超市订单管理系统

　　GitHub: github.com/hsowan/somsSOMS
　　Supermarket Orders Management System 超市订单管理系统Day 01
　　使用MyBatisMyBatis 官方文档
　　Refer: www.mybatis.org/mybatis-3/z…类型别名
　　类型别名是你的好帮手。使用它们，你就可以不用输入类的完全限定名称了。比如：       select id, username, hashedPassword   from some_table   where id = #{id}  复制代码log4j2
　　Refer: logging.apache.org/log4j/2.x/m…Eclipse for Mac 快捷键删除一行
　　Command + D
　　Refer: www.cnblogs.com/TankXiao/p/…格式化代码
　　Shift + Command + FDay 02
　　MyBatis 核心配置mybatis-config.xml 配置configuration（配置）properties（属性）settings（设置）typeAliases（类型别名）typeHandlers（类型处理器）objectFactory（对象工厂）plugins（插件）environments（环境配置） environment（环境变量） transactionManager（事务管理器） dataSource（数据源）databaseIdProvider（数据库厂商标识）mappers（映射器）
　　Refer: www.mybatis.org/mybatis-3/z…mapper.xml 配置insert – 映射插入语句update – 映射更新语句delete – 映射删除语句select – 映射查询语句resultMap – 是最复杂也是最强大的元素，用来描述如何从数据库结果集中来加载对象。sql – 可被其他语句引用的可重用语句块。cache – 对给定命名空间的缓存配置。cache-ref – 对其他命名空间缓存配置的引用。
　　Refer: www.mybatis.org/mybatis-3/z…使用单例模式创建SqlSessionFactory/**   * 主配置文件路径   */ private static String config = ＂mybatis-config.xml＂; private static SqlSessionFactory sqlSessionFactory;  /**   * 使用单例模式获取SqlSessionFactory   * @return   */ private static synchronized SqlSessionFactory getSqlSessionFactory() { 	 	if (sqlSessionFactory == null) { 		try { 			// 创建输入流读取配置文件 			InputStream is = Resources.getResourceAsStream(config); 			// 创建SQLSession工厂 			sqlSessionFactory = new SqlSessionFactoryBuilder().build(is); 			 		} catch (IOException e) { 			// TODO Auto-generated catch block 			e.printStackTrace(); 		} 	} 	return sqlSessionFactory; } 复制代码MavenUsing JUnit
　　添加下面的插件到pom.xml中: 	org.apache.maven.plugins 	maven-surefire-plugin 	3.0.0-M3  复制代码
　　执行单元测试: mvn test
　　Refer: maven.apache.org/surefire/ma…Skipping Tests
　　mvn install -DskipTests
　　Refer: maven.apache.org/surefire/ma…JSP 九大内置对象+四大域对象
　　Refer: my.oschina.net/u/3805464/b…Java 八大基本类型byte/8 char/16 short/16 int/32 float/32 long/64 double/64 boolean/~ 复制代码Day 03
　　动态SQL官方文档ifchoose (when, otherwise)trim (where, set)foreachbind
　　www.mybatis.org/mybatis-3/z…if
　　改写UserMapper.xml: 	select id, username, password 	from user 	where username like #{username} 	 	 		limit #{start}, #{count} 	  复制代码
　　改写单元测试 testListByUsername(使用map进行传参):Map params = new HashMap(); params.put(＂username＂, ＂%user%＂);  List users = session.selectList(＂com.ncucoder.mapper.UserMapper.listByUsername＂, params); 复制代码
　　执行结果:==>  Preparing: select id, username, password from user where username like ?  ==> Parameters: %user%(String) 复制代码
　　添加单元测试 testListByUsernameUsingLimit:Map params = new HashMap(); params.put(＂username＂, ＂%user%＂); params.put(＂start＂, 0); params.put(＂count＂, 2);  List users = session.selectList(＂com.ncucoder.mapper.UserMapper.listByUsername＂, params); 复制代码
　　执行结果:==>  Preparing: select id, username, password from user where username like ? limit ?, ?  ==> Parameters: %user%(String), 0(Integer), 2(Integer) 复制代码bind 模糊查询
　　修改UserMapper.xml:  	 	select id, username, password 	from user 	where username like #{username} 	 		limit #{start}, #{count} 	  复制代码
　　修改单元测试 testListByUsername():Map params = new HashMap(); // params.put(＂username＂, ＂%user%＂); params.put(＂username＂, ＂user＂);  List users = session.selectList(＂com.ncucoder.mapper.UserMapper.listByUsername＂, params); 复制代码
　　执行结果:==>  Preparing: select id, username, password from user where username like ?  ==> Parameters: %user%(String) 复制代码SQL优化 in
　　查询user表中id小于5的记录
　　使用in的查询执行计划(QEP):mysql> explain select id, username, password from user where id in (1, 2, 3, 4, 5); +----+-------------+-------+------------+------+---------------+------+---------+------+------+----------+-------------+ | id | select_type | table | partitions | type | possible_keys | key  | key_len | ref  | rows | filtered | Extra       | +----+-------------+-------+------------+------+---------------+------+---------+------+------+----------+-------------+ |  1 | SIMPLE      | user  | NULL       | ALL  | PRIMARY       | NULL | NULL    | NULL |   10 |    50.00 | Using where | +----+-------------+-------+------------+------+---------------+------+---------+------+------+----------+-------------+ 1 row in set, 1 warning (0.00 sec) 复制代码
