【mybatis】第一个mybatis程序

视频

MyBatis原理分析（通俗易懂）

入门JDBC

创建数据库

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,'张若尘','123hho'),
(2,'唐三','21h3u1h'),
(3,'石昊','h32h4'),
(4,'萧炎','4h5oi'),
(5,'林动','j4l65jho'),
(6,'霍雨浩','5ho34ho')

导入依赖

    <dependencies>
        
        <dependency>
            <groupId>mysqlgroupId>
            <artifactId>mysql-connector-javaartifactId>
            <version>8.0.25version>
        dependency>
        
        <dependency>
            <groupId>org.mybatisgroupId>
            <artifactId>mybatisartifactId>
            <version>3.5.7version>
        dependency>
        
        <dependency>
            <groupId>junitgroupId>
            <artifactId>junitartifactId>
            <version>4.13.2version>
            <scope>testscope>
        dependency>
    dependencies>

创建一个连接数据库的核心配置文件

DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">

<configuration>
	<settings>
        <setting name="mapUnderscoreToCamelCase" value="true"/>
    settings>
    <typeAliases>
        <package name="com.pojo"/>
    typeAliases>
    <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/test?useSSL=false&useUnicode=true&characterEncoding=utf8"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            dataSource>
        environment>
    environments>

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

pojo:写每一个数据库表对应的类
dao:是对数据库增删查改的接口
impl:实现对dao层的接口

从 XML 中构建 SqlSessionFactory，从 SqlSessionFactory 中获取 SqlSession
主要是为了获取执行sql语句的对象

package com.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 MybatisUtils {
    private static SqlSessionFactory sqlSessionFactory;
    static {
        try{
            //获取sqlSessionFactory对象
            String resource = "config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        }catch (IOException e){
            e.printStackTrace();
        }

    }

    //获取SqlSession实例
    public static SqlSession getSqlSession(){
        return sqlSessionFactory.openSession();
    }
}

package com.pojo;

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 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 + '\'' +
                '}';
    }
}

<?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="getUserList" resultType="com.pojo.User">
        select * from user
    </select>
</mapper>

注册映射器

    <build>
        <resources>
            <resource>
                <directory>src/main/resourcesdirectory>
                <includes>
                    <include>**/*.propertiesinclude>
                    <include>**/*.xmlinclude>
                includes>
                <filtering>truefiltering>
            resource>
            <resource>
                <directory>src/main/javadirectory>
                <includes>
                    <include>**/*.propertiesinclude>
                    <include>**/*.xmlinclude>
                includes>
                <filtering>truefiltering>
            resource>
        resources>
    build>

package com.dao;

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

import java.util.List;

public class UserTest {

    @Test
    public void getUserList(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();//获取能够执行sql语句的对象

        //执行sql
        UserDao userDao = sqlSession.getMapper(UserDao.class);

        List<User> userList = userDao.getUserList();

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

        //关闭sqlSession
        sqlSession.close();


    }
}

注意：增删改需要提交事物

//增删改需要提交失物
    @Test
    public void addTest(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();//获取能够执行sql语句的对象

        //执行sql
        UserDao userDao = sqlSession.getMapper(UserDao.class);

        User user = new User();
        user.setId(7);
        user.setName("李逍遥");
        user.setPwd("4g3ui12gi");
        
        boolean flag = userDao.add(user);
        if(flag){
            System.out.println("插入成功");
        }

        //提交事务
        sqlSession.commit();
        //关闭sqlSession
        sqlSession.close();
    }

Dao层
理解参数是一个map和返回值是一个map特别有作用

public boolean add2(Map<String,Object> map);


public User findById2(Map<String,Object> map);


public Map<String,Object> findById(int id);

Mapper层
这个就可以不用和实体类定义的属性名保持一致了，

<insert id="add2" parameterType="map">
        insert into user(id,name,pwd) values(#{Userid},#{Username},#{Userpwd})
</insert>


<select id="findById2" parameterType="map" resultType="com.pojo.User">
        select * from user where id = #{userId};
</select>


<select id="findById" resultType="map">
    select name,pwd from user where id = #{id}
</select>

@Test
    public void add2Test(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();//获取能够执行sql语句的对象

        //执行sql
        UserDao userDao = sqlSession.getMapper(UserDao.class);

        Map<String,Object> map = new HashMap<String,Object>();
        map.put("Userid",7);
        map.put("Username","张楚岚");
        map.put("Userpwd","32yh4oy");

        boolean flag = userDao.add2(map);
        if(flag){
            System.out.println("插入成功");
        }else{
            System.out.println("插入失败");
        }

        //提交事务
        sqlSession.commit();
        //关闭sqlSession
        sqlSession.close();
    }



@Test
    public void findById2Test(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();//获取能够执行sql语句的对象

        //执行sql
        UserDao userDao = sqlSession.getMapper(UserDao.class);
        Map<String,Object> map = new HashMap<>();
        map.put("userId",1);
        User user = userDao.findById2(map);
        System.out.println(user);
    }




@Test
    public void findByIdTest(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();//获取能够执行sql语句的对象

        //执行sql
        UserDao userDao = sqlSession.getMapper(UserDao.class);

        Map<String, Object> map = userDao.findById(2);
        map.forEach((key,value) ->{
            System.out.println(key + ":" +value);
        });


        //关闭sqlSession
        sqlSession.close();
    }

注意点：
在pom.xml文件中build中配置resources，来防止我们资源导出失败的问题
在config.xml主要记得编辑数据库、用户名、密码、注册映射器
在Mapper.xml文件中要记得编辑实现哪个接口