java NIO 多线程_course

<div class="iteye-blog-content-contain" style="font-size: 14px;"> <pre name="code" class="java">public void run() { exitRequest = false ; while( !exitRequest) { try { // 初期化 socketChannel = SocketChannel.open() ; selector = Selector.open() ; socketChannel.socket().setReuseAddress( true) ; socketChannel.configureBlocking( false) ; socketChannel.socket().setReceiveBufferSize( RECV_BUFFER) ; selectionKey = socketChannel.register( selector, SelectionKey.OP_CONNECT) ; selectionKey.attach( new SocketNioControl( notifyObject, selector, socketChannel, selectionKey)) ; socketChannel.connect( inetAddress) ; int timer = 0 ; while( !socketChannel.isConnected()) { selector.select(100) ; if( exitRequest) { break ; } for( SelectionKey key : selector.selectedKeys()) { if( key.isConnectable()) { SocketChannel socketChannel = ( SocketChannel)key.channel() ; SocketNioControl socketControl = ( SocketNioControl)key.attachment() ; socketChannel.finishConnect() ; key.interestOps( SelectionKey.OP_READ) ; socketControl.connect() ; break ; } } if( timer &gt;= TIMER_CONNECT * 1000) { throw new ConnectException() ; } timer += 100 ; } try { while( !exitRequest) { selector.select() ; for( SelectionKey key : selector.selectedKeys()) { SocketNioControl socketControl = ( SocketNioControl)key.attachment() ; if( key.isReadable()) { socketControl.read() ; } if( key.isWritable()) { socketControl.write() ; } } } } catch ( ConnectException ioex) { } catch ( CancelledKeyException ckex) { } } catch ( UnknownHostException uhex) { ErrorMessage.logging( uhex) ; } catch ( Exception ex) { ErrorMessage.logging( ex) ; } finally { try { for( SelectionKey key : selector.keys()) { SocketNioControl socketControl = ( SocketNioControl)key.attachment() ; socketControl.disconnect() ; } if( selector != null) { selector.close() ; selector = null ; } for( int timer = 0; timer &lt; TIMER_RETRY * 1000; timer += 100) { Thread.sleep( 100) ; if( exitRequest) { break ; } } } catch( IOException ioe) { } catch( InterruptedException iex) { } } } }</pre> <p> 线程一直被占用，导致系统hungup.是哪里出问题呢？另外<span style="font-family: monospace; font-size: 1em; line-height: 1.5;"> selector.select() 的值一直是0；</span><span style="font-family: monospace; font-size: 1em; line-height: 1.5;">这一句是起什么作用的？</span></p> </div>

java nio 业务接收多线程处理是否必要_course

<p>nio在服务器收到客户端请求的时候，是单线程的，即使自己在后续的业务流程处理中使用了线程池操作，由于接收部分是单线程的，也没有什么意义？有何办法提高效率？</p>

Java多线程写入同一文件该怎么写_course

创建4个线程，线程A，线程B，线程C，线程D。同时向一个文件夹里写入，线程A写入“A”，线程B写入“B”…… 要求写入内容为 ABCDABCD…… 我是个初学者，有没有大神能教教我该怎么写。

java nio reactor疑惑_course

1：最近学习Java nio的线程模型 参考了很多资料 都提到了reactor模式 有个疑问 这里的reactor模式（包括单线程reactor模式多线程reactor模式主从reactor模式） 这个是由java nio实现的 还是需要开发的时候自己封装成reactor模式的nio框架？ 2：reactor模式我的理解是把网络IO放在了内核中执行 轮询selector会有注册的感兴趣的 OP_ACCEPT OP_Read等的selectionKey。真正提高的是以非阻塞的方式读取IO，完成后会 触发事件通知selector，之后的业务处理还是可以另起线程池来处理。所以才说selector模式 降低的是网络IO的开销。不知道这样理解对不对 希望大神不吝赐教

NIO技术一个线程处理多个连接的问题有人知道吗？_course

请教下，想在服务端使用一个线程处理多个连接，在服务端的selector中注册多个通道服务端serverSocketchannel吗？还是服务端只建立一个serverSocketchannel注册到selector就可以，在客户端建立多个客户端socketchannel注册到客户端的selector？

java的nio可以做客户端吗_course

我我看到的demo源码，都是用java nio做服务器的 但是我现在需要开发客户端程序，连接数以千计的服务器 由服务器给我推送数据 这个情形使用多线程模式肯定是不可以的 需要用nio机制 但是我看到的nio的demo都是服务器用nio处理客户端连接的 有没有用客户端nio处理大量服务器推送数据的呢？ 还是说根本不能这么做？谢谢。

