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并行设计模式属于设计优化的一部分,它是对一些常用的多线程结构的总结和抽象。与串行程序相比,并行程序的结构通常更为复杂。因此合理的使用并行模式在多线程开发中更具有意义,在这里主要介绍Future、Master-Worker和生产者-消费者模型。
1、Future模式有点类似于商品订单。比如在网购时,当看中某一件商品时,就可以提交订单,当订单处理完成后,在家里等待商品送货上门即可。或者说更形象的我们发送Ajax请求的时候,页面是异步的进行后台处理,用户无需一直等待请求的结果,可以继续浏览或操作其他内容。
示例如下:
package com.bfbc.height.design014;public interface Data { String getRequest();}
package com.bfbc.height.design014;public class FutureData implements Data{ private RealData realData ; private boolean isReady = false; public synchronized void setRealData(RealData realData) { //如果已经装载完毕了,就直接返回 if(isReady){ return; } //如果没装载,进行装载真实对象 this.realData = realData; isReady = true; //进行通知 notify(); } @Override public synchronized String getRequest() { //如果没装载好 程序就一直处于阻塞状态 while(!isReady){ try { wait(); } catch (InterruptedException e) { e.printStackTrace(); } } //装载好直接获取数据即可 return this.realData.getRequest(); }}
package com.bfbc.height.design014;public class RealData implements Data{ private String result ; public RealData (String queryStr){ System.out.println("根据" + queryStr + "进行查询,这是一个很耗时的操作.."); try { Thread.sleep(5000); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println("操作完毕,获取结果"); result = "查询结果"; } @Override public String getRequest() { return result; }}
package com.bfbc.height.design014;public class FutureClient { public Data request(final String queryStr){ //1 我想要一个代理对象(Data接口的实现类)先返回给发送请求的客户端,告诉他请求已经接收到,可以做其他的事情 final FutureData futureData = new FutureData(); //2 启动一个新的线程,去加载真实的数据,传递给这个代理对象 new Thread(new Runnable() { @Override public void run() { //3 这个新的线程可以去慢慢的加载真实对象,然后传递给代理对象 RealData realData = new RealData(queryStr); futureData.setRealData(realData); } }).start(); return futureData; } }
package com.bfbc.height.design014;public class Main { public static void main(String[] args) throws InterruptedException { FutureClient fc = new FutureClient(); Data data = fc.request("请求参数"); System.out.println("请求发送成功!"); System.out.println("做其他的事情..."); String result = data.getRequest(); System.out.println(result); }}
2、Master-Worker模式
Master-Worker模式是常用的并行计算模式。它的核心思想是系统由两类进程协作工作:Master进程和Worker进程。Master负责接收和分配任务,Worker负责处理子任务。当哥哥Worker子任务进程处理完成后,会将结果返回给Master,由Master做归纳和总结。其好处是能将一个大任务分解成若干个小任务,并行执行,从而提高系统的吞吐量。
Master-Worker模式分析
示例如下:
package test;public class Task { private int id ; private String name; private int price; public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public int getPrice() { return price; } public void setPrice(int price) { this.price = price; } }
package test;import java.util.HashMap;import java.util.Map;import java.util.concurrent.ConcurrentHashMap;import java.util.concurrent.ConcurrentLinkedQueue;public class Master { //1 应该有一个承装任务的集合 private ConcurrentLinkedQueueworkQueue = new ConcurrentLinkedQueue (); //2 使用HashMap去承装所有的worker对象 private HashMap workers = new HashMap (); //3 使用一个容器承装每一个worker并非执行任务的结果集 private ConcurrentHashMap resultMap = new ConcurrentHashMap (); //4 构造方法 public Master(Worker worker, int workerCount){ // 每一个worker对象都需要有Master的引用 workQueue用于任务的领取,resultMap用于任务的提交 worker.setWorkerQueue(this.workQueue); worker.setResultMap(this.resultMap); for(int i = 0 ; i < workerCount; i++){ //key表示每一个worker的名字, value表示线程执行对象 workers.put("子节点" + Integer.toString(i), new Thread(worker)); } } //5 提交方法 public void submit(Task task){ this.workQueue.add(task); } //6 需要有一个执行的方法(启动应用程序 让所有的worker工作) public void execute(){ for(Map.Entry me : workers.entrySet()){ me.getValue().start(); } } //8 判断线程是否执行完毕 public boolean isComplete() { for(Map.Entry me : workers.entrySet()){ if(me.getValue().getState() != Thread.State.TERMINATED){ return false; } } return true; } //9 返回结果集数据 public int getResult() { int ret = 0; for(Map.Entry me : resultMap.entrySet()){ //汇总的逻辑.. ret += (Integer)me.getValue(); } return ret; } }
package test;import java.util.concurrent.ConcurrentHashMap;import java.util.concurrent.ConcurrentLinkedQueue;public class Worker implements Runnable { private ConcurrentLinkedQueueworkQueue; private ConcurrentHashMap resultMap; public void setWorkerQueue(ConcurrentLinkedQueue workQueue) { this.workQueue = workQueue; } public void setResultMap(ConcurrentHashMap resultMap) { this.resultMap = resultMap; } @Override public void run() { while(true){ Task input = this.workQueue.poll(); if(input == null) break; //真正的去做业务处理 Object output = MyWorker.handle(input); this.resultMap.put(Integer.toString(input.getId()), output); } } public static Object handle(Task input) { return null; }}
