è®°å¾—åŽÕd¹´è¯»Jettyæºç çš„æ—¶å€™ï¼Œå› äØ“(f¨´)代ç 太庞大，òq¶ä¸”自己的HTTP Server的了解太ž®‘ï¼Œå› è€Œåªèƒ½è‡ªåº•å‘上的一个一个模å—çš„å åŠ åQŒç›´åˆ°æœ€åŽæŠŠæ‰€ä»¥çš„模嗘qžæŽ¥åœ¨ä¸€èµ¯‚€Œçœ‹æ¸…它的真æ£æ ¸å¿ƒéª¨æž¶ã€‚现在读æºç åQŒå¼€å§‹ä¹ (f¨¤n)惯先把骨架ç†æ¸…，然åŽå»¶äŽ×åˆîC¸åŒçš„器官ã€è¡€è‚‰è€Œçœ‹æ¸…整个äh体ã€?br />
本文从Reactor模å¼åœ¨Netty3ä¸çš„应用åQŒå¼•å‡ºNetty3的整体架构以å?qi¨¢ng)控制浽E‹ï¼›ç„¶è€Œé™¤äº†Reactor模å¼åQŒNetty3˜q˜åœ¨ChannelPipelineä¸ä‹É用了Intercepting Filter模å¼åQŒè¿™ä¸ªæ¨¡å¼ä¹Ÿåœ¨Servletçš„Filterä¸æˆåŠŸä‹Éç”¨ï¼Œå› è€Œæœ¬æ–‡è¿˜ä¼?x¨¬)从Intercepting Filter模å¼å‡ºå‘详细介ç»ChannelPipeline的设计ç†å¿üc(di¨£n)€‚本文å‡è®¾è¯»è€…å·²¾l对Netty有一定的了解åQŒå› 而ä¸ä¼?x¨¬)包å«è¿‡å¤šå…¥é—¨ä»‹¾l，以åŠ(qi¨¢ng)帮Nettyåšå®£ä¼ çš„æ–‡å—ã€?br />
Netty3ä¸çš„Reactor模å¼
Reactor模å¼åœ¨Nettyä¸åº”用éžå¸¸æˆåŠŸï¼Œå› 而它也是在Nettyä¸å—å¤§è‚†å®£ä¼ çš„æ¨¡å¼ï¼Œå…³äºŽReactor模å¼å¯ä»¥è¯¦ç»†å‚考本人的å¦ä¸€½‹‡æ–‡ç«?a href="http://www.aygfsteel.com/DLevin/archive/2015/09/02/427045.html">《Reactor模å¼è¯¦è§£ã€?/a>åQŒå¯¹Reactor模å¼çš„实现是Netty3的基本骨æžÓž¼Œå› 而本ž®èŠ‚ä¼?x¨¬)详¾l†ä»‹¾lReactor模å¼å¦‚何应用Netty3ä¸ã€?br />如果诅R€ŠReactor模å¼è¯¦è§£ã€‹ï¼Œæˆ‘们知é“Reactor模å¼ç”±Handleã€Synchronous Event Demultiplexerã€Initiation Dispatcherã€Event Handlerã€Concrete Event Handleræž„æˆåQŒåœ¨Java的实现版本ä¸åQŒChannel对应HandleåQŒSelector对应Synchronous Event DemultiplexeråQŒåƈ且Netty3˜q˜ä‹É用了两层ReactoråQšMain Reactor用于处ç†Client的连接请求，Sub Reactor用于处ç†å’ŒClient˜qžæŽ¥åŽçš„è¯Õd†™è¯äh±‚åQˆå…³äºŽè¿™ä¸ªæ¦‚念还å¯ä»¥å‚考Doug Leaçš„è¿™½‹‡PPTåQ?a >Scalable IO In JavaåQ‰ã€‚所以我们先è¦è§£å†³Netty3ä¸ä‹É用什么类实现所有的上述模å—òq¶æŠŠä»–们è”系在一èµïL(f¨¥ng)š„åQŒä»¥NIO实现方å¼ä¸ÞZ¾‹åQ?br />
模å¼æ˜¯ä¸€¿U抽象，但是在实çŽîC¸åQŒç»å¸æ€¼š(x¨¬)å› äØ“(f¨´)è¯è¨€ç‰ÒŽ(gu¨©)€§ã€æ¡†æž¶å’Œæ€§èƒ½éœ€è¦è€Œåšä¸€äº›æ”¹å˜ï¼Œå› 而Netty3对Reactor模å¼çš„实现有一套自å·Þqš„设计åQ?br />1. ChannelEventåQ?/strong>Reactor是基于事件编½E‹çš„åQŒå› 而在Netty3ä¸ä‹É用ChannelEvent抽象的表达Netty3内部å¯ä»¥äº§ç”Ÿçš„å„¿U事ä»Óž¼Œæ‰€æœ‰è¿™äº›äº‹ä»¶å¯¹è±¡åœ¨Channels帮助¾cÖM¸äº§ç”ŸåQŒåƈ且由它将事äšg推入到ChannelPipelineä¸ï¼ŒChannelPipelineæž„å¾ChannelHandler½Ž¡é“åQŒChannelEvent‹¹ç»˜q™ä¸ª½Ž¡é“实现所有的业务逻辑处ç†ã€‚ChannelEvent对应的事件有åQšChannelStateEvent表示Channel状æ€çš„å˜åŒ–事äšgåQŒè€Œå¦‚果当å‰Channelå˜åœ¨Parent ChannelåQŒåˆ™è¯¥äº‹ä»¶è¿˜ä¼?x¨¬)ä¼ é€’åˆ°Parent