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<div id='write' class=''><h1><a name="netty学习笔记一nio模块）" class="md-header-anchor"></a><span>Netty学习笔记一（NIO模块）</span></h1><h2><a name="1nio" class="md-header-anchor"></a><span>1.NIO</span></h2><p><font color=blac><span> IO的方式通常分为几种，同步阻塞的BIO、同步非阻塞的NIO、异步非阻塞的AIO。</span></font></p><h3><a name="11bionioaio" class="md-header-anchor"></a><span>1.1BIO、NIO、AIO</span></h3><p><span>一、BIO</span></p><p><span> </span><strong><span>thread-based architecture</span></strong></p><p><strong><span>基于线程</span></strong><span>的体系结构通常会使用多线程来处理客户端的请求，每当接收到一个请求，便开启一个独立的线程来处理。这种方式虽然是直观的，但是仅适用于并发访问量不大的场景，因为线程需要占用一定的内存资源，且操作系统在线程之间的切换也需要一定的开销，当线程数过多时显然会降低web服务器的性能。并且，当线程在处理I/O操作，在等待输入的这段时间线程处于空闲的状态，同样也会造成cpu资源的浪费。一个典型的设计如下：</span></p><p><img src="https://gitee.com/luojianghao/pic-repo/raw/master/image-20221215135910810.png" alt="image-20221215135910810" style="zoom:50%;" /></p><p><span>在JDK1.4出来之前，我们建立网络连接的时候采用BIO模式，需要先在服务端启动一个ServerSocket，然后在客户端启动Socket来对服务端进行通信，默认情况下服务端需要对每个请求建立一堆线程等待请求，而客户端发送请求后，先咨询服务端是否有线程相应，如果没有则会一直等待或者遭到拒绝请求，如果有的话，客户端会线程会等待请求结束后才继续执行。</span></p><p><span>二、NIO</span></p><p><span>NIO基于</span><a href='https://www.jianshu.com/p/eef7ebe28673'><span>Reactor</span></a><span>，当</span><a href='https://so.csdn.net/so/search?q=socket&spm=1001.2101.3001.7020'><span>socket</span></a><span>有流可读或可写入socket时，操作系统会相应的通知引用程序进行处理，应用再将流读取到缓冲区或写入操作系统。 也就是说，这个时候，已经不是一个连接就要对应一个处理线程了，而是有效的请求，对应一个线程，当连接没有数据时，是没有工作线程来处理的。</span></p><p><span>Java NIO 可以让我们</span><strong><span>非阻塞</span></strong><span>的使用 IO 操作。例如：</span></p><ul><li><span>当一个线程执行从 Channel 执行读取 IO 操作时，当此时有数据，则读取数据并返回；当此时无数据，则直接返回</span><strong><span>而不会阻塞当前线程</span></strong><span>。</span></li><li><span>当一个线程执行向 Channel 执行写入 IO 操作时，</span><strong><span>不需要阻塞等待它完全写入</span></strong><span>，这个线程同时可以做别的事情。</span></li></ul><p><span>也就是说，线程可以将非阻塞 IO 的空闲时间用于在其他 Channel 上执行 IO 操作。所以，一个单独的线程，可以管理多个 Channel 的读取和写入 IO 操作。</span></p><h3><a name="12-stream流和buffer" class="md-header-anchor"></a><span>1.2 Stream流和Buffer</span></h3><p><span>BIO 是面向字节流或者字符流的，而在 NIO 中，它摒弃了传统的 IO 流，而是引入 Channel 和 Buffer 的概念：从 Channel 中读取数据到 Buffer 中，或者将数据从 Buffer 中写到 Channel 中。</span></p><p><span>① 那么什么是</span><strong><span>基于 Stream</span></strong><span>呢？</span></p><p><span>在一般的 Java IO 操作中，我们以</span><strong><span>流式</span></strong><span>的方式，</span><strong><span>顺序</span></strong><span>的从一个 Stream 中读取一个或者多个字节，直至读取所有字节。因为它没有缓存区，所以我们就不能随意改变读取指针的位置。</span></p><p><span>② 那么什么是</span><strong><span>基于 Buffer</span></strong><span> 呢？</span></p><p><span>基于 Buffer 就显得有点不同了。我们在从 Channel 中读取数据到 Buffer 中，这样 Buffer 中就有了数据后，我们就可以对这些数据进行操作了。并且不同于一般的 Java IO 操作那样是</span><strong><span>顺序</span></strong><span>操作，NIO 中我们可以随意的读取</span><strong><span>任意</span></strong><span>位置的数据，这样大大增加了处理过程中的灵活性。</span></p><p> </p><h2><a name="2-channel" class="md-header-anchor"></a><span>2. Channel</span></h2><h3><a name="21-概述" class="md-header-anchor"></a><span>2.1. 概述</span></h3><p><span>在 Java NIO 中，基本上所有的 IO 操作都是从 Channel 开始。数据可以从 Channel 读取到 Buffer 中，也可以从 Buffer 写到 Channel 中。</span></p><p><span>如下图所示：</span></p><p><img src="https://gitee.com/luojianghao/pic-repo/raw/master/image-20221216162333056.png" alt="image-20221216162333056" style="zoom:150%;" /></p><h3><a name="2-2--nio-channel-对比-java-stream" class="md-header-anchor"></a><span>2. 2 NIO Channel 对比 Java Stream</span></h3><p><span>NIO Channel </span><strong><span>类似</span></strong><span> Java Stream ，但又有几点不同：</span></p><ol><li><span>对于</span><strong><span>同一个</span></strong><span> Channel ，我们可以从它读取数据，也可以向它写入数据。而对于</span><strong><span>同一个</span></strong><span> Stream ，通畅要么只能读，要么只能写，二选一( 有些文章也描述成“单向”，也是这个意思 )。</span></li><li><span>Channel 可以</span><strong><span>非阻塞</span></strong><span>的读写 IO 操作，而 Stream 只能</span><strong><span>阻塞</span></strong><span>的读写 IO 操作。