Java nio, javanio

Java nio, javanio

Java NIO's first bullet ---- Overview

 

Abstract:

Non-blocking I/O(Usually calledNIO, And sometimes called "New I/O") is a collection of Java programming language APIs that offer features for intensive I/Ooperations. it was introduced with the J2SE 1.4 release of Java by Sun Microsystems to complement an existing standard I/O. NIO was developed under the Java Community Process as JSR 51.^[1]

Non-blocking I/O (usually called NIO, or sometimes new I/O) is a set of java APIs that provide enhanced I/O operation features. Sun introduced it at java1.4.

 

This series focuses on the network and does not involve operations on local files. Next, let's take a look at a piece of code to demonstrate the simplest Echo server.

Sample Code

1 ByteBuffer bb = ByteBuffer. allocate (1024); 2/** create Selector */3 selector Selector = Selector. open (); 4/** open a server channel */5 ServerSocketChannel ssc = ServerSocketChannel. open (); 6/** set to non-blocking */7 ssc. configureBlocking (false); 8/** get the server socket from the channel */9 ServerSocket ss = ssc. socket (); 10/** bind a port */11 InetSocketAddress addr = new InetSocketAddress (1234); 12 ss. bind (addr); 13/** register events of interest. The server channel can only register and accept events */14 ssc. regist Er (selector, SelectionKey. OP_ACCEPT); 15 String receivedMsg = ""; 16/** main loop */17 while (true) {18 int num = selector. select (); 19 System. out. println (num + "events occur... "); 20 Set <SelectionKey> selectedKeys = selector. selectedKeys (); 21 Iterator <SelectionKey> it = selectedKeys. iterator (); 22 23/** process events in each channel cyclically */24 while (it. hasNext () {25 SelectionKey key = it. next (); 26 it. remove (); 27 if (key. readyOps () = SelectionKey. OP_ACCEPT) {28 System. out. println ("New Connection establishment event"); 29 ServerSocketChannel serverSocketChannel = (ServerSocketChannel) key. channel (); 30 SocketChannel SC = serverSocketChannel. accept (); 31 SC. configureBlocking (false); 32 SC. register (selector, SelectionKey. OP_READ); 33} else if (key. readyOps () & SelectionKey. OP_READ) = SelectionKey. OP_READ) {34 System. out. println ("read event"); 35 SocketChannel SC = (SocketChannel) key. channel (); 36 SC. read (bb); 37 receivedMsg = new String (bb. array (), 0, bb. position (); 38 bb. clear (); 39 SC. register (selector, SelectionKey. OP_WRITE); 40} else if (key. readyOps () = SelectionKey. OP_WRITE) {41 System. out. println ("Write Data"); 42 SocketChannel SC = (SocketChannel) key. channel (); 43 SC. write (ByteBuffer. wrap (receivedMsg. getBytes (); 44/** if no cancel exists, the data will be cyclically entered here. As long as the channel is not blocked, write events will always exist, so you need to cancel */45 key after use. cancel (); 46} else {47 System. out. println ("other event"); 48} 49} 50}

 

The code here is a server code that sends the received information back, providing a general process for writing data to the server using nio.

Here, you can first have a general understanding of the concept, and then introduce the important classes involved. You are welcome to criticize and correct them and discuss the progress.

Note: In this example, IOException is not handled. The actual code must be processed. Otherwise, the server will be suspended if a client forcibly closes the socket.

 

What is java nio?

Nio is short for java New IO, a New api provided in jdk1.4. Sun officially advertised the following features:
-Buffer caching is supported for all original types.
-Character set encoding and decoding solution.
-Channel: A new original I/O abstraction.
-Supports file access interfaces for lock and memory ing files.
-Provides non-bloking non-blocking high-scalability network I/O.

I used java nio to copy files, but I didn't find any obvious advantage in operating with the traditional stream. Why?

Read the Thinking in java document. From 1.5 onwards, Java has rewritten InputStream/OutputStream and uses NIO. Therefore, even if you do not display the declaration, you must use NIO, as long as your class inherits InputStream/OutputStream, NIO is already in use. If you don't believe it, do this.
FileChannel channel = new FileInputStream. getChannel ();
If XXStream is not constructed using NIO, how does one return a Channel object?