# Channel \`\`\`java public static void write(String path) throws Exception { RandomAccessFile aFile = new RandomAccessFile(path, "rw"); FileChannel channel = aFile.getChannel(); ByteBuffer buf = ByteBuffer.allocate(100); buf.put("i will come back!!".getBytes()); buf.flip(); while(buf.hasRemaining()) { channel.write(buf); } channel.close(); aFile.close(); System.out.println("end"); if(buf.hasRemaining()) System.out.println(buf.get()); System.out.println(buf.get()); System.out.println(buf.get()); } public static void read(String path) throws Exception { RandomAccessFile aFile = new RandomAccessFile(path, "rw"); FileChannel channel = aFile.getChannel(); ByteBuffer buf = ByteBuffer.allocate(10); int byteRead = channel.read(buf); while (byteRead != -1) { System.out.println("读取了：" + byteRead); buf.flip(); while (buf.hasRemaining()) { System.out.print((char) buf.get()); } buf.clear(); byteRead = channel.read(buf); } channel.close(); aFile.close(); System.out.println("end"); } public static void writeTOFile() { } } \`\`\` \`\`\`java InetSocketAddress address = new InetSocketAddress("www.baidu.com",80); // SocketChannel socketChanne = SocketChannel.open(address); SocketChannel socketChanne2 = SocketChannel.open(); socketChanne2.connect(address); socketChanne2.configureBlocking(false); // udp 没有服务端 ，双方边监听边发送 \`\`\` # ByteBuffer \`\`\`java package org.child2; import java.nio.ByteBuffer; import java.nio.MappedByteBuffer; import junit.framework.TestCase; /\*\* \* Unit test for simple App. \*/ public class AppTest extends TestCase { public void testApp() { ByteBuffer buffer = ByteBuffer.allocate(3); buffer.rewind(); //重复读的时候使用 buffer.clear(); //初始化 buffer.compact(); //读一半，想写了，清除读过的，把没读的移到前边 buffer.slice();// 缓冲区分片，可影响原数据 buffer.asReadOnlyBuffer();//只读缓冲区分片，原数据影响分片 buffer.allocateDirect(1024); // 直接用系统内存，速度快，allocate:系统分配后，获取值赋值给jvm，所以速度慢 buffer.mark(); //标记 buffer.reset();// 恢复 buffer.remaining(); // 是否有剩余：limit-position buffer.hasRemaining();// 同上 // MappedByteBuffer mbb = fc.map(FileChannel.MapMode.REWA_WRITE,0,1024) 内存映射文件IO，只读到的内容映射到内存 buffer.put((byte)49); buffer.put((byte)50); // buffer.rewind(); buffer.clear(); buffer.put((byte)51); buffer.put((byte)51); buffer.put((byte)51); buffer.flip(); System.out.println((char)buffer.get()); System.out.println((char)buffer.get()); System.out.println((char)buffer.get()); } } \`\`\` # Selector - 可以被复用的channel：SocketChannel，继承了Selectable，FileChannel没有继承，不能被复用 - 一个通道可以被注册到多个select，但，对于选择器只能注册一次 #### 通道注册 \`\`\`java channel.register(selector,ops) ops:read,write,connect,accept 可通过 "\|" 选择多个 \`\`\` #### 状态查询 \`\`\`java selector.select()---\>选择键集合SelectionKey \`\`\` \`\`\`java package org.child2; 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; public class SelectorDemo { public static void main(String\[\] args) throws Exception { Selector selector = Selector.open(); ServerSocketChannel serverSocketChannel = ServerSocketChannel.open(); serverSocketChannel.configureBlocking(false); serverSocketChannel.bind(new InetSocketAddress(9000)); serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT); while(selector.select()\>0) { Set selectedKeys = selector.selectedKeys(); // 获取所有操作 Iterator iterator = selectedKeys.iterator(); while(iterator.hasNext()) { // 处理操作 SelectionKey next = iterator.next(); if(next.isAcceptable()) {// 连接事件 SocketChannel accept = serverSocketChannel.accept(); // 获取通道 accept.configureBlocking(false); accept.register(selector,SelectionKey.OP_READ\|SelectionKey.OP_WRITE); }else if(next.isConnectable()) { }else if(next.isWritable()) { SocketChannel channel = (SocketChannel)next.channel(); ByteBuffer buffer = ByteBuffer.allocate(1024); int length=0; while((length = channel.read(buffer))\>0) { buffer.flip(); System.out.println("received:"+channel.socket().getRemoteSocketAddress()+new String(buffer.array())); buffer.clear(); } }else if(next.isReadable()) { } iterator.remove(); } Thread.sleep(2000); } } } \`\`\` #### Pipe 管道 \`\`\`java package org.child2; import java.io.IOException; import java.nio.ByteBuffer; import java.nio.channels.Pipe; import java.nio.channels.Pipe.SinkChannel; import java.nio.channels.Pipe.SourceChannel; public class PipeDemo { public static void main(String\[\] args) throws Exception { // 获取管道 Pipe pipe =Pipe.open(); // 获取sink SinkChannel sink = pipe.sink(); // 创建缓冲区 ByteBuffer allocate = ByteBuffer.allocate(1024); allocate.put("dzf".getBytes()); allocate.flip(); // 写入 sink.write(allocate); // 获取source SourceChannel source = pipe.source(); // 创建缓冲区 ByteBuffer allocate2 = ByteBuffer.allocate(1024); source.read(allocate2); System.out.println(new String(allocate2.array())); // 关闭 sink.close(); source.close(); } } \`\`\`