Apache Mina通信框架架构与应用

Apache Mina Server 是一个网络通信应用框架，也就是说，它主要是对基于 TCP/ip、UDP/IP协议栈的通信框架（当然，也可以提供 java 对象的序列化服务、虚拟机管道通信服务等），Mina 可以帮助我们快速开发高性能、高扩展性的网络通信应用，Mina 提供了事件驱动、异步（Mina 的异步 IO 默认使用的是 JAVA NIO 作为底层支持）操作的编程模型。从官网文档“MINA based application Architecture”中可以看到Mina作为一个通信层框架，在实际应用所处的位置，如图所示： apparch_small Mina位于用户应用程序和底层Java网络API（和in-VM通信）之间，我们开发基于Mina的网络应用程序，就无需关心复杂的通信细节。

应用整体架构

再看一下，Mina提供的基本组件，如图所示： mina_app_arch 也就是说，无论是客户端还是服务端，使用Mina框架实现通信的逻辑分层在概念上统一的，即包含如下三层：

I/O Service – Performs actual I/OI/O Filter Chain – Filters/Transforms bytes into desired Data Structures and vice-versaI/O Handler – Here resides the actual business logic

想要开发基于MIna的应用程序，你只需要做如下事情：

Create an I/O service – Choose from already available Services (*Acceptor) or create your ownCreate a Filter Chain – Choose from already existing Filters or create a custom Filter for transforming request/responseCreate an I/O Handler – Write business logic, on handling different messages

下面看一下使用Mina的应用程序，在服务器端和客户端的架构细节：

服务器端架构服务器端监听指定端口上到来的请求，对这些请求经过处理后，回复响应。它也会创建并处理一个链接过来的客户会话对象（session）。服务器端架构如图所示： Server_arch 对服务器端的说明，引用官网文档，如下所示：

IOAcceptor listens on the network for incoming connections/packetsFor a new connection, a new session is created and all subsequent request from IP Address/Port combination are handled in that SessionAll packets received for a Session, traverses the Filter Chain as specified in the diagram. Filters can be used to modify the content of packets (like converting to Objects, adding/removing information etc). For converting to/from raw bytes to High Level Objects, PacketEncoder/Decoder are particularly usefulFinally the packet or converted object lands in IOHandler. IOHandlers can be used to fulfill business needs.

客户端架构客户端主要做了如下工作：

连接到服务器端向服务器发送消息等待服务器端响应，并处理响应

客户端架构，如图所示： clientdiagram 对客户端架构的说明，引用官网文档内容，如下所示：

Client first creates an IOConnector (MINA Construct for connecting to Socket), initiates a bind with ServerUpon Connection creation, a Session is created and is associated with ConnectionApplication/Client writes to the Session, resulting in data being sent to Server, after traversing the Filter ChainAll the responses/messages received from Server are traverses the Filter Chain and lands at IOHandler, for PRocessing

应用实例开发

下面根据上面给出的架构设计描述，看一下Mina（版本2.0.7）自带的例子，如何实现一个简单的C/S通信的程序，非常容易。服务端首先，服务器端需要使用的组件有IoAdaptor、IoHandler、IoFilter，其中IoFilter可选.我们基于Mina自带的例子进行了简单地修改，实现服务端IoHandler的代码如下所示：

`01`	`package` `org.shirdrn.mina.server;`

02

`03`	`import` `org.apache.mina.core.service.IoHandlerAdapter;`

`04`	`import` `org.apache.mina.core.session.IdleStatus;`

`05`	`import` `org.apache.mina.core.session.IoSession;`

`06`	`import` `org.slf4j.Logger;`

`07`	`import` `org.slf4j.LoggerFactory;`

08

`09`	`public` `class` `TinyServerProtocolHandler` `extends` `IoHandlerAdapter {`

`10`	`private` `final` `static` `Logger LOGGER = LoggerFactory.getLogger(TinyServerProtocolHandler.class);`

