll" resultType="org.malred.entity.User"> -->
    <!-- 配置完别名（org.malred.entity），可以省略org.malred.entity，并且类名可以不区分大小写 -->
    <select id="selectAll" resultType="user">
        select * from tb_user;
    </select>
</mapper>

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "https://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <typeAliases>
        <package name="org.malred.entity" />
    </typeAliases>
    <!-- ... -->
</configuration>

写标签要按顺序（xml 的特点）

mybatis(crud) 案例

环境准备

他这个好像是内部网站？我用一开始的 User

查询

package org.malred;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

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 org.malred.entity.User;
import org.malred.mappers.UserMapper;

public class UnitTest {
    InputStream inputStream;
    SqlSession sqlSession;
    UserMapper userMapper;

    @Before
    public void before() throws IOException {
        // 1. 加载mybatis核心配置文件，获取SqlSessionFactory
        String resource = "mybatis-config.xml";
        inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        // 2. 获取SqlSession对象，用它执行sql
        sqlSession = sqlSessionFactory.openSession();
        userMapper = sqlSession.getMapper(UserMapper.class);
    }

    @Test
    public void selectAll() {
        List<User> users = userMapper.selectAll();
        System.out.println(users);
    }

    @After
    public void after() throws IOException {
        inputStream.close();
        sqlSession.close();
    }
}

查看详情

package org.malred.mappers;

import java.util.List;

import org.malred.entity.User;

public interface UserMapper {
    // 查询所有
    public List<User> findAll();

    // 查询单个
    public User findById(int id);
}

    @Test
    public void findById() {
        User user = userMapper.findById(1);
        System.out.println(user);
    }

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!-- 名称空间 -->
<mapper namespace="org.malred.mappers.UserMapper">
    <!-- <select id="selectAll" resultType="org.malred.entity.User"> -->
    <!-- 配置完别名（org.malred.entity），可以省略org.malred.entity，并且类名可以不区分大小写 -->
    <select id="findAll" resultType="user">
        select * from tb_user;
    </select>
    <select id="findById" resultType="user">
        select * from tb_user where id = #{id}
    </select>
</mapper>

条件查询

package org.malred.mappers;

import java.util.List;
import java.util.Map;

import org.apache.ibatis.annotations.Param;
import org.malred.entity.User;
import org.malred.entity.UserDTO;

public interface UserMapper {
    // 查询所有
    List<User> findAll();

    // 查询单个
    User findById(int id);

    // 条件查询
    // 1. 散装参数：通过@Param("sql参数占位符名称")
//    List<User> findByCondition(
//            @Param("gender") String gender,
//            @Param("username") String username,
//            @Param("addr") String addr);

    // 2. 对象参数：对象的属性名称要和参数占位符名称一致
//    List<User> findByCondition(UserDTO userDTO);
    // 3. Map参数：键的名称要和参数占位符名称一致
    List<User> findByCondition(Map map);
}

    @Test
    public void findByCondition() {
        List<User> users = null;
//        users = userMapper.findByCondition("男", "%李%", "%东%");
//        users = userMapper.findByCondition(new UserDTO("男", "%李%", "%东%"));

        Map map = new HashMap();
        map.put("gender", "男");
        map.put("username", "%李%");
        map.put("addr", "%东%");
        users = userMapper.findByCondition(map);
        System.out.println(users);
    }

package org.malred.entity;

public class UserDTO {
    String gender;
    String username;
    String addr;

    public UserDTO(String gender, String username, String addr) {
        this.gender = gender;
        this.username = username;
        this.addr = addr;
    }

    public UserDTO() {
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getAddr() {
        return addr;
    }

    public void setAddr(String addr) {
        this.addr = addr;
    }
}

<!-- UserMapper.xml -->
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!-- 名称空间 -->
<mapper namespace="org.malred.mappers.UserMapper">
    <!-- ... -->
    <select id="findByCondition" resultType="user">
        select * from tb_user
        where gender = #{gender}
        and username like #{username}
        and addr like #{addr}
    </select>
</mapper>

动态条件查询

此时有个问题，我们必须所有条件都有值，但是又不能保证用户都输入，很不灵活

    @Test
    public void findByCondition() {
        List<User> users = null;

        users = userMapper.findByCondition(new UserDTO(null, "%李%", null));

