# 1、Mybatis
Mybatis官网：https://mybatis.org/mybatis-3/index.html
Mybatis-Spring官网：https://mybatis.org/spring/index.html
Mybatis Plus官网：https://mp.baomidou.com/
# 1.1、mybatis安装
新建一个Maven项目，导入mybatis包即可
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
</dependency>
<!--mybatis-->
<!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.7</version>
</dependency>
<!--mysql驱动-->
<!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.23</version>
</dependency>
<!--slf4j-->
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.8.0-beta4</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-log4j12</artifactId>
<version>1.8.0-beta4</version>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.17</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.projectlombok/lombok -->
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.18.20</version>
</dependency>
<!-- ehcache缓存 -->
<!-- https://mvnrepository.com/artifact/org.mybatis.caches/mybatis-ehcache -->
<dependency>
<groupId>org.mybatis.caches</groupId>
<artifactId>mybatis-ehcache</artifactId>
<version>1.2.1</version>
</dependency>
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# 1.2、mybatisConfig.xml设置
<?xml version="1.0" encoding="UTF8" ?>
<!DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<!--configuration核心配置文件-->
<configuration>
<!--引入外部配置文件-->
<properties resource="db.properties">
<!--可以在此增加一些属性配置
如果两个文件有同一个字段，优先使用外部配置文件-->
</properties>
<!--设置-->
<settings>
<setting name="logImpl" value="LOG4J2"/>
</settings>
<!--可以给实体类起别名-->
<typeAliases>
<!--实体类多选择-->
<package name="com.yixihan.pojo"/>
<!--实体类少选择-->
<!--<typeAlias type="com.yixihan.pojo.User" alias="User"/>-->
</typeAliases>
<environments default="development">
<environment id="development">
<!--事务管理-->
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="${driver}"/>
<property name="url" value="${url}"/>
<property name="username" value="${username}"/>
<property name="password" value="${password}"/>
</dataSource>
</environment>
</environments>
<!--每个Mapper.xml都需要在Mybatis核心配置文件中注册-->
<mappers>
<!--方式一
推荐使用-->
<mapper resource="com/yixihan/dao/UserMapper.xml"/>
<!--方式二
接口和他的Mapper配置文件必须同名
接口和他的Mapper配置文件必须在同一包下-->
<!--<mapper class="com.yixihan.dao.UserMapper"/>-->
<!--方式三
接口和他的Mapper配置文件必须同名
接口和他的Mapper配置文件必须在同一包下-->
<!--<package name="com.yixihan.dao"/>-->
</mappers>
</configuration>
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# 1.3、db.properties设置
driver = com.mysql.cj.jdbc.Driver
url = jdbc:mysql://localhost:3306/mybatis?useSSL=true&useUnicode=true&characterEncoding=UTF-8&serverTimezone=UTC
username = root
password = Theyear123
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# 1.4、log4j.properties设置
#将等级为DEBUG的日志信息输出到console和file这两个目的地，console和file的定义在下面的代码
log4j.rootLogger=DEBUG,console,file
#控制台输出的相关设置
log4j.appender.console = org.apache.log4j.ConsoleAppender
log4j.appender.console.Target = System.out
log4j.appender.console.Threshold=DEBUG
log4j.appender.console.layout = org.apache.log4j.PatternLayout
log4j.appender.console.layout.ConversionPattern=[%c]-%m%n
#文件输出的相关设置
log4j.appender.file = org.apache.log4j.RollingFileAppender
log4j.appender.file.File=./log/yixihan.log
log4j.appender.file.MaxFileSize=10mb
log4j.appender.file.Threshold=DEBUG
log4j.appender.file.layout=org.apache.log4j.PatternLayout
log4j.appender.file.layout.ConversionPattern=[%p][%d{yy-MM-dd}][%c]%m%n
#日志输出级别
log4j.logger.org.mybatis=DEBUG
log4j.logger.java.sql=DEBUG
log4j.logger.java.sql.Statement=DEBUG
log4j.logger.java.sql.ResultSet=DEBUG
log4j.logger.java.sql.PreparedStatement=DEBUG
# 输出消息编码
log4j.appender.Console.encoding=UTF-8
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# 1.5、Mybatis.java
package com.yixihan.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 = "mybatisconfig.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命令所需的所以方法
public static SqlSession getSqlSession () {
/*自动提交事务*/
return sqlSessionFactory.openSession(true);
}
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# 1.6、Mapper.xml
