目录

• 一、前言
• 二、直接把list怼进Mysql
• 三、分组把list导入Mysql中
• 四、多线程分批导入Mysql
• 五、小结

一、前言
前两天做了一个导入的功能，导入开始的时候非常慢，导入2w条数据要1分多钟，后来一点一点的优化，从直接把list怼进Mysql中，到分配把list导入Mysql中，到多线程把list导入Mysql中。时间是一点一点的变少了。非常的爽，最后变成了10s以内。下面就展示一下过程。

二、直接把list怼进Mysql
使用mybatis的批量导入操作：

@Transactional(rollbackFor = Exception.class)public int addFreshStudentsNew2(List list, String schoolNo) {if (list == null || list.isEmpty()) {return 0; }List studentEntityList = new LinkedList<>(); List enrollStudentEntityList = new LinkedList<>(); List allusersEntityList = new LinkedList<>(); for (FreshStudentAndStudentModel freshStudentAndStudentModel : list) {EnrollStudentEntity enrollStudentEntity = new EnrollStudentEntity(); StudentEntity studentEntity = new StudentEntity(); BeanUtils.copyProperties(freshStudentAndStudentModel, studentEntity); BeanUtils.copyProperties(freshStudentAndStudentModel, enrollStudentEntity); String operator = TenancyContext.UserID.get(); String studentId = BaseUuidUtils.base58Uuid(); enrollStudentEntity.setId(BaseUuidUtils.base58Uuid()); enrollStudentEntity.setStudentId(studentId); enrollStudentEntity.setIdentityCardId(freshStudentAndStudentModel.getIdCard()); enrollStudentEntity.setOperator(operator); studentEntity.setId(studentId); studentEntity.setIdentityCardId(freshStudentAndStudentModel.getIdCard()); studentEntity.setOperator(operator); studentEntityList.add(studentEntity); enrollStudentEntityList.add(enrollStudentEntity); AllusersEntity allusersEntity = new AllusersEntity(); allusersEntity.setId(enrollStudentEntity.getId()); allusersEntity.setUserCode(enrollStudentEntity.getNemtCode()); allusersEntity.setUserName(enrollStudentEntity.getName()); allusersEntity.setSchoolNo(schoolNo); allusersEntity.setTelNum(enrollStudentEntity.getTelNum()); allusersEntity.setPassword(enrollStudentEntity.getNemtCode()); //密码设置为考生号allusersEntityList.add(allusersEntity); }enResult = enrollStudentDao.insertAll(enrollStudentEntityList); stuResult = studentDao.insertAll(studentEntityList); allResult = allusersFacade.insertUserList(allusersEntityList); if (enResult > 0 && stuResult > 0 && allResult) {return 10; }return -10; }

Mapper.xml

insert into tb_enroll_studentid,remark,nEMT_aspiration,nEMT_code,nEMT_score,student_id,identity_card_id,level,major,name,nation,secondary_college,operator,sex,is_delete,account_address,native_place,original_place,used_name,pictrue,join_party_date,political_status,tel_num,is_registry,graduate_school,create_time,update_timevalues(#{item.id,jdbcType=VARCHAR},#{item.remark,jdbcType=VARCHAR},#{item.nemtAspiration,jdbcType=VARCHAR},#{item.nemtCode,jdbcType=VARCHAR},#{item.nemtScore,jdbcType=VARCHAR},#{item.studentId,jdbcType=VARCHAR},#{item.identityCardId,jdbcType=VARCHAR},#{item.level,jdbcType=VARCHAR},#{item.major,jdbcType=VARCHAR},#{item.name,jdbcType=VARCHAR},#{item.nation,jdbcType=VARCHAR},#{item.secondaryCollege,jdbcType=VARCHAR},#{item.operator,jdbcType=VARCHAR},#{item.sex,jdbcType=VARCHAR},0,#{item.accountAddress,jdbcType=VARCHAR},#{item.nativePlace,jdbcType=VARCHAR},#{item.originalPlace,jdbcType=VARCHAR},#{item.usedName,jdbcType=VARCHAR},#{item.pictrue,jdbcType=VARCHAR},#{item.joinPartyDate,jdbcType=VARCHAR},#{item.politicalStatus,jdbcType=VARCHAR},#{item.telNum,jdbcType=VARCHAR},#{item.isRegistry,jdbcType=TINYINT},#{item.graduateSchool,jdbcType=VARCHAR},now(),now())

