JavaEE之Mybatis简单应用

JavaEE之Mybatis简单应用

• ​​创建Maven项目​​
• ​​Mybatis环境搭建​​
• ​​MyBatis具体步骤​​

• ​​创建数据库和数据表​​
• ​​定义实体类User​​
• ​​定义DAO接口​​
• ​​编写Mapper.xml​​
• ​​注册Mapper​​
• ​​测试代码​​

创建Maven项目

Mybatis环境搭建

pom.xml中引入MyBatis核心依赖

<!--依赖-->
    <dependencies>
        <!--MyBatis核心依赖-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.6</version>
        </dependency>

        <!--MySql驱动依赖-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.15</version>
        </dependency>
    </dependencies>

在resources中，创建MyBatis配置文件

配置文件，内容如下

<?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配置-->
<configuration>
    <!--JDBC环境配置、选中默认环境-->
    <environments default="edu_config">
        <!--MySql数据库环境配置-->
        <environment id="edu_config">
            <!--事务管理-->
            <transactionManager type="jdbc"></transactionManager>
            <!--连接池-->
            <dataSource type="org.apache.ibatis.datasource.pooled.PooledDataSourceFactory">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <!-- &转义& -->
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis_edu?useUnicode=true&characterEncoding=utf-8"/>
                <property name="username" value="****"/>
                <property name="password" value="****"/>
            </dataSource>
        </environment>
    </environments>

    <!--Mapper注册-->
    <mappers>
        <!--注册Mapper文件的所在位置-->
        <mapper resource="UserDAOMapper.xml"/>
    </mappers>
</configuration>

MyBatis具体步骤

创建数据库和数据表

console内容如下

create database mybatis_edu default charset =utf8;

create table t_user(
                       id int primary key auto_increment,
                       username varchar(50),
                       password varchar(50),
                       gender tinyint,
                       regist_time datetime
)default charset =utf8

自己添加一点数据，方便最后测试

定义实体类User

package com.edu.entity;

import java.util.Date;

public class User{
    private Integer id;
    private String username;
    private String password;
    private Boolean gender;
    private Date registTime;

    public User(){}
    public User(Integer id, String username, String password, Boolean gender, Date registTime) {
        this.id = id;
        this.username = username;
        this.password = password;
        this.gender = gender;
        this.registTime = registTime;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                ", gender=" + gender +
                ", registTime=" + registTime +
                '}';
    }

    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 Boolean getGender() {
        return gender;
    }

    public void setGender(Boolean gender) {
        this.gender = gender;
    }

    public Date getRegistTime() {
        return registTime;
    }

    public void setRegistTime(Date registTime) {
        this.registTime = registTime;
    }
}

定义DAO接口

package com.edu.dao;

import com.edu.entity.User;

public interface UserDAO {
    User queryUserByID(Integer id);
}

编写Mapper.xml

在resources目录中，创建UserDaoMapper.xml文件

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapperg 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<!--namespace = 所需实现的接口全限定名-->
<mapper namespace="com.edu.dao.UserDAO">
    <!--id = 所需重写的接口抽象方法，resultType = 查询后所需返回的对象类型-->
    <select id="queryUserByID" resultType="com.edu.entity.User">
        select id,username,password,gender,regist_time
        from t_user
        <!--#{arg0} = 方法的第一个形参-->
        where id=#{arg0}
    </select>
</mapper>

注册Mapper

<!--Mapper注册-->
    <mappers>
        <!--注册Mapper文件的所在位置-->
        <mapper resource="UserDAOMapper.xml"/>
    </mappers>

测试代码

import com.edu.dao.UserDAO;
import com.edu.entity.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.io.InputStream;

public class MybatisTest {
    public static void main(String[] args) throws IOException {

        //1.获得读取MyBatis配置文件的流对象
        InputStream inputStream = Resources.getResourceAsStream("mybatis-config.xml");

        //2.构建sqlSessionfactory
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        //3.通过sqlsessionFactory创建sqlSession
        SqlSession sqlSession =sqlSessionFactory.openSession();
        //4。通过sqlsession获得DAO实现类的对象
        //UserDAO mapper = sqlSession.getMapper(UserDAO.class);//获取UserDAO对应的实现类的对象
        UserDAO mapper =sqlSession.getMapper(UserDAO.class);

        //5.测试查询方法是否好用
        User user1 = mapper.queryUserByID(1);
        User user2 = mapper.queryUserByID(2);

        System.out.println(user1);
        System.out.println(user2);
    }
}