</span></li><li><span>Channel </span><strong><span>必须配合</span></strong><span> Buffer 使用，总是先读取到一个 Buffer 中，又或者是向一个 Buffer 写入。也就是说，我们无法绕过 Buffer ，直接向 Channel 写入数据。</span></li></ol><h3><a name="23--channel-的实现" class="md-header-anchor"></a><span>2.3 Channel 的实现</span></h3><p><span>Channel 在 Java 中，作为一个</span><strong><span>接口</span></strong><span>，</span><code>java.nio.channels.Channel</code><span> ，定义了 IO 操作的</span><strong><span>连接与关闭</span></strong><span>。代码如下：</span></p><pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="java"><div class="CodeMirror cm-s-inner CodeMirror-wrap" lang="java"><div style="overflow: hidden; position: relative; width: 3px; height: 0px; top: 0px; left: 4px;"><textarea autocorrect="off" autocapitalize="off" spellcheck="false" tabindex="0" style="position: absolute; bottom: -1em; padding: 0px; width: 1000px; height: 1em; outline: none;"></textarea></div><div class="CodeMirror-scrollbar-filler" cm-not-content="true"></div><div class="CodeMirror-gutter-filler" cm-not-content="true"></div><div class="CodeMirror-scroll" tabindex="-1"><div class="CodeMirror-sizer" style="margin-left: 0px; margin-bottom: 0px; border-right-width: 0px; padding-right: 0px; padding-bottom: 0px;"><div style="position: relative; top: 0px;"><div class="CodeMirror-lines" role="presentation"><div role="presentation" style="position: relative; outline: none;"><div class="CodeMirror-measure"><pre><span>xxxxxxxxxx</span></pre></div><div class="CodeMirror-measure"></div><div style="position: relative; z-index: 1;"></div><div class="CodeMirror-code" role="presentation" style=""><div class="CodeMirror-activeline" style="position: relative;"><div class="CodeMirror-activeline-background CodeMirror-linebackground"></div><div class="CodeMirror-gutter-background CodeMirror-activeline-gutter" style="left: 0px; width: 0px;"></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"><span class="cm-keyword">public</span> <span class="cm-keyword">interface</span> <span class="cm-def">Channel</span> <span class="cm-keyword">extends</span> <span class="cm-variable">Closeable</span> { </span></pre></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"> <span class="cm-tab" role="presentation" cm-text=" "> </span><span class="cm-comment">/** * 判断此通道是否处于打开状态。 */</span> </span></pre><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"> <span class="cm-keyword">public</span> <span class="cm-variable-3">boolean</span> <span class="cm-variable">isOpen</span>(); </span></pre><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"> <span class="cm-comment">/** *关闭此通道。 */</span> </span></pre><div class="" style="position: relative;"><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"> <span class="cm-keyword">public</span> <span class="cm-variable-3">void</span> <span class="cm-variable">close</span>() <span class="cm-keyword">throws</span> <span class="cm-variable">IOException</span>;</span></pre></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;">}</span></pre></div></div></div></div></div><div style="position: absolute; height: 0px; width: 1px; border-bottom: 0px solid transparent; top: 156px;"></div><div class="CodeMirror-gutters" style="display: none; height: 156px;"></div></div></div></pre><p><span>Channel 有非常多的实现类，最为重要的</span><strong><span>四个</span></strong><span> Channel 实现类如下：</span></p><ul><li><span>SocketChannel ：一个客户端用来</span><strong><span>发起</span></strong><span> TCP 的 Channel 。</span></li><li><span>ServerSocketChannel ：一个服务端用来</span><strong><span>监听</span></strong><span>新进来的连接的 TCP 的 Channel 。对于每一个新进来的连接，都会创建一个对应的 SocketChannel 。</span></li><li><span>DatagramChannel ：通过 UDP 读写数据。</span></li><li><span>FileChannel ：从文件中，读写数据。