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Java NIO (Non-blocking I/O) with Server-Client Example – java.nio.ByteBuffer 和 channels.Selector – Java NIO Vs. IO

已發表: 2021-08-06
帶有服務器-客戶端示例的 Java NIO（非阻塞 I:O） - CrunchifyNIOServer.java

Java NIO是我最喜歡的話題。 自過去 2 年以來，我一直在與 NIO 合作，我想為我的讀者分享簡單Server-Client code ，他們可以在他們的生產環境中免費使用這些代碼。

從 JDK 1.4 開始，創建 NIO 是為了允許所有 Java 程序員實現非常高速的輸入/輸出，而無需處理自定義的本機代碼。 NIO 使用java.nio.buffer庫與簡單的 I/O 相比，後者在任何操作系統內部耗盡和填充緩衝區。

在本教程中，我們將java.nio.channels和java.nio.channels.Selector庫。

  • channels表示與能夠執行 I/O 操作的實體的連接，例如文件和套接字； 定義 selectors ，用於多路復用的非阻塞 I/O 操作。
  • 可以通過調用該類的open method來創建selector ，該方法將使用系統默認的選擇器提供程序來創建一個新的選擇器。
帶有 API 詳細信息的 java.nio 包說明

如果您有below questions ，那麼您來對地方了：

  • 如何開始使用 Java NIO
  • 什麼是Java NIO和Java NIO教程
  • 異步 Java NIO
  • java nio包的具體用途是什麼
  • Java NIO 教程
  • 如何使用 Java NIO 實現高性能 I/O

讓我們開始吧：

第1步

  • 創建CrunchifyNIOServer.java在port 1111上打開連接
  • 使用isAcceptable()檢查通道是否準備好接受新的套接字連接
    • 如果是 - 連接它
  • 使用isReadable()檢查通道是否準備好讀取
    • 如果是 - 從緩衝區讀取並在 Eclipse 控制台上打印
  • 一旦你得到最後的公司名稱“crunchify”
    • 緊密連接

第2步

  • 創建CrunchifyNIOClient.java嘗試連接到port 1111上的服務器
  • 使用 5 個公司名稱創建 ArrayList
  • 遍歷 ArrayList 並將每個 companyName 發送到服務器
  • 任務完成後關閉連接

看看這個Java代碼：

服務器代碼——CrunchifyNIOServer.java

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package crunchify . com . tutorials ;
 
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 ;
 
/**
* @author Crunchify.com
* Java NIO (Non-blocking I/O) with Server-Client Example - java.nio.ByteBuffer and channels.Selector
* This is CrunchifyNIOServer.java
*/
 
public class CrunchifyNIOServer {
 
@ SuppressWarnings ( "unused" )
public static void main ( String [ ] args ) throws IOException {
 
// Selector: A multiplexor of SelectableChannel objects.
// A selector may be created by invoking the open method of this class, which will use the system's default selector provider to create a new selector.
// A selector may also be created by invoking the openSelector method of a custom selector provider. A selector remains open until it is closed via its close method.
Selector selector = Selector . open ( ) ; // selector is open here
 
// ServerSocketChannel: A selectable channel for stream-oriented listening sockets.
// A server-socket channel is created by invoking the open method of this class.
// It is not possible to create a channel for an arbitrary, pre-existing ServerSocket.
ServerSocketChannel crunchifySocket = ServerSocketChannel . open ( ) ;
// InetSocketAddress: This class implements an IP Socket Address (IP address + port number) It can also be a pair (hostname + port number),
// in which case an attempt will be made to resolve the hostname.
// If resolution fails then the address is said to be unresolved but can still be used on some circumstances like connecting through a proxy.
InetSocketAddress crunchifyAddr = new InetSocketAddress ( "localhost" , 1111 ) ;
 
// Binds the channel's socket to a local address and configures the socket to listen for connections
crunchifySocket . bind ( crunchifyAddr ) ;
 
// Adjusts this channel's blocking mode.
crunchifySocket . configureBlocking ( false ) ;
 
int ops = crunchifySocket . validOps ( ) ;
// SelectionKey: A token representing the registration of a SelectableChannel with a Selector.
// A selection key is created each time a channel is registered with a selector.
// A key remains valid until it is cancelled by invoking its cancel method, by closing its channel, or by closing its selector.
SelectionKey selectKy = crunchifySocket . register ( selector , ops , null ) ;
 
// Infinite loop..
// Keep server running
while ( true ) {
 
log ( "I'm a server and I'm waiting for new connection and buffer select..." ) ;
// Selects a set of keys whose corresponding channels are ready for I/O operations
selector . select ( ) ;
 
// token representing the registration of a SelectableChannel with a Selector
Set < SelectionKey > crunchifyKeys = selector . selectedKeys ( ) ;
Iterator < SelectionKey > crunchifyIterator = crunchifyKeys . iterator ( ) ;
 
while ( crunchifyIterator . hasNext ( ) ) {
SelectionKey myKey = crunchifyIterator . next ( ) ;
 
// Tests whether this key's channel is ready to accept a new socket connection
if ( myKey . isAcceptable ( ) ) {
SocketChannel crunchifyClient = crunchifySocket . accept ( ) ;
 
// Adjusts this channel's blocking mode to false
crunchifyClient . configureBlocking ( false ) ;
 
// Operation-set bit for read operations
crunchifyClient . register ( selector , SelectionKey . OP_READ ) ;
log ( "Connection Accepted: " + crunchifyClient . getLocalAddress ( ) + "\n" ) ;
 