<?xml version="1.0" encoding="UTF8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!--namespace=绑定一个对应的Dao/Mapper接口-->
<mapper namespace="com.yixihan.dao.UserMapper">
</mapper>
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# 1.7、简单CRUD
# 1.7.1、利用Mapper.xml开发
User.java
package com.yixihan.pojo;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import org.apache.ibatis.type.Alias;
//实体类
@Data
@AllArgsConstructor
@NoArgsConstructor
public class User {
private int id; //id
private String name; //名字
private String pwd; //密码
}
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UserMaper.java
package com.yixihan.dao;
import com.yixihan.pojo.User;
import java.util.List;
import java.util.Map;
public interface UserMapper {
//查询全部用户
List<User> GetUserList ();
//根据ID查询用户
User GetUserByID (int id);
//模糊查询
List<User> GetUserLike(String value);
//添加用户
int addUser (User user);
//利用map添加用户
int addUser2 (Map<String, Object> map);
//修改用户
int updateUser (User user);
//利用map修改用户
int updateUser2 (Map<String, Object> map);
//删除用户
int deleteUser (int id);
}
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UserMapper.xml
<?xml version="1.0" encoding="UTF8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!--namespace=绑定一个对应的Dao/Mapper接口-->
<mapper namespace="com.yixihan.dao.UserMapper">
<!--select查询语句-->
<!--
id:对应的namespace中的方法名
resultType:SQL语句执行的返回值
parameterType:参数类型
-->
<!--无条件查找-->
<select id="GetUserList" resultType="com.yixihan.pojo.User">
select *
from mybatis.user
</select>
<!--按ID查找-->
<select id="GetUserByID" resultType="com.yixihan.pojo.User" parameterType="int">
select *
from mybatis.user
where id = #{id}
</select>
<!--模糊查询-->
<select id="GetUserLike" resultType="com.yixihan.pojo.User">
select *
from user
where user.name like #{value}
</select>
<!--插入-->
<insert id="addUser" parameterType="com.yixihan.pojo.User">
insert into `user`(`user`.id,`user`.`name`,`user`.pwd) value (#{id},#{name},#{pwd});
</insert>
<!--利用map插入-->
<!--
对象中的属性，可以直接取出来
传递map的key
-->
<insert id="addUser2" parameterType="map">
insert into `user`(`user`.id,`user`.`name`,`user`.pwd) value (#{userid},#{username},#{userpassword});
</insert>
<!--更新-->
<update id="updateUser" parameterType="com.yixihan.pojo.User">
update mybatis.user
set user.name = #{name}, user.pwd = #{pwd}
where user.id = #{id};
</update>
<!--利用map更新-->
<update id="updateUser2" parameterType="map">
update mybatis.user
set user.pwd = #{password}
where user.id = #{id};
</update>
<!--删除-->
<delete id="deleteUser" parameterType="int" >
delete from mybatis.user
where user.id = #{id}
</delete>
</mapper>
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# 1.7.2、结果集映射
User.java
同上
UserMapper.java
package com.yixihan.dao;
import com.yixihan.pojo.User;
import java.util.List;
import java.util.Map;
public interface UserMapper {
//查询全部用户
List<User> GetUserList ();
List<User> GetUserByLimit (Map<String, Object> map);
}
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UserMapper.xml
<?xml version="1.0" encoding="UTF8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!--namespace=绑定一个对应的Dao/Mapper接口-->
<mapper namespace="com.yixihan.dao.UserMapper">
<!--select查询语句-->
<!--
id:对应的namespace中的方法名
resultType:SQL语句执行的返回值
parameterType:参数类型-->
<!--无条件查找-->
<select id="GetUserList" resultType="user">
select *
from mybatis.user
</select>
<!--结果集映射-->
<resultMap id="UserMap" type="user">
<!--column数据库中的字段，property实体类中的属性-->
<result column="id" property="id"/>
<result column="name" property="name"/>
<result column="pwd" property="pwd"/>
</resultMap>
<!--按ID查找-->
<select id="GetUserByID" resultMap="UserMap" parameterType="int">
select *
from mybatis.user
where id = #{id}
</select>
<select id="GetUserByLimit" resultType="user" parameterType="map">
select *
from mybatis.user limit #{startIndex}, #{pageSize}
</select>
</mapper>
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# 1.7.3、利用注解开发(仅适用于简单的CRUD)
四种语句的注解
@Select
@Insert
@Update
@Delete
注意：使用简单类型时，最好加上注解@Param("id")
User.java
同上
UserMapper.java