Channelçš„ChannelPipelineä¸ï¼Œå¦‚OPENã€BOUNDã€CONNECTEDã€INTEREST_OPS½{‰ï¼Œè¯¥äº‹ä»¶å¯ä»¥åœ¨å„ç§ä¸åŒå®žçŽ°çš„Channelã€ChannelSinkä¸äñ”生；MessageEvent表示从Socketä¸è¯»å–æ•°æ®å®Œæˆã€éœ€è¦å‘Socket写数æ®æˆ–ChannelHandler对当å‰Message解æž(如Decoderã€Encoder)åŽè§¦å‘的事äšgåQŒå®ƒç”±NioWorkerã€éœ€è¦å¯¹Messageåšè¿›ä¸€æ¥å¤„ç†çš„ChannelHandler产生åQ›WriteCompletionEvent表示写完æˆè€Œè§¦å‘的事äšgåQŒå®ƒç”±NioWorker产生åQ›ExceptionEvent表示在处ç†è¿‡½E‹ä¸å‡ºçŽ°çš„ExceptionåQŒå®ƒå¯ä»¥å‘生在å„个构件ä¸åQŒå¦‚Channelã€ChannelSinkã€NioWorkerã€ChannelHandlerä¸ï¼›IdleStateEventç”±IdleStateHandler触å‘åQŒè¿™ä¹Ÿæ˜¯ä¸€ä¸ªChannelEventå¯ä»¥æ— ç¼æ‰©å±•çš„例å。注åQšåœ¨Netty4åŽï¼Œå·²ç»æ²¡æœ‰ChannelEvent¾c»ï¼Œæ‰€æœ‰ä¸åŒäº‹ä»‰™ƒ½ç”¨å¯¹åº”方法表达，˜q™ä¹Ÿæ„味˜q™C(j¨©)hannelEventä¸å¯æ‰©å±•åQŒNetty4采用在ChannelInboundHandlerä¸åŠ å…¥userEventTriggered()æ–ÒŽ(gu¨©)³•æ¥å®žçŽ°è¿™¿U扩展，具体å¯ä»¥å‚è€?a >˜q™é‡Œã€?br />2. ChannelHandleråQ?/strong>在Netty3ä¸ï¼ŒChannelHandler用于表示Reactor模å¼ä¸çš„EventHandler。ChannelHandleråªæ˜¯ä¸€ä¸ªæ ‡è®°æŽ¥å£ï¼Œå®ƒæœ‰ä¸¤ä¸ªå接å£ï¼š(x¨¬)ChannelDownstreamHandlerå’ŒChannelUpstreamHandleråQŒå…¶ä¸ChannelDownstreamHandler表示从用户应用程åºæµå‘Netty3内部直到å‘Socket写数æ®çš„½Ž¡é“åQŒåœ¨Netty4ä¸æ”¹åäØ“(f¨´)ChannelOutboundHandleråQ›ChannelUpstreamHandler表示数æ®ä»ŽSocket˜q›å…¥Netty3内部å‘用户应用程åºåšæ•°æ®å¤„ç†çš„管é“，在Netty4ä¸æ”¹åäØ“(f¨´)ChannelInboundHandlerã€?br />3. ChannelPipelineåQ?/strong>用于½Ž¡ç†ChannelHandler的管é“，æ¯ä¸ªChannel一个ChannelPipeline实例åQŒå¯ä»¥è¿è¡Œè¿‡½E‹ä¸åŠ¨æ€çš„å‘这个管é“ä¸æ·ÕdŠ ã€åˆ 除ChannelHandleråQˆç”±äºŽå®žçŽ°çš„é™åˆ¶åQŒåœ¨æœ€æœ«ç«¯çš„ChannelHandlerå‘åŽæ·ÕdŠ æˆ–åˆ é™¤ChannelHandlerä¸ä¸€å®šåœ¨å½“å‰æ‰§è¡Œ‹¹ç¨‹ä¸è“v效，å‚è€?a >˜q™é‡ŒåQ‰ã€‚ChannelPipeline内部¾l´æŠ¤ä¸€ä¸ªChannelHandlerçš„åŒå‘链表，它以Upstream(Inbound)æ–¹å‘为æ£å‘，Downstream(Outbound)æ–¹å‘为方å‘。ChannelPipeline采用Intercepting Filter模å¼å®žçŽ°åQŒå…·ä½“å¯ä»¥å‚è€?a href="http://www.aygfsteel.com/DLevin/archive/2015/09/03/427086.html">˜q™é‡ŒåQŒè¿™ä¸ªæ¨¡å¼çš„实现在åŽä¸€èŠ‚丘q˜æ˜¯è¯¦ç»†ä»‹ç»ã€?br />4. NioSelectoråQ?/strong>Netty3使用NioSelectoræ¥å˜æ”¾SelectoråQˆSynchronous Event DemultiplexeråQ‰ï¼Œæ¯ä¸ªæ–îCñ”生的NIO Channel都员q™ä¸ªSelector注册自己以让˜q™ä¸ªSelector监嬘q™ä¸ªNIO Channelä¸å‘生的事äšgåQŒå½“事äšgå‘生æ—Óž¼Œè°ƒç”¨å¸®åŠ©¾c»Channelsä¸çš„æ–ÒŽ(gu¨©)³•ç”ŸæˆChannelEvent实例åQŒå°†è¯¥äº‹ä»¶å‘é€åˆ°˜q™ä¸ªNetty Channel对应的ChannelPipelineä¸ï¼Œè€Œäº¤¾l™å„¾U§ChannelHandler处ç†ã€‚å…¶ä¸åœ¨å‘Selector注册NIO Channelæ—Óž¼ŒNetty Channel实例以Attachmentçš„åÅžå¼ä¼ 入，该Netty Channel在其内部的NIO Channel事äšgå‘生æ—Óž¼Œä¼?x¨¬)以Attachmentçš„åÅžå¼å˜åœ¨äºŽSelectionKeyä¸ï¼Œå› 而æ¯ä¸ªäº‹ä»¶å¯ä»¥ç›´æŽ¥ä»Ž˜q™ä¸ªAttachmentä¸èŽ·å–相关链的Netty ChannelåQŒåƈ从Netty Channelä¸èŽ·å–与之相兌™”çš„ChannelPipelineåQŒè¿™ä¸ªå®žçŽ°å’ŒDoug Leaçš?a >Scalable IO In Javaä¸€æ¨¡ä¸€æ —÷€‚å¦å¤–Netty3˜q˜é‡‡ç”¨äº†Scalable IO In Javaä¸ç›¸åŒçš„Main Reactorå’ŒSub Reactor设计åQŒå…¶ä¸NioSelector的两个实玎ͼš(x¨¬)Bosså³äØ“(f¨´)Main ReactoråQŒNioWorker为Sub Reactor。