// Tests whether this key's channel is ready for reading
} else if ( myKey . isReadable ( ) ) {
SocketChannel crunchifyClient = ( SocketChannel ) myKey . channel ( ) ;
// ByteBuffer: A byte buffer.
// This class defines six categories of operations upon byte buffers:
// Absolute and relative get and put methods that read and write single bytes;
// Absolute and relative bulk get methods that transfer contiguous sequences of bytes from this buffer into an array;
ByteBuffer crunchifyBuffer = ByteBuffer . allocate ( 256 ) ;
crunchifyClient . read ( crunchifyBuffer ) ;
String result = new String ( crunchifyBuffer . array ( ) ) . trim ( ) ;
 
log ( "Message received: " + result ) ;
 
if ( result . equals ( "Crunchify.com" ) ) {
crunchifyClient . close ( ) ;
log ( "\nIt's time to close connection as we got last company name 'Crunchify'" ) ;
log ( "\nServer will keep running. Try running client again to establish new connection" ) ;
}
}
crunchifyIterator . remove ( ) ;
}
}
}
 
private static void log ( String str ) {
System . out . println ( str ) ;
}
}
 

客戶端代碼——CrunchifyNIOClient.java

帶有服務器-客戶端示例的 Java NIO（非阻塞 I:O） - CrunchifyNIOClient.java
Java
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package crunchify . com . tutorials ;
 
import java . io . IOException ;
import java . net . InetSocketAddress ;
import java . nio . ByteBuffer ;
import java . nio . channels . SocketChannel ;
import java . util . ArrayList ;
 
/**
* @author Crunchify.com
* Java NIO (Non-blocking I/O) with Server-Client Example - java.nio.ByteBuffer and channels.Selector
* This is CrunchifyNIOClient.java
*/
 
public class CrunchifyNIOClient {
 
public static void main ( String [ ] args ) throws IOException , InterruptedException {
 
InetSocketAddress crunchifyAddr = new InetSocketAddress ( "localhost" , 1111 ) ;
//  selectable channel for stream-oriented connecting sockets
SocketChannel crunchifyClient = SocketChannel . open ( crunchifyAddr ) ;
 
log ( "Connecting to Server on port 1111..." ) ;
 
ArrayList <String> companyDetails = new ArrayList <String> ( ) ;
 
// create a ArrayList with companyName list
companyDetails . add ( "Facebook" ) ;
companyDetails . add ( "Twitter" ) ;
companyDetails . add ( "IBM" ) ;
companyDetails . add ( "Google" ) ;
companyDetails . add ( "Crunchify" ) ;
 
for ( String companyName : companyDetails ) {
 
byte [ ] message = new String ( companyName ) . getBytes ( ) ;
ByteBuffer buffer = ByteBuffer . wrap ( message ) ;
crunchifyClient . write ( buffer ) ;
 
log ( "sending: " + companyName ) ;
buffer . clear ( ) ;
 
// wait for 2 seconds before sending next message
Thread . sleep ( 2000 ) ;
}
// close(): Closes this channel.
// If the channel has already been closed then this method returns immediately.
// Otherwise it marks the channel as closed and then invokes the implCloseChannel method in order to complete the close operation.
crunchifyClient . close ( ) ;
}
 
private static void log ( String str ) {
System . out . println ( str ) ;
}
}

服務器端的結果：

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I 'm a server and I' m waiting for new connection and buffer select . . .
Connection Accepted : / 127.0.0.1 : 1111
 
I 'm a server and <meta charset="utf-8"/>I' m waiting for new connection and buffer select . . .
Message received : Facebook
< meta charset = "utf-8" / > I 'm a server and <meta charset="utf-8"/>I' m waiting for new connection and buffer select . . .
Message received : Twitter
< meta charset = "utf-8" / > I 'm a server and <meta charset="utf-8"/>I' m waiting for new connection and buffer select . . .
Message received : IBM
< meta charset = "utf-8" / > I 'm a server and <meta charset="utf-8"/>I' m waiting for new connection and < a href = "https://crunchify.com/how-to-remove-duplicate-elements-from-csv-or-any-other-file-in-java/" target = "_blank" rel = "noreferrer noopener" > buffer < / a > select . . .
Message received : Google
< meta charset = "utf-8" / > I 'm a server and <meta charset="utf-8"/>I' m waiting for new connection and buffer select . . .
Message received : Crunchify
 
It 's time to <a href="https://crunchify.com/json-manipulation-in-java-examples/" target="_blank" rel="noreferrer noopener">close connection</a> as we got last company name ' Crunchify '
 
Server will keep running. Try running client again to establish new connection
<meta charset="utf-8"/>I' m a server and < meta charset = "utf-8" / > I ' m waiting for new connection and buffer select . . .

客戶端結果：

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Connecting to Server on port 1111...
sending : Facebook
sending : Twitter
sending : IBM
sending : Google
sending : Crunchify

幾個常見問題解答：

  1. 從客戶端，我如何維護持久連接？
    • 你可以使用socket.setKeepAlive(true); 從客戶端建立連接。
  2. 如何閱讀對發送到服務器的消息的響應。 服務器每 10 秒不斷生成消息。 我只需要閱讀對我的請求的回复。 據我了解，TCP“流”數據而不是記錄結束等。
    • 對於客戶端服務器通信，需要明確定義協議。 readLine()調用將被阻塞，直到所有數據都返回，所以不要使用它。 Try reading bytes from the stream until -1 is returned.

讓我知道這是否有效。