第一个mybatis项目

1,首先创建一个数据库和一个表
2,创建一个maven父工程，删掉里面的src文件在pom.xml文件中添加

   <dependencies>
    <!-- https://mvnrepository.com/artifact/junit/junit -->
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.12</version>
        <scope>test</scope>
    </dependency>
        <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.7</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.21</version>
        </dependency>
    </dependencies>
 <build>
      <resources>
        <resource>
            <directory>src/main/resources</directory>
            <includes>
            <include>**/*.xproperties</include>
            <include>**/*.xml</include>
          </includes>
            <filtering>false</filtering>
        </resource>

         <resource>
            <directory>src/main/java</directory>
            <includes>
            <include>**/*.xml/</include>
            <include>**/*.properties</include>
          </includes>
   <filtering>false</filtering>
         </resource>
    </resources>
    </build>

3(编写MyBatis核心配置文件)，mybatis-config.xml文件里面的内容

<?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=false&amp;serverTimezone=UTC&amp;Unicode=true&amp;characterEncoding=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="010616"/>
            </dataSource>
        </environment>
    </environments>
<!--每一个Mapper.xml文件都需要在mybatis核心配置文件中注册-->
<!--这个Mapper.xml文件也是包名+/+UserMapper.xml,同理包名里面的.要换成/  -->
    <mappers>
        <mapper resource="UserMapper.xml"/>
    </mappers>
</configuration>

4(编写MyBatis工具类)，创建一个utils包，里面添加一个MybatisUtils工具类，先定义一个静态的sqlSessionFactory： private static SqlSessionFactory sqlSessionFactory
再定义一个静态代码快(可以首先执行)里面写mybatis官网里面给出的三行代码：

String resource = "mybatis-config.xml"(如果在包下面创建，则需要写包名+/mybatis-config.xml。包名里面的.都要换成/);
InputStream inputStream =Resources.getResourceAsStream(resource);
sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

之后抛出异常用try catch来捕获
最后我们既然有了sqlSessionFactory对象，那么我们就可以获得SqlSession实例(通过sqlSessionFactory对象的openSession()方法来获得sqlSession

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

5(创建实体类),然后添加一个子项目,里面创建一个pojo实体类，实体类里面写一个class类User，User里面定义的参数于数据库里面的参数一致。重写他的get，set方法toString方法以及无参有参的构造方法。
6(编写Mapper接口类),:创建com.chen.dao包，包里面添加一个UserDao接口，接口里面写Lsit<>集合,<>里面的参数就是实体类(因为这个接口就是操作数据库对象的实体),List后面跟一个方法getUserList()
7(编写UserMapper.xml文件中的内容),

<?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">
<!--namespace:绑定一个对应的UsaerDao、UserMapper接口-->
<mapper namespace="com.chen.dao.UserDao">
<!--id相当于UserDao接口中方法的名字-->
<!-- resultType返回结果类型局势UserDao接口中的List<User>(里面就一个User-->
   <select id="getUserList" resultType="com.chen.pojo.User">
       select * from mybatis.user
   </select>
</mapper>

8,test测试类里面的内容

import com.chen.dao.UserDao;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
import pojo.User;
import utils.MybatisUtils;

import java.util.List;

public class MyTest {
    @Test
    public void run(){
//        获得Sqlsession对象
        SqlSession sqlSession = MybatisUtils.getSqlSession();
       
//        执行sql
        UserDao userdao = sqlSession.getMapper(UserDao.class);
   
        List<User> userList = userdao.getUserList();
        for (User user : userList) {
            System.out.println(user);
        }


    }
}