一个线程池处理线程死亡造成的血案

心已赠人 2022-05-16 13:22 227阅读 0赞

真不知道大家有没有遇到过这种问题：  
1.任务处理一半，线程挂了怎么办？  
2.线程池有没有补齐线程的功能？

这里举一个小demo，用来处理线程死掉，重启线程处理任务。  
并未使用多个线程，而是使用一个线程来处理：

在抓去到异常的时候，在catch中将该任务重新调用。

import java.util.concurrent.ExecutorService;
    import java.util.concurrent.Executors;
    
    /** * 即使线程出现问题，可以通过线程池管理线程，重新启动线程来执行任务 * * 这里展示的是一个计算1+2+...100的计算，在加到50的时候抛出异常，然后再catch中重新启动一个线程继续执行任务 * */
    public class SingleThreadExecutor { 
    
    	public static void main(String[] args) { 
    		ExecutorService executorService = Executors.newSingleThreadExecutor();
    		executorService.execute(new Runnable() { 
    			int count = 1;
    			int sum = 0;
    			public void run() { 
    				while (true){ 
    					try { 
    						Thread.sleep(10);
    						if(count == 101){ 
    							break;
    						}
    						if (count == 50){ 
    							sum = sum + count;
    							count ++;
    							throw new RuntimeException("我是异常");
    						}
    						sum = sum + count;
    						System.out.println("##count:"+count+",sum:"+sum);
    						count ++;
    					}catch (Exception e){ 
    						e.printStackTrace();
    						//注意这个地方
    						System.out.println("重启一个线程，继续执行");
    						executorService.execute(this);
    					}
    				}
    			}
    		});
    	}
    }

执行结果：

##count:1,sum:1
    ##count:2,sum:3
    ##count:3,sum:6
    ##count:4,sum:10
    ##count:5,sum:15
    ##count:6,sum:21
    ##count:7,sum:28
    ##count:8,sum:36
    ##count:9,sum:45
    ##count:10,sum:55
    ##count:11,sum:66
    ##count:12,sum:78
    ##count:13,sum:91
    ##count:14,sum:105
    ##count:15,sum:120
    ##count:16,sum:136
    ##count:17,sum:153
    ##count:18,sum:171
    ##count:19,sum:190
    ##count:20,sum:210
    ##count:21,sum:231
    ##count:22,sum:253
    ##count:23,sum:276
    ##count:24,sum:300
    ##count:25,sum:325
    ##count:26,sum:351
    ##count:27,sum:378
    ##count:28,sum:406
    ##count:29,sum:435
    ##count:30,sum:465
    ##count:31,sum:496
    ##count:32,sum:528
    ##count:33,sum:561
    ##count:34,sum:595
    ##count:35,sum:630
    ##count:36,sum:666
    ##count:37,sum:703
    ##count:38,sum:741
    ##count:39,sum:780
    ##count:40,sum:820
    ##count:41,sum:861
    ##count:42,sum:903
    ##count:43,sum:946
    ##count:44,sum:990
    ##count:45,sum:1035
    ##count:46,sum:1081
    ##count:47,sum:1128
    ##count:48,sum:1176
    ##count:49,sum:1225
    java.lang.RuntimeException: 我是异常
    	at com.threadpool.SingleThreadExecutor$1.run(SingleThreadExecutor.java:29)
    	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    	at java.lang.Thread.run(Thread.java:748)
    重启一个线程，继续执行
    ##count:51,sum:1326
    ##count:52,sum:1378
    ##count:53,sum:1431
    ##count:54,sum:1485
    ##count:55,sum:1540
    ##count:56,sum:1596
    ##count:57,sum:1653
    ##count:58,sum:1711
    ##count:59,sum:1770
    ##count:60,sum:1830
    ##count:61,sum:1891
    ##count:62,sum:1953
    ##count:63,sum:2016
    ##count:64,sum:2080
    ##count:65,sum:2145
    ##count:66,sum:2211
    ##count:67,sum:2278
    ##count:68,sum:2346
    ##count:69,sum:2415
    ##count:70,sum:2485
    ##count:71,sum:2556
    ##count:72,sum:2628
    ##count:73,sum:2701
    ##count:74,sum:2775
    ##count:75,sum:2850
    ##count:76,sum:2926
    ##count:77,sum:3003
    ##count:78,sum:3081
    ##count:79,sum:3160
    ##count:80,sum:3240
    ##count:81,sum:3321
    ##count:82,sum:3403
    ##count:83,sum:3486
    ##count:84,sum:3570
    ##count:85,sum:3655
    ##count:86,sum:3741
    ##count:87,sum:3828
    ##count:88,sum:3916
    ##count:89,sum:4005
    ##count:90,sum:4095
    ##count:91,sum:4186
    ##count:92,sum:4278
    ##count:93,sum:4371
    ##count:94,sum:4465
    ##count:95,sum:4560
    ##count:96,sum:4656
    ##count:97,sum:4753
    ##count:98,sum:4851
    ##count:99,sum:4950
    ##count:100,sum:5050

顺利的执行了任务。  
这里面可能有个疑问就是catch中的executorService.execute(this)。这里面的this指的是什么？  
其实这里的this就是指new Runnable()的任务。其实不需要执行executorService.execute(this)也能顺利的完成

为了方便看清，将代码做一些变更。

public class SingleThreadExecutor { 
    
    	public static void main(String[] args) { 
    		ExecutorService executorService = Executors.newSingleThreadExecutor();
    		TaskInner taskInner = new TaskInner(executorService);
    		System.out.println("1==>"+taskInner.getClass());
    		executorService.execute(taskInner);
    	}
    
    	static class TaskInner implements Runnable{ 
    		private ExecutorService es;
    		public TaskInner(ExecutorService es) { 
    			this.es = es;
    		}
    
    		int count = 1;
    		int sum = 0;
    		public void run() { 
    			while (true){ 
    				try { 
    					Thread.sleep(10);
    					if(count == 101){ 
    						break;
    					}
    					if (count == 50){ 
    						sum = sum + count;
    						count ++;
    						throw new RuntimeException("我是异常");
    					}
    					sum = sum + count;
    					System.out.println("##count:"+count+",sum:"+sum);
    					count ++;
    				}catch (Exception e){ 
    					e.printStackTrace();
    					System.out.println("2==>"+this.getClass());
    					System.out.println("重启一个线程，继续执行");
    					//es.execute(this);
    				}
    			}
    		}
    	}
    }

打印的结果：

1==>class com.threadpool.SingleThreadExecutor$TaskInner
    2==>class com.threadpool.SingleThreadExecutor$TaskInner