Netty——网络编程 NIO（Selector处理read事件）代码示例
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目录
一、服务端代码示例
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服务端代码示例
package com.example.nettytest.nio.day3; import com.example.nettytest.nio.day1.ByteBufferUtil; import lombok.extern.slf4j.Slf4j; import java.io.IOException; import java.net.InetSocketAddress; import java.nio.ByteBuffer; import java.nio.channels.SelectionKey; import java.nio.channels.Selector; import java.nio.channels.ServerSocketChannel; import java.nio.channels.SocketChannel; import java.util.Iterator; import java.util.Set; /** * @description: Selector处理read事件 代码示例 * @author: xz * @create: 2022-09-01 */ @Slf4j public class Test3Server public static void main(String[] args) nioselectorReadServer(); /** * Selector处理read事件 方法 * */ private static void nioSelectorReadServer() try (ServerSocketChannel channel = ServerSocketChannel.open()) //1、创建服务器 //绑定监听端口 channel.bind(new InetSocketAddress(8080)); //设置为非阻塞模式 channel.configureBlocking(false); System.out.println(channel); /** * 2、创建Selector，管理多个channel */ Selector selector = Selector.open(); /** * 3、建立Selector与channel的联系（也称为注册） * key只关注事件,绑定的事件类型4种，connect - 客户端连接成功时触发；accept - 服务器端成功接受连接时触发; read - 数据可读入时触发;write - 数据可写出时触发， * */ channel.register(selector, SelectionKey.OP_ACCEPT); while (true) /** * 4、select 方法, 没有事件发生，线程阻塞，有事件，线程才会恢复运行 * select 在事件未处理时，它不会阻塞 */ int count = selector.select(); log.debug("select count: ", count); // 获取所有事件 Set<SelectionKey> keys = selector.selectedKeys(); // 遍历所有事件，逐一处理 Iterator<SelectionKey> iter = keys.iterator(); while (iter.hasNext()) SelectionKey key = iter.next(); // 判断事件类型 如果事件类型是 accept - 服务器端成功接受连接时触发; if (key.isAcceptable()) //channel中有哪些key ServerSocketChannel c = (ServerSocketChannel) key.channel(); // 必须处理 selector 上的 channel SocketChannel sc = c.accept(); //设置为非阻塞模式 sc.configureBlocking(false); //建立Selector与channel的联系（也称为注册） sc.register(selector, SelectionKey.OP_READ); log.debug("连接已建立: ", sc); // 判断事件类型 如果事件类型是read - 数据可读入时触发 else if (key.isReadable()) //channel中有哪些key SocketChannel sc = (SocketChannel) key.channel(); //申请ByteBuffer容量 ByteBuffer buffer = ByteBuffer.allocate(128); //从channel中读并写入到buffer int read = sc.read(buffer); if(read == -1) //如果读到末尾 //取消注册在 selector 上的 channel key.cancel(); //关闭channel sc.close(); else //如果没有读到末尾 //切换到读模式 buffer.flip(); //打印可读取内容 ByteBufferUtil.debugRead(buffer); // 处理完毕，必须将事件移除 iter.remove(); catch (IOException e) e.printStackTrace();
二、客户端代码示例
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客户端代码示例
package com.example.nettytest.nio.day3; import java.io.IOException; import java.net.Socket; /** * @description: * @author: xz * @create: 2022-09-01 */ public class Test3Client public static void main(String[] args) try (Socket socket = new Socket("localhost", 8080)) System.out.println(socket); socket.getOutputStream().write("hello world".getBytes()); System.in.read(); catch (IOException e) e.printStackTrace();
三、工具类
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工具类，打印输入、输出数据使用
package com.example.nettytest.nio.day1; import io.netty.util.internal.StringUtil; import java.nio.ByteBuffer; import static io.netty.util.internal.MathUtil.isOutOfBounds; import static io.netty.util.internal.StringUtil.NEWLINE; public class ByteBufferUtil private static final char[] BYTE2CHAR = new char[256]; private static final char[] HEXDUMP_TABLE = new char[256 * 4]; private static final String[] HEXPADDING = new String[16]; private static final String[] HEXDUMP_ROWPREFIXES = new String[65536 >>> 4]; private static final String[] BYTE2HEX = new String[256]; private static final String[] BYTEPADDING = new String[16]; static final char[] DIGITS = "0123456789abcdef".toCharArray(); for (int i = 0; i < 256; i++) HEXDUMP_TABLE[i << 1] = DIGITS[i >>> 4 & 0x0F]; HEXDUMP_TABLE[(i << 1) + 1] = DIGITS[i & 0x0F]; int i; // Generate the lookup table for hex dump paddings for (i = 0; i < HEXPADDING.length; i++) int padding = HEXPADDING.length - i; StringBuilder buf = new StringBuilder(padding * 3); for (int j = 0; j < padding; j++) buf.append(" "); HEXPADDING[i] = buf.toString(); // Generate