java nio selector怎么达到与Linux select一样的效果_course

前几天做了一个linux下的socket实验使用了select，可以让程序在不使用多线程的情况下，实现io的异步，也就是可以收数据，也可以发数据，但不阻塞。 于是我就想能不能移植到Java下来实现。结果我发现Java也有select类似的功能，但是我发现Java nio的Chanel无法对标准输入进行处理，要发数据的时候就会阻塞。 可能是我技术不够，我想问问大家Java nio到底能不能实现与linux select一样的效果？ package server; import java.io.BufferedReader; import java.io.BufferedWriter; import java.io.IOException; import java.io.InputStreamReader; import java.io.OutputStreamWriter; import java.net.InetAddress; import java.net.InetSocketAddress; import java.net.ServerSocket; import java.net.Socket; import java.nio.channels.SocketChannel; import java.util.Iterator; import java.util.Scanner; import java.nio.ByteBuffer; import java.nio.channels.Channel; import java.nio.channels.SelectionKey; import java.nio.channels.Selector; import java.nio.channels.ServerSocketChannel; public class ServerSock { public ServerSock() { // TODO Auto-generated constructor stub try { ServerSocketChannel server= ServerSocketChannel.open(); server.bind(new InetSocketAddress(InetAddress.getLocalHost(), 8899), 5); System.out.println("服务器启动...."); Selector selector = Selector.open(); server.configureBlocking(false); server.register(selector, SelectionKey.OP_ACCEPT); ByteBuffer buf = ByteBuffer.allocate(48); SocketChannel channel = null; while(true){ int a=selector.select(); Iterator<SelectionKey> keyIter = selector.selectedKeys().iterator(); while(keyIter.hasNext()){ SelectionKey key = keyIter.next(); if (key.isAcceptable()) { channel = server.accept(); System.out.println("接受: "); channel.configureBlocking(false); channel.register(selector, SelectionKey.OP_READ | SelectionKey.OP_WRITE); }else if (key.isReadable()) { System.out.println("读取："); int bytesRead = channel.read(buf); buf.flip(); String aString = new String(buf.array()).trim(); System.out.println(aString); buf.clear(); }else if (key.isWritable()) { System.out.println("写入："); Scanner scanner = new Scanner(System.in); String b = scanner.nextLine(); buf.put(b.getBytes()); buf.flip(); channel.write(buf); buf.clear(); } keyIter.remove(); } } } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } public static void main(String[] args) { new ServerSock(); } } ``` ```

如何利用 java 多线程 爬取大量网页？_course

大家好，我现在遇到一个问题，手里有50，000多url，需要一一下载下来，由于都是国外的网址，因此相当慢，现在想弄成多线程抓取网页，不过我的代码无法正常运行，请达人不吝指教，多谢了，以下是我的代码： [code="java"] import ...... public class Down2011CaseMeshTread extends Thread { public static int count = 0; public static List<String> docDoiList = getCaseDoiList2(); private static URL url; private static String doi; static int BUFFER_SIZE = 1024*10; public Down2011CaseMeshTread(String doi) throws MalformedURLException{ String urlStr = "http://www.iteye.com/" + doi; this.url = new URL(urlStr); this.doi = doi; } public static Connection getConnection() throws Exception { //连接数据库的 } public static String getDocNameByDoi(String docDoi){ //获得docDoi对应的文件名，就是下载下来之后文件的存储名字 } public void Test() throws IOException, InterruptedException{ StringBuffer sb = null; BufferedReader in = null; BufferedWriter out = null; try { sb = new StringBuffer(); int ch =0; URLConnection conn = (HttpURLConnection)url.openConnection(); conn.setRequestProperty("User-Agent", "Mozilla/4.76"); conn.setDoOutput(true); conn.setConnectTimeout(1000*60*10); in = new BufferedReader(new InputStreamReader(url.openStream())); FileOutputStream fo = new FileOutputStream("/home/" + getDocNameByDoi(doi)); OutputStreamWriter writer = new OutputStreamWriter(fo, "utf-8"); out = new BufferedWriter(writer); while (!in.ready()) { Thread.sleep(500); // wait for stream to be ready. } char[] buffer = new char[BUFFER_SIZE]; int charsRead = 0; while ( (charsRead = in.read(buffer, 0, BUFFER_SIZE)) != -1 ) { out.write(buffer, 0, charsRead); } out.close(); in.close(); }catch(Exception e){ e.printStackTrace(); } } public void run(){ try { Test(); } catch (IOException e) { e.printStackTrace(); } catch (InterruptedException e) { e.printStackTrace(); } } //应该是run()这里的问题，但我不知道改怎么改？？？？ public static List<String> getCaseDoiList2(){ //获得url链表，一共五万多 } public static void main(String args[]) throws MalformedURLException{ for(String docDoi : docDoiList){ Down2011CaseMeshTread down = new Down2011CaseMeshTread(docDoi); down.start(); } } } [/code] 情况就是这么个情况， 请问这个该怎么改阿，非常感谢～ 这个程序的问题是，开始执行特别快，大概一分钟能下两三百，但下到大约800的时候就报错 先是读到异常文件终止“EOF” 但这时还可以断断续续的下载 [code] java.io.IOException: Premature EOF at sun.net.www.http.ChunkedInputStream.fastRead(ChunkedInputStream.java:252) at sun.net.www.http.ChunkedInputStream.read(ChunkedInputStream.java:680) at java.io.FilterInputStream.read(FilterInputStream.java:133) at sun.net.www.protocol.http.HttpURLConnection$HttpInputStream.read(HttpURLConnection.java:2582) at sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:282) at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:324) at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:176) at java.io.InputStreamReader.read(InputStreamReader.java:184) at java.io.BufferedReader.read1(BufferedReader.java:202) at java.io.BufferedReader.read(BufferedReader.java:278) at org.Down2011CaseMeshTread.Test(Down2011CaseMeshTread.java:138) at org.Down2011CaseMeshTread.run(Down2011CaseMeshTread.java:150) [/code] 然后再报连接超时错误，这个时候下载就都中断了 [code] java.net.ConnectException: Connection timed out at java.net.PlainSocketImpl.socketConnect(Native Method) at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:327) at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:193) at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:180) at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:384) at java.net.Socket.connect(Socket.java:546) at java.net.Socket.connect(Socket.java:495) at sun.net.NetworkClient.doConnect(NetworkClient.java:178) at sun.net.www.http.HttpClient.openServer(HttpClient.java:409) at sun.net.www.http.HttpClient.openServer(HttpClient.java:530) at sun.net.www.http.HttpClient.<init>(HttpClient.java:240) at sun.net.www.http.HttpClient.New(HttpClient.java:321) at sun.net.www.http.HttpClient.New(HttpClient.java:338) at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:935) at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:876) at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:801) at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1139) at java.net.URL.openStream(URL.java:1029) at org.Down2011CaseMeshTread.Test(Down2011CaseMeshTread.java:127) at org.Down2011CaseMeshTread.run(Down2011CaseMeshTread.java:150) [/code] 这个是连接的错误 估计是我没有设定线程的数量，所以在存在大量线程请求连接的时候出了问题， 但怎么修改我还不知道哦~

