Mybatis核心配置mybatis-config解析以及sqlmapper文件的解析-----Mybatis框架

拼搏现实的明天。 2024-03-04 01:31 138阅读 0赞

>     mybatis小技巧
>     #{}和${}的区别
>     ${}的效果
>     org.apache.ibatis.exceptions.PersistenceException:
>     ### Error querying database.  Cause: java.sql.SQLSyntaxErrorException: Unknown column '新能源' in 'where clause'
>     ### The error may exist in CarMapper.xml
>     ### The error may involve defaultParameterMap
>     ### The error occurred while setting parameters
>     ### SQL: select             id as id,             car_num as carNum,             brand as brand,             guide_price as guidePrice,             produce_time as produceTime,             car_type as carType         from             t_car         where             car_type = 新能源
>     ### Cause: java.sql.SQLSyntaxErrorException: Unknown column '新能源' in 'where clause'
>     因为${}不会生成?然后直接以字段的形式填入了Sql语句
>     区别:
>     #{}底层使用prepareStatement,先进行编译,然后用?传值
>     ${}底层使用statement,先进行拼接语句,再对语句进行编译(存在SQL注入风险)
>     可以扭曲原SQL语句的含义
>     如果向SQL中拼接表名,就需要使用${}
>     现实业务中,可能存在分表储存的情况,因为一张表存的话,数据量过大,查询效率比较低
>     可以将这些数据有规律的分表储存,这样在查询的时候效率比较高,因为扫描的数据量变少了
>     日志表,专门存储日志信息的,如果t_log,这个表中每天都会产生很多log,慢慢这个表内容会爆炸
>     可以每天生成一张表,每张表以当天日期作为名称
>     如果我们需要知道某天的日志信息怎么办
>     假设今天20230901,那么直接查询t_log_20230901即可
>     批量删除的写法,如何一次删除多条记录
>     第一种,delete from xxx where id = ? or id = ? or id = ?
>     第二种,delete from t_car where id in(1,2,3);
>     //因为我们是通过拼接SQL的方式实现的,所以占位符会导致留下单引号
>     所以我们需要使用${}这个底层调用statement的方法的,因为它是先拼接后编译
>     #{}这个底层是preparedStatement,会先编译后拼接SQL语句
>     模糊查询like做法:需求根据汽车品牌进行查询
>     select * from t_car where brand like '%奔驰%';
>     select * from t_car where brand like '%比亚迪%';
>     这个位置也不能用底层preparedStatement的#{}因为,会添加上''导致无法实现语义
>     第一种方案${}
>     第二种方案:使用concat函数,这个是mysql数据库专门用于字符串拼接的一个函数
>     concat('%',#{brand},'%')
>     第三种方案:concat('%','${brand}','%')
>     第四种方案:concat("%"#{brand}"%")
>     nameSpace不能起别名,必须是全限定类名,带有包名在内的
>     <typeAliases>
>     
>             <typeAlias type="com.powernode.mybatis.POJO.Car" alias="Car"></typeAlias>
>             <typeAlias type="com.powernode.mybatis.POJO.Log" alias="Log"></typeAlias>
>         </typeAliases>
>         TypeAliases这个属性可以给我们的类起别名,起到简化的效果,必须在settings标签后配置
>     <TypeAliases>如果我们不指定别名,就自动以类名作为别名,在namespace下使用的时候,不区分大小写
>     Mapper标签可以用三个配置文件,resource和url和class,要求类的根路径必须有这个文件
>     resource是从根路径加载资源文件,url通过绝对路径找文件,这种方式移植性太差
>     class写的是全限定接口名,带有包名的,这个位置提供的是Mapper接口的全限定类名带包名的
>     如果写的是class,mybatis会自动去com.powernode.mybatis.Mapper下找这个XML文件
>     也就是说,这个Mapper接口必须是和xml在同一个文件夹下
>     建包只能在java包下实现,我们在Resource下只能建Directory而且他需要用/做层级切割
> 
>     mybatis小技巧
>     #{}和${}的区别
>     ${}的效果
>     org.apache.ibatis.exceptions.PersistenceException:
>     ### Error querying database.  Cause: java.sql.SQLSyntaxErrorException: Unknown column '新能源' in 'where clause'
>     ### The error may exist in CarMapper.xml
>     ### The error may involve defaultParameterMap
>     ### The error occurred while setting parameters
>     ### SQL: select             id as id,             car_num as carNum,             brand as brand,             guide_price as guidePrice,             produce_time as produceTime,             car_type as carType         from             t_car         where             car_type = 新能源
>     ### Cause: java.sql.SQLSyntaxErrorException: Unknown column '新能源' in 'where clause'
>     因为${}不会生成?然后直接以字段的形式填入了Sql语句
>     区别:
>     #{}底层使用prepareStatement,先进行编译,然后用?传值
>     ${}底层使用statement,先进行拼接语句,再对语句进行编译(存在SQL注入风险)
>     可以扭曲原SQL语句的含义
>     如果向SQL中拼接表名,就需要使用${}
>     现实业务中,可能存在分表储存的情况,因为一张表存的话,数据量过大,查询效率比较低
>     可以将这些数据有规律的分表储存,这样在查询的时候效率比较高,因为扫描的数据量变少了
>     日志表,专门存储日志信息的,如果t_log,这个表中每天都会产生很多log,慢慢这个表内容会爆炸
>     可以每天生成一张表,每张表以当天日期作为名称
>     如果我们需要知道某天的日志信息怎么办
>     假设今天20230901,那么直接查询t_log_20230901即可
>     批量删除的写法,如何一次删除多条记录
>     第一种,delete from xxx where id = ? or id = ? or id = ?
>     第二种,delete from t_car where id in(1,2,3);
>     //因为我们是通过拼接SQL的方式实现的,所以占位符会导致留下单引号
>     所以我们需要使用${}这个底层调用statement的方法的,因为它是先拼接后编译
>     #{}这个底层是preparedStatement,会先编译后拼接SQL语句
>     模糊查询like做法:需求根据汽车品牌进行查询
>     select * from t_car where brand like '%奔驰%';
>     select * from t_car where brand like '%比亚迪%';
>     这个位置也不能用底层preparedStatement的#{}因为,会添加上''导致无法实现语义
>     第一种方案${}
>     第二种方案:使用concat函数,这个是mysql数据库专门用于字符串拼接的一个函数
>     concat('%',#{brand},'%')
>     第三种方案:concat('%','${brand}','%')
>     第四种方案:concat("%"#{brand}"%")
>     nameSpace不能起别名,必须是全限定类名,带有包名在内的
>     <typeAliases>
>     
>             <typeAlias type="com.powernode.mybatis.POJO.Car" alias="Car"></typeAlias>
>             <typeAlias type="com.powernode.mybatis.POJO.Log" alias="Log"></typeAlias>
>         </typeAliases>
>         TypeAliases这个属性可以给我们的类起别名,起到简化的效果,必须在settings标签后配置
>     <TypeAliases>如果我们不指定别名,就自动以类名作为别名,在namespace下使用的时候,不区分大小写
>     Mapper标签可以用三个配置文件,resource和url和class,要求类的根路径必须有这个文件
>     resource是从根路径加载资源文件,url通过绝对路径找文件,这种方式移植性太差
>     class写的是全限定接口名,带有包名的,这个位置提供的是Mapper接口的全限定类名带包名的
>     如果写的是class,mybatis会自动去com.powernode.mybatis.Mapper下找这个XML文件
>     也就是说,这个Mapper接口必须是和xml在同一个文件夹下
>     建包只能在java包下实现,我们在Resource下只能建Directory而且他需要用/做层级切割

