Mybatis入门程序

1.项目结构

2.引入依赖

<?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.fy</groupId>
    <artifactId>mybatistest</artifactId>
    <version>1.0-SNAPSHOT</version>
    <dependencies>
    <!--mybatis核心包-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.7</version>
        </dependency>
    <!--mysql驱动-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.26</version>
        </dependency>
    <!--JUnit测试包-->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.13.2</version>
        </dependency>
    </dependencies>
    <!--编译src/main/java中的xml和properties文件-->
    <build>
        <resources>
            <resource>
                <directory>
                    src/main/java
                </directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
        </resources>
    </build>
</project>

3.创建数据库

create database mybatis;

4.创建数据库配置文件

mysql.driver=com.mysql.cj.jdbc.Driver
mysql.url=jdbc:mysql://localhost:3306/mybatis?serverTimezone=UTC&\
  characterEncoding=utf8&useUnicode=true&useSSL=false
mysql.username=root
mysql.password=123456

5.创建Mybatis核心配置文件

<?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>
    <properties resource="db.properties"/>
    <typeAliases>
        <package name="com.pojo"/>
    </typeAliases>
    <environments default="development">
        <environment id="development">
            <transactionManager  type="JDBC"/><!--  单独使用时配置成MANAGED没有事务 -->
            <dataSource type="POOLED">
                <property name="driver" value="${mysql.driver}"/>
                <property name="url" value="${mysql.url}"/>
                <property name="username" value="${mysql.username}"/>
                <property name="password" value="${mysql.password}"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
    <!--配置映射文件的路径-->
        <mapper resource="mapper/UserMapper.xml"/>
    </mappers>
</configuration>

6.创建用户表并添加数据

use mybatis;
create table users(
  id int primary key auto_increment,
  name varchar(20) not null,
  age int not null
);
insert into users(id,name,age) values(null,'李四',20),(null,'王五',18);

7.创建pojo实体类

package com.pojo;
public class User {
    private int id;
    private String name;
    private String  age;
    public User() {
    }
    public User(int id, String name, String age) {
        this.id = id;
        this.name = name;
        this.age = age;
    }
    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 getAge() {
        return age;
    }
    public void setAge(String age) {
        this.age = age;
    }
    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", age='" + age + '\'' +
                '}';
    }
}

8.创建UserDao接口

package com.dao;
import com.pojo.User;
public interface UserDao {
    public User findById(int id);
}

9.创建映射文件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">
<mapper namespace="com.dao.UserDao">
    <select id="findById" parameterType="int" resultType="user">
        SELECT * FROM user WHERE id=#{id}
    </select>
</mapper>

10.编写测试类

import com.pojo.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 org.junit.Test;
import java.io.IOException;
import java.io.Reader;
public class UserTest {
    @Test
    public void userFindByIdTest(){
        //创建流
        Reader reader = null;
        SqlSession session = null;
        try{
            //读取mybatis-config.xml文件内容到reader对象中
            reader = Resources.getResourceAsReader("mybatis-config.xml");
            //初始化Mybatis数据库，创建sqlSessionFactory类的实例
            SqlSessionFactory sqlMapper =new SqlSessionFactoryBuilder().build(reader);
            //创建SqlSession实例
            session = sqlMapper.openSession();
            //传入参数查询，返回结果
            User user = session.selectOne("findById",1);
            //输出结果
            System.out.println(user);
        }catch (IOException e){
            e.printStackTrace();
        }finally {
            //关闭session
            session.close();
        }
    }
}

11.运行结果