1.MyBatis概述

1.1 ORM框架

对象关系映射（Java中的对象 对应 数据库中的表）

1.2 官网地址

mybatis

1.3 MyBatis Plus

MyBatis-Plus (baomidou.com)官网

1.4 JPA

Java 持久层API

2. MAVEN引入

2.1 配置maven

2.2 导入MyBatis

<dependency><groupId>org.mybatis</groupId><artifactId>mybatis</artifactId><version>3.5.13</version>
</dependency>

2.3 MySQL driver

<dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>8.0.32</version>
</dependency>

2.4 建立目录com/itheima/mapper

2.4.1 创建mapper接口和xml文件

note：因为此时为入门所以放在一块后续则不然

2.5 配置resources

2.5.1 配置db.properties

db.driver=com.mysql.cj.jdbc.Driver
db.url=jdbc:mysql:/db（数据库名）
db.username=//自己的用户名
db.password=//密码

2.5.2 src/main/resocurces文件夹下创建mybatis-config.xml/mybatis-conf.xml

建议直接复制 需要注意 里面的映射关系需要修改

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configurationPUBLIC "-//mybatis.org//DTD Config 3.0//EN""https://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration><properties resource="db.properties"/><environments default="development"><environment id="development"><transactionManager type="JDBC"/><dataSource type="POOLED"><property name="driver" value="${db.driver}"/><property name="url" value="${db.url}"/><property name="username" value="${db.username}"/><property name="password" value="${db.password}"/></dataSource></environment></environments><mappers><package name="com/itheima/mapper"/></mappers>
</configuration>

2.5.3 日志文件log4j2

（1）导入依赖

<dependency><groupId>org.apache.logging.log4j</groupId><artifactId>log4j-core</artifactId><version>2.20.0</version>
</dependency>

（2）配置log4j2.xml文件

note：这里我的包名为com 也就是src/main/java/com 如果是别的需要修改对应的名字下方会有标注

log4j2.xml文件

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="WARN"><Appenders><Console name="LogToConsole" target="SYSTEM_OUT"><PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/></Console><File name="LogToFile" fileName="log/test.log"><PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/></File></Appenders><Loggers><!--  注意包名 这里为com      --><Logger name="com" level="error"><AppenderRef ref="LogToConsole"/></Logger><!--  level 自己查 默认为error      --><Logger name="com" level="debug" additivity="false"><!--    分别为打印再控制台和log.txt文件中        --><AppenderRef ref="LogToConsole"/><AppenderRef ref="LogToFile"/></Logger><!--  全局配置文件 无论哪有错误都会输出再控制台     --><Root level="error"><AppenderRef ref="LogToConsole"/></Root></Loggers>
</Configuration>

整体项目结构如图（log4j2.xml 为日志文件）

2.6 编写XxxMapper和XxxMapper.xml

2.6.1 映射编写sql

Xxmapper

public interface DbMapper {
String selectversion();
}
Xxmapper.xml

<?xml version="1.0" encoding="UTF-8" ?> select version(); 2.6.2 注解形式 @Select("show databases ") List dbs(); 两种方式都可正常运行

2.6.3 注意事项

因为xml文件和mapper接口在java包下系统不会自动编译其下的xml文件需要pom.xml文件中添加buder

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

因为添加之后resources文件也有可能不会自动编译建议加上

是否编译可以看一下打包后的target/classes文件夹下是否有这个xml文件

2.7 编写测试代码

在test目录下编写测试代码 这一种需要配置mybatis-conf.xml文件链接数据库

public class Demo {public static void main(String[] args) {try (InputStream is = Resources.getResourceAsStream("mybatis-conf.xml")) {//建立会话工厂SqlSessionFactory build = new SqlSessionFactoryBuilder().build(is);SqlSession sqlSession = build.openSession();DbMapper mapper = sqlSession.getMapper(DbMapper.class);Book book = new Book();book.setPrice(10.0D);book.setNumber(15);book.setBname("《斗feng大陆》");book.setCratedate(LocalDateTime.now());System.out.println(mapper.add(book));sqlSession.commit();System.out.println(mapper.selectAll());System.out.println(mapper.selectversion());System.out.println(mapper.dbs());} catch (Exception e) {e.printStackTrace();}}
}

也可以直接在代码中链接数据库 但是大部分时间基本不用

public class Deno {public static void main(String[] args) {PooledDataSource ds = new PooledDataSource("com.mysql.cj.jdbc.Driver","jdbc:mysql://localhost:3306/mybatis","root","");TransactionFactory ts = new JdbcTransactionFactory();Environment env = new Environment("dev",ts,ds);Configuration cfg = new Configuration(env);cfg.addMapper(DbMapper.class);SqlSessionFactory sf = new SqlSessionFactoryBuilder().build(cfg);SqlSession ss = sf.openSession();DbMapper mapper = ss.getMapper(DbMapper.class);System.out.println(mapper.selectversion());System.out.println(mapper.dbs());System.out.println(mapper.selectAll());}
}

2.8 结果

……………………………………day01…………………………………………