多线程-设计模式-保护性暂停-解耦实现方式

缺乏、安全感 2022-12-04 01:22 92阅读 0赞

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mzk5OTMyNw_size_16_color_FFFFFF_t_70_pic_center]

图中Futures就好比居民楼一层的信箱（每个信箱有房间编号），左侧t0、t2、t4就好比等待邮件的居民，右侧的t1、t3、t5就好比邮递员

如果需要在多个类之间使用GuardedObject对象，作为参数传递不是很方便，因此设计一个用来解耦的中间类，这样不仅能够`解耦`【结果等待着】和【结果生产者】，还能够同时支持多个任务处理

import lombok.extern.slf4j.Slf4j;
    
    import java.util.Hashtable;
    import java.util.Map;
    import java.util.Set;
    
    public class Test20 {
        
        public static void main(String[] args) throws InterruptedException {
        
            for (int i = 0; i < 3; i++) {
        
                new People().start();
            }
    
            Thread.sleep(1000);
            for(Integer id : MailBoxes.getIds()){
        
                new Postman(id,"内容" + id).start();
            }
        }
    }
    
    @Slf4j
    class People extends Thread{
        
        @Override
        public void run() {
        
            //收信
            GuardedObject guardedObject = MailBoxes.createGuardedObject();
            log.debug("开始收信 id: {}",guardedObject.getId());
            Object mail = guardedObject.get(5000);
            log.debug("收到信 id:{},内容:{}",guardedObject.getId(),mail);
        }
    }
    
    @Slf4j
    class Postman extends Thread{
        
        private int id;
        private String mail;
    
        public Postman(int id,String mail){
        
            this.id = id;
            this.mail = mail;
        }
    
        @Override
        public void run() {
        
            //送信
            GuardedObject guardedObject = MailBoxes.getGuardedObject(id);
            log.debug("送信 id:{},内容:{}",id,mail);
            guardedObject.complete(mail);
        }
    }
    
    @Slf4j
    class MailBoxes{
        
        private static int id = 0;
    
        private static Map<Integer,GuardedObject> boxes = new Hashtable<>();
    
        public static synchronized int generateId(){
        
            return id++;
        }
    
        public static GuardedObject getGuardedObject(int id){
        
            return boxes.remove(id);    //返回并删除，防止堆内存溢出
        }
    
        public static GuardedObject createGuardedObject(){
        
            GuardedObject go = new GuardedObject(generateId());
            boxes.put(go.getId(),go);
            return go;
        }
    
        public static Set<Integer> getIds(){
        
            return boxes.keySet();
        }
    }
    
    
    //此处理解为信箱
    @Slf4j
    class GuardedObject{
        
    
        private int id = 0;
    
        //结果
        private Object response;
    
        public GuardedObject(int id) {
        
            this.id = id;
        }
    
        public int getId() {
        
            return id;
        }
    
        //获取结果
        //timeout 表示等待多久
        public Object get(long timeout){
        
            synchronized (this){
        
                //开始时间
                long begin = System.currentTimeMillis();
                //经历的时间
                long passTime = 0;
                //没有结果
                while(response == null){
        
                    //经历的时间超过了最大的等待时间，退出循环
                    if(passTime >= timeout){
        
                        break;
                    }
    
                    try {
        
                        this.wait();
                    } catch (InterruptedException e) {
        
                        e.printStackTrace();
                    }
                    //求得经历时间
                    passTime = System.currentTimeMillis() - begin;
    
                }
                return response;
            }
        }
    
        //产生结果
        public void complete(Object response){
        
            synchronized (this){
        
                //给结果成员赋值
                this.response = response;
                this.notifyAll();
            }
        }
    }

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mzk5OTMyNw_size_16_color_FFFFFF_t_70_pic_center]: /images/20221123/5933143aca4640978dbb0b137ac88985.png