</span></li></ul><h3><a name="24--java-channel-的使用" class="md-header-anchor"></a><span>2.4 java Channel 的使用</span></h3><p> </p><p><span>Java NIO中的SocketChannel是一个连接到TCP网络套接字的通道。可以通过以下2种方式创建SocketChannel：</span></p><ol><li><span>打开一个SocketChannel并连接到互联网上的某台服务器。</span></li><li><span>一个新连接到达ServerSocketChannel时，会创建一个SocketChannel。</span></li></ol><p> </p><h4><a name="241-打开-socketchannel" class="md-header-anchor"></a><span>2.4.1 打开 SocketChannel</span></h4><p><span>下面是SocketChannel的打开方式：</span></p><pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="java"><div class="CodeMirror cm-s-inner CodeMirror-wrap" lang="java"><div style="overflow: hidden; position: relative; width: 3px; height: 0px; top: 0px; left: 4px;"><textarea autocorrect="off" autocapitalize="off" spellcheck="false" tabindex="0" style="position: absolute; bottom: -1em; padding: 0px; width: 1000px; height: 1em; outline: none;"></textarea></div><div class="CodeMirror-scrollbar-filler" cm-not-content="true"></div><div class="CodeMirror-gutter-filler" cm-not-content="true"></div><div class="CodeMirror-scroll" tabindex="-1"><div class="CodeMirror-sizer" style="margin-left: 0px; margin-bottom: 0px; border-right-width: 0px; padding-right: 0px; padding-bottom: 0px;"><div style="position: relative; top: 0px;"><div class="CodeMirror-lines" role="presentation"><div role="presentation" style="position: relative; outline: none;"><div class="CodeMirror-measure"><pre><span>xxxxxxxxxx</span></pre></div><div class="CodeMirror-measure"></div><div style="position: relative; z-index: 1;"></div><div class="CodeMirror-code" role="presentation"><div class="CodeMirror-activeline" style="position: relative;"><div class="CodeMirror-activeline-background CodeMirror-linebackground"></div><div class="CodeMirror-gutter-background CodeMirror-activeline-gutter" style="left: 0px; width: 0px;"></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"><span class="cm-variable">SocketChannel</span> <span class="cm-variable">socketChannel</span> <span class="cm-operator">=</span> <span class="cm-variable">SocketChannel</span>.<span class="cm-variable">open</span>();</span></pre></div><div class="" style="position: relative;"><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"><span class="cm-variable">socketChannel</span>.<span class="cm-variable">connect</span>(<span class="cm-keyword">new</span> <span class="cm-variable">InetSocketAddress</span>(<span class="cm-string">"http://jenkov.com"</span>, <span class="cm-number">80</span>));</span></pre></div></div></div></div></div></div><div style="position: absolute; height: 0px; width: 1px; border-bottom: 0px solid transparent; top: 52px;"></div><div class="CodeMirror-gutters" style="display: none; height: 52px;"></div></div></div></pre><h4><a name="242-关闭-socketchannel" class="md-header-anchor"></a><span>2.4.2 关闭 SocketChannel</span></h4><p><span>当用完SocketChannel之后调用SocketChannel.close()关闭SocketChannel：</span></p><pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="java"><div class="CodeMirror cm-s-inner CodeMirror-wrap" lang="java"><div style="overflow: hidden; position: relative; width: 3px; height: 0px; top: 0px; left: 4px;"><textarea autocorrect="off" autocapitalize="off" spellcheck="false" tabindex="0" style="position: absolute; bottom: -1em; padding: 0px; width: 1000px; height: 1em; outline: none;"></textarea></div><div class="CodeMirror-scrollbar-filler" cm-not-content="true"></div><div class="CodeMirror-gutter-filler" cm-not-content="true"></div><div class="CodeMirror-scroll" tabindex="-1"><div class="CodeMirror-sizer" style="margin-left: 0px; margin-bottom: 0px; border-right-width: 0px; padding-right: 0px; padding-bottom: 0px;"><div style="position: relative; top: 0px;"><div