Mybatis入门案例

打开idea，create new project，选择maven工程，不选模板，点击Next

如图:

接着创建数据库

CREATE DATABASE eesy;

use eesy;

DROP TABLE IF EXISTS `user`;

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');


DROP TABLE IF EXISTS `account`;

CREATE TABLE `account` (
  `ID` int(11) NOT NULL COMMENT '编号',
  `UID` int(11) default NULL COMMENT '用户编号',
  `MONEY` double default NULL COMMENT '金额',
  PRIMARY KEY  (`ID`),
  KEY `FK_Reference_8` (`UID`),
  CONSTRAINT `FK_Reference_8` FOREIGN KEY (`UID`) REFERENCES `user` (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

insert  into `account`(`ID`,`UID`,`MONEY`) values (1,41,1000),(2,45,1000),(3,41,2000);

DROP TABLE IF EXISTS `role`;

CREATE TABLE `role` (
  `ID` int(11) NOT NULL COMMENT '编号',
  `ROLE_NAME` varchar(30) default NULL COMMENT '角色名称',
  `ROLE_DESC` varchar(60) default NULL COMMENT '角色描述',
  PRIMARY KEY  (`ID`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

insert  into `role`(`ID`,`ROLE_NAME`,`ROLE_DESC`) values (1,'院长','管理整个学院'),(2,'总裁','管理整个公司'),(3,'校长','管理整个学校');

DROP TABLE IF EXISTS `user_role`;

CREATE TABLE `user_role` (
  `UID` int(11) NOT NULL COMMENT '用户编号',
  `RID` int(11) NOT NULL COMMENT '角色编号',
  PRIMARY KEY  (`UID`,`RID`),
  KEY `FK_Reference_10` (`RID`),
  CONSTRAINT `FK_Reference_10` FOREIGN KEY (`RID`) REFERENCES `role` (`ID`),
  CONSTRAINT `FK_Reference_9` FOREIGN KEY (`UID`) REFERENCES `user` (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

insert  into `user_role`(`UID`,`RID`) values (41,1),(45,1),(41,2);

pom.xml 里添加打包方式 jar：<packaging>jar</packaging>

进入mybatis官网，点击 get started， pom.xml 里添加maven的坐标, 这里选择3.4.5

        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.5</version>
        </dependency>

由于我们操作的是mysql，所以还需要mysql的驱动

<!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.19</version>
        </dependency>

如果要打印日志，需要log4j

<!-- https://mvnrepository.com/artifact/log4j/log4j -->
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>

单元测试的话，还需要junit

        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.10</version>
        </dependency>

完整的pom.xml如下：

<?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.scott</groupId>
    <artifactId>day01_sc98k_mybatis</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>
    <dependencies>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.5</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.19</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/log4j/log4j -->
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.10</version>
        </dependency>
    </dependencies>
</project>

mytatis操作都是基于java实体类的，所以接下来创建java实体类:

ctr右键点击new class, 输入 com.scott.domain.User

package com.scott.domain;

import java.io.Serializable;
import java.util.Date;

/**
 * @ClassName: User
 * @description:
 * @date: 2020/6/17 5:26 PM
 * @author: Scott
 * @version: 1.0
 */
public class User implements Serializable {
    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 "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", birthday=" + birthday +
                ", sex='" + sex + '\'' +
                ", address='" + address + '\'' +
                '}';
    }
}

package com.scott.dao;

import com.scott.domain.User;

import java.util.List;

/**
 * @ClassName: UserDao
 * @description: 用户的持久层接口
 * @date: 2020/6/17 5:37 PM
 * @author: Scott
 * @version: 1.0
 */
public interface UserDao {
    /**
     * 查询所有操作
     * @return
     */
    List<User> findAll();
}

接下来在resources目录下创建matatis的配置文件, 名称可以随便取，这里取 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">
<configuration>
    <!--配置环境-->
    <environments default="development">
    <!-- 配置环境-->
        <environment id="development">
            <!--配置事务的类型-->
            <transactionManager type="JDBC"/>
            <!--配置数据源（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://localhost:3306/eesy"/>
                <property name="username" value="root"/>
                <property name="password" value="tanyun161019"/>
            </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/scott/dao/UserDao.xml"/>
    </mappers>
</configuration>

在对应目录下创建映射配置文件

<?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是dao的全限定类名-->
<mapper namespace="com.scott.dao.UserDao">
    <!--配置查询所有-->
    <!--id不能乱写，是接口的方法名-->
    <select id="findAll" resultType="com.scott.domain.User">
        select * from user
    </select>
</mapper>

总结：mybatis环境搭建分为四步

• 第一步：创建maven工程并导入坐标
• 第二步：创建实体类和dao的接口
• 第三步：创建Mybatis的主配置文件SqlMapConfig.xml
• 第四步: 创建映射配置文件 UserDao.xml