思路：

        搭建环境-->导入Mybatis-->编写代码-->测试

 

第一步：搭建环境

（1）搭建数据库

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,'zyy','123456'),
(2,'张三','123456'),
(3,'李四','123456');

（2）新建项目

1、新建一个普通的maven项目

2、删除src目录（作为父工程） 

3、 导入maven依赖

    <dependencies>
        <dependency>
            <groupId>mysqlgroupId>
            <artifactId>mysql-connector-javaartifactId>
            <version>5.1.47version>
        dependency>
 
        <dependency>
            <groupId>org.mybatisgroupId>
            <artifactId>mybatisartifactId>
            <version>3.5.7version>
        dependency>
 
        <dependency>
            <groupId>junitgroupId>
            <artifactId>junitartifactId>
            <version>4.12version>
        dependency>
    dependencies>

 

第二步：创建一个模板

（1）编写mybatis的核心配置文件

configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url"
                          value="jdbc:mysql://localhost:3306/mybatis?useSSL=false&useUnicode=true&characterEncoding=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            dataSource>
        environment>
    environments>
    
    
    <mappers>
        <mapper resource="com/zyy/dao/UserMapper.xml"/>
    mappers>
configuration>

（2）编写mybatis工具类

package com.gt.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;
 
//SqlSessionFactory --> sqlSession
public class MybatisUtils {
 
    private static SqlSessionFactory sqlSessionFactory;
 
    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。你可以通过 SqlSession 实例来直接执行已映射的 SQL 语句。
    public static SqlSession getSqlSession() {
        return sqlSessionFactory.openSession();
    }
 
 
}

第三步：编写代码

（1）实体类

package com.gt.pojo;
 
//实体类
public class User {
    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 void setId(int id) {
        this.id = id;
    }
 
    public void setName(String name) {
        this.name = name;
    }
 
    public void setPwd(String pwd) {
        this.pwd = pwd;
    }
 
    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", pwd='" + pwd + '\'' +
                '}';
    }
}

（2）Dao接口

package com.gt.dao;
 
import com.gt.pojo.User;
 
import java.util.List;
 
public interface UserDao {
    /**
     * 获取用户列表
     * @return
     */
    //获取全部用户
    List getUserList();
 
    //根据ID查询用户
    User getUserById(int id);
 
    //insert一个用户
    int addUser(User user);
 
    //修改用户
    int updateUser(User user);
 
    //删除一个用户
    int deleteUser(int id);
 
 
}

 

（3）接口实现类(由原来的UserDaoImpl转为一个Mapper配置文件)  

mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.zyy.dao.UserDao">
    <select id="getUserList" resultType="com.zyy.pojo.User">
    select id, name, pwd from `user`
    select>
mapper>

第四步：测试 

注意点：

org.apache.ibatis.binding.BindingException: Type interface com.zyy.dao.UserDao is not known to the MapperRegistry.

Caused by: java.io.IOException: Could not find resource com/zyy/dao/UserMapper.xml  

 pom改成：

<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">
    <parent>
        <artifactId>maven-studyartifactId>
        <groupId>com.zyygroupId>
        <version>1.0-SNAPSHOTversion>
    parent>
    <modelVersion>4.0.0modelVersion>
 
    <artifactId>mybatis-01artifactId>
    
    <build>
        <resources>
            <resource>
                <directory>src/main/resourcesdirectory>
                <includes>
                    <include>**/*.propertiesinclude>
                    <include>**/*.xmlinclude>
                includes>
                <filtering>falsefiltering>
            resource>
            <resource>
                <directory>src/main/javadirectory>
                <includes>
                    <include>**/*.propertiesinclude>
                    <include>**/*.xmlinclude>
                includes>
                <filtering>falsefiltering>
            resource>
        resources>
        <plugins>
            
            <plugin>
                <groupId>org.apache.maven.pluginsgroupId>
                <artifactId>maven-compiler-pluginartifactId>
                <version>3.10.0version>
                <configuration>
                    <source>1.8source>
                    <target>1.8target>
                configuration>
            plugin>
        plugins>
    build>
project>

（1）MapperRegistry是什么？

        核心配置文件中注册mappers

（2）junit测试

import com.zyy.pojo.User;
import com.zyy.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
 
import java.util.List;
 
/**
 * @Description: 类描述
 * @Author: zyy
 * @Date: 2022/03/12 09:48
 */
public class UserDaoTest {
 
    @Test
    public void getUserList() {
        SqlSession sqlSession = null;
        try {
            sqlSession = MybatisUtils.getSqlSession();
            UserDao userDao = sqlSession.getMapper(UserDao.class);
            List userList = userDao.getUserList();
            userList.forEach(user -> System.out.println(user.toString()));
        } finally {
            if (sqlSession != null) {
                sqlSession.close();
            }
        }
    }
}

输出结果：

可能会遇到的问题

1. 配置文件没有注册
2. 绑定接口错误
3. 方法名不对
4. 返回类型不对
5. Maven导出资源问题