package com.yixihan.dao;
import com.yixihan.pojo.User;
import org.apache.ibatis.annotations.*;
import java.util.List;
import java.util.Map;
public interface UserMapper {
@Select("select * from user")
List<User> getUsers ();
//方法存在多个参数时，所有的参数前面必须加上@Param("id")注解，即使只有一个参数，也建议加上
@Select("select * from user where id = #{id} and name = #{name}")
User getUserByID1 (@Param("id") int id, @Param("name") String name);
@Select("select * from user where id = #{id}")
User getUserByID2 (@Param("id") int id);
@Insert("insert into user(id,name,pwd) values (#{id},#{name},#{password})")
int addUser (User user);
@Update("update user set user.pwd = #{pwd} where user.id = #{id}")
int updateUser (Map<String, Object> map);
@Delete("delete from user where id = #{id}")
int deleteUser (@Param("id") int id);
}
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# 1.8、多对一
Student.java
package com.yixihan.pojo;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
@Data
@NoArgsConstructor
@AllArgsConstructor
public class Student {
private int id;
private String name;
//学生需要关联一个老师
private Teacher teacher;
}
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Teacher.java
package com.yixihan.pojo;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
@Data
@NoArgsConstructor
@AllArgsConstructor
public class Teacher {
private int id;
private String name;
}
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StudentMapper.java
package com.yixihan.dao;
import com.yixihan.pojo.Student;
import java.util.List;
public interface StudentMapper {
//查询所有的学生信息以及对应的老师信息
List<Student> getStudent1 ();
List<Student> getStudent2 ();
}
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StudentMapper.xml
<?xml version="1.0" encoding="UTF8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!--configuration核心配置文件-->
<mapper namespace="com.yixihan.dao.StudentMapper">
<!--方法一：按照查询嵌套处理
思路:
1.查询所有的学生信息
2.根据查询出来的学生tid，寻找对应的老师
子查询
-->
<select id="getStudent1" resultMap="StudentTeacher1">
select *
from mybatis.student
</select>
<resultMap id="StudentTeacher1" type="student">
<result property="id" column="id"/>
<result property="name" column="name"/>
<!--复杂的属性，需要单独处理
对象：association
集合：collection
-->
<association property="teacher" column="tid" javaType="teacher" select="getTeacher"/>
</resultMap>
<select id="getTeacher" resultType="teacher">
select *
from mybatis.teacher
where id = #{id}
</select>
<!--=====================================================================================-->
<!--方法二：按照结果嵌套处理
联表查询
-->
<select id="getStudent2" resultMap="StudentTeacher2">
select student.id as sid,student.name as sname,mybatis.teacher.name as tname
from mybatis.teacher,mybatis.student
where teacher.id=student.tid
</select>
<resultMap id="StudentTeacher2" type="student">
<result property="id" column="sid"/>
<result property="name" column="sname"/>
<association property="teacher" javaType="teacher">
<result property="name" column="tname"/>
</association>
</resultMap>
</mapper>
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# 1.9、一对多
Student.java 和 Teacher.java
同上
TeacherMapper.java
package com.yixihan.dao;
import com.yixihan.pojo.Teacher;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;
import java.util.List;
public interface TeacherMapper {
/*@Select("select * from teacher")*/
List<Teacher> getTeacher1 ();
List<Teacher> getTeacher2 ();
}
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TeacherMapper.xml
<?xml version="1.0" encoding="UTF8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!--configuration核心配置文件-->
<mapper namespace="com.yixihan.dao.TeacherMapper">
<!--按结果嵌套查询-->
<select id="getTeacher1" resultMap="TS1">
select teacher.id as tid,teacher.name as tname,student.id as sid,student.name as sname,student.tid as tid
from mybatis.teacher,mybatis.student
where student.tid=teacher.id;
</select>
<resultMap id="TS1" type="teacher">
<result property="id" column="tid"/>
<result property="name" column="tname"/>
<!--复杂的属性，我们需要单独处理
对象 ： association
集合 ： collection
javaType="" 指定属性的类型