Boss用æ¥å¤„ç†æ–°è¿žæŽ¥åŠ 入的事äšgåQŒNioWorker用æ¥å¤„ç†å„个˜qžæŽ¥å¯¹Socket的读写事ä»Óž¼Œå…¶ä¸Boss通过NioWorkerPool获å–NioWorker实例åQŒNetty3模å¼ä½¿ç”¨RoundRobinæ–¹å¼æ”‘Ö›žNioWorker实例。更形象一点的åQŒå¯ä»¥é€šè¿‡Scalable IO In Javaçš„è¿™å¼ å›¾è¡¨è¾¾åQ?br />
若与Ractor模å¼å¯¹åº”åQŒNioSelectorä¸åŒ…å«äº†Synchronous Event DemultiplexeråQŒè€ŒChannelPipelineä¸ç®¡ç†ç€æ‰€æœ‰EventHandleråQŒå› 而NioSelectorå’ŒChannelPipelineå…±åŒæž„æˆäº†Initiation Dispatcherã€?br />5. ChannelSinkåQ?/strong>在ChannelHandler处ç†å®Œæˆæ‰€æœ‰é€»è¾‘需è¦å‘客户端写å“应数æ®æ—Óž¼Œä¸€èˆ¬ä¼š(x¨¬)调用Netty Channelä¸çš„writeæ–ÒŽ(gu¨©)³•åQŒç„¶è€Œåœ¨˜q™ä¸ªwriteæ–ÒŽ(gu¨©)³•å®žçŽ°ä¸ï¼Œå®ƒä¸æ˜¯ç›´æŽ¥å‘其内部的Socket写数æ®ï¼Œè€Œæ˜¯äº¤ç»™C(j¨©)hannels帮助¾c»ï¼Œå†…部创å¾DownstreamMessageEventåQŒåå‘从ChannelPipeline的管é“下¹è¿‡åŽ»ï¼Œç›´åˆ°½W¬ä¸€ä¸ªChannelHandler处ç†å®Œæ¯•åQŒæœ€åŽäº¤¾l™C(j¨©)hannelSink处ç†åQŒä»¥é¿å…é˜Õd¡žå†™è€Œåª„å“程åºçš„åžåé‡ã€‚ChannelSinkž®†è¿™ä¸ªMessageEventæ交¾l™Netty Channelä¸çš„writeBufferQueueåQŒæœ€åŽNioWorkerä¼?x¨¬)ç‰åˆ°è¿™ä¸ªNIO Channelå·²ç»å¯ä»¥å¤„ç†å†™äº‹ä»¶æ—¶æ— 阻塞的å‘这个NIO Channel写数æ®ã€‚è¿™ž®±æ˜¯ä¸Šå›¾çš„send是从SubReactor直接出å‘çš„åŽŸå› ã€?br />6. ChannelåQ?/strong>Netty有自å·Þqš„Channel抽象åQŒå®ƒæ˜¯ä¸€ä¸ªèµ„æºçš„容器åQŒåŒ…å«äº†æ‰€æœ‰ä¸€ä¸ªè¿žæŽ¥æ¶‰å?qi¨¢ng)到的所有资æºçš„饮用åQŒå¦‚ž®è£…NIO Channelã€ChannelPipelineã€Bossã€NioWorkerPool½{‰ã€‚å¦å¤–它˜q˜æ供了å‘内部NIO Channel写å“应数æ®çš„接å£writeã€è¿žæŽ?¾l‘定到æŸä¸ªåœ°å€çš„connect/bind接壽{‰ï¼Œä¸ªäh感觉虽然对Channel本èínæ¥è¯´åQŒå› 为它?y¨u)®è£…了NIO ChannelåQŒå› 而这些接å£å®šä¹‰åœ¨˜q™é‡Œæ˜¯åˆç†çš„åQŒä½†æ˜¯å¦‚果考虑到Netty的架构，它的Channelåªæ˜¯ä¸€ä¸ªèµ„æºå®¹å™¨ï¼Œæœ‰è¿™ä¸ªChannel实例ž®±å¯ä»¥å¾—到和它相关的基本所有资æºï¼Œå› 而这¿Uwriteã€connectã€bind动作ä¸åº”该å†ç”±å®ƒè´Ÿè´£åQŒè€Œæ˜¯åº”该由其他类æ¥è´Ÿè´£ï¼Œæ¯”如在Netty4ä¸å°±åœ¨ChannelHandlerContextæ·ÕdŠ 了writeæ–ÒŽ(gu¨©)³•åQŒè™½ç„¶netty4òq¶æ²¡æœ‰åˆ 除Channelä¸çš„write接å£ã€?br />
Netty3ä¸çš„Intercepting Filter模å¼
