MyBatis的第一个程序

1.如何获得MyBatis：

• maven仓库地址：https://mvnrepository.com/artifact/org.mybatis/mybatis/3.5.2
• Github上源码：https://github.com/mybatis/mybatis-3/releases
• 中文文档：https://mybatis.org/mybatis-3/zh/index.html

2.第一个Mybatis程序

思路：搭建环境–》导入Mybatis–》编写代码–》测试

2.1 搭建数据库

USE mybatis;
CREATE TABLE USER(
id INT NOT NULL PRIMARY KEY,
NAME VARCHAR(32) DEFAULT NULL,
pwd VARCHAR(32) DEFAULT NULL
) ENGINE=INNODB DEFAULT CHARSET=utf8;

INSERT INTO USER(id,NAME,pwd) VALUES
(1,'狂神','123'),
(2,'张三','123'),
(3,'李四','123')

2.2 新建项目：导入maven依赖

• 新建一个普通项目
• 删除src文件，可以将这个项目作为父工程，以便创建子工程
• 导入maven依赖

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

    <!--mybatis驱动-->
    <dependency>
        <groupId>org.mybatis</groupId>
        <artifactId>mybatis</artifactId>
        <version>3.5.2</version>
    </dependency>

    <!--junit驱动-->
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.12</version>
        <scope>test</scope>
    </dependency>
</dependencies>

<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>

2.3 编写mybatis的核心配置文件

创建一个模块

<!--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.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?
                useSSL&amp;useUnicode=true&amp;characterEncoding=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="123"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="org/mybatis/example/BlogMapper.xml"/>
    </mappers>
</configuration>

2.4 编写mybatis工具类

package com.kuang.dao;

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 javax.annotation.Resource;
import java.io.IOException;
import java.io.InputStream;

//sqlSessionFactory--->sqlSession对象（生产）
public class MyBatisUtils {
    private SqlSessionFactory  sqlSessionFactory;
    static{
        try {
            //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，我们就可以从中获得 SqlSession 的实例了。
    //SqlSession 完全包含了面向数据库执行 SQL 命令所需的所有方法。
    public static SqlSession getSqlSession(){
        return sqlSessionFactory.openSession();
    }
}

2.5 编写代码

实体类：User.java

package com.kuang.pojo;

public class User {
    private int id;
    private String name;
    private String pwd;

    public User() {}
    public int getId() {
        return id;
    }
    public String getName() {
        return name;
    }
    public String getPwd() {
        return 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 + '\'' +
                '}';
    }
}

Dao接口：UserDao

//操作数据库的实体类
public interface UserDao {
    //返回所有的用户
   List<User> getUserList();
}

接口实现类：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">

<!--namespace=绑定一个Dao/Mapper接口-->
<!--让这个配置文件和UserDao接口绑定-->
<mapper namespace="com.kuang.dao.UserDao">
    <!--查询语句-->
    <select id="getUserList" resultType="com.kuang.pojo.User" >
         select * from mybatis.user;
    </select>
</mapper>

2.6 测试

package com.kuang.dao;

import com.kuang.pojo.User;
import com.kuang.utils.MyBatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class UserDaoTest {
    @Test
    public void test(){
        //获取sqlSession对象
        SqlSession sqlSession = MyBatisUtils.getSqlSession();
        //方式一：getMapper
        UserDao mapper = sqlSession.getMapper(UserDao.class);
        List<User> userList = mapper.getUserList();
        
        //方式二：不推荐
        User ouserlist1= (User)sqlSession.selectList("com.kuang.dao.UserDao.getUserList");
        
        for(User user:userList){
            System.out.println(user);
        }
        //关闭sqlSession
        sqlSession.close();
    }
}