11

`12`	`@Override`

`13`	`public` `void` `sessionCreated(IoSession session) {`

`14`	`session.getConfig().setIdleTime(IdleStatus.BOTH_IDLE,` `10);`

15 }

16

`17`	`@Override`

`18`	`public` `void` `sessionClosed(IoSession session)` `throws` `Exception {`

`19`	`LOGGER.info("CLOSED");`

20 }

21

`22`	`@Override`

`23`	`public` `void` `sessionOpened(IoSession session)` `throws` `Exception {`

`24`	`LOGGER.info("OPENED");`

25 }

26

`27`	`@Override`

`28`	`public` `void` `sessionIdle(IoSession session, IdleStatus status) {`

`29`	`LOGGER.info("* IDLE #"` `+ session.getIdleCount(IdleStatus.BOTH_IDLE) +` `" *");`

30 }

31

`32`	`@Override`

`33`	`public` `void` `exceptionCaught(IoSession session, Throwable cause) {`

`34`	`session.close(true);`

35 }

36

`37`	`@Override`

`38`	`public` `void` `messageReceived(IoSession session, Object message)`

`39`	`throws` `Exception {`

`40`	`LOGGER.info(` `"Received : "` `+ message );`

`41`	`if(!session.isConnected()) {`

`42`	`session.close(true);`

43 }

44 }

45 }

这个版本中，IoHandlerAdapter实现了IoHandler接口，里面封装了一组用于事件处理的空方法，其中包含服务端和客户端的事件。在实际应用中，客户端可以选择客户端具有的事件，服务器端选择服务器端具有的事件，然后分别对这两类事件进行处理（有重叠的事件，如连接事件、关闭事件、异常事件等）。客户端的IoHandler的具体实现也是类似的，不过多累述。下面看启动服务器的主方法类，代码如下所示：

`01`	`package` `org.shirdrn.mina.server;`

02

`03`	`import` `java.net.InetSocketAddress;`

04

`05`	`import` `org.apache.mina.filter.codec.ProtocolCodecFilter;`

`06`	`import` `org.apache.mina.filter.codec.textline.TextLineCodecFactory;`

`07`	`import` `org.apache.mina.transport.socket.SocketAcceptor;`

`08`	`import` `org.apache.mina.transport.socket.nio.NioSocketAcceptor;`

`09`	`import` `org.slf4j.Logger;`

`10`	`import` `org.slf4j.LoggerFactory;`

11

`12`	`public` `class` `TinyMinaServer {`

13

`14`	`private` `final` `static` `Logger LOG = LoggerFactory.getLogger(TinyMinaServer.class);`

`15`	`/** Choose your favorite port number. */`

`16`	`private` `static` `final` `int` `PORT =` `8080;`

17

`18`	`public` `static` `void` `main(String[] args)` `throws` `Exception {`

`19`	`SocketAcceptor acceptor =` `new` `NioSocketAcceptor();`

`20`	`acceptor.setReuseAddress(true);`

`21`	`acceptor.getFilterChain().addLast("codec",` `new` `ProtocolCodecFilter(newTextLineCodecFactory()));`

22

23 // Bind

`24`	`acceptor.setHandler(new` `TinyServerProtocolHandler());`

`25`	`acceptor.bind(new` `InetSocketAddress(PORT));`

`26`	`LOG.info("Listening on port "` `+ PORT);`

27

`28`	`LOG.info("Server started!");`

29

`30`	`for` `(;;) {`

`31`	`LOG.info("R: "` `+ acceptor.getStatistics().getReadBytesThroughput() +` `", W: "` `+ acceptor.getStatistics().getWrittenBytesThroughput());`

