多线程读POI

ゝ一纸荒年。 2022-05-25 14:07 162阅读 0赞

## 在做POI的时候，为了提高性能，我们一般会用多线程来分批读取大量数据。 ##

1.自己写一个类实现Runable接口专为poi实现多线程的线程类

public class POIThread implements Runnable{ 
    
        //从哪一行开始读
        private Integer startRows;
        //读取到哪一行
        private Integer endRows;
        //读取哪一个对象
    
        //POI线程的构造方法
        public POIThread(Integer startRows, Integer endRows, XSSFSheet sheet) {
            super();
            this.startRows = startRows;
            this.endRows = endRows;
            this.sheet = sheet;
        }
    
        public void run() {
            System.out.println("我是"+Thread.currentThread().getName());
            //读取规定的内容
            for (int i = startRows; i <= endRows; i++) {
                System.out.println(sheet.getRow(i).getCell(0)+"\t"+sheet.getRow(i).getCell(1)+"\t"+sheet.getRow(i).getCell(2));
            }
        }
    
        //set、get方法
        public Integer getStartRows() {
            return startRows;
        }
    
        public void setStartRows(Integer startRows) {
            this.startRows = startRows;
        }
    
        public Integer getEndRows() {
            return endRows;
        }
    
        public void setEndRows(Integer endRows) {
            this.endRows = endRows;
        }
    
        public XSSFSheet getSheet() {
            return sheet;
        }
    
        public void setSheet(XSSFSheet sheet) {
            this.sheet = sheet;
        }
    }

2.以springmvc为例，controller层

@Controller
    @RequestMapping("/poi")
    public class POIController throws Exception{ 
        @RequestMapping("test")
        public String test(MultipartFile excelFile) {
            System.out.println("姓名"+"\t"+"年龄"+"\t"+"性别");
            InputStream inputStream = excelFile.getInputStream();
                XSSFWorkbook excel = new XSSFWorkbook(inputStream);
                for(int i=0;i<excel.getNumberOfSheets();i++){
                    //当前页不为空
                    if (excel.getSheetAt(i)!=null) {
                        //获取当前页的所有行
                        int sumRows = excel.getSheetAt(i).getLastRowNum();
                        //开启的线程数(每两个开启一个线程)
                        int threadNum;  
                        if (sumRows%2==0) {
                                threadNum = sumRows/2;
                        }else{
                                threadNum = sumRows/2+1;
                        }
                        //因为刚开始和中间还有结束三种情况不一样
                        //比如0~1、1~2、最后一个
                        for(int currentTreadNum=0;currentTreadNum<threadNum;currentTreadNum++){
                            if (currentTreadNum == 0) {
                                POIThread poiThread = new POIThread(currentTreadNum, currentTreadNum+1, excel.getSheetAt(i));
                            new Thread(poiThread).strat();
                            }else if (currentTreadNum == threadNum-1) {
                                POIThread poiThread = new POIThread(currentTreadNum*2, sumRows-1, excel.getSheetAt(i));
                            new Thread(poiThread).strat();
                            }else {
                                POIThread poiThread = new POIThread(currentTreadNum*2, currentTreadNum*2+1, excel.getSheetAt(i));
                            new Thread(poiThread).strat();
                            }
                    }else{
                        countine;
                    }
                }
        }
    }

3.excel文件

## 重点：这里多线程读出来的是乱序的。 ##