class="CodeMirror-lines" role="presentation"><div role="presentation" style="position: relative; outline: none;"><div class="CodeMirror-measure"><pre><span>xxxxxxxxxx</span></pre></div><div class="CodeMirror-measure"></div><div style="position: relative; z-index: 1;"></div><div class="CodeMirror-code" role="presentation"><div class="CodeMirror-activeline" style="position: relative;"><div class="CodeMirror-activeline-background CodeMirror-linebackground"></div><div class="CodeMirror-gutter-background CodeMirror-activeline-gutter" style="left: 0px; width: 0px;"></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"><span class="cm-variable">socketChannel</span>.<span class="cm-variable">close</span>();</span></pre></div></div></div></div></div></div><div style="position: absolute; height: 0px; width: 1px; border-bottom: 0px solid transparent; top: 26px;"></div><div class="CodeMirror-gutters" style="display: none; height: 26px;"></div></div></div></pre><h4><a name="243-从-socketchannel-读取数据" class="md-header-anchor"></a><span>2.4.3 从 SocketChannel 读取数据</span></h4><p><span>要从SocketChannel中读取数据，调用一个read()的方法之一。以下是例子：</span></p><pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="java"><div class="CodeMirror cm-s-inner CodeMirror-wrap" lang="java"><div style="overflow: hidden; position: relative; width: 3px; height: 0px; top: 0px; left: 4px;"><textarea autocorrect="off" autocapitalize="off" spellcheck="false" tabindex="0" style="position: absolute; bottom: -1em; padding: 0px; width: 1000px; height: 1em; outline: none;"></textarea></div><div class="CodeMirror-scrollbar-filler" cm-not-content="true"></div><div class="CodeMirror-gutter-filler" cm-not-content="true"></div><div class="CodeMirror-scroll" tabindex="-1"><div class="CodeMirror-sizer" style="margin-left: 0px; margin-bottom: 0px; border-right-width: 0px; padding-right: 0px; padding-bottom: 0px;"><div style="position: relative; top: 0px;"><div class="CodeMirror-lines" role="presentation"><div role="presentation" style="position: relative; outline: none;"><div class="CodeMirror-measure"><pre>x</pre></div><div class="CodeMirror-measure"></div><div style="position: relative; z-index: 1;"></div><div class="CodeMirror-code" role="presentation"><div class="CodeMirror-activeline" style="position: relative;"><div class="CodeMirror-activeline-background CodeMirror-linebackground"></div><div class="CodeMirror-gutter-background CodeMirror-activeline-gutter" style="left: 0px; width: 0px;"></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"><span class="cm-variable">ByteBuffer</span> <span class="cm-variable">buf</span> <span class="cm-operator">=</span> <span class="cm-variable">ByteBuffer</span>.<span class="cm-variable">allocate</span>(<span class="cm-number">48</span>);</span></pre></div><div class="" style="position: relative;"><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"><span class="cm-variable-3">int</span> <span class="cm-variable">bytesRead</span> <span class="cm-operator">=</span> <span class="cm-variable">socketChannel</span>.<span class="cm-variable">read</span>(<span class="cm-variable">buf</span>);</span></pre></div></div></div></div></div></div><div style="position: absolute; height: 0px; width: 1px; border-bottom: 0px solid transparent; top: 52px;"></div><div class="CodeMirror-gutters" style="display: none; height: 52px;"></div></div></div></pre><p><span>首先，分配一个Buffer。从SocketChannel读取到的数据将会放到这个Buffer中。</span></p><p><span>然后，调用SocketChannel.read()。该方法将数据从SocketChannel 读到Buffer中。read()方法返回的int值表示读了多少字节进Buffer里。如果返回的是-1，表示已经读到了流的末尾（连接关闭了）。</span></p><h4><a name="244-写入-socketchannel" class="md-header-anchor"></a><span>2.4.4 写入 SocketChannel</span></h4><p><span>写数据到SocketChannel用的是SocketChannel.write()方法，该方法以一个Buffer作为参数。