MyBatis:
一款优秀的持久层框架，用于简化JDBC开发
MyBatis是Apache的一个开源项目iBatis，2010年此项目由apache software foundation迁移到google code，
并更名MyBatis。2013年11月迁移到Github
官网：https://mybatis.org/mybatis-3/zh/index.html
Mybatis使用前在官网复制入门的配置文件到pom.xml导入依赖坐标
持久层：
负责将数据保存到数据库的那层代码；
JavaEE三层架构：表现层、业务层、持久层
框架：
框架是一个半成品软件，是一套可重用的、通用的、软件基础代码模型；
在框架的基础上构建软件编写更高效、规范、通用、可扩展
JDBC缺点：硬编码(获取驱动，获取连接，sql语句)；操作繁琐
查询User表：
建立user表：
drop TABLE if exists tb_user;
CREATE TABLE tb_user(
id INT primary key auto_increment,
username VARCHAR(20),
PASSWORD VARCHAR(20),
gender char(1),
addr varchar(30)
);
INSERT INTO tb_user(username,password,gender,addr)
VALUES
('张三丰','taijizongshi','男','懿州'),
('李白','qinglianjianxian','男','青莲乡'),
('武则天','dazhounvdi','女','长安'),
('白起','wuanjun','男','郿');
创建模块，导入坐标：
File->project structure->+->new module->maven->更改名字->apply->ok
在pom文件中添加：
<dependencies>
<!--mybatis依赖-->
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.5</version>
</dependency>
<!--MySQL驱动-->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.16</version>
</dependency>
<!--junit单元测试-->
<dependency>
<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>1.7.7</version>
</dependency>
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-core</artifactId>
<version>1.1.7</version>
</dependency>
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-access</artifactId>
<version>1.1.7</version>
</dependency>
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-classic</artifactId>
<version>1.1.7</version>
</dependency>
</dependencies>
然后刷新
新建logback.xml;mybatis-config.xml;UserMapper.xml,依次是：
①
<?xml version="1.0" encoding="UTF-8"?>
<!-- 配置文件修改时重新加载，默认true -->
<configuration scan="true">
<!--定义日志文件的存储地址 勿在 LogBack 的配置中使用相对路径-->
<property name="CATALINA_BASE" value="**/logs"></property>
<!-- 控制台输出 -->
<appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">
<encoder charset="UTF-8">
<!-- 输出日志记录格式 -->
<pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern>
</encoder>
</appender>
<!-- 第一个文件输出,每天产生一个文件 -->
<appender name="FILE1" class="ch.qos.logback.core.rolling.RollingFileAppender">
<rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
<!-- 输出文件路径+文件名 -->
<fileNamePattern>${CATALINA_BASE}/aa.%d{yyyyMMdd}.log</fileNamePattern>
<!-- 保存30天的日志 -->
<maxHistory>30</maxHistory>
</rollingPolicy>
<encoder charset="UTF-8">
<!-- 输出日志记录格式 -->
<pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern>
</encoder>
</appender>
<!-- 第二个文件输出,每天产生一个文件 -->
<appender name="FILE2" class="ch.qos.logback.core.rolling.RollingFileAppender">
<file>${CATALINA_BASE}/bb.log</file>
<rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
<fileNamePattern>${CATALINA_BASE}/bb.%d{yyyyMMdd}.log</fileNamePattern>
<maxHistory>30</maxHistory>
</rollingPolicy>
<encoder charset="UTF-8">
<pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern>
</encoder>
</appender>
<appender name="CUSTOM" class="ch.qos.logback.core.rolling.RollingFileAppender">
<file>${CATALINA_BASE}/custom.log</file>
<rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
<!-- daily rollover -->
<fileNamePattern>${CATALINA_BASE}/custom.%d{yyyy-MM-dd}.log</fileNamePattern>
<!-- keep 30 days' worth of history -->
<maxHistory>30</maxHistory>
</rollingPolicy>
<encoder charset="UTF-8">
<pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern>
</encoder>
</appender>
<!-- 设置日志输出级别 -->
<root level="ERROR">
<appender-ref ref="CONSOLE" />
</root>
<logger name="file1" level="DEBUG">
<appender-ref ref="FILE1" />
</logger>
<logger name="file1" level="INFO">
<appender-ref ref="FILE2" />
</logger>
<!-- 自定义logger -->
<logger name="custom" level="INFO">
<appender-ref ref="CUSTOM" />
</logger>
</configuration>
②
<?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">
<!--数据库连接信息-->
<property name="driver" value="com.mysql.cj.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://127.0.0.1:3306/mybatis?useSLL=false"/>
<property name="username" value="root"/>
<property name="password" value="123456"/>
</dataSource>
</environment>
</environments>
<mappers>
<!--加载SQL映射文件-->
<mapper resource="UserMapper.xml"/>
</mappers>
</configuration>
③
<?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:名称空间-->
<mapper namespace="test">
<select id="selectAll" resultType="pojo.User">
select * from tb_user;
</select>
</mapper>
定义User类：
package pojo;
public class User {
private Integer id;
private String username;
private String PASSWORD;
private String gender;
private String addr;
@Override
public String toString() {
return "User{" +
"id=" + id +
", username='" + username + '\'' +
", PASSWORD='" + PASSWORD + '\'' +
", gender='" + gender + '\'' +
", addr='" + addr + '\'' +
'}';
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPASSWORD() {
return PASSWORD;
}
public void setPASSWORD(String PASSWORD) {
this.PASSWORD = PASSWORD;
}
public String getGender() {
return gender;
}
public void setGender(String gender) {
this.gender = gender;
}
public String getAddr() {
return addr;
}
public void setAddr(String addr) {
this.addr = addr;
}
}
获取连接，执行sql语句：
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 pojo.User;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
public class MybatisDemo {
public static void main(String[] args) throws IOException {
//加载mybatis的核心配置文件,获取sqlSessionFactory
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
//获取sqlSession对象用它执行sql
SqlSession sqlSession = sqlSessionFactory.openSession();
//执行sql
List<User> users = sqlSession.selectList("test.selectAll");
System.out.println(users);
sqlSession.close();
}
}
值得注意mysql8.0版本以上的时区问题：
在MySQL中执行下列操作:
set global time_zone = '+8:00'; ##修改mysql全局时区为北京时间，即我们所在的东8区
set time_zone = '+8:00'; ##修改当前会话时区
flush privileges; #立即生效
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