java多线程批量拆分List导入数据库的实现过程

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~~

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