mybatis详细教程

文章目录

@[toc]
1. 概述
1.1 什么是Mybatis?
1.2 Mybatis 操作数据库的方式
1.3 Mybatis 操作数据库的七大步骤?
1.4 Mybatis 的开发优点

2. Mybatis 操作数据库具体实现
2.1 创建一个数据库表
2.2 创建一个maven项目,配置pom.xml文件,导入相关依赖
2.3 创建mybatis 核心配置文件
2.4 创建与数据库对应的实体类
2.5 创建数据操作持久层接口
2.5-1 补充创建数据操作持久层接口实现配置文件`UserMapper.xml`
2.6 创建测试类,测试
2.7 基于注解开发修改
2.6 创建测试类,测试基于注解的mybatis开发

运行结果

1. 概述

1.1 什么是Mybatis?

Mybatis 是一个优秀的持久层框架,是对JDBC操作数据库的过程进行了封装.

1.2 Mybatis 操作数据库的方式

可以通过xml文件的方式执行sql;
可以通过注解的方式执行SQL;

1.3 Mybatis 操作数据库的七大步骤?

SQLSession 传递SQL骨架给MappedStatement
由MappedStatement 结合骨架和SQL参数映射成完整的SQL语句
将完整的SQL语句交给Executer
执行SQL语句
返回结果集给MappedStatement
封装结果集
将结果集返回给SQLSession

1.4 Mybatis 的开发优点

简化了JDBC代码
支持连接池,提高程序执行效率
Mybatis 是将SQL配置在mapper文件中,修改SQL不需要重新编译
将返回结果ResultSet自动封装成java对象

2. Mybatis 操作数据库具体实现

项目结构

2.1 创建一个数据库表

create database mytest;
DROP TABLE IF EXISTS `user`;
CREATE TABLE `user`  (`id` int(11) NOT NULL AUTO_INCREMENT,`NAME` varchar(20) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL DEFAULT '匿名',`age` int(11) NOT NULL,`sex` varchar(1) CHARACTER SET utf8 COLLATE utf8_unicode_ci NULL DEFAULT '男',`address` varchar(100) CHARACTER SET utf8 COLLATE utf8_unicode_ci NULL DEFAULT NULL,`email` varchar(20) CHARACTER SET utf8 COLLATE utf8_unicode_ci NULL DEFAULT NULL,PRIMARY KEY (`id`) USING BTREE,UNIQUE INDEX `email`(`email`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 1 CHARACTER SET = utf8 COLLATE = utf8_unicode_ci ROW_FORMAT = Dynamic;-- ----------------------------
-- Records of user
-- ----------------------------
INSERT INTO `user` VALUES (1, '匿名', 11, '男', '1111', '11111');

在这里插入图片描述

2.2 创建一个maven项目,配置pom.xml文件,导入相关依赖

在这里插入图片描述

<?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.it</groupId><artifactId>mybatis_lean</artifactId><version>1.0-SNAPSHOT</version><properties><maven.compiler.source>8</maven.compiler.source><maven.compiler.target>8</maven.compiler.target></properties><dependencies><dependency><groupId>org.mybatis</groupId><artifactId>mybatis</artifactId><version>3.5.5</version></dependency>
<!--        连接mysql数据库驱动,这里是8.0以上版本--><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>8.0.26</version></dependency><!-- 日志 --><dependency><groupId>org.slf4j</groupId><artifactId>slf4j-log4j12</artifactId><version>1.7.30</version></dependency></dependencies></project>

2.3 创建mybatis 核心配置文件

jdbc.properties文件,描述连接数据库的属性

jdbc.driver = com.mysql.cj.jdbc.Driver
jdbc.url = jdbc:mysql://localhost:3306/mytest
jdbc.username = root
jdbc.password = 123456

mybatis-config.xml , mybatis 核心配置文件

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configurationPUBLIC "-//mybatis.org//DTD Config 3.0//EN""http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<!--    导入jdbc配置资源--><properties resource="jdbc.properties"/><settings><setting name="mapUnderscoreToCamelCase" value="true"/><!-- 开启log4j来记录日志 --><setting name="logImpl" value="STDOUT_LOGGING"/></settings><environments default="test"><environment id="test">
<!--            使用jdbc管理事务  , MANAGER 是使用mybatis管理事务--><transactionManager type="JDBC"></transactionManager>
<!--开启连接池  ,   UNPOOLED 不开启--><dataSource type="POOLED"><property name="driver" value="${jdbc.driver}"/><property name="url" value="${jdbc.url}"/><property name="username" value="${jdbc.username}"/><property name="password" value="${jdbc.password}"/></dataSource></environment></environments>
<!--    加载映射文件 ,加载mapper文件夹下所有--><mappers><mapper resource="mapper/UserMapper.xml"></mapper></mappers>
</configuration>

注意：如果mapper/*.xml 报错，把*改成具体的mapper.xml文件名称，具体原因尚未明确

2.4 创建与数据库对应的实体类

package com.it.pojo;public class User {private long id;private String name;private int age;private String sex;private String address;private String email;public User(long id, String name, int age, String sex, String address, String email) {this.id = id;this.name = name;this.age = age;this.sex = sex;this.address = address;this.email = email;}public User() {}public long getId() {return id;}public void setId(long id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}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;}public String getEmail() {return email;}public void setEmail(String email) {this.email = email;}@Overridepublic String toString() {return "User{" +"id=" + id +", name='" + name + '\'' +", age=" + age +", sex='" + sex + '\'' +", address='" + address + '\'' +", email='" + email + '\'' +'}';}
}