多线程运行，cpu使用率过高_course

1 使用Fork/Join，类似代码如下，运行起来，CPU过高 public class MyTask extends RecursiveTask<Integer> { private static final long serialVersionUID = 1103203544619621157L; int THRESHOLD = 100;int start;int end; int[] arr; public MyTask(int[] arr,int start,int end){ this.arr = arr; this.start = start; this.end = end; } @Override protected Integer compute() { if(end - start <= THRESHOLD){ int sum = 0; for(int i= start;i<end;i++){ sum += arr[i]; } return sum; } int mid = (end + start)/2; MyTask t1 = new MyTask(arr,start,mid); MyTask t2 = new MyTask(arr,mid,end); invokeAll(t1, t2); return t1.join() + t2.join(); } public static void main(String args){ int[] arr = new int[5000]; random(arr); ForkJoinPool pool = new ForkJoinPool(); MyTask task = new MyTask(arr,0,arr.length); pool.invoke(task); } } 2 堆栈信息如下 "ForkJoinPool-1-worker-8" daemon prio=10 tid=0x00007fab88001000 nid=0x32d4 waiting on condition [0x00007fac178b7000] java.lang.Thread.State: WAITING (parking) at sun.misc.Unsafe.park(Native Method) - parking to wait for <0x000000070b86f138> (a java.util.concurrent.ForkJoinPool) at java.util.concurrent.locks.LockSupport.park(LockSupport.java:186) at java.util.concurrent.ForkJoinPool.tryAwaitWork(ForkJoinPool.java:864) at java.util.concurrent.ForkJoinPool.work(ForkJoinPool.java:647) at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:398) "ForkJoinPool-1-worker-6" daemon prio=10 tid=0x00007fab8c004800 nid=0x32d2 waiting on condition [0x00007fac17ab9000] java.lang.Thread.State: WAITING (parking) at sun.misc.Unsafe.park(Native Method) - parking to wait for <0x000000070b86f138> (a java.util.concurrent.ForkJoinPool) at java.util.concurrent.locks.LockSupport.park(LockSupport.java:186) at java.util.concurrent.ForkJoinPool.tryAwaitWork(ForkJoinPool.java:864) at java.util.concurrent.ForkJoinPool.work(ForkJoinPool.java:647) at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:398) "ForkJoinPool-1-worker-5" daemon prio=10 tid=0x00007fab90003000 nid=0x32d1 waiting on condition [0x00007fac17bba000] java.lang.Thread.State: WAITING (parking) at sun.misc.Unsafe.park(Native Method) - parking to wait for <0x000000070b86f138> (a java.util.concurrent.ForkJoinPool) at java.util.concurrent.locks.LockSupport.park(LockSupport.java:186) at java.util.concurrent.ForkJoinPool.tryAwaitWork(ForkJoinPool.java:864) at java.util.concurrent.ForkJoinPool.work(ForkJoinPool.java:647) at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:398) "ForkJoinPool-1-worker-4" daemon prio=10 tid=0x00007fab90001000 nid=0x32d0 waiting on condition [0x00007fac17cbb000] java.lang.Thread.State: TIMED_WAITING (parking) at sun.misc.Unsafe.park(Native Method) - parking to wait for <0x000000070b86f138> (a java.util.concurrent.ForkJoinPool) at java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:226) at java.util.concurrent.ForkJoinPool.idleAwaitWork(ForkJoinPool.java:894) at java.util.concurrent.ForkJoinPool.tryAwaitWork(ForkJoinPool.java:830) at java.util.concurrent.ForkJoinPool.work(ForkJoinPool.java:647) at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:398) "ForkJoinPool-1-worker-2" daemon prio=10 tid=0x00007fab8c001000 nid=0x32ce waiting on condition [0x00007fac17ebd000] java.lang.Thread.State: WAITING (parking) at sun.misc.Unsafe.park(Native Method) - parking to wait for <0x000000070b86f138> (a java.util.concurrent.ForkJoinPool) at java.util.concurrent.locks.LockSupport.park(LockSupport.java:186) at java.util.concurrent.ForkJoinPool.tryAwaitWork(ForkJoinPool.java:864) at java.util.concurrent.ForkJoinPool.work(ForkJoinPool.java:647) at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:398) "http-bio-3080-exec-10" daemon prio=10 tid=0x00007fabc8007000 nid=0x32b5 waiting on condition [0x00007fac34260000] java.lang.Thread.State: WAITING (parking) at sun.misc.Unsafe.park(Native Method) - parking to wait for <0x000000070bac9f78> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject) at java.util.concurrent.locks.LockSupport.park(LockSupport.java:186) at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2043) at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442) at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:104) at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:32) at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1068) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) at java.lang.Thread.run(Thread.java:745) "http-bio-3080-exec-9" daemon prio=10 tid=0x00007fabc8005000 nid=0x32b4 waiting on condition [0x00007fac34361000] java.lang.Thread.State: WAITING (parking) at sun.misc.Unsafe.park(Native Method) - parking to wait for <0x000000070bac9f78> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject) at java.util.concurrent.locks.LockSupport.park(LockSupport.java:186) at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2043) at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442) at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:104) at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:32) at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1068) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) at java.lang.Thread.run(Thread.java:745) "http-bio-3080-exec-8" daemon prio=10 tid=0x00007fabc8003800 nid=0x32b3 waiting on condition [0x00007fac34462000] java.lang.Thread.State: WAITING (parking) at sun.misc.Unsafe.park(Native Method) - parking to wait for <0x000000070bac9f78> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject) at java.util.concurrent.locks.LockSupport.park(LockSupport.java:186) at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2043) at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442) at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:104) at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:32) at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1068) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) at java.lang.Thread.run(Thread.java:745) "http-bio-3080-exec-7" daemon prio=10 tid=0x00007faba4001000 nid=0x32b2 waiting on condition [0x00007fac34563000] java.lang.Thread.State: WAITING (parking) at sun.misc.Unsafe.park(Native Method) - parking to wait for <0x000000070bac9f78> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject) at java.util.concurrent.locks.LockSupport.park(LockSupport.java:186) at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2043) at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442) at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:104) at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:32) at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1068) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) at java.lang.Thread.run(Thread.java:745) 

Java多线程中的异常问题_course

https://my.oschina.net/u/3205807/tweet/12033425

Netty多线程客户端服务器端通信_course

现在实现了Netty客户端服务器端编码解析json格式数据，如何是用多线程进行客户端服务器端的通信？进行tps统计？ 有没有有经验的大佬点拨一下？

JAVA NIO channel中同时执行两个写操作_course

NIO中设置 channel.register(this.selector,SelectionKey.OP_WRITE); 在相应的方法中，同时执行两个写操作 if (selectionKey.isWritable()){ write(selectionKey); writequotation(selectionKey); }