示例如下：</span></p><pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="java"><div class="CodeMirror cm-s-inner CodeMirror-wrap" lang="java"><div style="overflow: hidden; position: relative; width: 3px; height: 0px; top: 0px; left: 4px;"><textarea autocorrect="off" autocapitalize="off" spellcheck="false" tabindex="0" style="position: absolute; bottom: -1em; padding: 0px; width: 1000px; height: 1em; outline: none;"></textarea></div><div class="CodeMirror-scrollbar-filler" cm-not-content="true"></div><div class="CodeMirror-gutter-filler" cm-not-content="true"></div><div class="CodeMirror-scroll" tabindex="-1"><div class="CodeMirror-sizer" style="margin-left: 0px; margin-bottom: 0px; border-right-width: 0px; padding-right: 0px; padding-bottom: 0px;"><div style="position: relative; top: 0px;"><div class="CodeMirror-lines" role="presentation"><div role="presentation" style="position: relative; outline: none;"><div class="CodeMirror-measure"></div><div class="CodeMirror-measure"></div><div style="position: relative; z-index: 1;"></div><div class="CodeMirror-code" role="presentation" style=""><div class="CodeMirror-activeline" style="position: relative;"><div class="CodeMirror-activeline-background CodeMirror-linebackground"></div><div class="CodeMirror-gutter-background CodeMirror-activeline-gutter" style="left: 0px; width: 0px;"></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"><span class="cm-variable-3">String</span> <span class="cm-variable">newData</span> <span class="cm-operator">=</span> <span class="cm-string">"New String to write to file…"</span> <span class="cm-operator">+</span> <span class="cm-variable">System</span>.<span class="cm-variable">currentTimeMillis</span>();</span></pre></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"><span cm-text=""></span></span></pre><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"><span class="cm-variable">ByteBuffer</span> <span class="cm-variable">buf</span> <span class="cm-operator">=</span> <span class="cm-variable">ByteBuffer</span>.<span class="cm-variable">allocate</span>(<span class="cm-number">48</span>);</span></pre><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"><span class="cm-variable">buf</span>.<span class="cm-variable">clear</span>();</span></pre><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"><span class="cm-variable">buf</span>.<span class="cm-variable">put</span>(<span class="cm-variable">newData</span>.<span class="cm-variable">getBytes</span>());</span></pre><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"><span cm-text=""></span></span></pre><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"><span class="cm-variable">buf</span>.<span class="cm-variable">flip</span>();</span></pre><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"><span cm-text=""></span></span></pre><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"><span class="cm-keyword">while</span>(<span class="cm-variable">buf</span>.<span class="cm-variable">hasRemaining</span>()) {</span></pre><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"><span class="cm-variable">channel</span>.<span class="cm-variable">write</span>(<span class="cm-variable">buf</span>);</span></pre><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;">}</span></pre></div></div></div></div></div><div style="position: absolute; height: 0px; width: 1px; border-bottom: 0px solid transparent; top: 286px;"></div><div class="CodeMirror-gutters" style="display: none; height: 286px;"></div></div></div></pre><p><span>注意SocketChannel.write()方法的调用是在一个while循环中的。Write()方法无法保证能写多少字节到SocketChannel。所以，我们重复调用write()直到Buffer没有要写的字节为止。