>     <?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="jdbc.properties"/>
>         <settings>
>             <setting name="logImpl" value="SLF4J"/>
>         </settings>
>         <typeAliases>
>     
>     
>     
>     
>             <package name="com.powernode.mybatis.POJO"/>
>         </typeAliases>
>         <environments default="development">
>             <environment id="development">
>                 <transactionManager type="JDBC" />
>                 <dataSource type="POOLED">
>                     <property name="driver" value="${jdbc.driver}" />
>                     <property name="url" value="${jdbc.url}" />
>                     <property name="username" value="${jdbc.username}" />
>                     <property name="password" value="${jdbc.password}" />
>                 </dataSource>
>             </environment>
>         </environments>
>         <mappers>
>             
>     
>     
>     
>             
>             <package name="com.powernode.mybatis.Mapper"/>
>         </mappers>
>     </configuration>
> 
>     <?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="jdbc.properties"/>
>         <settings>
>             <setting name="logImpl" value="SLF4J"/>
>         </settings>
>         <typeAliases>
>     
>     
>     
>     
>             <package name="com.powernode.mybatis.POJO"/>
>         </typeAliases>
>         <environments default="development">
>             <environment id="development">
>                 <transactionManager type="JDBC" />
>                 <dataSource type="POOLED">
>                     <property name="driver" value="${jdbc.driver}" />
>                     <property name="url" value="${jdbc.url}" />
>                     <property name="username" value="${jdbc.username}" />
>                     <property name="password" value="${jdbc.password}" />
>                 </dataSource>
>             </environment>
>         </environments>
>         <mappers>
>             
>     
>     
>     
>             
>             <package name="com.powernode.mybatis.Mapper"/>
>         </mappers>
>     </configuration>

