1.netty介绍

1.介绍

是JBOSS通过的java开源框架
是异步的,基于事件驱动(点击一个按钮调用某个函数)的网络应用框架,高性能高可靠的网络IO程序
基于TCP,面向客户端高并发应用/点对点大量数据持续传输的应用
是NIO框架 (IO的一层层封装) TCP/IP->javaIO和网络编程–>NIO—>Netty

2.应用场景

互联网 RPC框架比如阿里的Dubbo
网络游戏可以定制TCP/UDP 和http协议栈
大数据 hadoop序列化组件和实时数据文件共享 AVRO
还有Flink Spark Akka…其他开源项目

3.IO模型

BIO(blocking原生javaIO,阻塞性,一个连接需要一个线程处理,连接不使用阻塞也占用线程)
//面试: 适用连接数目少架构稳定的,对服务器资源要求高,但程序简单容易理解 jdk1.4之前唯一的选择
NIO(No blocking/new 同步非阻塞)(一个线程使用selector维护多个客户端,轮询检测活动多路复用,可以开多个线程) 图1nettyNIO原理、

//适用连接数目多且连接比较短的(轻操作)的结果比如聊天,弹幕,服务器之间通信,编程复杂 jdk1.4开始支持
3. AIO(等待时间长才需要异步,异步非阻塞) 是有效请求才启动线程
//面试: 适合；连接数量多且连接长的, 比如相册服务器.编程复杂,jdk7开始支持

4.BIO实例(可以使用线程池改善)

win的 telnet 127.0.0.1 6666端口的ctrl+]的send xxx可以发送数据到服务器

5.NIO

结构如果通道没有事件,选择器不处理,线程也不阻塞 selector(选择器)<–>channel(通道)<—> buffer(缓冲区,数据先在这里实现了非阻塞)<—>socket //IntBuffer的使用
java除了boolean类型,是类型统一管理,所以比BIO更快 //!!!一定要flip()读写切换才能读取值
关系
1.buffer是内存块(面向缓冲/块的编程),是一个数组,达到一定量才给channel
2.selector由哪个channel有事件才切换过去的,不是自动切换的 ?
3.buffer channel是双向的,区别BIO 有in output流
4.一个thread对应一个selector,对应多个channel

6.Buffer的属性

position
filp()会使他变为0,读写的时候也会改变,一直往后移
limit(块的最大容量) 和capacity(自己设置的块容量)一样用来判断是否超出范围 capacity 自己设置的数组容量 mark 标记

//常用的api

IntBuffer in=IntBuffer.allocate(5);//5个容量 
                                   .flip //读写切换,如果是读的可以切换为写的,所以说NIO是双向的
                                  .position(1);//设置读写的位置
                                  .limit(3);//设置读写限制个数<3
                                  .get(); //得到元素通过iterator
                                  .put(1);
                                  .put(1,1);//在指定位置放数据
                                  .clear();//清除缓冲器 
                                  .hasRemain();//相当于hasNext()
                                  .isReadOnly();//是否为只读缓冲区
                                  //抽象方法jdk1.6引入 hasArray()缓冲区是否可访问底层的buffer数组 array()返回buffer数组
                                 //常用ByteBuffer

7.Channel 可以向buffer读写和拷贝

1.ServerSockerChannel 类似ServerSocker,SockerChannel就是Socket,还有一模一样的UDP的类
2.FileChannel类
  read() 通道读数据到buffer write() buffer写入通道 transferFrom()目标通道复制到本通道 transferTo() channel复制到目标通道

8.使用channel生成文件,与BIO的关系,底层就是BIO

          String str="aaa";
         out=new FileOutputStream("d;\\aaa.txt"); //输出流包括channel
          FileChannel channel=out.getChannel();

            byteBuffer=ByteBuffer.allocate(1024);
            byteBuffer.put(str.getBytes);
            byteBuffer.flip(); //初始状态是读,切换成写
            channel.write(byteBuffer);//向其他通道写
            out.close();//关闭流
public class bufferDemo {
    public static void main(String[] args) throws IOException {
        String str="helloworld";