</span></p><h4><a name="245-非阻塞模式" class="md-header-anchor"></a><span>2.4.5 非阻塞模式</span></h4><p><span>可以设置 SocketChannel 为非阻塞模式（non-blocking mode）.设置之后，就可以在异步模式下调用connect(), read() 和write()了。</span></p><h5><a name="connect" class="md-header-anchor"></a><span> connect()</span></h5><p><span>如果SocketChannel在非阻塞模式下，此时调用connect()，该方法可能在连接建立之前就返回了。为了确定连接是否建立，可以调用finishConnect()的方法。像这样：</span></p><pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="java"><div class="CodeMirror cm-s-inner CodeMirror-wrap" lang="java"><div style="overflow: hidden; position: relative; width: 3px; height: 0px; top: 0px; left: 4px;"><textarea autocorrect="off" autocapitalize="off" spellcheck="false" tabindex="0" style="position: absolute; bottom: -1em; padding: 0px; width: 1000px; height: 1em; outline: none;"></textarea></div><div class="CodeMirror-scrollbar-filler" cm-not-content="true"></div><div class="CodeMirror-gutter-filler" cm-not-content="true"></div><div class="CodeMirror-scroll" tabindex="-1"><div class="CodeMirror-sizer" style="margin-left: 0px; margin-bottom: 0px; border-right-width: 0px; padding-right: 0px; padding-bottom: 0px;"><div style="position: relative; top: 0px;"><div class="CodeMirror-lines" role="presentation"><div role="presentation" style="position: relative; outline: none;"><div class="CodeMirror-measure"><pre><span>xxxxxxxxxx</span></pre></div><div class="CodeMirror-measure"></div><div style="position: relative; z-index: 1;"></div><div class="CodeMirror-code" role="presentation" style=""><div class="CodeMirror-activeline" style="position: relative;"><div class="CodeMirror-activeline-background CodeMirror-linebackground"></div><div class="CodeMirror-gutter-background CodeMirror-activeline-gutter" style="left: 0px; width: 0px;"></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"><span class="cm-variable">socketChannel</span>.<span class="cm-variable">configureBlocking</span>(<span class="cm-atom">false</span>);</span></pre></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"><span class="cm-variable">socketChannel</span>.<span class="cm-variable">connect</span>(<span class="cm-keyword">new</span> <span class="cm-variable">InetSocketAddress</span>(<span class="cm-string">"http://jenkov.com"</span>, <span class="cm-number">80</span>));</span></pre><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"><span cm-text=""></span></span></pre><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"><span class="cm-keyword">while</span>(<span class="cm-operator">!</span> <span class="cm-variable">socketChannel</span>.<span class="cm-variable">finishConnect</span>() ){</span></pre><div class="" style="position: relative;"><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;"><span class="cm-comment">//wait, or do something else…</span></span></pre></div><pre class=" CodeMirror-line " role="presentation"><span role="presentation" style="padding-right: 0.1px;">}</span></pre></div></div></div></div></div><div style="position: absolute; height: 0px; width: 1px; border-bottom: 0px solid transparent; top: 156px;"></div><div class="CodeMirror-gutters" style="display: none; height: 156px;"></div></div></div></pre><h5><a name="write" class="md-header-anchor"></a><span>write()</span></h5><p><span>非阻塞模式下，write()方法在尚未写出任何内容时可能就返回了。所以需要在循环中调用write()。前面已经有例子了，这里就不赘述了。</span></p><h5><a name="read" class="md-header-anchor"></a><span>read()</span></h5><p><span>非阻塞模式下,read()方法在尚未读取到任何数据时可能就返回了。所以需要关注它的int返回值，它会告诉你读取了多少字节。</span></p><h4><a name="246-非阻塞模式与选择器" class="md-header-anchor"></a><span>2.4.6 非阻塞模式与选择器</span></h4><p><span>非阻塞模式与选择器搭配会工作的更好，通过将一或多个SocketChannel注册到Selector，可以询问选择器哪个通道已经准备好了读取，写入等。Selector与SocketChannel的搭配使用会在后面详讲。</span></p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p></div>
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