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java | 阻塞模式

发表于 更新于 分类于 ， ， ， ， Valine：

通过服务端和客户端进行演示。

引入自写的方法类。

下载 JAVA 文件

netty 包

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<dependency>
    <groupId>io.netty</groupId>
    <artifactId>netty-all</artifactId>
    <version>4.1.86.Final</version>
</dependency>

服务端

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package com.redisc;

import lombok.extern.slf4j.Slf4j;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.util.ArrayList;
import java.util.List;

import static com.redisc.ByteBufferUtil.debugRead;

@Slf4j(topic = "c.Test")
public class Server {

    public static void main(String[] args) throws IOException {
        // 使用 nio 单线程
        // bytebuffer
        ByteBuffer buffer = ByteBuffer.allocate(16);
        // 创建服务器
        ServerSocketChannel ssc = ServerSocketChannel.open();
        //绑定端口
        ssc.bind(new InetSocketAddress(8090));
        //连接集合
        List<SocketChannel> channelList = new ArrayList<>();
        while (true) {
            // accept 建立客户断连接，SocketChannel 用来与客户端通信
            log.debug("connectinging");
            SocketChannel sc = ssc.accept(); // accept 是一个阻塞方法
            log.debug("connected");
            channelList.add(sc);
            for (SocketChannel channel : channelList) {
                // 接收客户端发送的数据
                log.debug("before read... {}", channel);
                channel.read(buffer); // read 也是一个阻塞方法，需要等待客户端发送数据
                buffer.flip();
                debugRead(buffer);
                buffer.clear();
                log.debug("after read...{}", channel);
            }
        }
    }

}

要注意的是

  • ssc.accept();
  • channel.read(buffer);
    • 都是阻塞方法

下面使用客户端进行验证。

客户端

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package com.redisc;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.channels.SocketChannel;

public class Client {
    public static void main(String[] args) throws IOException {
        SocketChannel sc = SocketChannel.open();
        sc.connect(new InetSocketAddress("localhost", 8090));
        System.out.println("waiting...");
    }
}

验证

开启服务端。

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15:17:19.095 [main] DEBUG c.Test - connectinging 「阻塞」

开启第一个客户端。在客户端第 11 打一个断点。

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15:17:19.095 [main] DEBUG c.Test - connectinging
15:18:05.970 [main] DEBUG c.Test - connected
15:18:05.970 [main] DEBUG c.Test - before read... java.nio.channels.SocketChannel[connected local=/127.0.0.1:8090 remote=/127.0.0.1:52515]

客户端在断点处停下。在 sc 变量上右键，点击 evalute

输入

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sc.write(Charset.defaultCharset().encode("hi"))

并执行。

客户端输出

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15:17:19.095 [main] DEBUG c.Test - connectinging
15:18:05.970 [main] DEBUG c.Test - connected
15:18:05.970 [main] DEBUG c.Test - before read... java.nio.channels.SocketChannel[connected local=/127.0.0.1:8090 remote=/127.0.0.1:52515]
15:19:40.632 [main] DEBUG io.netty.util.internal.logging.InternalLoggerFactory - Using SLF4J as the default logging framework
+--------+-------------------- read -----------------------+----------------+
position: [0], limit: [2]
         +-------------------------------------------------+
         |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
+--------+-------------------------------------------------+----------------+
|00000000| 68 69                                           |hi              |
+--------+-------------------------------------------------+----------------+
15:19:40.665 [main] DEBUG c.Test - after read...java.nio.channels.SocketChannel[connected local=/127.0.0.1:8090 remote=/127.0.0.1:52515]
15:19:40.666 [main] DEBUG c.Test - connectinging

在 evalute 再次执行

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sc.write(Charset.defaultCharset().encode("world"))

服务端输出没有变化。

这是因为，客户端在执行完上一个 hi 后，while 重新轮回，进入了 SocketChannel sc = ssc.accept(); // accept 是一个阻塞方法 阻塞。导致，world 没有接收到。

