Mybatis之第一个mybatis程序

一、环境说明，知识储备

环境说明

 MySQL 8，maven-3.6.1，IDEA，jdk8+ 

知识储备

  Java基础，Mysql，JDBC，maven，Junit 

二、创建和配置项目

创建Maven项目

在pom.xml中导入依赖

在这里我采用了父子工程，便于管理

父工程：

<?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>

    <!--父工程-->
    <groupId>com.me</groupId>
    <artifactId>mybatis-study</artifactId>
    <packaging>pom</packaging>
    <version>1.0-SNAPSHOT</version>
    <modules>
        <module>mybatis-01</module>
    </modules>

    <!--导入依赖-->
    <dependencies>
        <!--mysql驱动-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.15</version>
        </dependency>
        <!--mybatis-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.6.1</version>
        </dependency>
        <!--junit-->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>
    </dependencies>

    <!--在build中配置resources,防止资源导出失败-->
    <build>
        <resources>
            <resource>
                <directory>src/main/resources</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>false</filtering>
            </resource>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>false</filtering>
            </resource>
        </resources>
    </build>

</project>

子工程

<?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">
    <parent>
        <artifactId>mybatis-study</artifactId>
        <groupId>com.me</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>mybatis-01</artifactId>

    <!--在build中配置resources,防止资源导出失败-->
    <build>
        <resources>
            <resource>
                <directory>src/main/resources</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>false</filtering>
            </resource>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>false</filtering>
            </resource>
        </resources>
    </build>

</project>

注意：根据自己的版本修改version，因为是初次构建，只导入了一部分依赖

创建一个数据库并进行连接

创建mybatis数据库

CREATE DATABASE `mybatis`;

USE `mybatis`;

CREATE TABLE `user` (
  `id` INT(20) NOT NULL PRIMARY KEY,
  `name` VARCHAR(30) DEFAULT NULL,
  `pwd` VARCHAR(30) DEFAULT NULL
) ENGINE=INNODB DEFAULT CHARSET=utf8;

INSERT  INTO `user`(`id`,`name`,`pwd`) VALUES (1,'张三','12345'),(2,'李四','12321'),(3,'王五','12390');

将数据库与IDEA进行连接

 

 

 之后输入自己的用户名以及密码，测试连接即可

Mybatis核心配置文件

右键resourse点击New -> File 创建核心配置文件mybatis-config.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核心配置文件-->
<configuration>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=true&amp;useUnicode=true&amp;characterEncoding=UTF-8&amp;serverTimezone=UTC"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <mapper resource="com/me/dao/UserMapper.xml"/>
    </mappers>

</configuration>

MybatisUtils工具类

在utils包中的MybatisUtils中添加代码

public class MybatisUtils {

    private static SqlSessionFactory sqlSessionFactory;

    static {
        try {
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

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

User实体类

public class User {
    private int id;
    private String name;
    private String pwd;

    public User() {
    }

    public User(int id, String name, String pwd) {
        this.id = id;
        this.name = name;
        this.pwd = pwd;
    }

    public int getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPwd() {
        return pwd;
    }

    public void setPwd(String pwd) {
        this.pwd = pwd;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", pwd='" + pwd + '\'' +
                '}';
    }
}

UserMapper接口类

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

UserMapper.xml文件

select中的就是我们sql语句，后面要增删改都是在UserMapper.xml中修改
namespace十分重要！千万不能出错

<?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.me.dao.UserMapper">
    <select id="getUserList" resultType="com.me.pojo.User">
    select * from mybatis.user;
  </select>
</mapper>

UserMapperTest测试类

public class UserDaoTest {

    @Test
    public void getUserList() {

        //第一步:获取SqlSession对象
        SqlSession sqlSession = MybatisUtils.getSqlSession();

        //方式一:getMapper
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<User> userList = mapper.getUserList();

        for (User user : userList) {
            System.out.println(user);
        }

        //关闭SqlSession
        sqlSession.close();
    }
}

 

运行之后结果如下

三、增删改

我们费那么大力气搭建Mybatis项目，就是为了之后操作的方便，我们只用修改几个地方即可。

注意：增删改和查询的最大区别是必须提交事务，否则无法成功！

UserMapper接口类

在UserMapper接口类中定义新的抽象方法

public interface UserMapper {
    //查询全部用户
    List<User> getUserList();

    //根据id查询用户
    User getUserById(int id);

    //插入用户
    int addUser(User user);

    //修改用户
    void updateUser(User user);

    //删除用户
    void deleteUser(int id);
}

UserMapper.xml配置文件

增加对应功能的SQL语句

<?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.me.dao.UserMapper">
    <select id="getUserList" resultType="com.me.pojo.User">
    select * from mybatis.user;
    </select>

    <select id="getUserById" parameterType="int" resultType="com.me.pojo.User">
        select * from mybatis.user where id = #{id}
    </select>

    <insert id="addUser" parameterType="com.me.pojo.User">
        insert into mybatis.user (id, name, pwd) values (#{id}, #{name}, #{pwd});
    </insert>

    <update id="updateUser" parameterType="com.me.pojo.User">
        update mybatis.user set name = #{name}, pwd = #{pwd} where id = #{id} ;
    </update>

    <delete id="deleteUser" parameterType="int">
        delete from mybatis.user where id = #{id};
    </delete>

</mapper>

UserMapperTest测试类

public class UserDaoTest {

    @Test
    public void getUserList() {

        //第一步:获取SqlSession对象
        SqlSession sqlSession = MybatisUtils.getSqlSession();

        //方式一:getMapper
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<User> userList = mapper.getUserList();
        for (User user : userList) {
            System.out.println(user);
        }

        //关闭SqlSession
        sqlSession.close();
    }

    @Test
    public void getUserById() {
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        User user = mapper.getUserById(1);
        System.out.println(user);
        sqlSession.close();
    }

    //增删改需要提交事务
    @Test
    public void addUser() {
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        int res = mapper.addUser(new User(4, "赵六", "12333"));
        if (res > 0) {
            System.out.println("插入成功！");
        }
        //提交事务
        sqlSession.commit();
        sqlSession.close();
    }

    @Test
    public void updateUser() {
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        mapper.updateUser(new User(4, "田七", "12312"));
        sqlSession.commit();
        sqlSession.close();
    }

    @Test
    public void deleteUser() {
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        mapper.deleteUser(4);
        sqlSession.commit();
        sqlSession.close();
    }
}