the lookup table for the start-offset header in each row (up to 64KiB). for (i = 0; i < HEXDUMP_ROWPREFIXES.length; i++) StringBuilder buf = new StringBuilder(12); buf.append(NEWLINE); buf.append(Long.toHexString(i << 4 & 0xFFFFFFFFL | 0x100000000L)); buf.setCharAt(buf.length() - 9, '|'); buf.append('|'); HEXDUMP_ROWPREFIXES[i] = buf.toString(); // Generate the lookup table for byte-to-hex-dump conversion for (i = 0; i < BYTE2HEX.length; i++) BYTE2HEX[i] = ' ' + StringUtil.byteToHexStringPadded(i); // Generate the lookup table for byte dump paddings for (i = 0; i < BYTEPADDING.length; i++) int padding = BYTEPADDING.length - i; StringBuilder buf = new StringBuilder(padding); for (int j = 0; j < padding; j++) buf.append(' '); BYTEPADDING[i] = buf.toString(); // Generate the lookup table for byte-to-char conversion for (i = 0; i < BYTE2CHAR.length; i++) if (i <= 0x1f || i >= 0x7f) BYTE2CHAR[i] = '.'; else BYTE2CHAR[i] = (char) i; /** * 打印所有内容 * @param buffer */ public static void debugAll(ByteBuffer buffer) int oldlimit = buffer.limit(); buffer.limit(buffer.capacity()); StringBuilder origin = new StringBuilder(256); appendPrettyHexDump(origin, buffer, 0, buffer.capacity()); System.out.println("+--------+-------------------- all ------------------------+----------------+"); System.out.printf("position: [%d], limit: [%d]\\n", buffer.position(), oldlimit); System.out.println(origin); buffer.limit(oldlimit); /** * 打印可读取内容 * @param buffer */ public static void debugRead(ByteBuffer buffer) StringBuilder builder = new StringBuilder(256); appendPrettyHexDump(builder, buffer, buffer.position(), buffer.limit() - buffer.position()); System.out.println("+--------+-------------------- read -----------------------+----------------+"); System.out.printf("position: [%d], limit: [%d]\\n", buffer.position(), buffer.limit()); System.out.println(builder); public static void main(String[] args) ByteBuffer buffer = ByteBuffer.allocate(10); buffer.put(new byte[]97, 98, 99, 100); debugAll(buffer); private static void appendPrettyHexDump(StringBuilder dump, ByteBuffer buf, int offset, int length) if (isOutOfBounds(offset, length, buf.capacity())) throw new IndexOutOfBoundsException( "expected: " + "0 <= offset(" + offset + ") <= offset + length(" + length + ") <= " + "buf.capacity(" + buf.capacity() + ')'); if (length == 0) return; dump.append( " +-------------------------------------------------+" + NEWLINE + " | 0 1 2 3 4 5 6 7 8 9 a b c d e f |" + NEWLINE + "+--------+-------------------------------------------------+----------------+"); final int startIndex = offset; final int fullRows = length >>> 4; final int remainder = length & 0xF; // Dump the rows which have 16 bytes. for (int row = 0; row < fullRows; row++) int rowStartIndex = (row << 4) + startIndex; // Per-row prefix. appendHexDumpRowPrefix(dump, row, rowStartIndex); // Hex dump int rowEndIndex = rowStartIndex + 16; for (int j = rowStartIndex; j < rowEndIndex; j++) dump.append(BYTE2HEX[getUnsignedByte(buf, j)]); dump.append(" |"); // ASCII dump for (int j = rowStartIndex; j < rowEndIndex; j++) dump.append(BYTE2CHAR[getUnsignedByte(buf, j)]); dump.append('|'); // Dump the last row which has less than 16 bytes. if (remainder != 0) int rowStartIndex = (fullRows << 4) + startIndex; appendHexDumpRowPrefix(dump, fullRows, rowStartIndex); // Hex dump int rowEndIndex = rowStartIndex + remainder; for (int j = rowStartIndex; j < rowEndIndex; j++) dump.append(BYTE2HEX[getUnsignedByte(buf, j)]); dump.append(HEXPADDING[remainder]); dump.append(" |"); // Ascii dump for (int j = rowStartIndex; j < rowEndIndex; j++) dump.append(BYTE2CHAR[getUnsignedByte(buf, j)]); dump.append(BYTEPADDING[remainder]); dump.append('|'); dump.append(NEWLINE + "+--------+-------------------------------------------------+----------------+"); private static void appendHexDumpRowPrefix(StringBuilder dump, int row, int rowStartIndex) if (row < HEXDUMP_ROWPREFIXES.length) dump以上是关于Netty——网络编程 NIO（Selector处理read事件）代码示例的主要内容，如果未能解决你的问题，请参考以下文章Netty——网络编程 NIO（Selector处理read事件 消息边界问题）代码示例
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