标签：netty java buffer System ByteBuffer import socketChannel
Netty
Buffer
IntBuffer intBuffer = IntBuffer.allocate(5);
for (int i = 0; i < intBuffer.capacity(); i++) {
intBuffer.put(i);
}
// 读写切换
intBuffer.flip();
while (intBuffer.hasRemaining()) {
// 每次get，指针都会后移
System.out.println(intBuffer.get());
}
类型化放入
public static void main(String[] args) throws Exception {
ByteBuffer buffer = ByteBuffer.allocate(64);
// 类型化方式放入数据
buffer.putInt(100);
buffer.putChar('*');
buffer.putLong(1L);
buffer.flip();
// 取出的顺序必须一致
System.out.println(buffer.getInt());
System.out.println(buffer.getChar());
System.out.println(buffer.getLong());
}
只读
public static void main(String[] args) throws Exception {
ByteBuffer buffer = ByteBuffer.allocate(64);
for (int i = 0; i < buffer.capacity(); i++) {
buffer.put((byte) i);
}
buffer.flip();
// 只读
ByteBuffer readOnlyBuffer = buffer.asReadOnlyBuffer();
while (readOnlyBuffer.hasRemaining()) {
System.out.println(readOnlyBuffer.get());
}
// 会抛异常java.nio.ReadOnlyBufferException
readOnlyBuffer.put((byte) 1);
}
MappedByteBuffer
public static void main(String[] args) throws Exception {
RandomAccessFile randomAccessFile = new RandomAccessFile("file", "rw");
FileChannel channel = randomAccessFile.getChannel();
/**
* 可让文件直接在堆外内存修改，不需要OS拷贝一次
* 读写模式，可以直接修改的起始位置，映射到内存的大小（字节）
* 可以直接修改的位置[0,5)
* 实际类型是DirectByteBuffer
*/
MappedByteBuffer map = channel.map(FileChannel.MapMode.READ_WRITE, 0, 5);
map.put(0, (byte) 'X');
map.put(4, (byte) 'Y');
randomAccessFile.close();
}
Buffer数组
public static void main(String[] args) throws Exception {
ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
InetSocketAddress inetSocketAddress = new InetSocketAddress(8888);
// 绑定端口并启动
serverSocketChannel.socket().bind(inetSocketAddress);
ByteBuffer[] byteBuffers = new ByteBuffer[2];
byteBuffers[0] = ByteBuffer.allocate(5);
byteBuffers[1] = ByteBuffer.allocate(3);
SocketChannel socketChannel = serverSocketChannel.accept();
int count = 8;
while (true) {
int byteRead = 0;
while (byteRead < count) {
long l = socketChannel.read(byteBuffers);
byteRead += l;
System.out.println("byteRead:" + l);
// 流打印
Arrays.stream(byteBuffers)
.map(buffer -> "position:" + buffer.position()
+ ", limit:" + buffer.limit())
.forEach(System.out::println);
}
// flip
Arrays.asList(byteBuffers)
.forEach(ByteBuffer::flip);
// 读出数据显示在客户端
long byteWrite = 0;
while (byteWrite < count) {
long l = socketChannel.write(byteBuffers);
byteWrite += l;
}
// clear
Arrays.asList(byteBuffers)
.forEach(ByteBuffer::clear);
}
}
Channel
ByteBuffer
public static void main(String[] args) throws Exception {
FileInputStream fileInputStream = new FileInputStream("file");
FileChannel channel1 = fileInputStream.getChannel();
FileOutputStream fileOutputStream = new FileOutputStream("file.txt");
FileChannel channel2 = fileOutputStream.getChannel();
ByteBuffer byteBuffer = ByteBuffer.allocate(1024);
while (true) {
/* public Buffer clear() {
position = 0;
limit = capacity;
mark = -1;
return this;
}*/
byteBuffer.clear();
// 从channel读出，放入到byteBuffer
int read = channel1.read(byteBuffer);
if (read == -1) {
break;
}
// 将byteBuffer写入channel2
byteBuffer.flip();
channel2.write(byteBuffer);
}
fileInputStream.close();
fileOutputStream.close();
}
transferTo&transferFrom
public static void main(String[] args) throws Exception {
FileInputStream fileInputStream = new FileInputStream("file");