集合中的泛型信息，使用ofType获取
-->
<collection property="studentList" ofType="student">
<result property="id" column="sid"/>
<result property="name" column="sname"/>
<result property="tid" column="tid"/>
</collection>
</resultMap>
<!--=============================================================================================-->
<select id="getTeacher2" resultMap="TS2">
select *
from mybatis.teacher
</select>
<resultMap id="TS2" type="teacher">
<result property="id" column="id"/>
<result property="name" column="name"/>
<collection property="studentList" ofType="student" javaType="ArrayList" select="getUserByTID" column="id"/>
</resultMap>
<select id="getUserByTID" resultType="student">
select *
from mybatis.student
where student.tid = #{tid}
</select>
</mapper>
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# 1.10动态SQL
主要掌握
if
where/set
即可
Blog.java
package com.yixihan.pojo;
import lombok.Data;
import java.util.Date;
@Data
public class Blog {
private String id;
private String title;
private String author;
private Date createTime ; //属性名和字段名不一致
private int views;
}
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BlogMapper.java
package com.yixihan.dao;
import com.yixihan.pojo.Blog;
import java.util.List;
import java.util.Map;
public interface BlogMapper {
//插入数据
int addBook (Blog blog);
//查询博客
List<Blog> queryBlogIF (Map <String, Object> map) ;
List<Blog> queryBlogChoose (Map <String, Object> map) ;
//查询第1-2-3号记录的博客
List<Blog> queryBlogForeach (Map map);
//更新
int updateBolg (Map map);
}
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BlogMapper.xml
<?xml version="1.0" encoding="UTF8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!--configuration核心配置文件-->
<mapper namespace="com.yixihan.dao.BlogMapper">
<sql id="if_TAC">
<if test="title != null">
and title = #{title}
</if>
<if test="author != null">
and author = #{author}
</if>
<if test="createTime != null">
and creat_time = #{createTime}
</if>
</sql>
<insert id="addBook" parameterType="blog">
insert into mybatis.blog (id, title, author, creat_time, views)
value (#{id}, #{title}, #{author}, #{createTime}, #{views})
</insert>
<select id="queryBlogIF" resultType="blog" parameterType="map">
select *
from mybatis.blog
<where>
<include refid="if_TAC"/>
</where>
</select>
<select id="queryBlogChoose" parameterType="map" resultType="blog">
select *
from mybatis.blog
<where>
<choose>
<when test="title != null">
title = #{title}
</when>
<when test="author != null">
and author = #{author}
</when>
<when test="views != null">
and views = #{views}
</when>
<otherwise>
</otherwise>
</choose>
</where>
</select>
<update id="updateBolg" parameterType="map">
update mybatis.blog
<set>
<if test="title != null">
title = #{title},
</if>
<if test="author != null">
author = #{author},
</if>
<if test="createTime != null">
creat_time = #{createTime},
</if>
<if test="views != null">
views = #{views},
</if>
</set>
where id = #{id}
</update>
<!--
select * from mybatis.blog where (id=1 or id=2 or id=3)
现在传递一个万能的map，这个map中可以存在一个集合
foreach：
collection：传进来的参数（集合）
item：遍历出来的名字
open：开始符号
close：结尾符号
separator：中间的分隔符
-->
<select id="queryBlogForeach" parameterType="map" resultType="blog">
select *
from mybatis.blog
<where>
<foreach collection="ids" item="id" open="and (" close=")" separator="or">
id = #{id}
</foreach>
</where>
</select>
</mapper>
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# 1.10.1、关于sql语句使用示例
可以减少重复sql语句
<sql id="if_TAC">
<if test="title != null">
and title = #{title}
</if>
<if test="author != null">
and author = #{author}
</if>
<if test="createTime != null">
and creat_time = #{createTime}
</if>
</sql>
<insert id="addBook" parameterType="blog">
insert into mybatis.blog (id, title, author, creat_time, views)
value (#{id}, #{title}, #{author}, #{createTime}, #{views})
</insert>
<select id="queryBlogIF" resultType="blog" parameterType="map">
select *
from mybatis.blog
<where>
<include refid="if_TAC"/>
</where>
</select>
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