Mina客户端配置

当我们在使用Mina客户端发送信息配置示例如下：

package com.cucpay.fundswap.util;
  
import java.net.InetSocketAddress;  
import java.nio.charset.Charset;  
import java.util.concurrent.TimeUnit;  
  
import org.apache.mina.core.buffer.IoBuffer;  
import org.apache.mina.core.future.ConnectFuture;  
import org.apache.mina.core.future.ReadFuture;  
import org.apache.mina.core.service.IoConnector;  
import org.apache.mina.core.session.AttributeKey;  
import org.apache.mina.core.session.IoSession;  
import org.apache.mina.filter.codec.CumulativeProtocolDecoder;  
import org.apache.mina.filter.codec.ProtocolCodecFilter;  
import org.apache.mina.filter.codec.ProtocolDecoderOutput;  
import org.apache.mina.filter.codec.ProtocolEncoderAdapter;  
import org.apache.mina.filter.codec.ProtocolEncoderOutput;  
import org.apache.mina.transport.socket.nio.NioSocketConnector;  
  
/** 
 * 使用Mina2.x发送报文的工具类 
 * @see 详细说明请参阅我的博客http://blog.csdn.net/jadyer/article/details/8088068 
 * @version v1.5 
 * @history v1.1-->编码器和解码器中的字符处理,升级为Mina2.x提供的<code>putString()</code>方法来处理 
 * @history v1.2-->解码器采用CumulativeProtocolDecoder实现,以适应应答报文被拆分多次后发送Client的情况 
 * @history v1.3-->修复BUG:请求报文有误时,Server可能返回非约定报文,此时会抛java.lang.NumberFormatException 
 * @history v1.4-->增加全局异常捕获 
 * @history v1.5-->由于本工具类的作用是同步的客户端,故取消IoHandler设置,但注意必须setUseReadOperation(true) 
 * @update Jul 27, 2013 10:21:01 AM 
 * @create Oct 3, 2012 12:42:21 PM 
 * @author 玄玉<http://blog.csdn.net/jadyer> 
 */  
public class MinaUtil {  
    private MinaUtil(){}  
      
    /** 
     * 发送TCP消息 
     * @see 当通信发生异常时,如Fail to get session....返回<code>"MINA_SERVER_ERROR"</code>字符串 
     * @param message   待发送报文的中文字符串形式 
     * @param ipAddress 远程主机的IP地址 
     * @param port      远程主机的端口号 
     * @param charset   该方法与远程主机间通信报文为编码字符集(编码为byte[]发送到Server) 
     * @return 远程主机响应报文的字符串形式 
     */  
    public static String sendTCPMessage(String message, String ipAddress, int port, String charset){  
        IoConnector connector = new NioSocketConnector();  
        connector.setConnectTimeoutMillis(1000);  
        connector.getSessionConfig().setUseReadOperation(true); //同步的客户端,必须设置此项,其默认为false  
        connector.getFilterChain().addLast("codec", new ProtocolCodecFilter(new ClientProtocolEncoder(charset), new ClientProtocolDecode(charset)));  
        //connector.setHandler(this); //作为同步的客户端,可以不需要IoHandler,Mina会自动添加一个默认的IoHandler实现,即AbstractIoConnector  
        IoSession session = null;  
        Object respData = null;  
        try{  
            ConnectFuture connectFuture = connector.connect(new InetSocketAddress(ipAddress, port));  
            connectFuture.awaitUninterruptibly();          //等待连接成功,相当于将异步执行转为同步执行  
            session = connectFuture.getSession();          //获取连接成功后的会话对象  
            session.write(message).awaitUninterruptibly(); //由于上面已经设置setUseReadOperation(true),故IoSession.read()方法才可用  
            ReadFuture readFuture = session.read();        //因其内部使用BlockingQueue,故Server端用之可能会内存泄漏,但Client端可适当用之  
            if(readFuture.awaitUninterruptibly(90, TimeUnit.SECONDS)){ //Wait until the message is received  
                respData = readFuture.getMessage();                    //Get the received message  
            }else{  
                LogUtil.getLogger().info("读取[/" + ipAddress + ":" + port + "]超时");  
            }  
        }catch(Exception e){  
            LogUtil.getLogger().error("请求通信[/" + ipAddress + ":" + port + "]偶遇异常,堆栈轨迹如下", e);  
        }finally{  
            if(session != null){  
                //关闭IoSession,该操作是异步的,true为立即关闭,false为所有写操作都flush后关闭  
                //这里仅仅是关闭了TCP的连接通道,并未关闭Client端程序  
                session.close(true);  
                //客户端发起连接时,会请求系统分配相关的文件句柄,而在连接失败时记得释放资源,否则会造成文件句柄泄露  
                //当总的文件句柄数超过系统设置值时[ulimit -n],则抛异常"java.io.IOException: Too many open files",导致新连接无法创建,服务器挂掉  
                //所以,若不关闭的话,其运行一段时间后可能抛出too many open files异常,导致无法连接  
                session.getService().dispose();  
            }  
        }  
        return respData==null ? "MINA_SERVER_ERROR" : respData.toString();  
    }  
      
