Java多线程批量拆分List导入数据库

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来源：https://blog.csdn.net/kisscatforever/article/details/79817039

# 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。

# 直接把list怼进Mysql

使用mybatis的批量导入操作：

@Transactional(rollbackFor = Exception.class)publicintaddFreshStudentsNew2(List<FreshStudentAndStudentModel> list, String schoolNo) {if (list == null || list.isEmpty()) {return0; } List<StudentEntity> studentEntityList = new LinkedList<>(); List<EnrollStudentEntity> enrollStudentEntityList = new LinkedList<>(); List<AllusersEntity> 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) {return10; }return-10; }

Mapper.xml

代码说明：

<insert id="insertAll" parameterType="com.dmsdbj.itoo.basicInfo.entity.EnrollStudentEntity"> insert into tb_enroll_student <trim prefix="(" suffix=")" suffixOverrides=","> id, 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_time </trim> values <foreach collection="list" item="item" index="index" separator=","> ( #{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() ) </foreach> </insert>

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。

# 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：

代码说明：

@Transactional(rollbackFor = Exception.class) public int addFreshStudentsNew2(List<FreshStudentAndStudentModel> list, String schoolNo) { if (list == null || list.isEmpty()) { return 0; } List<StudentEntity> studentEntityList = new LinkedList<>(); List<EnrollStudentEntity> enrollStudentEntityList = new LinkedList<>(); List<AllusersEntity> 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; }

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。

# 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。

代码说明：

@Transactional(rollbackFor = Exception.class)public int addFreshStudentsNew(List<FreshStudentAndStudentModel> list, String schoolNo) {if (list == null || list.isEmpty()) {return0; }List<StudentEntity> studentEntityList = new LinkedList<>();List<EnrollStudentEntity> enrollStudentEntityList = new LinkedList<>();List<AllusersEntity> 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<Future<Integer>> futures = new ArrayList<Future<Integer>>(nThreads);for (int i = 0; i < nThreads; i++) {

finalList<EnrollStudentEntity> EnrollStudentEntityImputList = enrollStudentEntityList.subList(size / nThreads * i, size / nThreads * (i + 1));

finalList<StudentEntity> studentEntityImportList = studentEntityList.subList(size / nThreads * i, size / nThreads * (i + 1));

finalList<AllusersEntity> allusersEntityImportList = allusersEntityList.subList(size / nThreads * i, size / nThreads * (i + 1));

Callable<Integer> task1 = () -> { studentSave.saveStudent(EnrollStudentEntityImputList,studentEntityImportList,allusersEntityImportList);return1; }; futures.add(executorService.submit(task1)); } executorService.shutdown();if (!futures.isEmpty() && futures != null) {return10; }return-10; }

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。

# 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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