>     <?xml version="1.0" encoding="UTF-8" ?>
>     
>     <configuration debug="false">
>         <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
>             <encoder class="ch.qos.logback.classic.encoder.PatternLayoutEncoder">
>                 <pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger{50} - %msg%n</pattern>
>             </encoder>
>         </appender>
>     
>         <logger name="org.apache.ibatis" level="TRACE">
>     
>         </logger>
>         <logger name="java.sql.Connection" level="DEBUG">
>     
>         </logger>
>         <logger name="java.sql.Statement" level="DEBUG">
>     
>         </logger>
>         <logger name="java.sql.PreparedStatement" level="DEBUG">
>     
>         </logger>
>         
>         
>         <root level="DEBUG">
>             <appender-ref ref="STDOUT">
>     
>             </appender-ref>
>             <appender-ref ref="FILE">
>     
>             </appender-ref>
>         </root>
>     
>     </configuration>
> 
>     <?xml version="1.0" encoding="UTF-8" ?>
>     
>     <configuration debug="false">
>         <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
>             <encoder class="ch.qos.logback.classic.encoder.PatternLayoutEncoder">
>                 <pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger{50} - %msg%n</pattern>
>             </encoder>
>         </appender>
>     
>         <logger name="org.apache.ibatis" level="TRACE">
>     
>         </logger>
>         <logger name="java.sql.Connection" level="DEBUG">
>     
>         </logger>
>         <logger name="java.sql.Statement" level="DEBUG">
>     
>         </logger>
>         <logger name="java.sql.PreparedStatement" level="DEBUG">
>     
>         </logger>
>         
>         
>         <root level="DEBUG">
>             <appender-ref ref="STDOUT">
>     
>             </appender-ref>
>             <appender-ref ref="FILE">
>     
>             </appender-ref>
>         </root>
>     
>     </configuration>

>     jdbc.driver=com.mysql.cj.jdbc.Driver
>     jdbc.url=jdbc:mysql://localhost:13306/powernode
>     jdbc.username=root
>     jdbc.password=abc123
> 
>     jdbc.driver=com.mysql.cj.jdbc.Driver
>     jdbc.url=jdbc:mysql://localhost:13306/powernode
>     jdbc.username=root
>     jdbc.password=abc123

>     <?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.powernode.mybatis.Mapper.CarMapper">
>         <delete id="deleteBatch">
>             delete from
>                 t_car
>             where
>                 car_num
>             in
>                 (${carNums});
>         </delete>
>         <select id="selectByBrand" resultType="Car">
>             select
>                 id as id,
>                 car_num as carNum,
>                 brand as brand,
>                 guide_price as guidePrice,
>                 produce_time as produceTime,
>                 car_type as carType
>             from
>                 t_car
>             where
>     --             brand like '%${brand}%'
>     --             brand like concat('%',#{brand},'%')
>                 brand like concat('%','${brand}','%')
>                 brand like concat("%"#{brand}"%")
>         </select>
>         <select id="selectByCarType" resultType="Car">
>             select
>                 id as id,
>                 car_num as carNum,
>                 brand as brand,
>                 guide_price as guidePrice,
>                 produce_time as produceTime,
>                 car_type as carType
>             from
>                 t_car
>             where
>                 car_type = #{carType}
>         </select>
>         <select id="selectAllByAscOrDesc" resultType="Car">
>             select
>                 id as id,
>                 car_num as carNum,
>                 brand as brand,
>                 guide_price as guidePrice,
>                 produce_time as produceTime,
>                 car_type as carType
>             from
>                 t_car
>             order by
>                 guide_price ${DescOrAsc};
>         </select>
>     </mapper>
> 
>     <?xml version="1.0" encoding="UTF-8"?>
>     
>     <!DOCTYPE mapper
>             PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
>             "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
>     
>     <mapper namespace="com.powernode.mybatis.Mapper.CarMapper">
>         <delete id="deleteBatch">
>             delete from
>                 t_car
>             where
>                 car_num
>             in
>                 (${carNums});
>         </delete>
>         <select id="selectByBrand" resultType="Car">
>             select
>                 id as id,
>                 car_num as carNum,
>                 brand as brand,
>                 guide_price as guidePrice,
>                 produce_time as produceTime,
>                 car_type as carType
>             from
>                 t_car
>             where
>     --             brand like '%${brand}%'
>     --             brand like concat('%',#{brand},'%')
>                 brand like concat('%','${brand}','%')
>                 brand like concat("%"#{brand}"%")
>         </select>
>         <select id="selectByCarType" resultType="Car">
>             select
>                 id as id,
>                 car_num as carNum,
>                 brand as brand,
>                 guide_price as guidePrice,
>                 produce_time as produceTime,
>                 car_type as carType
>             from
>                 t_car
>             where
>                 car_type = #{carType}
>         </select>
>         <select id="selectAllByAscOrDesc" resultType="Car">
>             select
>                 id as id,
>                 car_num as carNum,
>                 brand as brand,
>                 guide_price as guidePrice,
>                 produce_time as produceTime,
>                 car_type as carType
>             from
>                 t_car
>             order by
>                 guide_price ${DescOrAsc};
>         </select>
>     </mapper>