如果说Reactor模å¼æ˜¯Netty3的骨æžÓž¼Œé‚£ä¹ˆIntercepting Filter模å¼åˆ™æ˜¯Nettyçš„ä¸æž¢ã€‚Reactor模å¼ä¸»è¦åº”用在Netty3的内部实玎ͼŒå®ƒæ˜¯Netty3å…ähœ‰è‰¯å¥½æ€§èƒ½çš„基¼‹€åQŒè€ŒIntercepting Filter模å¼åˆ™æ˜¯ChannelHandler¾l„åˆå®žçŽ°ä¸€ä¸ªåº”用程åºé€»è¾‘的基¼‹€åQŒåªæœ‰å¾ˆå¥½çš„ç†è§£äº†è¿™ä¸ªæ¨¡å¼æ‰èƒ½ä‹É用好NettyåQŒç”šè‡Œ™ƒ½å¾—心应手ã€?br />关于Intercepting Filter模å¼çš„详¾l†ä»‹¾lå¯ä»¥å‚è€?a href="http://www.aygfsteel.com/DLevin/archive/2015/09/03/427086.html">˜q™é‡ŒåQŒæœ¬èŠ‚主è¦ä»‹¾lNetty3ä¸å¯¹Intercepting Filter模å¼çš„实玎ͼŒå…¶å®žž®±æ˜¯DefaultChannelPipeline对Intercepting Filter模å¼çš„实现。在上文有æ到Netty3çš„ChannelPipeline是ChannelHandler的容器，用于å˜å‚¨ä¸Žç®¡ç†ChannelHandleråQŒåŒæ—¶å®ƒåœ¨Netty3ä¸ä¹Ÿèµ·åˆ°æ¡¥æ¢çš„作用，å›_®ƒæ˜¯è¿žæŽ¥Netty3内部到所有ChannelHandlerçš„æ¡¥æ¢ã€‚作为ChannelPipeline的实现者DefaultChannelPipelineåQŒå®ƒä½¿ç”¨ä¸€ä¸ªChannelHandlerçš„åŒå‘链表æ¥å˜å‚¨åQŒä»¥DefaultChannelPipelineContext作äØ“(f¨´)节点åQ?br />
public interface ChannelHandlerContext {
Channel getChannel();
ChannelPipeline getPipeline();
String getName();
ChannelHandler getHandler();
boolean canHandleUpstream();
boolean canHandleDownstream();
void sendUpstream(ChannelEvent e);
void sendDownstream(ChannelEvent e);
Object getAttachment();
void setAttachment(Object attachment);
}
private final class DefaultChannelHandlerContext implements ChannelHandlerContext {
volatile DefaultChannelHandlerContext next;
volatile DefaultChannelHandlerContext prev;
private final String name;
private final ChannelHandler handler;
private final boolean canHandleUpstream;
private final boolean canHandleDownstream;
private volatile Object attachment;
.....
}
在DefaultChannelPipelineä¸ï¼Œå®ƒå˜å‚¨äº†å’Œå½“å‰ChannelPipeline相关è”çš„Channelã€ChannelSink以åŠ(qi¨¢ng)ChannelHandler链表的headã€tailåQŒæ‰€æœ‰ChannelEvent通过sendUpstreamã€sendDownstream为入å£æµ¾l整个链表：(x¨¬)Channel getChannel();
ChannelPipeline getPipeline();
String getName();
ChannelHandler getHandler();
boolean canHandleUpstream();
boolean canHandleDownstream();
void sendUpstream(ChannelEvent e);
void sendDownstream(ChannelEvent e);
Object getAttachment();
void setAttachment(Object attachment);
}
private final class DefaultChannelHandlerContext implements ChannelHandlerContext {
volatile DefaultChannelHandlerContext next;
volatile DefaultChannelHandlerContext prev;
private final String name;
private final ChannelHandler handler;
private final boolean canHandleUpstream;
private final boolean canHandleDownstream;
private volatile Object attachment;
.....