JAVA项目运行cup占用率100%，使用explorer工具查询java.exe下的线程占用率过高（如图），谁帮助分析下？_course

 定位在如下的的日志上，请帮助分析。谢谢！ 2019-06-26 14:34:07 "XNIO-1 Accept" #19 daemon prio=5 os_prio=0 tid=0x0000000058231000 nid=0x3ec runnable [0x000000005badf000] java.lang.Thread.State: RUNNABLE at java.lang.Object.notifyAll(Native Method) at sun.nio.ch.WindowsSelectorImpl$StartLock.startThreads(WindowsSelectorImpl.java:189) - locked <0x00000000d3d825c0> (a sun.nio.ch.WindowsSelectorImpl$StartLock) at sun.nio.ch.WindowsSelectorImpl$StartLock.access$300(WindowsSelectorImpl.java:181) at sun.nio.ch.WindowsSelectorImpl.doSelect(WindowsSelectorImpl.java:153) at sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:86) - locked <0x00000000d3d71eb8> (a sun.nio.ch.Util$2) - locked <0x00000000d3d71ec8> (a java.util.Collections$UnmodifiableSet) - locked <0x00000000d3d71e38> (a sun.nio.ch.WindowsSelectorImpl) at sun.nio.ch.SelectorImpl.select(SelectorImpl.java:97) at sun.nio.ch.SelectorImpl.select(SelectorImpl.java:101) at org.xnio.nio.WorkerThread.run(WorkerThread.java:511) Locked ownable synchronizers: - None "XNIO-1 I/O-1" #18 daemon prio=5 os_prio=0 tid=0x0000000054092800 nid=0xf54 runnable [0x000000005b85f000] java.lang.Thread.State: RUNNABLE at sun.nio.ch.WindowsSelectorImpl$SubSelector.poll0(Native Method) at sun.nio.ch.WindowsSelectorImpl$SubSelector.poll(WindowsSelectorImpl.java:296) at sun.nio.ch.WindowsSelectorImpl$SubSelector.access$400(WindowsSelectorImpl.java:278) at sun.nio.ch.WindowsSelectorImpl.doSelect(WindowsSelectorImpl.java:159) at sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:86) - locked <0x00000000d3d751e0> (a sun.nio.ch.Util$2) - locked <0x00000000d3d751f0> (a java.util.Collections$UnmodifiableSet) - locked <0x00000000d3d75160> (a sun.nio.ch.WindowsSelectorImpl) at sun.nio.ch.SelectorImpl.select(SelectorImpl.java:97) at sun.nio.ch.SelectorImpl.select(SelectorImpl.java:101) at org.xnio.nio.WorkerThread.run(WorkerThread.java:511) Locked ownable synchronizers: - None

Java nio服务端对同一个消息多次select如何处理_course

服务端代码 ``` private void listen() throws IOException { SocketChannel client; while (selector.select() > 0) { System.out.println("select"); Set<SelectionKey> selectionKeys = selector.selectedKeys(); Iterator<SelectionKey> keyIterator = selectionKeys.iterator(); while (keyIterator.hasNext()) { SelectionKey key = keyIterator.next(); //置空迭代器 keyIterator.remove(); try { if (key.isAcceptable()) { server = (ServerSocketChannel) key.channel(); client = server.accept(); client.configureBlocking(false); client.register(selector,SelectionKey.OP_READ); }else if (key.isReadable()) { System.out.println("read"); ByteBuffer readBuffer = ByteBuffer.allocate(1024); SocketChannel readChannel = (SocketChannel) key.channel(); readChannel.read(readBuffer); readBuffer.flip(); int i = readBuffer.getInt(); System.out.println("输出 " +i); } if (key.isWritable()) { } }catch (IOException e) { key.channel().close(); key.cancel(); } } } } ``` 客户端代码 ``` ByteBuffer writeBuffer = ByteBuffer.allocate(1024); writeBuffer.putInt(111); try { client.write(writeBuffer); } catch (IOException e) { e.printStackTrace(); } ``` 服务端输出3次select 其中一次是连接accept 一次是接收消息 还有一次呢？ 另外 在另一个程序中 服务端不断地对同一个消息处理 大概6次直到报错（这个程序是持续连接 另起线程） 求助

关于Java的nio的FileChannel类读取数据的问题_course

本人新手，在使用nio时出现了一些问题。在nio的api中，有一个FileChannel类，其中的read方法说明是非阻塞的，但是我在使用的时候它却是阻塞在程序中了，不知道为什么出现这样错误。还有就是，在api中的read方法说明可以在另外线程关闭通道而导致此正在使用的read方法抛出异常。可是我使用的时候它并没有抛出，仍然阻塞在那里。我看的不是盗版api吧。。。期待大神的解答！！！十分感谢！！！

Java程序服务器性能调优_course

Java程序对cpu的利用很低，如何让cpu的利用得到提高? 现在在系统中的部分地方使用了多线程来提高计算速度，但是整个程序对cpu的利用率依然不高，如果继续 提高并发数，tps依然不会上升，而且cpu利用率还是不高，如何才能让整个java程序 是多线程的？ 不太清除java程序的是单线程的还是多线程的？而这个线程数量又是如何改变的 上面的结论都是经过严格的压力测试得到的

