1. 简介
![](https://img.laitimes.com/img/__Qf2AjLwojIjJCLyojI0JCLiAzNfRHLGZkRGZkRfJ3bs92YsYTMfVmepNHL4lkeNJTV65EMjpmTzJlMMBjVtJWd0ckW65UbM5WOHJWa5kHT20ESjBjUIF2X0hXZ0xCMx81dvRWYoNHLrdEZwZ1Rh5WNXp1bwNjW1ZUba9VZwlHdssmch1mclRXY39CXldWYtlWPzNXZj9mcw1ycz9WL49zZuBnL0MTOxEjNzQTM4ITNwkTMwIzLc52YucWbp5GZzNmLn9Gbi1yZtl2Lc9CX6MHc0RHaiojIsJye.png)
- 表现层:展示数据
- 业务层:处理业务需求
- 持久层:与数据库交互
mybatis官方地址:http://www.mybatis.org/mybatis-3/zh/getting-started.html
- mybatis是一个持久层框架,封装了jdbc的细节,使我们只需关注sql语句本身,而无需关注注册驱动、创建连接等繁杂的过程。它使用了ORM思想
- ORM(object relational mapping):对象关系映射。就是把数据库和实体类及实体类的属性对应起来,让我们可以操作实体类就实现操作数据库表
2. 配置一个简单案例的流程
整体结构如下:
① 创建maven工程,配置pom文件
<packaging>jar</packaging>
<dependencies>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.4.5</version>
</dependency>
<!--mybatis和数据库交互,所以需要有mysql的依赖-->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<!--勿用5.1.6-->
<!--<version>8.0.16</version>-->
<version>5.1.46</version>
</dependency>
<!--日志-->
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.12</version>
</dependency>
<!--单元测试-->
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
</dependency>
</dependencies>
② 创建实体类(User)
public class User {
private Integer id;
private String username;
private Date birthday;
private String sex;
private String address;
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 Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
@Override
public String toString() {
return "com.itheima.domain.User{" +
"id=" + id +
", username='" + username + '\'' +
", birthday=" + birthday +
", sex='" + sex + '\'' +
", address='" + address + '\'' +
'}';
}
}
③ 创建用户的持久层接口(IUserDao)
public interface IUserDao {
//查询所有操作
List<User> findAll();
}
④ 配置mybatis的主配置文件 (SqlMapConfig.xml)
<?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">
<!--mybatis的主配置文件-->
<configuration>
<!--配置环境-->
<environments default="mysql">
<!--配置数据库环境-->
<environment id="mysql">
<!--配置事务类型JDBC-->
<transactionManager type="JDBC"></transactionManager>
<!--配置连接池-->
<dataSource type="POOLED">
<!--配置连接数据库的4个基本信息-->
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://172.20.10.13:3306/dl?useSSL=false&useUnicode=true&characterEncoding=UTF-8"/>
<property name="username" value="root"/>
<property name="password" value="11250825"/>
</dataSource>
</environment>
</environments>
<!--指定映射配置文件的位置,映射配置文件指的是每个dao独立的配置文件-->
<mappers>
<mapper resource="com/itheima/dao/IUserDao.xml"/>
</mappers>
</configuration>
mybatis的映射配置文件(IUserDao.xml)的位置必须和dao接口的包结构类似
⑤ 配置每个dao独立的配置文件,即映射配置文件(IUserDao.xml)
<?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表示方法findAll在哪个dao实现接口-->
<mapper namespace="com.itheima.dao.IUserDao">
<!--配置查询所有-->
<!--resultType表示要封装到哪里去-->
<select id="findAll" resultType="com.itheima.domain.User">
select * from user
</select>
</mapper>
namespace表示方法findAll在哪个dao实现接口。
resultType表示要封装到哪里去。
映射配置文件的mapper标签里namespace属性的取值必须是dao接口的全限定类名
映射配置文件的操作配置(select等),id属性的取值必须是dao接口的方法名
遵从上面黄色底线的三点后,在开发中就无须再写dao的实现类了。
在映射配置文件(IUserDao.xml)中,需告知mybatis要封装到哪个实体类中。配置的方式是指定实体类的全限定类名。
⑥ 在resources中导入log4j.properties文件
# Set root category priority to INFO and its only appender to CONSOLE.
#log4j.rootCategory=INFO, CONSOLE debug info warn error fatal
log4j.rootCategory=debug, CONSOLE, LOGFILE
# Set the enterprise logger category to FATAL and its only appender to CONSOLE.
log4j.logger.org.apache.axis.enterprise=FATAL, CONSOLE
# CONSOLE is set to be a ConsoleAppender using a PatternLayout.
log4j.appender.CONSOLE=org.apache.log4j.ConsoleAppender
log4j.appender.CONSOLE.layout=org.apache.log4j.PatternLayout
log4j.appender.CONSOLE.layout.ConversionPattern=%d{ISO8601} %-6r [%15.15t] %-5p %30.30c %x - %m\n
# LOGFILE is set to be a File appender using a PatternLayout.
log4j.appender.LOGFILE=org.apache.log4j.FileAppender
log4j.appender.LOGFILE.File=d:\axis.log
log4j.appender.LOGFILE.Append=true
log4j.appender.LOGFILE.layout=org.apache.log4j.PatternLayout
log4j.appender.LOGFILE.layout.ConversionPattern=%d{ISO8601} %-6r [%15.15t] %-5p %30.30c %x - %m\n
⑦ 在test - java 中创建测试类(MybatisTest)
/**
* Mybatis 入门案例
*/
public class MybatisTest {
public static void main(String[] args) throws IOException {
//1.读取配置文件
InputStream in = Resources.getResourceAsStream("SqlMapConfig.xml");
//2.创建SqlSessionFactory工厂
SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
SqlSessionFactory factory = builder.build(in);
//3.使用工厂生产SqlSession对象
SqlSession session = factory.openSession();
//4.创建Dao接口的代理对象(动态代理)
IUserDao userDao = session.getMapper(IUserDao.class);
//5.使用代理对象执行方法
List<User> users = userDao.findAll();
for (User user : users) {
System.out.println(user);
}
//6.释放资源
session.close();
in.close();
}
}
上面程序的含义:
⑧ 配置mysql
CREATE TABLE `user` (
`id` int(11) NOT NULL auto_increment,
`username` varchar(32) NOT NULL COMMENT '用户名称',
`birthday` datetime default NULL COMMENT '生日',
`sex` char(1) default NULL COMMENT '性别',
`address` varchar(256) default NULL COMMENT '地址',
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
insert into `user`(`id`,`username`,`birthday`,`sex`,`address`) values (41,'老王','2018-02-27 17:47:08','男','北京'),(42,'小二王','2018-03-02 15:09:37','女','北京金燕龙'),(43,'小二王','2018-03-04 11:34:34','女','北京金燕龙'),(45,'传智播客','2018-03-04 12:04:06','男','北京金燕龙'),(46,'老王','2018-03-07 17:37:26','男','北京'),(48,'小马宝莉','2018-03-08 11:44:00','女','北京修正');