當我們在使用Mina客戶端發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發送報文的工具類
* @see 詳細說明請參閱我的博客http://blog.csdn.net/jadyer/article/details/8088068
* @version v1.5
* @history v1.1-->編碼器和解碼器中的字符處理,升級爲Mina2.x提供的<code>putString()</code>方法來處理
* @history v1.2-->解碼器採用CumulativeProtocolDecoder實現,以適應應答報文被拆分多次後發送Client的情況
* @history v1.3-->修復BUG:請求報文有誤時,Server可能返回非約定報文,此時會拋java.lang.NumberFormatException
* @history v1.4-->增加全局異常捕獲
* @history v1.5-->由於本工具類的作用是同步的客戶端,故取消IoHandler設置,但注意必須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(){}
/**
* 發送TCP消息
* @see 當通信發生異常時,如Fail to get session....返回<code>"MINA_SERVER_ERROR"</code>字符串
* @param message 待發送報文的中文字符串形式
* @param ipAddress 遠程主機的IP地址
* @param port 遠程主機的端口號
* @param charset 該方法與遠程主機間通信報文爲編碼字符集(編碼爲byte[]發送到Server)
* @return 遠程主機響應報文的字符串形式
*/
public static String sendTCPMessage(String message, String ipAddress, int port, String charset){
IoConnector connector = new NioSocketConnector();
connector.setConnectTimeoutMillis(1000);
connector.getSessionConfig().setUseReadOperation(true); //同步的客戶端,必須設置此項,其默認爲false
connector.getFilterChain().addLast("codec", new ProtocolCodecFilter(new ClientProtocolEncoder(charset), new ClientProtocolDecode(charset)));
//connector.setHandler(this); //作爲同步的客戶端,可以不需要IoHandler,Mina會自動添加一個默認的IoHandler實現,即AbstractIoConnector
IoSession session = null;
Object respData = null;
try{
ConnectFuture connectFuture = connector.connect(new InetSocketAddress(ipAddress, port));
connectFuture.awaitUninterruptibly(); //等待連接成功,相當於將異步執行轉爲同步執行
session = connectFuture.getSession(); //獲取連接成功後的會話對象
session.write(message).awaitUninterruptibly(); //由於上面已經設置setUseReadOperation(true),故IoSession.read()方法纔可用
ReadFuture readFuture = session.read(); //因其內部使用BlockingQueue,故Server端用之可能會內存泄漏,但Client端可適當用之
if(readFuture.awaitUninterruptibly(90, TimeUnit.SECONDS)){ //Wait until the message is received
respData = readFuture.getMessage(); //Get the received message
}else{
LogUtil.getLogger().info("讀取[/" + ipAddress + ":" + port + "]超時");
}
}catch(Exception e){
LogUtil.getLogger().error("請求通信[/" + ipAddress + ":" + port + "]偶遇異常,堆棧軌跡如下", e);
}finally{
if(session != null){
//關閉IoSession,該操作是異步的,true爲立即關閉,false爲所有寫操作都flush後關閉
//這裏僅僅是關閉了TCP的連接通道,並未關閉Client端程序
session.close(true);
//客戶端發起連接時,會請求系統分配相關的文件句柄,而在連接失敗時記得釋放資源,否則會造成文件句柄泄露
//當總的文件句柄數超過系統設置值時[ulimit -n],則拋異常"java.io.IOException: Too many open files",導致新連接無法創建,服務器掛掉
//所以,若不關閉的話,其運行一段時間後可能拋出too many open files異常,導致無法連接
session.getService().dispose();
}
}
return respData==null ? "MINA_SERVER_ERROR" : respData.toString();
}
/**
* 客戶端編碼器
* @see 將Client的報文編碼後發送到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);
}
}
/**
* 客戶端解碼器
* @see 解碼Server的響應報文給Client
* @see 樣例報文[000064100030010000120121101210419100000000000028`18622233125`10`]
*/
private static class ClientProtocolDecode extends CumulativeProtocolDecoder {
private final String charset;
//注意這裏使用了Mina自帶的AttributeKey類來定義保存在IoSession中對象的鍵值,其可有效防止鍵值重複
//通過查詢AttributeKey類源碼發現,它的構造方法採用的是"類名+鍵名+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()){ //判斷position和limit之間是否有元素
buffer.put(in.get()); //get()讀取buffer的position的字節,然後position+1
if(messageCount++ == 5){ //約定:報文的前6個字符串表示報文總長度,不足6位則左側補0
buffer.flip(); //Set limit=position and position=0 and mark=-1
//當Server的響應報文中含0x00時,Mina2.x的buffer.getString(fieldSize, decoder)方法會break
//該方法的處理細節,詳見org.apache.mina.core.buffer.AbstractIoBuffer類的第1718行源碼,其說明如下
//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{
//請求報文有誤時,Server可能返回非約定報文,此時會拋java.lang.NumberFormatException
ctx.setMessageLength(Integer.parseInt(new String(messageLength, charset)));
}catch(NumberFormatException e){
ctx.setMessageLength(in.limit());
}
buffer.limit(in.limit()); //讓兩個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; //用於累積數據的IoBuffer
private int messageCount; //記錄已讀取的報文字節數
private int messageLength; //記錄已讀取的報文頭標識的報文長度
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;
}
}
}
}