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# 前言

前兩天做了一個導(dǎo)入的功能，導(dǎo)入開始的時候非常慢，導(dǎo)入2w條數(shù)據(jù)要1分多鐘，后來一點一點的優(yōu)化，從直接把list懟進(jìn)Mysql中，到分配把list導(dǎo)入Mysql中，到多線程把list導(dǎo)入Mysql中。時間是一點一點的變少了。非常的爽，最后變成了10s以內(nèi)。下面就展示一下過程。

# 直接把list懟進(jìn)Mysql

使用mybatis的批量導(dǎo)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());  //密碼設(shè)置為考生號            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

代碼說明：

          insert into tb_enroll_student                        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                        values                (                #{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()                )

底層的mapper是通過逆向工程來生成的，批量插入如下，是拼接成類似：insert into tb_enroll_student（）values （），（）…….（）；

這樣的缺點是，數(shù)據(jù)庫一般有一個默認(rèn)的設(shè)置，就是每次sql操作的數(shù)據(jù)不能超過4M。這樣插入，數(shù)據(jù)多的時候，數(shù)據(jù)庫會報錯Packet for query is too large (6071393 > 4194304). You can change this value on the server by setting the max_allowed_packet' variable.，雖然我們可以通過

類似修改 my.ini 加上 max_allowed_packet =67108864，67108864=64M，默認(rèn)大小4194304 也就是4M

修改完成之后要重啟mysql服務(wù)，如果通過命令行修改就不用重啟mysql服務(wù)。

完成本次操作，但是我們不能保證項目單次最大的大小是多少，這樣是有弊端的。所以可以考慮進(jìn)行分組導(dǎo)入。

# 分組把list導(dǎo)入Mysql中

同樣適用mybatis批量插入，區(qū)別是對每次的導(dǎo)入進(jìn)行分組計算，然后分多次進(jìn)行導(dǎo)入：

代碼說明：

 @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());  //密碼設(shè)置為考生號            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;    }

這樣操作，可以避免上面的錯誤，但是分多次插入，無形中就增加了操作實踐，很容易超時。所以這種方法還是不值得提倡的。

再次改進(jìn)，使用多線程分批導(dǎo)入。

# 多線程分批導(dǎo)入Mysql

依然使用mybatis的批量導(dǎo)入，不同的是，根據(jù)線程數(shù)目進(jìn)行分組，然后再建立多線程池，進(jìn)行導(dǎo)入。

代碼說明：

  @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());  //密碼設(shè)置為考生號            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;????}

上面是通過應(yīng)用ExecutorService 建立了固定的線程數(shù)，然后根據(jù)線程數(shù)目進(jìn)行分組，批量依次導(dǎo)入。一方面可以緩解數(shù)據(jù)庫的壓力，另一個面線程數(shù)目多了，一定程度會提高程序運行的時間。缺點就是要看服務(wù)器的配置，如果配置好的話就可以開多點線程，配置差的話就開小點。

# 小結(jié)

通過使用這個操作真是不斷的提高了，項目使用技巧也是不錯。加油~~ 多線程哦

Java多線程批量拆分List導(dǎo)入數(shù)據(jù)庫