线程池：第四章：ThreadPoolTaskExecutor和ThreadPoolExecutor有何区别?

   ThreadPoolTaskExecutor是spring core包中的，而ThreadPoolExecutor是JDK中的JUC。
    ThreadPoolTaskExecutor是对ThreadPoolExecutor进行了封装处理。

看看ThreadPoolTaskExecutor源码

看看ThreadPoolExecutor源码

    public ThreadPoolExecutor(int corePoolSize,
                                  int maximumPoolSize,
                                  long keepAliveTime,
                                  TimeUnit unit,
                                  BlockingQueue<Runnable> workQueue,
                                  ThreadFactory threadFactory,
                                  RejectedExecutionHandler handler) {
            if (corePoolSize < 0 ||
                maximumPoolSize <= 0 ||
                maximumPoolSize < corePoolSize ||
                keepAliveTime < 0)
                throw new IllegalArgumentException();
            if (workQueue == null || threadFactory == null || handler == null)
                throw new NullPointerException();
            this.corePoolSize = corePoolSize;
            this.maximumPoolSize = maximumPoolSize;
            this.workQueue = workQueue;
            this.keepAliveTime = unit.toNanos(keepAliveTime);
            this.threadFactory = threadFactory;
            this.handler = handler;
        }

int corePoolSize:线程池维护线程的最小数量. 

int maximumPoolSize:线程池维护线程的最大数量. 

long keepAliveTime:空闲线程的存活时间. 

TimeUnit unit: 时间单位,现有纳秒,微秒,毫秒,秒枚举值. 

BlockingQueue<Runnable> workQueue:持有等待执行的任务队列.

ThreadFactory:线程工厂

RejectedExecutionHandler handler:用来拒绝一个任务的执行

而拒绝策略有四种：

(1)ThreadPoolExecutor.AbortPolicy策略，是默认的策略,处理程序遭到拒绝将抛出运行时 RejectedExecutionException。

(2)ThreadPoolExecutor.CallerRunsPolicy策略 ,调用者的线程会执行该任务,如果执行器已关闭,则丢弃.

(3)ThreadPoolExecutor.DiscardPolicy策略，不能执行的任务将被丢弃.

(4)ThreadPoolExecutor.DiscardOldestPolicy策略，如果执行程序尚未关闭，则位于工作队列头部的任务将被删除，然后重试执行程序（如果再次失败，则重复此过程）.

上一章有详细讲解

那我们现在来用一用ThreadPoolTaskExecutor

弄一个工具类

    package utils;
     
    import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;
    import org.springframework.ui.ModelMap;
     
    import java.lang.reflect.Method;
    import java.util.concurrent.CountDownLatch;
     
    public class ThreadTool {
     
        static ThreadPoolTaskExecutor threadPoolTaskExecutor;
     
        static {
            threadPoolTaskExecutor = new ThreadPoolTaskExecutor();
            threadPoolTaskExecutor.setCorePoolSize(5);
            threadPoolTaskExecutor.setMaxPoolSize(10);
            threadPoolTaskExecutor.setQueueCapacity(100);
            threadPoolTaskExecutor.initialize();
        }
     
        /**
         * 使用线程池执行业务方法并加入视图
         * @param tasks 计数器
         * @param modelMap 视图
         * @param modelName 视图名
         * @param service 要调用的service
         * @param method 被调用的方法
         * @param param 方法参数
         */
        public static void runMethod(CountDownLatch tasks, ModelMap modelMap, String modelName, Object service, Method method, Object... param){
            threadPoolTaskExecutor.submit(new RunInThreadPool(
                    tasks,modelMap,modelName,service,method,param));
        }
        
     
    }

RunInThreaddPool

    package utils;
     
    import java.lang.reflect.InvocationTargetException;
    import java.lang.reflect.Method;
    import java.util.Map;
    import java.util.concurrent.CountDownLatch;
     
    public class RunInThreadPool implements Runnable {
     
        CountDownLatch countDownLatch;
        Map modelMap;
        String keyName;
        Object service;
        Method method;
        Object[] param;
     
        /**
         * @param countDownLatch 计数器
         * @param modelMap       视图
         * @param keyName        参数名
         * @param service        要调用的service
         * @param method         被调用的方法
         * @param param          方法参数
         */
        public RunInThreadPool(CountDownLatch countDownLatch, Map modelMap, String keyName, Object service, Method method, Object... param) {
            this.countDownLatch = countDownLatch;
            this.modelMap = modelMap;
            this.keyName = keyName;
            this.service = service;
            this.method = method;
            this.param = param;
        }
     
        @Override
        public void run() {
            Object result = null;
            try {
                Long start = System.currentTimeMillis();
                result = method.invoke(service, param);
                Long end = System.currentTimeMillis();
                System.out.println(String.format("%s *** 执行 ((( %s ))) 方法,耗时 <<< %s 秒 >>> 参数",
                        service.getClass(),
                        method.getName(),
                        (end - start),
                        JsonUtils.toJson(param)));
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            } catch (InvocationTargetException e) {
                e.printStackTrace();
            }
            modelMap.put(keyName, result);
            countDownLatch.countDown();
        }
    }

实战案例：

            @RequestMapping("/goodsDetail")
            public String goodsDetail(GoodsBean goodsBean, PageBean pageBean, ModelMap modelMap) throws Exception {
                final CountDownLatch latch = new CountDownLatch(7);
                Method getRelatedGoods = goodsService.getClass().getMethod("getRelatedGoods", GoodsBean.class, String.class);
                getRelatedGoods.setAccessible(Boolean.TRUE);
                ThreadTool.runMethod(latch , modelMap, "relatedGoods0", goodsService, getRelatedGoods, goodsBean, "0");
                //剩下六个类似的业务。。。。
                ...............................
                latch.await();
                return "production/index";
            }

对比：

        @RequestMapping("/getRelatedGoods")
        @AppController
        public String getRelatedGoods(GoodsBean goodsBean, String show_type,ModelMap modelMap) {
            modelMap.addAttribute("getRelatedGoods",goodsService.getRelatedGoods(goodsBean, show_type));
            return "production/index";
        }