}
public class DefaultChannelPipeline implements ChannelPipeline {
private volatile Channel channel;
private volatile ChannelSink sink;
private volatile DefaultChannelHandlerContext head;
private volatile DefaultChannelHandlerContext tail;
......
public void sendUpstream(ChannelEvent e) {
DefaultChannelHandlerContext head = getActualUpstreamContext(this.head);
if (head == null) {
return;
}
sendUpstream(head, e);
}
void sendUpstream(DefaultChannelHandlerContext ctx, ChannelEvent e) {
try {
((ChannelUpstreamHandler) ctx.getHandler()).handleUpstream(ctx, e);
} catch (Throwable t) {
notifyHandlerException(e, t);
}
}
public void sendDownstream(ChannelEvent e) {
DefaultChannelHandlerContext tail = getActualDownstreamContext(this.tail);
if (tail == null) {
try {
getSink().eventSunk(this, e);
return;
} catch (Throwable t) {
notifyHandlerException(e, t);
return;
}
}
sendDownstream(tail, e);
}
void sendDownstream(DefaultChannelHandlerContext ctx, ChannelEvent e) {
if (e instanceof UpstreamMessageEvent) {
throw new IllegalArgumentException("cannot send an upstream event to downstream");
}
try {
((ChannelDownstreamHandler) ctx.getHandler()).handleDownstream(ctx, e);
} catch (Throwable t) {
e.getFuture().setFailure(t);
notifyHandlerException(e, t);
}
}
对Upstream事äšgåQŒå‘åŽæ‰¾åˆ°æ‰€æœ‰å®žçŽîCº†ChannelUpstreamHandler接å£çš„ChannelHandler¾l„æˆé“¾ï¼ˆgetActualUpstreamContext()åQ?/span>åQŒè€Œå¯¹Downstream事äšgåQŒå‘å‰æ‰¾åˆ°æ‰€æœ‰å®žçŽîCº†ChannelDownstreamHandler接å£çš„ChannelHandler¾l„æˆé“¾ï¼ˆgetActualDownstreamContext()åQ‰ï¼š(x¨¬)private volatile Channel channel;
private volatile ChannelSink sink;
private volatile DefaultChannelHandlerContext head;
private volatile DefaultChannelHandlerContext tail;
......
public void sendUpstream(ChannelEvent e) {
DefaultChannelHandlerContext head = getActualUpstreamContext(this.head);
if (head == null) {
return;
}
sendUpstream(head, e);
}
void sendUpstream(DefaultChannelHandlerContext ctx, ChannelEvent e) {
try {
((ChannelUpstreamHandler) ctx.getHandler()).handleUpstream(ctx, e);
} catch (Throwable t) {
notifyHandlerException(e, t);
}
}
public void sendDownstream(ChannelEvent e) {
DefaultChannelHandlerContext tail = getActualDownstreamContext(this.tail);
if (tail == null) {
try {
getSink().eventSunk(this, e);
return;
} catch (Throwable t) {
notifyHandlerException(e, t);
return;
}
}
sendDownstream(tail, e);
}
void sendDownstream(DefaultChannelHandlerContext ctx, ChannelEvent e) {
if (e instanceof UpstreamMessageEvent) {
throw new IllegalArgumentException("cannot send an upstream event to downstream");
}
try {
((ChannelDownstreamHandler) ctx.getHandler()).handleDownstream(ctx, e);
} catch (Throwable t) {
e.getFuture().setFailure(t);
notifyHandlerException(e, t);
}
}
private DefaultChannelHandlerContext getActualUpstreamContext(DefaultChannelHandlerContext ctx) {
if (ctx == null) {
return null;
}
DefaultChannelHandlerContext realCtx = ctx;
while (!realCtx.canHandleUpstream()) {
realCtx = realCtx.next;
if (realCtx == null) {
return null;
}
}
return realCtx;
}
private DefaultChannelHandlerContext getActualDownstreamContext(DefaultChannelHandlerContext ctx) {
if (ctx == null) {
return null;
}
DefaultChannelHandlerContext realCtx = ctx;
while (!realCtx.canHandleDownstream()) {
realCtx = realCtx.prev;
if (realCtx == null) {
return null;
}
}
return realCtx;
}
在实际实现ChannelUpstreamHandler或ChannelDownstreamHandleræ—Óž¼Œè°ƒç”¨
ChannelHandlerContextä¸çš„sendUpstream或sendDownstreamæ–ÒŽ(gu¨©)³•ž®†æŽ§åˆ¶æµ½E‹äº¤¾l™ä¸‹ä¸€ä¸?
ChannelUpstreamHandler或下一个ChannelDownstreamHandleråQŒæˆ–调用Channelä¸çš„writeæ–ÒŽ(gu¨©)³•å‘é€?
å“应消æ¯ã€?br />if (ctx == null) {
return null;
}
DefaultChannelHandlerContext realCtx = ctx;
while (!realCtx.canHandleUpstream()) {
realCtx = realCtx.next;
if (realCtx == null) {
return null;
}
}
return realCtx;
}
private DefaultChannelHandlerContext getActualDownstreamContext(DefaultChannelHandlerContext ctx) {
if (ctx == null) {
return null;
}
DefaultChannelHandlerContext realCtx = ctx;
while (!realCtx.canHandleDownstream()) {
realCtx = realCtx.prev;
if (realCtx == null) {
return null;
}
}
return realCtx;
}
public class MyChannelUpstreamHandler implements ChannelUpstreamHandler {
public void handleUpstream(ChannelHandlerContext ctx, ChannelEvent e) throws Exception {
// handle current logic, use Channel to write response if needed.