        FileOutputStream out = new FileOutputStream("D:\\abs.txt");
        FileChannel channel = out.getChannel();
        ByteBuffer byteBuffer=ByteBuffer.allocate(1024);
        byteBuffer.position(2);
        byteBuffer.put(str.getBytes()); //放在limit后面会报错,这个是限制容量
        //相当于截断写入的数据
        byteBuffer.limit(7);

        //必须要写
        byteBuffer.flip();
        channel.write(byteBuffer);
        channel.close();
        out.close();


    }
}

9.读数据

      File file=new File("d:\\aa.txt");
        in=new FileInputStream(file);
         fileChannel=in.getChannel();
         byteBuffer= ByteBuffer.allocate((int)file.length());
         fileChannel.read(byteBuffer);
              sout(new String(  byteBuffer.array()));
               in.close();
public class bfDemo {
    public static void main(String[] args) throws IOException {
        File file = new File("D:\\abs.txt");
        FileInputStream inputStream = new FileInputStream(file);
        FileChannel channel = inputStream.getChannel();
        ByteBuffer byteBuffer = ByteBuffer.allocate((int) file.length());
        channel.read(byteBuffer);

            System.out.println(new java.lang.String(byteBuffer.array()));


    }
}

10.一个buffer 多个channel(创建两个流)拷贝文件边读边写
//在java写路径相对位置是本项目最父类的项目路径!!!(以前写相对路径总是出错)
//必须需要不然position=limit

      byteBytebuffer.clear();
                             .flip();
     public class bfDemo3Copy {
    public static void main(String[] args) throws IOException {
        FileInputStream inputStream = new FileInputStream("D:\\abs.txt");
        FileChannel c1 = inputStream.getChannel();
        FileOutputStream fileOutputStream = new FileOutputStream("D:\\abs1.txt");
        FileChannel c2 = fileOutputStream.getChannel();
        ByteBuffer allocate = ByteBuffer.allocate(inputStream.available());
        c1.read(allocate);
        allocate.flip();
        c2.write(allocate);

    }

}

//一块一块读,反转写入.steps are combinate bytes to buffer and send to another channel(outputStream)

public class NIOFileChannel03 {
    public static void main(String[] args) throws Exception {

        FileInputStream fileInputStream = new FileInputStream("1.txt");
        FileChannel fileChannel01 = fileInputStream.getChannel();

        FileOutputStream fileOutputStream = new FileOutputStream("2.txt");
        FileChannel fileChannel02 = fileOutputStream.getChannel();

        ByteBuffer byteBuffer = ByteBuffer.allocate(512);

        while (true) { //循环读取
            byteBuffer.clear(); //清空buffer!!!
            int read = fileChannel01.read(byteBuffer);
            System.out.println("read =" + read);
            if(read == -1) { //表示读完
                break;
            }
            //将buffer 中的数据写入到 fileChannel02 -- 2.txt
            byteBuffer.flip();
            fileChannel02.write(byteBuffer);
        }

        //关闭相关的流
        fileInputStream.close();
        fileOutputStream.close();
    }
}

11.拷贝图片

     destch.transferFrom(sourceCh,0,sourceCh.size());
    //关闭所有通道和流
public class bfDemo4transferCopy {
    public static void main(String[] args) throws IOException {
        FileInputStream inputStream = new FileInputStream("D:\\abs.txt");
        FileChannel c1 = inputStream.getChannel();
        FileOutputStream fileOutputStream = new FileOutputStream("D:\\abs3.txt");
        FileChannel c2 = fileOutputStream.getChannel();
        c2.transferFrom(c1,0,c1.size());
    }
}

12.buffer放的顺序和取的顺序一样不然抛出异常BufferUnderflowException

  ByteBuffer bf= ByteBuffer.allocate(64);
     bf.putInt(100); 
     bf.putLong(100L);
    bf.flip();
   bf.getInt(); 
     bf.getLong();

