[Java知识库]Mybatis入门----狂神学习记录

Mybatis

环境搭建

1.建表

CREATE DATABASE MYBATIS;

USE MYBATIS;

CREATE TABLE user(
id INT(20) NOT NULL PRIMARY KEY,
name VARCHAR(30) DEFAULT NULL,
pwd VARCHAR(30) DEFAULT NULL
)ENGINE = INNODB DEFAULT CHARSET = utf8;

INSERT INTO user(id, name, pwd) VALUES 
(1, '辛巴', 123456),
(2, '张三', 138775),
(3, '李四', 175383);

2.pox.xml添加maven依赖

 <dependencies>
        <!--mysqlq驱动-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.12</version>
        </dependency>
        <!--mybatis-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.4</version>
        </dependency>
        <!--junit-->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <!-- 在build中配置resources，防止资源导出失败的问题 -->
    <build>
        <resources>
            <resource>
                <directory>src/main/resources</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
        </resources>
    </build>

搭建

1.resources下创建mybatis核心配置文件

mybatis-config.xml

<?xml version="1.0" encoding="UTF8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<!-- configuration核心配置文件 -->
<configuration>

    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=false&amp;useUnicode=true&amp;characterEncoding=UTF-8&amp;serverTimezone=UTC"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>

        <mappers>
            <mapper resource="com/liu/dao/UserMapper.xml"/>
        </mappers>

</configuration>

2.编写对应Sql表的实体类User

package com.liu.pojo;
public class User {

    //实体类
    private int id;
    private String name;
    private String pwd;

    public User() {
    }

    public User(int id, String name, String pwd) {
        this.id = id;
        this.name = name;
        this.pwd = pwd;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPwd() {
        return pwd;
    }

    public void setPwd(String pwd) {
        this.pwd = pwd;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", pwd='" + pwd + '\'' +
                '}';
    }
}

3.编写UserDao接口

package com.liu.dao;

import com.liu.pojo.User;

import java.util.List;

public interface UserDao {
    public List<User> getUserList();
}

4.编写UserMapper.xml

<?xml version="1.0" encoding="UTF8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<!-- namespace=绑定一个对应的Dao/Mapper接口 -->
<mapper namespace="com.liu.dao.UserDao">
    <!-- select查询语句 -->
    <select id="getUserList" resultType="com.liu.pojo.User">
        select * from mybatis.user;
    </select>
</mapper>

5.抽取工具类MybatisUtil

package com.liu.utils;

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 MybatisUtil {

    static SqlSessionFactory sqlSessionFactory = null;

    static {
        try {
            //使用Mybatis第一步 ：获取sqlSessionFactory对象
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    //既然有了 SqlSessionFactory，顾名思义，我们可以从中获得 SqlSession 的实例.
    // SqlSession 提供了在数据库执行 SQL 命令所需的所有方法。
    public static SqlSession getSqlSession(){
        return sqlSessionFactory.openSession();
    }
}

6.编写测试类UserDaoTest

package com.liu.dao;

import com.liu.pojo.User;
import com.liu.utils.MybatisUtil;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class    UserDaoTest {
    @Test
    public void test(){
        //第一步：获得SqlSession对象
        SqlSession sqlSession = MybatisUtil.getSqlSession();

        //方式一：getMapper
        UserDao userDao = sqlSession.getMapper(UserDao.class);
        List<User> userList = userDao.getUserList();

        for(User user : userList){
            System.out.println(user.toString());
        }

        //关闭SqlSession
        sqlSession.close();
    }
}

验证测试：

包目录结构

MySql8.0以上的 url格式

jdbc:mysql://localhost:3306/mybatis?useSSL=false&useUnicode=true&characterEncoding=UTF-8&serverTimezone=UTC