>     package com.powernode.mybatis.Mapper;
>     
>     import com.powernode.mybatis.POJO.Car;
>     
>     import java.util.List;
>     
>     public interface CarMapper
>     {
>         //根据汽车类型,获取汽车信息
>         List<Car> selectByCarType(String carType);
>         //查询所有的汽车信息,通过DESC或者ASC升降序
>         List<Car> selectAllByAscOrDesc(String AscOrDesc);
>         //根据ID进行批量删除
>         int deleteBatch(String carNums);
>         List<Car> selectByBrand(String brand);
>     }
> 
>     package com.powernode.mybatis.Mapper;
>     
>     import com.powernode.mybatis.POJO.Car;
>     
>     import java.util.List;
>     
>     public interface CarMapper
>     {
>         //根据汽车类型,获取汽车信息
>         List<Car> selectByCarType(String carType);
>         //查询所有的汽车信息,通过DESC或者ASC升降序
>         List<Car> selectAllByAscOrDesc(String AscOrDesc);
>         //根据ID进行批量删除
>         int deleteBatch(String carNums);
>         List<Car> selectByBrand(String brand);
>     }

>     package com.powernode.mybatis.Mapper;
>     
>     import com.powernode.mybatis.POJO.Log;
>     
>     import java.util.List;
>     
>     public interface LogMapper
>     {
>         //根据日期查询不同的表,获取表中所有的日志
>         List<Log> selectAllByTable(String time);
>     }
> 
>     package com.powernode.mybatis.Mapper;
>     
>     import com.powernode.mybatis.POJO.Log;
>     
>     import java.util.List;
>     
>     public interface LogMapper
>     {
>         //根据日期查询不同的表,获取表中所有的日志
>         List<Log> selectAllByTable(String time);
>     }