此时，开启另一个客户端。服务端输出

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15:17:19.095 [main] DEBUG c.Test - connectinging
15:18:05.970 [main] DEBUG c.Test - connected
15:18:05.970 [main] DEBUG c.Test - before read... java.nio.channels.SocketChannel[connected local=/127.0.0.1:8090 remote=/127.0.0.1:52515]
15:19:40.632 [main] DEBUG io.netty.util.internal.logging.InternalLoggerFactory - Using SLF4J as the default logging framework
+--------+-------------------- read -----------------------+----------------+
position: [0], limit: [2]
         +-------------------------------------------------+
         |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
+--------+-------------------------------------------------+----------------+
|00000000| 68 69                                           |hi              |
+--------+-------------------------------------------------+----------------+
15:19:40.665 [main] DEBUG c.Test - after read...java.nio.channels.SocketChannel[connected local=/127.0.0.1:8090 remote=/127.0.0.1:52515]
15:19:40.666 [main] DEBUG c.Test - connectinging
15:21:44.402 [main] DEBUG c.Test - connected
15:21:44.402 [main] DEBUG c.Test - before read... java.nio.channels.SocketChannel[connected local=/127.0.0.1:8090 remote=/127.0.0.1:52515]
+--------+-------------------- read -----------------------+----------------+
position: [0], limit: [5]
         +-------------------------------------------------+
         |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
+--------+-------------------------------------------------+----------------+
|00000000| 77 6f 72 6c 64                                  |world           |
+--------+-------------------------------------------------+----------------+
15:21:44.403 [main] DEBUG c.Test - after read...java.nio.channels.SocketChannel[connected local=/127.0.0.1:8090 remote=/127.0.0.1:52515]
15:21:44.403 [main] DEBUG c.Test - before read... java.nio.channels.SocketChannel[connected local=/127.0.0.1:8090 remote=/127.0.0.1:52600]

发现上一个连接的 world 输出出来了。在新开启的客户端执行。

这是因为，当有新的连接出现后，SocketChannel sc = ssc.accept(); // accept 是一个阻塞方法 向下执行。执行了所有连接的接收，所以，world 也就接收到了。

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sc.write(Charset.defaultCharset().encode("123"))

服务端输出

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15:17:19.095 [main] DEBUG c.Test - connectinging
15:18:05.970 [main] DEBUG c.Test - connected
15:18:05.970 [main] DEBUG c.Test - before read... java.nio.channels.SocketChannel[connected local=/127.0.0.1:8090 remote=/127.0.0.1:52515]
15:19:40.632 [main] DEBUG io.netty.util.internal.logging.InternalLoggerFactory - Using SLF4J as the default logging framework
+--------+-------------------- read -----------------------+----------------+
position: [0], limit: [2]
         +-------------------------------------------------+
         |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
+--------+-------------------------------------------------+----------------+
|00000000| 68 69                                           |hi              |
+--------+-------------------------------------------------+----------------+
15:19:40.665 [main] DEBUG c.Test - after read...java.nio.channels.SocketChannel[connected local=/127.0.0.1:8090 remote=/127.0.0.1:52515]
15:19:40.666 [main] DEBUG c.Test - connectinging
15:21:44.402 [main] DEBUG c.Test - connected
15:21:44.402 [main] DEBUG c.Test - before read... java.nio.channels.SocketChannel[connected local=/127.0.0.1:8090 remote=/127.0.0.1:52515]
+--------+-------------------- read -----------------------+----------------+
position: [0], limit: [5]
         +-------------------------------------------------+
         |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
+--------+-------------------------------------------------+----------------+
|00000000| 77 6f 72 6c 64                                  |world           |
+--------+-------------------------------------------------+----------------+
15:21:44.403 [main] DEBUG c.Test - after read...java.nio.channels.SocketChannel[connected local=/127.0.0.1:8090 remote=/127.0.0.1:52515]
15:21:44.403 [main] DEBUG c.Test - before read... java.nio.channels.SocketChannel[connected local=/127.0.0.1:8090 remote=/127.0.0.1:52600]
+--------+-------------------- read -----------------------+----------------+
position: [0], limit: [3]
         +-------------------------------------------------+
         |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
+--------+-------------------------------------------------+----------------+
|00000000| 31 32 33                                        |123             |
+--------+-------------------------------------------------+----------------+
15:22:51.812 [main] DEBUG c.Test - after read...java.nio.channels.SocketChannel[connected local=/127.0.0.1:8090 remote=/127.0.0.1:52600]
15:22:51.812 [main] DEBUG c.Test - connectinging

在上述，我们可以得知，阻塞中，各种连接和接收都是线性执行的。

请我喝杯咖啡吧～