MyBatis基础 - 《MySQL》

mybatis
- 概述
- 利用MyBatis框架，从MySQL中查询所有的用户

mybatis

概述

MyBatis 是一款优秀的持久层框架，用于简化 JDBC 开发

案例

利用MyBatis框架，从MySQL中查询所有的用户

查询user表中所有数据

创建user表，添加数据
创建模块，导入坐标
编写用户实体类（User）
编写 MyBatis 核心配置文件复制资料里面的mybatis-config.xml到resources
创建UserMapper接口
编写 SQL 映射文件复制资料里面的UserMapper.xml到resources
加载核心配置文件，获取 SqlSessionFactory 对象
获取 SqlSession 对象，执行 SQL 语句
释放资源

<?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>com.GDKM</groupId>
    <artifactId>mybatis-day01-01-helloword</artifactId>
    <version>1.0-SNAPSHOT</version>
    <dependencies>
        <!--单元测试-->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
        <!--MySQL驱动-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.46</version>
        </dependency>
        <!--MyBatis核心包-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.5</version>
        </dependency>
        <!--MyBatis日志配置-->
        <!-- 添加slf4j日志api -->
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>1.7.20</version>
        </dependency>
        <!-- 添加logback-classic依赖 -->
        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-classic</artifactId>
            <version>1.2.3</version>
        </dependency>
        <!-- 添加logback-core依赖 -->
        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-core</artifactId>
            <version>1.2.3</version>
        </dependency>
    </dependencies>
</project>

import java.sql.Date;
public class User {
    private int id;
    private String username;
    private Date birthday;
    private String sex;
    private String address;
构造方法 set get toString方法
}

<?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>
    <settings>
        <setting name="logImpl" value="STDOUT_LOGGING"/>
    </settings>
    <!--配置所有别名-->
    <typeAliases>
        <!--typeAlias标签: 给一个实体类配置别名 type属性:包名.类名 alias属性:别名-->
        <!--<typeAlias type="com.gdkm.pojo.User" alias="User"/>-->
        <!--package标签:包扫描,扫描包中所有类取别名,别名就是类名
                name属性:包名-->
        <package name="com.gdkm.pojo"/>
    </typeAliases>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <!--配置连接池需要的参数-->
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/day18?useSSL=false"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <!--<mapper resource="UserMapper.xml"/>-->
        <!--package标签: 包扫描, 扫描包里面的接口和映射文件
            前提1: 接口名要和映射文件名字相同
            前提2: 编译后接口和映射文件要在同一个包中-->
        <package name="com.gdkm.mapper"/>
    </mappers>
</configuration>

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

<?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.gdkm.mapper.UserMapper">
    <select id="findAllUsers" resultType="User">
        SELECT * FROM USER;
    </select>
</mapper>

public class TestMybatis {
    @Test
    public void testHello() throws IOException {
        String resource = "mybatis-config.xml";
        //把文件变成流 import org.apache.ibatis.io.Resources
        InputStream inputStream = Resources.getResourceAsStream(resource);
        //解析xml文件 sqlSessionFactory相当于数据库连接池
        SqlSessionFactory sqlSessionFactory = 
            new SqlSessionFactoryBuilder().build(inputStream);
        //sqlSessionFactory.openSession()理解为从连接池中获取连接
        //sqlSession 表示数据库连接
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //给UserMapper接口生成一个实现类(代理对象)
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        //调用方法,执行对应的SQL语句,把结果封装成对象
        List<User> userList = mapper.findAllUsers();
        userList.forEach(System.out::println);
        sqlSession.close();
    }
}