代码说明：
【java多线程批量拆分List导入数据库的实现过程】底层的mapper是通过逆向工程来生成的，批量插入如下，是拼接成类似： insert into tb_enroll_student（）values （），（）…….（） ；
这样的缺点是，数据库一般有一个默认的设置，就是每次sql操作的数据不能超过4M。这样插入，数据多的时候，数据库会报错Packet for query is too large (6071393 > 4194304). You can change this value on the server by setting the max_allowed_packet' variable.，虽然我们可以通过
类似 修改 my.ini 加上 max_allowed_packet =67108864
67108864=64M
默认大小4194304 也就是4M
修改完成之后要重启mysql服务，如果通过命令行修改就不用重启mysql服务。
完成本次操作，但是我们不能保证项目单次最大的大小是多少，这样是有弊端的。所以可以考虑进行分组导入。

三、分组把list导入Mysql中
同样适用mybatis批量插入，区别是对每次的导入进行分组计算，然后分多次进行导入：

@Transactional(rollbackFor = Exception.class)public int addFreshStudentsNew2(List list, String schoolNo) {if (list == null || list.isEmpty()) {return 0; }List studentEntityList = new LinkedList<>(); List enrollStudentEntityList = new LinkedList<>(); List allusersEntityList = new LinkedList<>(); for (FreshStudentAndStudentModel freshStudentAndStudentModel : list) {EnrollStudentEntity enrollStudentEntity = new EnrollStudentEntity(); StudentEntity studentEntity = new StudentEntity(); BeanUtils.copyProperties(freshStudentAndStudentModel, studentEntity); BeanUtils.copyProperties(freshStudentAndStudentModel, enrollStudentEntity); String operator = TenancyContext.UserID.get(); String studentId = BaseUuidUtils.base58Uuid(); enrollStudentEntity.setId(BaseUuidUtils.base58Uuid()); enrollStudentEntity.setStudentId(studentId); enrollStudentEntity.setIdentityCardId(freshStudentAndStudentModel.getIdCard()); enrollStudentEntity.setOperator(operator); studentEntity.setId(studentId); studentEntity.setIdentityCardId(freshStudentAndStudentModel.getIdCard()); studentEntity.setOperator(operator); studentEntityList.add(studentEntity); enrollStudentEntityList.add(enrollStudentEntity); AllusersEntity allusersEntity = new AllusersEntity(); allusersEntity.setId(enrollStudentEntity.getId()); allusersEntity.setUserCode(enrollStudentEntity.getNemtCode()); allusersEntity.setUserName(enrollStudentEntity.getName()); allusersEntity.setSchoolNo(schoolNo); allusersEntity.setTelNum(enrollStudentEntity.getTelNum()); allusersEntity.setPassword(enrollStudentEntity.getNemtCode()); //密码设置为考生号allusersEntityList.add(allusersEntity); }int c = 100; int b = enrollStudentEntityList.size() / c; int d = enrollStudentEntityList.size() % c; int enResult = 0; int stuResult = 0; boolean allResult = false; for (int e = c; e <= c * b; e = e + c) {enResult = enrollStudentDao.insertAll(enrollStudentEntityList.subList(e - c, e)); stuResult = studentDao.insertAll(studentEntityList.subList(e - c, e)); allResult = allusersFacade.insertUserList(allusersEntityList.subList(e - c, e)); }if (d != 0) {enResult = enrollStudentDao.insertAll(enrollStudentEntityList.subList(c * b, enrollStudentEntityList.size())); stuResult = studentDao.insertAll(studentEntityList.subList(c * b, studentEntityList.size())); allResult = allusersFacade.insertUserList(allusersEntityList.subList(c * b, allusersEntityList.size())); }if (enResult > 0 && stuResult > 0 && allResult) {return 10; }return -10; }