// ctx.getChannel().write(message);
ctx.sendUpstream(e);
}
}
public class MyChannelDownstreamHandler implements ChannelDownstreamHandler {
public void handleDownstream(
ChannelHandlerContext ctx, ChannelEvent e) throws Exception {
// handle current logic
ctx.sendDownstream(e);
}
}
当ChannelHandlerå‘ChannelPipelineContextå‘é€äº‹ä»¶æ—¶åQŒå…¶å†…部从当å‰ChannelPipelineContext节点出å‘扑ֈ°ä¸‹ä¸€ä¸ªChannelUpstreamHandler或ChannelDownstreamHandler实例åQŒåƈå‘å…¶å‘é€ChannelEventåQŒå¯¹äºŽDownstream链，如果到达铑ְ¾åQŒåˆ™ž®†ChannelEventå‘é€ç»™C(j¨©)hannelSinkåQ?br />public void handleUpstream(ChannelHandlerContext ctx, ChannelEvent e) throws Exception {
// handle current logic, use Channel to write response if needed.
// ctx.getChannel().write(message);
ctx.sendUpstream(e);
}
}
public class MyChannelDownstreamHandler implements ChannelDownstreamHandler {
public void handleDownstream(
ChannelHandlerContext ctx, ChannelEvent e) throws Exception {
// handle current logic
ctx.sendDownstream(e);
}
}
public void sendDownstream(ChannelEvent e) {
DefaultChannelHandlerContext prev = getActualDownstreamContext(this.prev);
if (prev == null) {
try {
getSink().eventSunk(DefaultChannelPipeline.this, e);
} catch (Throwable t) {
notifyHandlerException(e, t);
}
} else {
DefaultChannelPipeline.this.sendDownstream(prev, e);
}
}
public void sendUpstream(ChannelEvent e) {
DefaultChannelHandlerContext next = getActualUpstreamContext(this.next);
if (next != null) {
DefaultChannelPipeline.this.sendUpstream(next, e);
}
}
æ£æ˜¯å› äØ“(f¨´)˜q™ä¸ªå®žçŽ°åQŒå¦‚果在一个末ž®„¡š„ChannelUpstreamHandlerä¸å…ˆ¿U»é™¤è‡ªå·±åQŒåœ¨å‘末ž®¾æ·»åŠ 一个新的ChannelUpstreamHandleråQŒå®ƒæ˜¯æ— 效的åQŒå› 为它的nextå·²ç»åœ¨è°ƒç”¨å‰ž®±å›ºå®šè®¾¾|®äØ“(f¨´)null了ã€?br />DefaultChannelHandlerContext prev = getActualDownstreamContext(this.prev);
if (prev == null) {
try {
getSink().eventSunk(DefaultChannelPipeline.this, e);
} catch (Throwable t) {
notifyHandlerException(e, t);
}
} else {
DefaultChannelPipeline.this.sendDownstream(prev, e);
}
}
public void sendUpstream(ChannelEvent e) {
DefaultChannelHandlerContext next = getActualUpstreamContext(this.next);
if (next != null) {
DefaultChannelPipeline.this.sendUpstream(next, e);
}
}
ChannelPipeline作äØ“(f¨´)ChannelHandler的容器，它还æ供了儿U增ã€åˆ ã€æ”¹ChannelHandler链表ä¸çš„æ–ÒŽ(gu¨©)³•åQŒè€Œä¸”如果æŸä¸ªChannelHandler˜q˜å®žçŽîCº†LifeCycleAwareChannelHandleråQŒåˆ™è¯¥ChannelHandler在被æ·ÕdŠ ˜q›ChannelPipeline或从ä¸åˆ 除时都会(x¨¬)得到åŒå¿—åQ?br />
public interface LifeCycleAwareChannelHandler extends ChannelHandler {
void beforeAdd(ChannelHandlerContext ctx) throws Exception;
void afterAdd(ChannelHandlerContext ctx) throws Exception;
void beforeRemove(ChannelHandlerContext ctx) throws Exception;
void afterRemove(ChannelHandlerContext ctx) throws Exception;
}
public interface ChannelPipeline {
void addFirst(String name, ChannelHandler handler);
void addLast(String name, ChannelHandler handler);
void addBefore(String baseName, String name, ChannelHandler handler);
void addAfter(String baseName, String name, ChannelHandler handler);
void remove(ChannelHandler handler);
ChannelHandler remove(String name);
<T extends ChannelHandler> T remove(Class<T> handlerType);
ChannelHandler removeFirst();
ChannelHandler removeLast();
void replace(ChannelHandler oldHandler, String newName, ChannelHandler newHandler);
ChannelHandler replace(String oldName, String newName, ChannelHandler newHandler);
<T extends ChannelHandler> T replace(Class<T> oldHandlerType, String newName, ChannelHandler newHandler);
