mybatis 快速入门

1.pom.xml

<?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>

    <groupId>org.example</groupId>
    <artifactId>mybits-demo</artifactId>
    <version>1.0-SNAPSHOT</version>

    <dependencies>
<!--        mybatis 的依赖-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.5</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.46</version>
        </dependency>

        <dependency>
<!--            单元测试的-->
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.13.1</version>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>1.7.30</version>
        </dependency>

        <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>

2.

<?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">
<!--    根标签里面有
                    namespace：名称空间
                    resultType:返回结果的类型，一般来说是我自己定义的类。
                    select 中的id  是唯一标识，不能够重复。
    -->

<mapper namespace="test">
    <select id="selectAll" resultType="com.itheima.pojo.User">
    select * from tb_user;
  </select>
</mapper>

3.

<?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>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <!--数据库的连接信息-->
<!--                <property name="driver" value="${driver}"/>-->
<!--                <property name="url" value="${url}"/>-->
<!--                <property name="username" value="${username}"/>-->
<!--                <property name="password" value="${password}"/>-->

                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis"/>
                <property name="username" value="root"/>
                <property name="password" value="wgs"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
<!--        这个是sql映射文件的路径的。也是需要更改的-->
        <mapper resource="UserMapper.xml"/>
    </mappers>
</configuration>

4.logback

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
    <!--
        CONSOLE ：表示当前的日志信息是可以输出到控制台的。
    -->
    <appender name="Console" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <pattern>[%level] %blue(%d{HH:mm:ss.SSS}) %cyan([%thread]) %boldGreen(%logger{15}) - %msg %n</pattern>
        </encoder>
    </appender>

    <logger name="com.itheima" level="DEBUG" additivity="false">
        <appender-ref ref="Console"/>
    </logger>

    <root level="DEBUG">
        <appender-ref ref="Console"/>
    </root>
</configuration>

5.

package com.itheima;

import com.itheima.pojo.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 java.io.IOException;
import java.io.InputStream;
import java.util.List;

/**
 * mybatis  快速入门代码
 */

public class MybatisDemo {

    public static void main(String[] args) throws IOException {
        //1.加载Mybatis 的核心配置文件，获取  sqlSessionFactory,用来执行sql语句的。
        String resource = "mybatis-config.xml";//配置文件的路径，就是加载url 用户名和密码之类的。

        InputStream inputStream = Resources.getResourceAsStream(resource);
        //通过mybatis 提供的一个资源加载的类 Resources类 ，将字符串输入的进来，得到一个字节输入流。

        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        //然后得到一个sqlSessionFactory 对象。

        /**
         * 2.获取sqlSession 对象 ，用来执行sql 语句
         */

        SqlSession sqlSession = sqlSessionFactory.openSession();

        /**
         * 3.执行sql 语句
         *
         * test.selectAll :是  namespace.id
         */
        List<User> users = sqlSession.selectList("test.selectAll");
        System.out.println(users);

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