环境：

• JDK1.8
• MySQL 5.7
• maven 3.6.1
• IDEA

回顾

• JDBC
• Mysql
• java基础
• Maven
• Junit

第一个Mybatis程序

搭建环境

• 搭建数据库

create database mybatis;
use mybatis;
create table user (
id int(20) not null primary key,
name varchar(20) default null,
pwd varchar(40) default null
)engine=Innodb default charset=utf8;
insert into user values
(1,'zhangsan','123456'),
(2,'lisi','123456'),
(3,'wangwu','123456');

• 新建一个Maven项目
• 导入jar包依赖

创建一个模块

• 编写Mybatis核心配置文件
• 编写Mybatis工具类

package com.lili.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 {
            //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();
        }
    }
    private static SqlSession getSqlSession(){
        return sqlSessionFactory.openSession();
    }
}

• 编写代码
  • 实体类
  • Dao接口
  • Dao实现类

CRUD

• 编写接口

package com.lili.dao;

import com.lili.pojo.User;

import java.util.List;

public interface UserDao {
    //查询全部用户
    List<User> getUserList();
    //根据ID查询用户
    User getUserById(int id);
    //insert 一个用户
    int addUser(User user);
    //update一个用户
    int updateUser(User user);
    //删除一个用户
    int deleteUser(int id);
}

• 编写对应的sql语句

<?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.lili.dao.UserDao">

    <select id="getUserList" resultType="com.lili.pojo.User">
        select * from mybatis.user
    </select>
    <select id="getUserById" parameterType="int" resultType="com.lili.pojo.User">
        select * from mybatis.user where id = #{id}
    </select>
    <insert id="addUser" parameterType="com.lili.pojo.User">
        insert into mybatis.user values (#{id},#{name},#{pwd});
    </insert>
    <update id="updateUser" parameterType="com.lili.pojo.User">
        update mybatis.user
        set name = #{name},pwd = #{pwd}
        where id = #{id};
    </update>
    <delete id="deleteUser" parameterType="int">
        delete from mybatis.user where id = #{id}
    </delete>
</mapper>

• 测试

package com.lili.dao;

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

import java.util.List;

public class UserDaoTest {
    @Test
    public void test(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserDao mapper = sqlSession.getMapper(UserDao.class);
        List<User> userList = mapper.getUserList();
        for (User user : userList) {
            System.out.println(user);
        }
        sqlSession.close();
    }

    @Test
    public void getUserById(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserDao mapper = sqlSession.getMapper(UserDao.class);
        User userById = mapper.getUserById(1);
        System.out.println(userById);
        sqlSession.close();
    }

    @Test
    public void addUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserDao mapper = sqlSession.getMapper(UserDao.class);
        int add = mapper.addUser(new User(4, "得到", "123456"));
        if (add>0){
            System.out.println("数据插入成功！");
        }
        sqlSession.commit();
        sqlSession.close();
    }
    @Test
    public void updateUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserDao mapper = sqlSession.getMapper(UserDao.class);
        int did = mapper.updateUser(new User(4, "地点", "123123"));
        if (did>0){
            System.out.println("成功修改！");
        }
        sqlSession.commit();
        sqlSession.close();
    }
    @Test
    public void deleteUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserDao mapper = sqlSession.getMapper(UserDao.class);
        mapper.deleteUser(4);
        sqlSession.commit();
        sqlSession.close();
    }

}

• 万能map

    //万能map
    int addUser2(Map<String,Object> map);
<insert id="addUser2" parameterType="map">
        insert into mybatis.user (id,pwd) values (#{id},#{pwd});
    </insert>
@Test
public void addUser2(){
    SqlSession sqlSession = MybatisUtils.getSqlSession();
    UserDao mapper = sqlSession.getMapper(UserDao.class);
    Map<String, Object> map = new HashMap<>();
    map.put("id",5);
    map.put("pwd","123123");
    mapper.addUser2(map);
    sqlSession.commit();
    sqlSession.close();
}

环境配置（envirouments）

属性（properties）

类型别名（typeAliases）

设置（settings）

映射器（mappers）

日志

logImpl

• SLF4J

• LOG4J【掌握】

• LOG4J2

• JDK_LOGGING

• COMMONS_LOGGING

• STDOUT_LOGGING [掌握]

• NO_LOGGING

STDOUT_LOGGING

标准日志输出

Logging initialized using 'class org.apache.ibatis.logging.stdout.StdOutImpl' adapter.
PooledDataSource forcefully closed/removed all connections.
PooledDataSource forcefully closed/removed all connections.
PooledDataSource forcefully closed/removed all connections.
PooledDataSource forcefully closed/removed all connections.
Opening JDBC Connection
Created connection 1027591600.
Setting autocommit to false on JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@3d3fcdb0]
==>  Preparing: select * from mybatis.user where id = ? 
==> Parameters: 1(Integer)
<==    Columns: id, name, pwd
<==        Row: 1, zhangsan, 123456
<==      Total: 1
User(id=1, name=zhangsan, pwd=123456)
Resetting autocommit to true on JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@3d3fcdb0]
Closing JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@3d3fcdb0]
Returned connection 1027591600 to pool.

LOG4J

先导包

分页

• //分页
  List<User> getUserByLimit(Map<String,Integer> map);
  //分页2
  List<User> getUserRowBounds();
  

注解的用法

复杂查询环境搭建

create table teacher(
id int(10) not null,
name varchar(30) default null,
primary key (id)
)engine=innodb default charset=utf8;

insert into teacher(id,name) values(1,'秦老师');

create table students(
id int(10) not null,
name varchar(30) default null,
tid int(10) default null,
primary key (id),
key fktid (tid),
constraint fktid foreign key (tid) references teacher (id)
)engine=innodb default charset=utf8;
insert into students (id,name,tid) values 
('1','小明','1'),
('2','小红','1'),
('3','小王','1'),
('4','小虎','1'),
('5','小天','1');

按照查询嵌套处理

<select id="getStudents" resultMap="StudentsTeacher">
    select * from mybatis.students
</select>
<resultMap id="StudentsTeacher" type="Students">
    <result property="id" column="id"/>
    <result property="name" column="name"/>
    <association property="tid" column="tid" javaType="Teacher" select="getTeacher"/>
</resultMap>
<select id="getTeacher" resultType="Teacher">
    select * from mybatis.teacher where id = #{id}
</select>

缓存

查询数据库，耗资源

一次查询，把数据放在一个缓存的地方

一定程度解决了三高问题，高并发，高可用，高性能