创建线程过多会出现线程不执行问题?_course

#include "stdafx.h" #include <Windows.h> #include <conio.h> #include <process.h> #include <iostream> using namespace std; DWORD CALLBACK ThreadFun_02(LPVOID lp); bool PrintLog(const char * pString); CRITICAL_SECTION g_Cs; int g_iTickets = 20; int main() { InitializeCriticalSection(&g_Cs); PrintLog("开始创建线程"); for(int i=0;i<g_iTickets;i++) { if(!CreateThread(NULL, 0, ThreadFun_02, NULL, 0, NULL)) { PrintLog("创建线程失败!\n"); } } cin.get(); cout<<g_iTickets<<endl; cin.get(); return 0; } DWORD CALLBACK ThreadFun_02(LPVOID lp) { EnterCriticalSection(&g_Cs); if(g_iTickets > 0) { char szChar[20]; sprintf_s(szChar, "Sell ticket: %d", g_iTickets); cout<<szChar<<endl; PrintLog(szChar); g_iTickets--; } LeaveCriticalSection(&g_Cs); return 0; } bool PrintLog(const char * pString) { EnterCriticalSection(&g_Cs); FILE *cLog = NULL; cLog = fopen("Test.log", "a"); if(!cLog) { return false; } fputs(pString, cLog); fputc('\n', cLog); fclose(cLog); LeaveCriticalSection(&g_Cs); return true; } 代码如上,正常情况下最后输出的g_iTickets应该为0,但是如果g_iTickets过多(如50,100),就会出现最后的g_iTickets不为0的情况.这是什么情况呢? g_iTickets=20情况下输出: ... Sell ticket: 9 Sell ticket: 8 Sell ticket: 7 Sell ticket: 6 Sell ticket: 5 Sell ticket: 4 Sell ticket: 3 Sell ticket: 2 Sell ticket: 1 0 g_iTickets=50情况下输出: ... Sell ticket: 9 Sell ticket: 8 Sell ticket: 7 Sell ticket: 6 Sell ticket: 5 Sell ticket: 4 Sell ticket: 3 Sell ticket: 2 1 g_iTickets=1000情况下输出: Sell ticket: 45 Sell ticket: 44 Sell ticket: 43 Sell ticket: 42 Sell ticket: 41 Sell ticket: 40 Sell ticket: 39 Sell ticket: 38 Sell ticket: 37 36

