Java多线程批量拆分List导入数据库

# 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

推荐阅读：[看看人家 SpringBoot + vue后台管理系统，多么优雅...](https://mp.weixin.qq.com/s/jGEkHTf2X8l-wUenc-PpEw)

```
<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。

# 二、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：

for (FreshStudentAndStudentModel freshStudentAndStudentModel : list) {

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);

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~~

Java多线程批量拆分List导入数据库

全部评论: 0 条

最新发布

最新评论