2.5 创建数据操作持久层接口

package com.it.dao;import com.it.pojo.User;
import java.util.Collection;
@Mapper
public interface UserDao {Collection<User> findAll();User findById(long id);void save(User user);void update(User user);void delete(long id);
}

2.5-1 补充创建数据操作持久层接口实现配置文件`UserMapper.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" >
<mapper namespace="com.it.dao.UserDao"><select id="findAll" resultType="com.it.pojo.User">select * from user</select><select id="findById" resultType="com.it.pojo.User">select * from user where id = #{id}</select><insert id="save">insert into user value(#{id},#{name},#{age},#{sex},#{address},#{email})</insert><update id="update">update user set name = #{name} where id = #{id}</update><delete id="delete">delete from user where id = #{id}</delete>
</mapper>

2.6 创建测试类,测试

package com.it.test;import com.it.dao.UserDao;
import com.it.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.util.Collection;public class Test01 {static SqlSessionFactoryBuilder builder  =new SqlSessionFactoryBuilder();static  UserDao userDao;public static void findAll(){Collection<User> all = userDao.findAll();System.out.println("查询所有结果");System.out.println("---------------------------------");for (User user:all){System.out.println(user.toString());}}public static void findById(){User user = userDao.findById(1);System.out.println("查询所有结果");System.out.println("---------------------------------");System.out.println(user.toString());}public static void save(){User user = new User(3,"ls",22,"男","llll.","000000");userDao.save(user);System.out.println("新增数据"+user.toString()+"成功");}public static void update(){User user = new User(2,"zhangs",22,null,"","");userDao.update(user);System.out.println("修改数据"+user.toString()+"成功");}public static void delete(){userDao.delete(2);System.out.println("删除成功");}public static void main(String[] args) {SqlSession session=null;SqlSessionFactory factory = null;try {factory = builder.build(Resources.getResourceAsStream("mybatis-config.xml"));session = factory.openSession();userDao = session.getMapper(UserDao.class);System.out.println("============================");findAll();System.out.println("============================");findById();System.out.println("============================");save();findAll();System.out.println("============================");update();findAll();System.out.println("============================");delete();findAll();} catch (IOException e) {e.printStackTrace();}finally {if (session!=null){session.commit();session.close();}}}
}

2.7 基于注解开发修改

修改dao层的代码,创建数据操作接口

package com.it.dao;import com.it.pojo.User;
import org.apache.ibatis.annotations.Delete;
import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.annotations.Update;import java.util.Collection;/*** 使用注解执行sql* @author ZRY* @version 1.0*/
public interface UserDao1 {@Select("select * from user")Collection<User> findAll();@Select("select * from user where id = #{id}")User findById(long id);@Insert("insert into user value(#{id},#{name},#{age},#{sex},#{address},#{email})")void save(User user);@Update(" update user set name = #{name}  where id=#{id}")void update(User user);@Delete("delete from user where id=#{id}")void delete(long id);
}

修改核心配置文件,mybatis-config.xml
新增 <mapper class="com.it.dao.UserDao1"/>

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configurationPUBLIC "-//mybatis.org//DTD Config 3.0//EN""http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<!--    导入jdbc配置资源--><properties resource="jdbc.properties"/><environments default="test"><environment id="test">
<!--            使用jdbc管理事务  , MANAGER 是使用mybatis管理事务--><transactionManager type="JDBC"></transactionManager>
<!--开启连接池  ,   UNPOOLED 不开启--><dataSource type="POOLED"><property name="dirver" value="${jdbc.driver}"/><property name="url" value="${jdbc.url}"/><property name="username" value="${jdbc.username}"/><property name="password" value="${jdbc.password}"/></dataSource></environment></environments>
<!--    加载映射文件 ,加载mapper文件夹下所有--><mappers><!--        基于xml配置文件的--><mapper resource="mapper/UserMapper.xml"></mapper>
<!--        基于注解的,需要绑定类--><mapper class="com.it.dao.UserDao1"/></mappers>
</configuration>

2.6 创建测试类,测试基于注解的mybatis开发

package com.it.test;import com.it.dao.UserDao;
import com.it.dao.UserDao1;
import com.it.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.util.Collection;public class Test02 {static SqlSessionFactoryBuilder builder  =new SqlSessionFactoryBuilder();static UserDao1 userDao1;public static void findAll(){Collection<User> all = userDao1.findAll();System.out.println("查询所有结果");System.out.println("---------------------------------");for (User user:all){System.out.println(user.toString());}}public static void findById(){User user = userDao1.findById(1);System.out.println("查询所有结果");System.out.println("---------------------------------");System.out.println(user.toString());}public static void save(){User user = new User(2,"ls",22,"男","llll","");userDao1.save(user);System.out.println("新增数据"+user.toString()+"成功");}public static void update(){User user = new User(3,"zhangs",22,null,"","");userDao1.update(user);System.out.println("修改数据"+user.toString()+"成功");}public static void delete(){userDao1.delete(2);System.out.println("删除成功");}public static void main(String[] args) {SqlSession session=null;SqlSessionFactory factory = null;try {factory = builder.build(Resources.getResourceAsStream("mybatis-config.xml"));session = factory.openSession();userDao1 = session.getMapper(UserDao1.class);System.out.println("============================");findAll();System.out.println("============================");findById();System.out.println("============================");save();findAll();System.out.println("============================");update();findAll();System.out.println("============================");delete();findAll();} catch (IOException e) {e.printStackTrace();}finally {if (session!=null){session.commit();session.close();}}}
}