tomcat在一台电脑上运行出现一两个小时后cpu占用从0%到18%并一直这样_course

系统版本 windows server 2008 R2 64位 JDK 1.8.0_162-win32 Tomcat-9.0.5-win32 数据库 MySQL 5.7.21-win32  32线程 32g内存 问题描述：在一台以上配置的电脑，开启一两个小时后cpu占用从0%变成18%，没有定时任务，有6个线程都占用3.11%的cpu（在其他电脑上系统版本和jdk tomcat mysql版本一样未出现该种情况） 通过jstack吧进程发现以下6个线程占用cpu，没有发现与业务代码的关联 "ajp-nio-28009-ClientPoller-1" #47 daemon prio=5 os_prio=0 tid=0x169a4000 nid=0x3e4c runnable [0x1d73f000] java.lang.Thread.State: RUNNABLE at sun.nio.ch.WindowsSelectorImpl$SubSelector.poll0(Native Method) at sun.nio.ch.WindowsSelectorImpl$SubSelector.poll(WindowsSelectorImpl.java:296) at sun.nio.ch.WindowsSelectorImpl$SubSelector.access$400(WindowsSelectorImpl.java:278) at sun.nio.ch.WindowsSelectorImpl.doSelect(WindowsSelectorImpl.java:159) at sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:86) - locked <0x0bc44db8> (a sun.nio.ch.Util$3) - locked <0x0bc44dc8> (a java.util.Collections$UnmodifiableSet) - locked <0x0bc44d40> (a sun.nio.ch.WindowsSelectorImpl) at sun.nio.ch.SelectorImpl.select(SelectorImpl.java:97) at org.apache.tomcat.util.net.NioEndpoint$Poller.run(NioEndpoint.java:710) at java.lang.Thread.run(Thread.java:748) Locked ownable synchronizers: - None "ajp-nio-28009-ClientPoller-0" #46 daemon prio=5 os_prio=0 tid=0x169a3c00 nid=0x81064 runnable [0x1d52f000] java.lang.Thread.State: RUNNABLE at sun.nio.ch.WindowsSelectorImpl.resetWakeupSocket0(Native Method) at sun.nio.ch.WindowsSelectorImpl.resetWakeupSocket(WindowsSelectorImpl.java:473) - locked <0x0bc63958> (a java.lang.Object) at sun.nio.ch.WindowsSelectorImpl.doSelect(WindowsSelectorImpl.java:174) at sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:86) - locked <0x0bc48040> (a sun.nio.ch.Util$3) - locked <0x0bc48050> (a java.util.Collections$UnmodifiableSet) - locked <0x0bc47fc8> (a sun.nio.ch.WindowsSelectorImpl) at sun.nio.ch.SelectorImpl.select(SelectorImpl.java:97) at org.apache.tomcat.util.net.NioEndpoint$Poller.run(NioEndpoint.java:710) at java.lang.Thread.run(Thread.java:748) Locked ownable synchronizers: - None "http-nio-28080-ClientPoller-0" #32 daemon prio=5 os_prio=0 tid=0x17b34400 nid=0x687dc runnable [0x1cb0f000] java.lang.Thread.State: RUNNABLE at sun.nio.ch.WindowsSelectorImpl.resetWakeupSocket0(Native Method) at sun.nio.ch.WindowsSelectorImpl.resetWakeupSocket(WindowsSelectorImpl.java:473) - locked <0x0bc641d0> (a java.lang.Object) at sun.nio.ch.WindowsSelectorImpl.doSelect(WindowsSelectorImpl.java:174) at sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:86) - locked <0x0bc4fc20> (a sun.nio.ch.Util$3) - locked <0x0bc4fc30> (a java.util.Collections$UnmodifiableSet) - locked <0x0bc4fba8> (a sun.nio.ch.WindowsSelectorImpl) at sun.nio.ch.SelectorImpl.select(SelectorImpl.java:97) at