13.写完转为只读buffer
//12的代码

    buffer.asReadOnlyBuffer();public class OnlyWrite {
    public static void main(String[] args) {
        ByteBuffer bf= ByteBuffer.allocate(64);
        bf.putInt(100);
        bf.putLong(100L);
        bf.flip();
        ByteBuffer byteBuffer = bf.asReadOnlyBuffer();
        byteBuffer.getInt();
        byteBuffer.getLong();
        byteBuffer.putLong(10);//错误不能写,只能读
    }
}

14.MappedByteBuffer可以在堆外内存修改文件(效率高)操作系统不用拷贝一次到内存

access=new RandAccessFile("1.txt","rw");
 channel=access.getChannel();
map=channel.map(FileChannel.MapMode.READ_WRITE,0,5);模式,开始位置,结束位置 <5byte
   map.put(0,(byte)'H'); //在内存直接修改文件内容,然后放回磁盘
  access.close();

 public class MapBuffer {
    public static void main(String[] args) throws IOException {
        RandomAccessFile access = new RandomAccessFile("1.txt", "rw");
        FileChannel channel = access.getChannel();
        //到内存修改的大小范围是 0-5, if out of the bound will throw an expection
        MappedByteBuffer map = channel.map(FileChannel.MapMode.READ_WRITE, 0, 5);
        map.put(0,(byte)'A');
        map.put(4,(byte)'H');

        access.close();
        System.out.println("修改成功");
    }
}

//idea需要在文件夹外打开,不然看不到效果

15.分散和聚集 scatter(写的时候放到多个buffer[数组array])和gather(读的时候多个buffer) 加快读写效率(the key is using many buffer to read and read)(read and write only once that can get more buffer)

  
public class scatterAndGather {
    public static void main(String[] args) throws IOException {
        ServerSocketChannel serverSocket =  ServerSocketChannel.open().bind(new InetSocketAddress(6666));
        ByteBuffer[] byteBuffers= new ByteBuffer[2];
        byteBuffers[0]=ByteBuffer.allocate(3);
        byteBuffers[1]=ByteBuffer.allocate(5);

        SocketChannel accept = serverSocket.accept();
        int msgLen=8;
       while (true){
           int byteRead=0;
          while (byteRead<msgLen){

              long read = accept.read(byteBuffers);
              byteRead++;
              System.out.println("bufferRead:"+byteRead);
              Arrays.asList(byteBuffers).stream()
                      .map(
                              buffer->"position"+buffer.position()+
                                      ",limit="+buffer.limit()
                      )
                              .forEach(System.out::println);



          }
           Arrays.asList(byteBuffers).stream().forEach(buffer ->buffer.flip() );
          long byteWrite=0;
          while (byteWrite<msgLen){
              //一次读出多少个字节
              long l=accept.write(byteBuffers);
              byteWrite+=l;
              System.out.println(byteWrite);
          }
          Arrays.asList(byteBuffers).forEach(byteBuffer -> {
              System.out.println(new String(byteBuffer.array() ));
              byteBuffer.clear();});
           System.out.println("byteRead:="+byteRead+"byteWrite:"+byteWrite+"msgLen:"+msgLen);

       }


    }
}

16.selector管理多个连接(channel) 不停如轮询检测事件,有事件处理,阻塞不等待,处理其他通道的请求,解决了多线程单通道的问题,提高了性能

   selector类selects()//得到channel的连接的selectkey集合阻塞,
  selector.select(1000)//阻塞1000毫秒,必须返回数据
  selector.wakeup()//唤醒selector,阻塞中可以唤醒
  selector.selectNow()//非阻塞,立即返回结果,核心方法
           selector.selectedKeys() //select获取绑定channel产生事件的selectkey集合
//可以注册channel到selector上返回selectionKey  (集合)