利用多线程批量拆分 List 导入数据库，效率杠杠的！

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<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);  
    }  
        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 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>   

代码说明：

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<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;  
}  

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<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<>();  

    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++) {  
        final List<EnrollStudentEntity> EnrollStudentEntityImputList = enrollStudentEntityList.subList(size / nThreads * i, size / nThreads * (i + 1));  
        final List<StudentEntity> studentEntityImportList = studentEntityList.subList(size / nThreads * i, size / nThreads * (i + 1));  
        final List<AllusersEntity> allusersEntityImportList = allusersEntityList.subList(size / nThreads * i, size / nThreads * (i + 1));  

       Callable<Integer> 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~~