org.apache.tomcat.util.net.NioEndpoint$Poller.run(NioEndpoint.java:710) at java.lang.Thread.run(Thread.java:748) Locked ownable synchronizers: - None "http-nio-28080-ClientPoller-1" #33 daemon prio=5 os_prio=0 tid=0x17b34800 nid=0xb3230 runnable [0x1cc5f000] java.lang.Thread.State: RUNNABLE at sun.nio.ch.WindowsSelectorImpl.resetWakeupSocket0(Native Method) at sun.nio.ch.WindowsSelectorImpl.resetWakeupSocket(WindowsSelectorImpl.java:473) - locked <0x0bc64028> (a java.lang.Object) at sun.nio.ch.WindowsSelectorImpl.doSelect(WindowsSelectorImpl.java:174) at sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:86) - locked <0x0bc4c998> (a sun.nio.ch.Util$3) - locked <0x0bc4c9a8> (a java.util.Collections$UnmodifiableSet) - locked <0x0bc4c920> (a sun.nio.ch.WindowsSelectorImpl) at sun.nio.ch.SelectorImpl.select(SelectorImpl.java:97) at org.apache.tomcat.util.net.NioEndpoint$Poller.run(NioEndpoint.java:710) at java.lang.Thread.run(Thread.java:748) Locked ownable synchronizers: - None "NioBlockingSelector.BlockPoller-2" #14 daemon prio=5 os_prio=0 tid=0x15a96000 nid=0x48494 runnable [0x1669f000] java.lang.Thread.State: RUNNABLE at sun.nio.ch.WindowsSelectorImpl$SubSelector.poll0(Native Method) at sun.nio.ch.WindowsSelectorImpl$SubSelector.poll(WindowsSelectorImpl.java:296) at sun.nio.ch.WindowsSelectorImpl$SubSelector.access$400(WindowsSelectorImpl.java:278) at sun.nio.ch.WindowsSelectorImpl.doSelect(WindowsSelectorImpl.java:159) at sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:86) - locked <0x0a12db98> (a sun.nio.ch.Util$3) - locked <0x0a12dba8> (a java.util.Collections$UnmodifiableSet) - locked <0x0a12db20> (a sun.nio.ch.WindowsSelectorImpl) at sun.nio.ch.SelectorImpl.select(SelectorImpl.java:97) at org.apache.tomcat.util.net.NioBlockingSelector$BlockPoller.run(NioBlockingSelector.java:298) Locked ownable synchronizers: - None "NioBlockingSelector.BlockPoller-1" #13 daemon prio=5 os_prio=0 tid=0x15a8ec00 nid=0x8b6c8 runnable [0x1664f000] java.lang.Thread.State: RUNNABLE at sun.nio.ch.WindowsSelectorImpl$SubSelector.poll0(Native Method) at sun.nio.ch.WindowsSelectorImpl$SubSelector.poll(WindowsSelectorImpl.java:296) at sun.nio.ch.WindowsSelectorImpl$SubSelector.access$400(WindowsSelectorImpl.java:278) at sun.nio.ch.WindowsSelectorImpl.doSelect(WindowsSelectorImpl.java:159) at sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:86) - locked <0x0a130e08> (a sun.nio.ch.Util$3) - locked <0x0a130e18> (a java.util.Collections$UnmodifiableSet) - locked <0x0a130d90> (a sun.nio.ch.WindowsSelectorImpl) at sun.nio.ch.SelectorImpl.select(SelectorImpl.java:97) at org.apache.tomcat.util.net.NioBlockingSelector$BlockPoller.run(NioBlockingSelector.java:298) Locked ownable synchronizers: - None

