Hello MyBatis !

 1.导包  2.编写配置文件  3.编写实体类  4.编写实体类对应的Mapper接口和Mapper.XML文件  5.测试

 

 导入依赖

<?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>org.example</groupId>
    <artifactId>Mybatis_Study</artifactId>
    <packaging>pom</packaging>
    <version>1.0-SNAPSHOT</version>
    <modules>
        <module>mybatis_01</module>
    </modules>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
    </properties>

    <dependencies>
        <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.3</version>
        </dependency>

        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.47</version>
        </dependency>



    </dependencies>


</project>

配置环境(设置与数据库连接的一些条件)

<?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">
<!--核心配置文件-->
<configuration>

    <environments default="development">
<!--        可以配置多个环境-->
        <environment id="development">
<!--            JDBC的事务管理-->
            <transactionManager type="JDBC"/>

            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=false&amp;useUnicode=true&amp;characterEncoding=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="my7shig69l>A"/>
            </dataSource>
        </environment>
    </environments>
<!--    每一个mapper.xml都需要在mybatis核心配置文件中注册-->
    <mappers>
        <mapper resource="com/ljm/dao/UserMapper.xml"/>
    </mappers>

</configuration>

编写工具类(获取SqlSession对象,用来实现对数据库的操作)

import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class UserDao_test {
    @Test
    public void test(){
        //获得SqlSession对象
        SqlSession sqlSession=MybatisUtils.getSqlSession();
        //执行sql
        UserDao mapper=sqlSession.getMapper(UserDao.class);
        //com.ljm.dao.UserDao 需要去配置
        List<User> userList = mapper.getUserList();

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

        sqlSession.close();
    }
}

接口(公有操作,这里用来获取用户信息)

 

 用户类(的字段与数据库的对象字段相同?)

 

 Mapper.xml  (实现接口,取代以前的*lmp实现类)

<?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">
<!--命名控件  绑定一个对应的Mapper接口-->
<mapper namespace="com.ljm.dao.UserDao">
<!--    实现对应的接口方法-->
<!--    由原来的UserDaoImp转换为一个Mapper配置文件-->
<!--    id与方法名一致-->
    <select id="getUserList" resultType="com.ljm.pojo.User">
        select * from mybatis.user
    </select>


</mapper>

测试

import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class UserDao_test {
    @Test
    public void test(){
        //获得SqlSession对象
        SqlSession sqlSession=MybatisUtils.getSqlSession();
        //获取用来执行sql的mapper

//        获取方式一(推荐):
        UserDao mapper=sqlSession.getMapper(UserDao.class);
        //com.ljm.dao.UserDao 需要去配置
//        List<User> userList = mapper.getUserList();

//        方式二
        List<User> userList=sqlSession.selectList("com.ljm.dao.UserDao.getUserList");

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

        sqlSession.close();
    }
}

 官方建议(为了确保每次都能执行关闭操作，你应该把这个关闭操作放到 finally 块中)

import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class UserDao_test {
    @Test
    public void test(){
        //获得SqlSession对象
        SqlSession sqlSession = null;
        //获取用来执行sql的mapper
        try {
            sqlSession=MybatisUtils.getSqlSession();
            //        获取方式一(推荐):
            UserDao mapper=sqlSession.getMapper(UserDao.class);
            List<User> userList = mapper.getUserList();

//        方式二
//            List<User> userList=sqlSession.selectList("com.ljm.dao.UserDao.getUserList");
            for(User user:userList){
                System.out.println(user);
            }
        } finally {
            sqlSession.close();
        }
    }
}

 

可能遇到的问题

 [静态资源过滤]   解决方法  pom.xml中添加

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