FileChannel sourceChannel = fileInputStream.getChannel();
FileOutputStream fileOutputStream = new FileOutputStream("file.txt");
FileChannel destChannel = fileOutputStream.getChannel();
// destChannel.transferFrom(sourceChannel, 0, sourceChannel.size());
sourceChannel.transferTo(0, sourceChannel.size(), destChannel);
fileInputStream.close();
fileOutputStream.close();
}
Selector
-
一个EventLoopGroup 包含一个或者多个EventLoop；
-
一个EventLoop 在它的生命周期内只和一个Thread 绑定；
-
所有由EventLoop 处理的I/O 事件都将在它专有的Thread 上被处理；
-
一个Channel 在它的生命周期内只注册于一个EventLoop；
-
一个EventLoop 可能会被分配给一个或多个Channel。
-
有客户端连接时，会通过ServerSocketChannel得到SocketChannel
-
将SocketChannel注册到Selector上，
register(Selector sel, int ops, Object att)，返回SelectionKey，会和该Selector上关联(集合)。一个Selector上可以注册多个SocketChannel -
Selector会用select方法进行监听，返回发生事件的通道个数
-
得到有事件发生的Channel的SelectionKey，然后得到该Channel
selector.select(); // 阻塞
selector.select(100); // 阻塞100ms后返回
selector.wakeup(); // 唤醒
selector.selectNow();// 不阻塞，立刻返回
服务器
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.nio.charset.StandardCharsets;
import java.util.Iterator;
import java.util.Set;
class NIOServer {
public static void main(String[] args) throws Exception {
ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
Selector selector = Selector.open();
serverSocketChannel.socket().bind(new InetSocketAddress(7899));
// 设为非阻塞
serverSocketChannel.configureBlocking(false);
// 把serverSocketChannel注册到selector上，关心事件为OP_ACCEPT
serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
// 等待连接
while (true) {
if (selector.select(1000) == 0) {
System.out.println("服务器等待1s，无连接");
continue;
}
// 返回关注事件的集合
Set<SelectionKey> selectionKeys = selector.selectedKeys();
// 迭代器遍历
Iterator<SelectionKey> iterator = selectionKeys.iterator();
while (iterator.hasNext()) {
// 获取SelectionKey
SelectionKey key = iterator.next();
// 根据事件做相应处理
if (key.isAcceptable()) {
// 新客户端连接
// accept实际不会阻塞，因为已经知道是OP_ACCEPT事件
SocketChannel socketChannel = serverSocketChannel.accept();
socketChannel.configureBlocking(false);
System.out.println("客户端连接成功" + socketChannel.hashCode());
// 注册到selector，关心事件为OP_READ，同时关联一个buffer
socketChannel.register(selector, SelectionKey.OP_READ, ByteBuffer.allocate(10));
}
if (key.isReadable()) {
// 通过key反向获取对应的Channel
SocketChannel channel = (SocketChannel) key.channel();
// 通过key获取Buffer
ByteBuffer byteBuffer = (ByteBuffer) key.attachment();
channel.read(byteBuffer);
System.out.println("客户端发来：" + new String(byteBuffer.array(), StandardCharsets.UTF_8));
}
// 从集合移动当前selectionKey，防止重复操作
iterator.remove();
}
}
}
}
客户端
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SocketChannel;
import java.nio.charset.StandardCharsets;
class NIOClient {
public static void main(String[] args) throws Exception {
SocketChannel socketChannel = SocketChannel.open();
// 设置非阻塞
socketChannel.configureBlocking(false);
InetSocketAddress inetSocketAddress = new InetSocketAddress("127.0.0.1", 7899);
if (!socketChannel.connect(inetSocketAddress)) {
while (!socketChannel.finishConnect()) {
System.out.println("连接中，客户端不会阻塞，可以做其他事");
}
}
// 连接成功后
ByteBuffer byteBuffer = ByteBuffer.wrap("haha".getBytes(StandardCharsets.UTF_8));
// 将buffer写入channel
socketChannel.write(byteBuffer);
System.in.read();
}
}
标签：netty,java,buffer,System,ByteBuffer,import,socketChannel 来源： https://www.cnblogs.com/sprinining/p/15910578.html
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