代码说明：
这样操作，可以避免上面的错误，但是分多次插入，无形中就增加了操作实践，很容易超时。所以这种方法还是不值得提倡的。
再次改进，使用多线程分批导入。

四、多线程分批导入Mysql
依然使用mybatis的批量导入，不同的是，根据线程数目进行分组，然后再建立多线程池，进行导入。

@Transactional(rollbackFor = Exception.class)public int addFreshStudentsNew(List list, String schoolNo) {if (list == null || list.isEmpty()) {return 0; }List studentEntityList = new LinkedList<>(); List enrollStudentEntityList = new LinkedList<>(); List allusersEntityList = new LinkedList<>(); list.forEach(freshStudentAndStudentModel -> {EnrollStudentEntity enrollStudentEntity = new EnrollStudentEntity(); StudentEntity studentEntity = new StudentEntity(); BeanUtils.copyProperties(freshStudentAndStudentModel, studentEntity); BeanUtils.copyProperties(freshStudentAndStudentModel, enrollStudentEntity); String operator = TenancyContext.UserID.get(); String studentId = BaseUuidUtils.base58Uuid(); enrollStudentEntity.setId(BaseUuidUtils.base58Uuid()); enrollStudentEntity.setStudentId(studentId); enrollStudentEntity.setIdentityCardId(freshStudentAndStudentModel.getIdCard()); enrollStudentEntity.setOperator(operator); studentEntity.setId(studentId); studentEntity.setIdentityCardId(freshStudentAndStudentModel.getIdCard()); studentEntity.setOperator(operator); studentEntityList.add(studentEntity); enrollStudentEntityList.add(enrollStudentEntity); AllusersEntity allusersEntity = new AllusersEntity(); allusersEntity.setId(enrollStudentEntity.getId()); allusersEntity.setUserCode(enrollStudentEntity.getNemtCode()); allusersEntity.setUserName(enrollStudentEntity.getName()); allusersEntity.setSchoolNo(schoolNo); allusersEntity.setTelNum(enrollStudentEntity.getTelNum()); allusersEntity.setPassword(enrollStudentEntity.getNemtCode()); //密码设置为考生号allusersEntityList.add(allusersEntity); }); int nThreads = 50; int size = enrollStudentEntityList.size(); ExecutorService executorService = Executors.newFixedThreadPool(nThreads); List> futures = new ArrayList>(nThreads); for (int i = 0; i < nThreads; i++) {final List EnrollStudentEntityImputList = enrollStudentEntityList.subList(size / nThreads * i, size / nThreads * (i + 1)); final List studentEntityImportList = studentEntityList.subList(size / nThreads * i, size / nThreads * (i + 1)); final List allusersEntityImportList = allusersEntityList.subList(size / nThreads * i, size / nThreads * (i + 1)); Callable task1 = () -> {studentSave.saveStudent(EnrollStudentEntityImputList,studentEntityImportList,allusersEntityImportList); return 1; }; futures.add(executorService.submit(task1)); }executorService.shutdown(); if (!futures.isEmpty() && futures != null) {return 10; }return -10; }

代码说明：
上面是通过应用ExecutorService 建立了固定的线程数，然后根据线程数目进行分组，批量依次导入。一方面可以缓解数据库的压力，另一个面线程数目多了，一定程度会提高程序运行的时间。缺点就是要看服务器的配置，如果配置好的话就可以开多点线程，配置差的话就开小点。

五、小结
通过使用这个操作真是不断的提高了，项目使用技巧也是不错。加油~~ 多线程哦~~
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