`32`	`Thread.sleep(3000);`

33 }

34 }

35

36 }

客户端实现客户端IoHandler的代码如下所示：

`01`	`package` `org.shirdrn.mina.client;`

02

`03`	`import` `org.apache.mina.core.service.IoHandlerAdapter;`

`04`	`import` `org.apache.mina.core.session.IdleStatus;`

`05`	`import` `org.apache.mina.core.session.IoSession;`

`06`	`import` `org.slf4j.Logger;`

`07`	`import` `org.slf4j.LoggerFactory;`

08

`09`	`public` `class` `TinyClientProtocolHandler` `extends` `IoHandlerAdapter {`

10

`11`	`private` `final` `static` `Logger LOGGER = LoggerFactory`

`12`	`.getLogger(TinyClientProtocolHandler.class);`

13

`14`	`@Override`

`15`	`public` `void` `sessionCreated(IoSession session) {`

`16`	`LOGGER.info("CLIENT::CREATED");`

17 }

18

`19`	`@Override`

`20`	`public` `void` `sessionClosed(IoSession session)` `throws` `Exception {`

`21`	`LOGGER.info("CLIENT::CLOSED");`

22 }

23

`24`	`@Override`

`25`	`public` `void` `sessionOpened(IoSession session)` `throws` `Exception {`

`26`	`LOGGER.info("CLIENT::OPENED");`

27 }

28

`29`	`@Override`

`30`	`public` `void` `sessionIdle(IoSession session, IdleStatus status) {`

`31`	`LOGGER.info("CLIENT::*** IDLE #"`

`32`	`+ session.getIdleCount(IdleStatus.BOTH_IDLE) +` `" ***");`

33 }

34

`35`	`@Override`

`36`	`public` `void` `exceptionCaught(IoSession session, Throwable cause) {`

`37`	`LOGGER.info("CLIENT::EXCEPTIONCAUGHT");`

`38`	`cause.printStackTrace();`

39 }

40

`41`	`public` `void` `messageSent(IoSession session, Object message)` `throws` `Exception {`

`42`	`LOGGER.info("CLIENT::MESSAGESENT: "` `+ message);`

43 }

44 }

下面看启动客户端的主方法类，代码如下所示：

`01`	`package` `org.shirdrn.mina.client;`

02

`03`	`import` `java.net.InetSocketAddress;`

04

`05`	`import` `org.apache.mina.core.future.ConnectFuture;`

`06`	`import` `org.apache.mina.filter.codec.ProtocolCodecFilter;`

`07`	`import` `org.apache.mina.filter.codec.textline.TextLineCodecFactory;`

`08`	`import` `org.apache.mina.transport.socket.SocketConnector;`

`09`	`import` `org.apache.mina.transport.socket.nio.NioSocketConnector;`

`10`	`import` `org.slf4j.Logger;`

`11`	`import` `org.slf4j.LoggerFactory;`

12

`13`	`public` `class` `TinyMinaClient {`

14

`15`	`private` `final` `static` `Logger LOG = LoggerFactory.getLogger(TinyMinaClient.class);`

`16`	`/** Choose your favorite port number. */`

`17`	`private` `static` `final` `int` `PORT =` `8080;`

18

`19`	`public` `static` `void` `main(String[] args)` `throws` `Exception {`

`20`	`SocketConnector connector =` `new` `NioSocketConnector();`

21

`22`	`// Connect`

`23`	`connector.getFilterChain().addLast("codec",` `new` `ProtocolCodecFilter(newTextLineCodecFactory()));`

`24`	`connector.setHandler(new` `TinyClientProtocolHandler());`

25

`26`	`for` `(int` `i =` `0; i <` `10; i++) {`

`27`	`ConnectFuture future = connector.connect(new` `InetSocketAddress(PORT));`

`28`	`LOG.info("Connect to port "` `+ PORT);`

`29`	`future.awaitUninterruptibly();`

`30`	`future.getSession().write(String.valueOf(i));`

`31`	`Thread.sleep(1500);`

32 }

33

34 }

35 }

我们只是发送了十个数字，每发一次间隔1500ms。测试上述服务器端与客户端交互，首先启动服务器端，监听8080端口。接着启动客户端，连接到服务器端8080端口，然后发送消息，服务器端接收到消息后，直接将到客户端的连接关闭掉。