>     package com.powernode.mybatis.POJO;
>     
>     public class Car
>     {
>         //这是一个封装汽车相关信息的普通的java类,数据库表中的字段应该和属性一一对应
>         //为什么使用包装类,因为当我们查值的时候,返回值有可能是null
>         //避免数据不兼容
>         private Long id;
>         private String carNum;
>         private String brand;
>         private Double guidePrice;
>         private String produceTime;
>         private String carType;
>         public Car(){};
>     
>         public Car(Long id, String carNum, String brand, Double guidePrice, String produceTime, String carType) {
>             this.id = id;
>             this.carNum = carNum;
>             this.brand = brand;
>             this.guidePrice = guidePrice;
>             this.produceTime = produceTime;
>             this.carType = carType;
>         }
>     
>         public Long getId() {
>             return id;
>         }
>     
>         public void setId(Long id) {
>             this.id = id;
>         }
>     
>         public String getCarNum() {
>             return carNum;
>         }
>     
>         public void setCarNum(String carNum) {
>             this.carNum = carNum;
>         }
>     
>         public String getBrand() {
>             return brand;
>         }
>     
>         public void setBrand(String brand) {
>             this.brand = brand;
>         }
>     
>         public Double getGuidePrice() {
>             return guidePrice;
>         }
>     
>         public void setGuidePrice(Double guidePrice) {
>             this.guidePrice = guidePrice;
>         }
>     
>         public String getProduceTime() {
>             return produceTime;
>         }
>     
>         public void setProduceTime(String produceTime) {
>             this.produceTime = produceTime;
>         }
>     
>         public String getCarType() {
>             return carType;
>         }
>     
>         public void setCarType(String carType) {
>             this.carType = carType;
>         }
>     
>         @Override
>         public String toString() {
>             return "Car{" +
>                     "id=" + id +
>                     ", carNum='" + carNum + '\'' +
>                     ", brand='" + brand + '\'' +
>                     ", guidePrice=" + guidePrice +
>                     ", produceTime='" + produceTime + '\'' +
>                     ", carType='" + carType + '\'' +
>                     '}';
>         }
>     }
> 
>     package com.powernode.mybatis.POJO;
>     
>     public class Car
>     {
>         //这是一个封装汽车相关信息的普通的java类,数据库表中的字段应该和属性一一对应
>         //为什么使用包装类,因为当我们查值的时候,返回值有可能是null
>         //避免数据不兼容
>         private Long id;
>         private String carNum;
>         private String brand;
>         private Double guidePrice;
>         private String produceTime;
>         private String carType;
>         public Car(){};
>     
>         public Car(Long id, String carNum, String brand, Double guidePrice, String produceTime, String carType) {
>             this.id = id;
>             this.carNum = carNum;
>             this.brand = brand;
>             this.guidePrice = guidePrice;
>             this.produceTime = produceTime;
>             this.carType = carType;
>         }
>     
>         public Long getId() {
>             return id;
>         }
>     
>         public void setId(Long id) {
>             this.id = id;
>         }
>     
>         public String getCarNum() {
>             return carNum;
>         }
>     
>         public void setCarNum(String carNum) {
>             this.carNum = carNum;
>         }
>     
>         public String getBrand() {
>             return brand;
>         }
>     
>         public void setBrand(String brand) {
>             this.brand = brand;
>         }
>     
>         public Double getGuidePrice() {
>             return guidePrice;
>         }
>     
>         public void setGuidePrice(Double guidePrice) {
>             this.guidePrice = guidePrice;
>         }
>     
>         public String getProduceTime() {
>             return produceTime;
>         }
>     
>         public void setProduceTime(String produceTime) {
>             this.produceTime = produceTime;
>         }
>     
>         public String getCarType() {
>             return carType;
>         }
>     
>         public void setCarType(String carType) {
>             this.carType = carType;
>         }
>     
>         @Override
>         public String toString() {
>             return "Car{" +
>                     "id=" + id +
>                     ", carNum='" + carNum + '\'' +
>                     ", brand='" + brand + '\'' +
>                     ", guidePrice=" + guidePrice +
>                     ", produceTime='" + produceTime + '\'' +
>                     ", carType='" + carType + '\'' +
>                     '}';
>         }
>     }

>     package com.powernode.mybatis.POJO;
>     
>     public class Log
>     {
>         private Long id;
>         private String log;
>         private String time;
>     
>         @Override
>         public String toString() {
>             return "Log{" +
>                     "id=" + id +
>                     ", log='" + log + '\'' +
>                     ", time='" + time + '\'' +
>                     '}';
>         }
>     
>         public Long getId() {
>             return id;
>         }
>     
>         public void setId(Long id) {
>             this.id = id;
>         }
>     
>         public String getLog() {
>             return log;
>         }
>     
>         public void setLog(String log) {
>             this.log = log;
>         }
>     
>         public String getTime() {
>             return time;
>         }
>     
>         public void setTime(String time) {
>             this.time = time;
>         }
>     
>         public Log(Long id, String log, String time) {
>             this.id = id;
>             this.log = log;
>             this.time = time;
>         }
>     
>         public Log() {
>         }
>     }
> 
>     package com.powernode.mybatis.POJO;
>     
>     public class Log
>     {
>         private Long id;
>         private String log;
>         private String time;
>     
>         @Override
>         public String toString() {
>             return "Log{" +
>                     "id=" + id +
>                     ", log='" + log + '\'' +
>                     ", time='" + time + '\'' +
>                     '}';
>         }
>     
>         public Long getId() {
>             return id;
>         }
>     
>         public void setId(Long id) {
>             this.id = id;
>         }
>     
>         public String getLog() {
>             return log;
>         }
>     
>         public void setLog(String log) {
>             this.log = log;
>         }
>     
>         public String getTime() {
>             return time;
>         }
>     
>         public void setTime(String time) {
>             this.time = time;
>         }
>     
>         public Log(Long id, String log, String time) {
>             this.id = id;
>             this.log = log;
>             this.time = time;
>         }
>     
>         public Log() {
>         }
>     }