关于访问数据库的线程卡死的疑问_course

"http-nio-8080-exec-5" #82 daemon prio=5 os_prio=0 tid=0x00007f7a18004800 nid=0x7be5 runnable [0x00007f79a1459000] java.lang.Thread.State: RUNNABLE at java.net.SocketInputStream.socketRead0(Native Method) at java.net.SocketInputStream.socketRead(SocketInputStream.java:116) at java.net.SocketInputStream.read(SocketInputStream.java:170) at java.net.SocketInputStream.read(SocketInputStream.java:141) at oracle.net.ns.Packet.receive(Unknown Source) at oracle.net.ns.DataPacket.receive(Unknown Source) at oracle.net.ns.NetInputStream.getNextPacket(Unknown Source) at oracle.net.ns.NetInputStream.read(Unknown Source) at oracle.net.ns.NetInputStream.read(Unknown Source) at oracle.net.ns.NetInputStream.read(Unknown Source) at oracle.jdbc.driver.T4CMAREngine.unmarshalUB1(T4CMAREngine.java:1104) at oracle.jdbc.driver.T4CMAREngine.unmarshalSB1(T4CMAREngine.java:1075) at oracle.jdbc.driver.T4C8Oall.receive(T4C8Oall.java:480) at oracle.jdbc.driver.T4CPreparedStatement.doOall8(T4CPreparedStatement.java:216) at oracle.jdbc.driver.T4CPreparedStatement.fetch(T4CPreparedStatement.java:1038) at oracle.jdbc.driver.OracleResultSetImpl.close_or_fetch_from_next(OracleResultSetImpl.java:291) - locked <0x00000000a4258628> (a oracle.jdbc.driver.T4CConnection) at oracle.jdbc.driver.OracleResultSetImpl.next(OracleResultSetImpl.java:213) - locked <0x00000000a3f455c0> (a oracle.jdbc.driver.OracleResultSetImpl) at com.mchange.v2.c3p0.impl.NewProxyResultSet.next(NewProxyResultSet.java:685) at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleRowValuesForSimpleResultMap(DefaultResultSetHandler.java:296) at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleRowValues(DefaultResultSetHandler.java:273) at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleResultSet(DefaultResultSetHandler.java:246) at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleResultSets(DefaultResultSetHandler.java:160) at org.apache.ibatis.executor.statement.PreparedStatementHandler.query(PreparedStatementHandler.java:63) at org.apache.ibatis.executor.statement.RoutingStatementHandler.query(RoutingStatementHandler.java:78) at org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:62) at org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:303) at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:154) at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:102) at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:82) at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:120) at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:113) at sun.reflect.GeneratedMethodAccessor113.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:497) at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:386) at com.sun.proxy.$Proxy21.selectList(Unknown Source) at org.mybatis.spring.SqlSessionTemplate.selectList(SqlSessionTemplate.java:205) at org.apache.ibatis.binding.MapperMethod.executeForMany(MapperMethod.java:122) at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:64) at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:53) at com.sun.proxy.$Proxy59.findInBillDay(Unknown Source) at cn.miaodai.task.service.impl.MKUserBillServiceImpl.createBill(MKUserBillServiceImpl.java:182) at cn.miaodai.task.action.MKBillAction.billCollect(MKBillAction.java:28) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:497) at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:221) at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:137) at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:111) at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:806) at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:729) at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85) at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:959) at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893) at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970) at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861) at javax.servlet.http.HttpServlet.service(HttpServlet.java:622) at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846) at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:85) at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:616) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518) at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1091) at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:673) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1526) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1482) - locked <0x00000000a3f4edd8> (a org.apache.tomcat.util.net.NioChannel) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Thread.java:745) Locked ownable synchronizers: - <0x00000000a0033b20> (a java.util.concurrent.ThreadPoolExecutor$Worker) 如上 ，是用jstack命令dump出的当前线程的信息，程序执行到com.sun.proxy.$Proxy59.findInBillDay 方法时线程卡死，正常情况下该操作在秒级即可完成，用jstack命令dump线程的时候时间已经过去一天多了，该线程依然存在，程序也没往下执行，findInBillDay方法就是一条简单的查询sql从数据库中查询数据，该查询返回的数据是5000多条 ，已排除锁表、网络阻塞等情况。已测试过当返回的数据库记录数很少时程序可正常执行，但是返回5000多条数据的时候线程就卡死 ，访问数据层用的mybatis自动生成的mapper