　　使用<的QEP:mysql> explain select id, username, password from user where id < 6; +----+-------------+-------+------------+-------+---------------+---------+---------+------+------+----------+-------------+ | id | select_type | table | partitions | type  | possible_keys | key     | key_len | ref  | rows | filtered | Extra       | +----+-------------+-------+------------+-------+---------------+---------+---------+------+------+----------+-------------+ |  1 | SIMPLE      | user  | NULL       | range | PRIMARY       | PRIMARY | 4       | NULL |    5 |   100.00 | Using where | +----+-------------+-------+------------+-------+---------------+---------+---------+------+------+----------+-------------+ 1 row in set, 1 warning (0.00 sec) 复制代码
　　使用between的QEP:mysql> explain select id, username, password from user where id between 1 and 5; +----+-------------+-------+------------+-------+---------------+---------+---------+------+------+----------+-------------+ | id | select_type | table | partitions | type  | possible_keys | key     | key_len | ref  | rows | filtered | Extra       | +----+-------------+-------+------------+-------+---------------+---------+---------+------+------+----------+-------------+ |  1 | SIMPLE      | user  | NULL       | range | PRIMARY       | PRIMARY | 4       | NULL |    5 |   100.00 | Using where | +----+-------------+-------+------------+-------+---------------+---------+---------+------+------+----------+-------------+ 1 row in set, 1 warning (0.00 sec) 复制代码type表示对表所使用的访问方式(最优到最差: NULL > system > const > eq_ref > ref > range > index > All)key表示MySQL Query Optimizer从possible_keys中所选择使用的索引rows表示MySQL Query Optimizer通过系统收集到的统计信息估算出来的结果集记录条数, 简单理解为查询需要扫描的记录数
　　分析: 使用in作为查询条件时没有使用索引而进行了全表扫描(ALL), 使用<和between作为查询条件时使用到主键索引以及索引范围扫描, 所以三者比较in的执行效率是最低的MySQL 批量插入测试数据-- 获取指定长度的随机字符串 drop function if exists `rand_string`; create function `rand_string`(n int) returns varchar(255) charset ＂utf8＂ begin     DECLARE chars_str varchar(100) DEFAULT ＂abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789＂;     DECLARE return_str varchar(255) DEFAULT ＂＂;     DECLARE i INT DEFAULT 0;     WHILE i < n DO     SET return_str = concat(return_str, substring(chars_str, FLOOR(1 + RAND() * 62), 1));     SET i = i + 1;     END WHILE;     RETURN return_str; end;  -- 插入指定数量的用户 drop procedure if exists `create_users`; create procedure `create_users`(n int) begin     declare i int default 0;     while (i < n) do         insert into user(username, password)         values (rand_string(10), rand_string(32));         set i = i + 1;     end while; end;  -- 调用存储过程 call create_users(1000);  复制代码Day 04MyBatis Generator官方文档
　　www.mybatis.org/generator/c…
　　问题:改用MySQL8时, 与其他数据库(mysql库)表名相同时出现错误添加依赖和插件
　　mybatis-generator-core:    org.mybatis.generator    mybatis-generator-core    ${mybatis-generator.version}   复制代码
　　mybatis-generator-maven-plugin:    org.mybatis.generator    mybatis-generator-maven-plugin    ${mybatis-generator.version}           true       true       复制代码添加配置文件generatorConfig.xml生成对应的映射文件、实体类和接口类cd ${your_project} mvn mybatis-generator:generator  复制代码
　　Refer:www.cnblogs.com/hhhshct/p/9…blog.csdn.net/liyonghong3…集成SpringMVC添加依赖      org.springframework     spring-core     ${spring.version}       org.springframework     spring-web     ${spring.version}       org.springframework     spring-webmvc     ${spring.version}       org.springframework     spring-beans     ${spring.version}       org.springframework     spring-context     ${spring.version}       org.springframework     spring-test     ${spring.version}     test       org.springframework     spring-jdbc     ${spring.version}       org.springframework     spring-tx     ${spring.version}       org.mybatis     mybatis-spring     ${mybatis-spring.version}         com.alibaba     druid     ${druid.version}   复制代码修改web.xml配置文件      soms-dispatcher     org.springframework.web.servlet.DispatcherServlet              contextConfigLocation         classpath:spring/spring-*.xml          1          true       soms-dispatcher     /        encodingFilter     org.springframework.web.filter.CharacterEncodingFilter              encoding         UTF-8                   forceEncoding         true            encodingFilter     /*  复制代码添加Spring的配置文件spring-web.xmlspring-dao.xmlspring-service.xml使用MySQL8
　　修改依赖版本(pom.xml):8.0.16 复制代码
　　修改驱动路径(db.properties):driver=com.mysql.cj.jdbc.Driver 复制代码Day 05JWT + SpringSecurity
　　github.com/hsowan/jwt-…
　　作者：K8sCat
　　链接：https://juejin.cn/post/7056040075947147295