synchronized 控制并发（活动秒杀）

package com.imooc.Controller;

import com.imooc.service.impl.SeckillServiceImpl;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

/**
 * Created by zhongliahi on 2018/6/11.
 * 秒杀测试
 */
@RestController
@RequestMapping(value = "/skill")
@Slf4j
public class SeckillController {

    @Autowired
    private SeckillServiceImpl seckillService;


    //@PathVariable 可以将 URL 中占位符参数绑定到控制器处理方法的入参中
    // URL 中的 {xxx} 占位符可以通过@PathVariable(“xxx“) 绑定到操作方法的入参中。
    @GetMapping(value = "/query/{productId}")
    public String query(@PathVariable String productId) throws Exception{
        return seckillService.querySeckillProductInfo(productId);
    }


    @GetMapping("/order/{productId}")
    public String skill(@PathVariable String productId) throws Exception{
        log.info("秒杀----productId:"+productId);
        seckillService.orderProductMockDiffUser(productId);

        return seckillService.querySeckillProductInfo(productId);
    }
}

package com.imooc.service.impl;

import com.imooc.Exception.SellException;
import com.imooc.enums.ExceptionEnum;
import com.imooc.service.SeckillService;
import com.imooc.util.KeyUtils;
import org.springframework.stereotype.Service;

import java.util.HashMap;
import java.util.Map;

/**
 * Created by zhonglihai on 2018/6/11.
 * 秒杀Serviceimpl
 * 演示
 */
@Service
public class SeckillServiceImpl implements SeckillService {

    /**
     * 秒杀特价 1000000份
     * @param productId
     * @return
     */
    static Map<String,Integer> products;
    static Map<String,Integer> stock;
    static Map<String,String> orders;

    static{
        /**
         * ，模拟多个表，商品信息表，库存表，秒杀成功订单表
         */
        products =new HashMap<>();
        stock=new HashMap<>();
        orders=new HashMap<>();
        products.put("123",1000000);
        stock.put("123",1000000);
    }

    @Override
    public String queryMap(String productId) {
        return "活动特价，限量："+products.get(productId)+",还剩："+stock.get(productId)
                +"份"+"，成功下单用户数："+orders.size()+"人。";
    }

    @Override
    public String querySeckillProductInfo(String productId) {
        return this.queryMap(productId);
    }

    /**
     * 主要秒杀的逻辑
     * @param productId
     */
    @Override
    public synchronized void   orderProductMockDiffUser(String productId) {
        //查询该商品库存，为0则活动结束
        int stockNum=stock.get(productId);
        if(stockNum==0){
            throw new SellException(ExceptionEnum.SECKILL_OVER);
        }else{
            //2.下单（模拟不同用户opendid不同）
            orders.put(KeyUtils.getUniqueKey(),productId);

            //3.减库存
            stockNum=stockNum-1;
            try{
                Thread.sleep(100);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            stock.put(productId,stockNum);
        }
    }
}