package test;public class MyWorker extends Worker { public static Object handle(Task input) { Object output = null; try { //表示处理task任务的耗时,可能是数据的加工,也可能是操作数据库... Thread.sleep(500); output = input.getPrice(); } catch (InterruptedException e) { e.printStackTrace(); } return output; }}
package test;import java.util.Random;public class Main { public static void main(String[] args) { System.out.println("我的机器可用Processor数量:" + Runtime.getRuntime().availableProcessors()); Master master = new Master(new MyWorker(), Runtime.getRuntime().availableProcessors()); Random r = new Random(); for(int i = 1; i<= 100; i++){ Task t = new Task(); t.setId(i); t.setName("任务"+i); t.setPrice(r.nextInt(1000)); master.submit(t); } master.execute(); long start = System.currentTimeMillis(); while(true){ if(master.isComplete()){ long end = System.currentTimeMillis() - start; int ret = master.getResult(); System.out.println("最终结果:" + ret + ", 执行耗时:" + end); break; } } }}
3、生产者消费者模式
生产者和消费者也是一个非常经典的多线程模式,我们在实际开发中应用非常广泛的思想理念。在生产-消费模式中:通常有两类线程,即若干个生产者的线程和若干个消费者的线程。生产者线程负责提交用户请求,消费者线程则负责具体处理生产者提交的任务,在生产者和消费者之间通过共享内存缓存区进行通信。
示例如下:
package com.bfbc.height.design016;public final class Data { private String id; private String name; public Data(String id, String name){ this.id = id; this.name = name; } public String getId() { return id; } public void setId(String id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } @Override public String toString(){ return "{id: " + id + ", name: " + name + "}"; } }
package com.bfbc.height.design016;import java.util.Random;import java.util.concurrent.BlockingQueue;import java.util.concurrent.TimeUnit;import java.util.concurrent.atomic.AtomicInteger;public class Provider implements Runnable{ //共享缓存区 private BlockingQueue queue; //多线程间是否启动变量,有强制从主内存中刷新的功能。即时返回线程的状态 private volatile boolean isRunning = true; //id生成器 private static AtomicInteger count = new AtomicInteger(); //随机对象 private static Random r = new Random(); public Provider(BlockingQueue queue){ this.queue = queue; } @Override public void run() { while(isRunning){ try { //随机休眠0 - 1000 毫秒 表示获取数据(产生数据的耗时) Thread.sleep(r.nextInt(1000)); //获取的数据进行累计... int id = count.incrementAndGet(); //比如通过一个getData方法获取了 Data data = new Data(Integer.toString(id), "数据" + id); System.out.println("当前线程:" + Thread.currentThread().getName() + ", 获取了数据,id为:" + id + ", 进行装载到公共缓冲区中..."); if(!this.queue.offer(data, 2, TimeUnit.SECONDS)){ System.out.println("提交缓冲区数据失败...."); //do something... 比如重新提交 } } catch (InterruptedException e) { e.printStackTrace(); } } } public void stop(){ this.isRunning = false; } }
package com.bfbc.height.design016;import java.util.Random;import java.util.concurrent.BlockingQueue;import java.util.concurrent.TimeUnit;public class Consumer implements Runnable{ private BlockingQueue queue; public Consumer(BlockingQueue queue){ this.queue = queue; } //随机对象 private static Random r = new Random(); @Override public void run() { while(true){ try { //获取数据 Data data = this.queue.take(); //进行数据处理。休眠0 - 1000毫秒模拟耗时 Thread.sleep(r.nextInt(1000)); System.out.println("当前消费线程:" + Thread.currentThread().getName() + ", 消费成功,消费数据为id: " + data.getId()); } catch (InterruptedException e) { e.printStackTrace(); } } }}
package com.bfbc.height.design016;import java.util.concurrent.BlockingQueue;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import java.util.concurrent.LinkedBlockingQueue;public class Main { public static void main(String[] args) throws Exception { //内存缓冲区 BlockingQueue queue = new LinkedBlockingQueue(10); //生产者 Provider p1 = new Provider(queue); Provider p2 = new Provider(queue); Provider p3 = new Provider(queue); //消费者 Consumer c1 = new Consumer(queue); Consumer c2 = new Consumer(queue); Consumer c3 = new Consumer(queue); //创建线程池运行,这是一个缓存的线程池,可以创建无穷大的线程,没有任务的时候不创建线程。空闲线程存活时间为60s(默认值) ExecutorService cachePool = Executors.newCachedThreadPool(); cachePool.execute(p1); cachePool.execute(p2); cachePool.execute(p3); cachePool.execute(c1); cachePool.execute(c2); cachePool.execute(c3); try { Thread.sleep(3000); } catch (InterruptedException e) { e.printStackTrace(); } p1.stop(); p2.stop(); p3.stop(); try { Thread.sleep(2000); } catch (InterruptedException e) { e.printStackTrace(); } // cachePool.shutdown(); // cachePool.shutdownNow(); } }
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