        System.out.println(users);
    }

    <select id="findByCondition" resultType="user">
        select * from tb_user
        <!--where 1=1-->
        <where>
            <if test="gender != null and gender!=''">
                and gender = #{gender}
            </if>
            <if test="username != null and username != ''">
                and username like #{username}
            </if>
            <if test="addr != null and addr != ''">
                and addr like #{addr}
            </if>
        </where>
    </select>

单条件动态查询

    @Test
    public void findByCondition() {
        users = userMapper.findByConditionSingle(
                new UserDTO("女", null, null));
        System.out.println(users);

        users = userMapper.findByConditionSingle(new UserDTO());
        System.out.println(users);
    }

    /**
     * 单条件动态查询
     *
     * @param userDTO
     * @return
     */
    List<User> findByConditionSingle(UserDTO userDTO);

    <select id="findByConditionSingle" resultType="user">
        select * from tb_user
        <!--防止用户什么都不传(自动去掉和加and-->
        <where>
            <choose> <!--相对于switch-->
                <when test="gender != null and gender!=''">
                    gender = #{gender}
                </when>
                <when test="username != null and username != ''">
                    username like #{username}
                </when>
                <when test="addr != null and addr != ''">
                    addr like #{addr}
                </when>
                <!--防止用户什么都不传-->
                <!--                <otherwise>-->
                <!--                    1 = 1-->
                <!--                </otherwise>-->
            </choose>
        </where>
    </select>

还可以用 where

添加

关闭了自动提交

创建 sqlsession 时可以设置自动提交

主键返回

    @Test
    public void save() {
        User u = new User("韩梅梅", "123", "女", "上海");
        userMapper.save(u);
        // 提交事务
        sqlSession.commit();
        System.out.println(u.getId());
    }

    <insert id="save" useGeneratedKeys="true" keyProperty="id">
        insert into tb_user (gender, username, addr)
        values (#{gender}, #{username}, #{addr})
    </insert>

    /**
     * 添加
     *
     * @param user
     */
    void save(User user);

修改

修改全部字段

    @Test
    public void upt() {
        User u = new User(9, "韩梅梅", "456", "女", "上海");
        int count = userMapper.update(u);
        // 提交事务
        sqlSession.commit();
        System.out.println("影响了" + count + "行");
    }

    <update id="update">
        update tb_user
        set
        username = #{username},
        gender = #{gender},
        password = #{password},
        addr = #{addr}
        where id = #{id};
    </update>

    /**
     * 修改
     *
     * @param user
     * @return
     */
    int update(User user);

修改动态字段

动态字段的问题

    @Test
    public void dynamic_upt() {
        User u = new User(8, null, "456", null, null);
        int count = userMapper.dynamicUpdate(u);
        // 提交事务
        sqlSession.commit();
        System.out.println("影响了" + count + "行");
    }

    <update id="dynamicUpdate">
        update tb_user
        <!--防止逗号和所有值都null只剩set导致语法错误-->
        <set>
            <if test="username != null and username != ''">
                username = #{username},
            </if>
            <if test="gender != null and gender != ''">
                gender = #{gender},
            </if>
            <if test="password != null and password != ''">
                password = #{password},
            </if>
            <if test="addr != null and addr != ''">
                addr = #{addr}
            </if>
        </set>
        where id = #{id};
    </update>

    /**
     * 动态修改
     *
     * @param user
     * @return
     */
    int dynamicUpdate(User user);

删除

    @Test
    public void deleteById() {
        userMapper.deleteById(8);
        sqlSession.commit();
    }

    @Test
    public void deleteByIds() {
        userMapper.deleteByIds(new int[]{12, 13});
        sqlSession.commit();
    }

    /**
     * 根据id删除
     *
     * @param id
     */
    void deleteById(int id);

    /**
     * 根据id批量删除
     *
     * @param ids
     */
    void deleteByIds(@Param("ids") int[] ids);

    <delete id="deleteById">
        delete from tb_user where id = #{id};
    </delete>
    <delete id="deleteByIds">
        delete from tb_user where id in
        <foreach collection="ids" item="id" separator="," open="(" close=")">
            #{id}
        </foreach>
    </delete>

参数传递

注解开发

    @Test
    public void findByIdUseAnnotation() {
        User u = userMapper.findByIdUseAnnotation(1);
        System.out.println(u);
    }

    @Select("select * from tb_user where id = #{id}")
    User findByIdUseAnnotation(int id);

over