>     package com.powernode.mybatis.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;
>     
>     public class SqlSessionUtils
>     {
>         private SqlSessionUtils(){}
>         private static SqlSessionFactory sqlSessionFactory;
>         private static ThreadLocal<SqlSession> local = new ThreadLocal<>();
>         static
>         {
>             try
>             {
>                 sqlSessionFactory = new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream("mybatis-config.xml"));
>             }
>             catch (IOException e)
>             {
>                 throw new RuntimeException(e);
>             }
>         }
>         public static SqlSession openSession()
>         {
>             SqlSession sqlSession = local.get();
>             if (sqlSession == null)
>             {
>                 sqlSession = sqlSessionFactory.openSession();
>                 local.set(sqlSession);
>             }
>             return sqlSession;
>         }
>     
>         public static void close(SqlSession sqlSession)
>         {
>             if(sqlSession != null)
>             {
>                 sqlSession.close();
>                 local.remove();
>             }
>         }
>     }
> 
>     package com.powernode.mybatis.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;
>     
>     public class SqlSessionUtils
>     {
>         private SqlSessionUtils(){}
>         private static SqlSessionFactory sqlSessionFactory;
>         private static ThreadLocal<SqlSession> local = new ThreadLocal<>();
>         static
>         {
>             try
>             {
>                 sqlSessionFactory = new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream("mybatis-config.xml"));
>             }
>             catch (IOException e)
>             {
>                 throw new RuntimeException(e);
>             }
>         }
>         public static SqlSession openSession()
>         {
>             SqlSession sqlSession = local.get();
>             if (sqlSession == null)
>             {
>                 sqlSession = sqlSessionFactory.openSession();
>                 local.set(sqlSession);
>             }
>             return sqlSession;
>         }
>     
>         public static void close(SqlSession sqlSession)
>         {
>             if(sqlSession != null)
>             {
>                 sqlSession.close();
>                 local.remove();
>             }
>         }
>     }

>     package com.powernode.mybatis.Test;
>     
>     import com.powernode.mybatis.Mapper.CarMapper;
>     import com.powernode.mybatis.Mapper.LogMapper;
>     import com.powernode.mybatis.POJO.Car;
>     import com.powernode.mybatis.POJO.Log;
>     import com.powernode.mybatis.utils.SqlSessionUtils;
>     import org.apache.ibatis.session.SqlSession;
>     import org.junit.Test;
>     
>     import java.util.Iterator;
>     import java.util.List;
>     
>     public class CarMapperTest
>     {
>         @Test
>         public void TestMapper()
>         {
>             SqlSession sqlSession = SqlSessionUtils.openSession();
>             CarMapper mapper = sqlSession.getMapper(CarMapper.class);
>             List<Car> carList = mapper.selectByCarType("新能源");
>             carList.forEach(car ->
>             {
>                 System.out.println(car);
>             });
>             SqlSessionUtils.close(sqlSession);
>         }
>         @Test
>         public void TestDescOrAsc()
>         {
>             SqlSession sqlSession = SqlSessionUtils.openSession();
>             CarMapper mapper = sqlSession.getMapper(CarMapper.class);
>             List<Car> carList = mapper.selectAllByAscOrDesc("DESC");
>             carList.forEach(car -> {
>                 System.out.println(car);
>             });
>             SqlSessionUtils.close(sqlSession);
>         }
>         @Test
>         public void TestLog()
>         {
>             SqlSession sqlSession = SqlSessionUtils.openSession();
>             LogMapper mapper = sqlSession.getMapper(LogMapper.class);
>             List<Log> logs = mapper.selectAllByTable("20230902");
>             Iterator<Log> iterator = logs.iterator();
>             while(iterator.hasNext())
>             {
>                 System.out.println((Log)iterator.next());
>             }
>         }
>         @Test
>         public void TestDelete()
>         {
>             SqlSession sqlSession = SqlSessionUtils.openSession();
>             CarMapper mapper = sqlSession.getMapper(CarMapper.class);
>             int count = mapper.deleteBatch("1003,1111");
>             System.out.println(count);
>             sqlSession.commit();
>             SqlSessionUtils.close(sqlSession);
>         }
>         @Test
>         public void SelectByBrandLike()
>         {
>             SqlSession sqlSession = SqlSessionUtils.openSession();
>             CarMapper mapper = sqlSession.getMapper(CarMapper.class);
>             List<Car> carList = mapper.selectByBrand("比亚迪");
>             carList.forEach(car -> {
>                 System.out.println(car);
>             });
>         }
>     }