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目录

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前言

本文大概内容:
例如:随着MongoDB的广泛应用,电商用到MongoDB也越来越多。本文主要是在将购物车模块切换到MongoDB框架前,如何快速将Mysql中购物车大批量订单拷贝到MongoDB数据库中?

一、原来代码

如下,我们将拷贝100万条数据到MongoDB中。

public void copyCartToMongo() {
   List<Cart> carts = cartMapper.selectAll();
   if(carts.size() >0 ){
      cartMongoService.saveCartList(carts);
   }
}

二、改进后代码

public void copyCartToMongoByThread() {
	// 1.我们先将批量查询及拷贝的数据分批
   EntityWrapper<Cart> wrapper = SQLHelper.buildEmptyWrapper(Cart.class);
   long count = cartMapper.selectCount(SQLHelper.build(Cart.class).geEntityWrapper());
   int preCount = 100;
   int operateCount = 0;
   int num = operateCount = (int)count / preCount;
   if(count % preCount == 0){
      operateCount = num;
   }else {
      operateCount = num + 1;
   }
   for(int i=0;i<operateCount;i++){
      logger.info("保存或更新第"+(i+1)*preCount+"条数据");
      Page<Cart> page = new Page<>(i,preCount);
      List<Cart> cartList = cartMapper.selectPage(page, wrapper);
      // 2.通过多线程、线程池(其他替换即可)
      this.copyCartToMongoThread(cartList);
   }
}

上述代码中有以下三种方式实现:

1.使用new Thread方式

代码如下:

 public void copyCartToMongoThread(List<Cart> cartList){
      final CountDownLatch latch = new CountDownLatch(cartList.size());
      try{
         for(Cart cart:cartList){
            Thread thread = new Thread(() -> {
               cartMongoService.saveCart(cart);
               latch.countDown();
            });
            thread.start();
         }
         latch.await();
      } catch (Exception e) {
         e.printStackTrace();
      }
   }

2.使用Runnable接口

代码如下:

public void copyCartToMongoThread(List<Cart> cartList){
        final CountDownLatch latch = new CountDownLatch(cartList.size());
        try {
            for (Cart cart:cartList){
                new Thread(new Runnable() {
                    @Override
                    public void run() {
                        cartMongoService.saveCart(cart);
                        latch.countDown();
                    }
                }).start();
            }
            latch.await();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

3.使用线程池

代码如下:


public void copyCartToMongoThreadPool(List<Cart> cartList){
     final CountDownLatch latch = new CountDownLatch(cartList.size());
     // 配置线程池个数
     ExecutorService executorService = Executors.newFixedThreadPool(1);
     try{
        for(Cart cart:cartList){
           executorService.submit(new Runnable() {
              @Override
              public void run() {
                 try{
                    cartMongoService.saveCart(cart);
                    // 一直阻塞当前线程,直到计数器值为0,保证并发
                    latch.await();
                 } catch (Exception e) {
                    e.printStackTrace();
                 }
              }
           });
           latch.countDown();
        }
     } catch (Exception e) {
        e.printStackTrace();
     }
}

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