ChannelHandler getFirst();
ChannelHandler getLast();
ChannelHandler get(String name);
<T extends ChannelHandler> T get(Class<T> handlerType);
ChannelHandlerContext getContext(ChannelHandler handler);
ChannelHandlerContext getContext(String name);
ChannelHandlerContext getContext(Class<? extends ChannelHandler> handlerType);
void sendUpstream(ChannelEvent e);
void sendDownstream(ChannelEvent e);
ChannelFuture execute(Runnable task);
Channel getChannel();
ChannelSink getSink();
void attach(Channel channel, ChannelSink sink);
boolean isAttached();
List<String> getNames();
Map<String, ChannelHandler> toMap();
}
void beforeAdd(ChannelHandlerContext ctx) throws Exception;
void afterAdd(ChannelHandlerContext ctx) throws Exception;
void beforeRemove(ChannelHandlerContext ctx) throws Exception;
void afterRemove(ChannelHandlerContext ctx) throws Exception;
}
public interface ChannelPipeline {
void addFirst(String name, ChannelHandler handler);
void addLast(String name, ChannelHandler handler);
void addBefore(String baseName, String name, ChannelHandler handler);
void addAfter(String baseName, String name, ChannelHandler handler);
void remove(ChannelHandler handler);
ChannelHandler remove(String name);
<T extends ChannelHandler> T remove(Class<T> handlerType);
ChannelHandler removeFirst();
ChannelHandler removeLast();
void replace(ChannelHandler oldHandler, String newName, ChannelHandler newHandler);
ChannelHandler replace(String oldName, String newName, ChannelHandler newHandler);
<T extends ChannelHandler> T replace(Class<T> oldHandlerType, String newName, ChannelHandler newHandler);
ChannelHandler getFirst();
ChannelHandler getLast();
ChannelHandler get(String name);
<T extends ChannelHandler> T get(Class<T> handlerType);
ChannelHandlerContext getContext(ChannelHandler handler);
ChannelHandlerContext getContext(String name);
ChannelHandlerContext getContext(Class<? extends ChannelHandler> handlerType);
void sendUpstream(ChannelEvent e);
void sendDownstream(ChannelEvent e);
ChannelFuture execute(Runnable task);
Channel getChannel();
ChannelSink getSink();
void attach(Channel channel, ChannelSink sink);
boolean isAttached();
List<String> getNames();
Map<String, ChannelHandler> toMap();
}
在DefaultChannelPipelineçš„ChannelHandler链æ¡çš„处ç†æµ½E‹äØ“(f¨´)åQ?br />
å‚考：(x¨¬)
《Netty主页ã€?/a>《Nettyæºç 解读åQˆå››åQ‰Netty与Reactor模å¼ã€?/a>
《Netty代ç 分æžã€?/a>
Scalable IO In Java
Intercepting Filter Pattern
DLevin 2015-09-04 09:40 å‘表评论
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问题解决
è¦å®žçŽ°è¿™¿U需求，最直观的方法就是在æ¯ä¸ªè¯äh±‚处熘q‡ç¨‹ä¸æ·»åŠ 所有这些逻辑åQŒäØ“(f¨´)了凞®‘代ç é‡å¤ï¼Œå¯ä»¥ž®†æ‰€æœ‰è¿™äº›æ£€æŸ¥æå–æˆæ–ÒŽ(gu¨©)³•åQŒè¿™æ ·åœ¨æ¯ä¸ªå¤„ç†æ–ÒŽ(gu¨©)³•ä¸è°ƒç”¨å³å¯ï¼š(x¨¬)public Response service1(Request request) {
validate(request);
request = transform(request);
Response response = process1(request);
return transform(response);
}
æ¤æ—¶åQŒå¦‚果出现service2æ–ÒŽ(gu¨©)³•åQŒä¾ç„‰™œ€è¦æ‹·è´service1ä¸çš„实现åQŒç„¶åŽå°†process1æ¢æˆprocess2å›_¯ã€‚这个时候我们å‘现很多é‡å¤ä»£ç ，¾l§ç®‹å¯¹å®ƒé‡æž„åQŒæ¯”如æå–公共逻辑到基¾cÀLˆæ¨¡ç‰ˆæ–ÒŽ(gu¨©)³•åQŒè¿™¿Uä‹É用ç‘ô承的方å¼ä¼?x¨¬)引起å¾cÕd¯¹çˆ¶ç±»çš„耦åˆåQŒå¦‚æžœè¦è®©æŸäº›æ¨¡å—å˜çš„å¯é…置需è¦æœ‰å¤ªå¤šçš„判æ–逻辑åQŒä»£ç å˜çš„è‡ƒè‚¿ï¼›å› è€Œå¯ä»¥æ›´˜q›ä¸€æ¥ï¼Œž®†æ‰€æœ‰å¤„ç†é€»è¾‘抽象å‡ÞZ¸€ä¸ªProcessor接å£åQŒç„¶åŽä‹É用Decorate模å¼åQˆå³å¼•ç”¨ä¼˜äºŽ¾l§æ‰¿åQ‰ï¼š(x¨¬)validate(request);
request = transform(request);
Response response = process1(request);
return transform(response);