      
    /** 
     * 客户端编码器 
     * @see 将Client的报文编码后发送到Server 
     */  
    private static class ClientProtocolEncoder extends ProtocolEncoderAdapter {  
        private final String charset;  
        public ClientProtocolEncoder(String charset){  
            this.charset = charset;  
        }  
        @Override  
        public void encode(IoSession session, Object message, ProtocolEncoderOutput out) throws Exception {  
            IoBuffer buffer = IoBuffer.allocate(100).setAutoExpand(true);  
            //二者等效--><code>buffer.put(message.toString().getBytes(charset))</code>  
            buffer.putString(message.toString(), Charset.forName(charset).newEncoder());  
            buffer.flip();  
            out.write(buffer);  
        }  
    }  
      
      
    /** 
     * 客户端解码器 
     * @see 解码Server的响应报文给Client 
     * @see 样例报文[000064100030010000120121101210419100000000000028`18622233125`10`] 
     */  
    private static class ClientProtocolDecode extends CumulativeProtocolDecoder {  
        private final String charset;  
        //注意这里使用了Mina自带的AttributeKey类来定义保存在IoSession中对象的键值,其可有效防止键值重复  
        //通过查询AttributeKey类源码发现,它的构造方法采用的是"类名+键名+AttributeKey的hashCode"的方式  
        private final AttributeKey CONTEXT = new AttributeKey(getClass(), "context");  
        public ClientProtocolDecode(String charset){  
            this.charset = charset;  
        }  
        private Context getContext(IoSession session){  
            Context context = (Context)session.getAttribute(CONTEXT);  
            if(null == context){  
                context = new Context();  
                session.setAttribute(CONTEXT, context);  
            }  
            return context;  
        }  
        @Override  
        protected boolean doDecode(IoSession session, IoBuffer in, ProtocolDecoderOutput out) throws Exception {  
            Context ctx = this.getContext(session);  
            IoBuffer buffer = ctx.innerBuffer;  
            int messageCount = ctx.getMessageCount();  
            while(in.hasRemaining()){    //判断position和limit之间是否有元素  
                buffer.put(in.get());    //get()读取buffer的position的字节,然后position+1  
                if(messageCount++ == 5){ //约定:报文的前6个字符串表示报文总长度,不足6位则左侧补0  
                    buffer.flip();       //Set limit=position and position=0 and mark=-1  
                    //当Server的响应报文中含0x00时,Mina2.x的buffer.getString(fieldSize, decoder)方法会break  
                    //该方法的处理细节,详见org.apache.mina.core.buffer.AbstractIoBuffer类的第1718行源码,其说明如下  
                    //Reads a NUL-terminated string from this buffer using the specified decoder and returns it  
                    //ctx.setMessageLength(Integer.parseInt(buffer.getString(6, decoder)));  
                    byte[] messageLength = new byte[6];  
                    buffer.get(messageLength);  
                    try{  
                        //请求报文有误时,Server可能返回非约定报文,此时会抛java.lang.NumberFormatException  
                        ctx.setMessageLength(Integer.parseInt(new String(messageLength, charset)));  
                    }catch(NumberFormatException e){  
                        ctx.setMessageLength(in.limit());  
                    }  
                    buffer.limit(in.limit()); //让两个IoBuffer的limit相等  
                }  
            }  
            ctx.setMessageCount(messageCount);  
            if(ctx.getMessageLength() == buffer.position()){  
                buffer.flip();  
                byte[] message = new byte[buffer.limit()];  
                buffer.get(message);  
                out.write(new String(message, charset));  
                ctx.reset();  
                return true;  
            }else{  
                return false;  
            }  
        }  
        private class Context{  
            private final IoBuffer innerBuffer; //用于累积数据的IoBuffer  
            private int messageCount;           //记录已读取的报文字节数  
            private int messageLength;          //记录已读取的报文头标识的报文长度  
            public Context(){  
                innerBuffer = IoBuffer.allocate(100).setAutoExpand(true);  
            }  
            public int getMessageCount() {  
                return messageCount;  
            }  
            public void setMessageCount(int messageCount) {  
                this.messageCount = messageCount;  
            }  
            public int getMessageLength() {  
                return messageLength;  
            }  
            public void setMessageLength(int messageLength) {  
                this.messageLength = messageLength;  
            }  
            public void reset(){  
                this.innerBuffer.clear(); //Set limit=capacity and position=0 and mark=-1  
                this.messageCount = 0;  
                this.messageLength = 0;  
            }  
        }  
    }  
}