}
public interface Processor {
Response process(Request request);
}
public class CoreProcessor implements Processor {
public Response process(Request request) {
// do process/calculation
}
}
public class DecoratedProcessor implements Processor {
private final Processor innerProcessor;
public DecoratedProcessor(Processor processor) {
this.innerProcessor = processor;
}
public Response process(Request request) {
request = preProcess(request);
Response response = innerProcessor.process(request);
response = postProcess(response);
return response;
}
protected Request preProcess(Request request) {
return request;
}
protected Response postProcess(Response response) {
return response;
}
}
public void Transformer extends DecoratedProcessor {
public Transformer(Processor processor) {
super(processor);
}
protected Request preProcess(Request request) {
return transformRequest(request);
}
protected Response postProcess(Response response) {
return transformResponse(response);
}
}
æ¤æ—¶åQŒå¦‚果需è¦åœ¨çœŸæ£çš„处ç†é€»è¾‘之å‰åŠ 入其他的预处ç†é€»è¾‘åQŒåªéœ€è¦ç‘ô承DecoratedProcessoråQŒå®žçŽ°preProcess或postProcessæ–ÒŽ(gu¨©)³•åQŒåˆ†åˆ«åœ¨è¯äh±‚处ç†ä¹‹å‰å’Œè¯·æ±‚处ç†ä¹‹åŽæ¨ªå‘切入一些逻辑åQŒä¹Ÿž®±æ˜¯æ‰€è°“çš„AOP¾~–程åQšé¢å‘切é¢çš„¾~–程åQŒç„¶åŽåªéœ€è¦æ ¹æ®éœ€æ±‚æž„å»ø™¿™ä¸ªé“¾æ¡ï¼š(x¨¬)Response process(Request request);
}
public class CoreProcessor implements Processor {
public Response process(Request request) {
// do process/calculation
}
}
public class DecoratedProcessor implements Processor {
private final Processor innerProcessor;
public DecoratedProcessor(Processor processor) {
this.innerProcessor = processor;
}
public Response process(Request request) {
request = preProcess(request);
Response response = innerProcessor.process(request);
response = postProcess(response);
return response;
}
protected Request preProcess(Request request) {
return request;
}
protected Response postProcess(Response response) {
return response;
}
}
public void Transformer extends DecoratedProcessor {
public Transformer(Processor processor) {
super(processor);
}
protected Request preProcess(Request request) {
return transformRequest(request);
}
protected Response postProcess(Response response) {
return transformResponse(response);
}
}
Processor processor = new MissingExceptionCatcher(new Debugger(new Transformer(new CoreProcessor());
Response response = processor.process(request);
......
˜q™å·²¾l是相对比较好的设计了，æ¯ä¸ªProcessoråªéœ€è¦å…³æ³¨è‡ªå·Þqš„实现逻辑å›_¯åQŒä»£ç å˜çš„简‹zï¼›òq¶ä¸”æ¯ä¸ªProcessorå„自独立åQŒå¯é‡ç”¨æ€§å¥½åQŒæµ‹è¯•æ–¹ä¾¿ï¼›æ•´æ¡é“¾ä¸Šèƒ½å®žçŽ°çš„功能åªæ˜¯å–å†³äºŽé“¾çš„æž„é€ ï¼Œå› è€Œåªéœ€è¦æœ‰ä¸€¿U方法酾|®é“¾çš„æž„é€ å³å¯ï¼Œå¯é…¾|®æ€§ä¹Ÿå˜å¾—ç‰|´»åQ›ç„¶è€Œå¾ˆå¤šæ—¶å€™å¼•ç”¨æ˜¯ä¸€¿Ué™æ€çš„ä¾èµ–åQŒè€Œæ— 法满‘›_Š¨æ€çš„需求。è¦æž„é€ è¿™æ¡é“¾åQŒæ¯ä¸ªå‰¾|®Processor需è¦çŸ¥é“å…¶åŽçš„ProcessoråQŒè¿™åœ¨æŸäº›æƒ…况下òq¶ä¸æ˜¯åœ¨èµ·åˆž®ÞqŸ¥é“的。æ¤æ—Óž¼Œæˆ‘们需è¦å¼•å…¥Intercepting Filter模å¼æ¥å®žçŽ°åŠ¨æ€çš„改å˜æ¡é“¾ã€?br />Response response = processor.process(request);
......
Intercepting Filter模å¼
在å‰æ–‡å·²¾læž„å»ÞZº†ä¸€æ¡ç”±å¼•ç”¨è€Œæˆçš„Processor链，然而这是一æ¡é™æ€é“¾åQŒåƈ且需è¦ä¸€å¼€å§‹å°±èƒ½æž„é€ å‡º˜q™æ¡é“¾ï¼Œä¸ÞZº†è§£å†³˜q™ä¸ªé™åˆ¶åQŒæˆ‘们å¯ä»¥å¼•å…¥ä¸€ä¸ªProcessorChainæ¥ç»´æŠ¤è¿™æ¡é“¾åQŒåƈ且这æ¡é“¾å¯ä»¥åŠ¨æ€çš„æž„å¾ã€?br />有多¿Uæ–¹å¼å¯ä»¥å®žçŽ°åƈ控制˜q™ä¸ªé“¾ï¼š(x¨¬)
- 在å˜å‚¨ä¸ŠåQŒå¯ä»¥ä‹É用数¾l„æ¥å˜å‚¨æ‰€æœ‰çš„ProcessoråQŒProcessor在数¾l„ä¸çš„ä½¾|®è¡¨½Cø™¿™ä¸ªProcessor在链æ¡ä¸çš„ä½¾|®ï¼›ä¹Ÿå¯ä»¥ç”¨é“¾è¡¨æ¥å˜å‚¨æ‰€æœ‰çš„ProcessoråQŒæ¤æ—¶Processor在这个链表ä¸çš„ä½¾|®å³æ˜¯åœ¨é“¾ä¸çš„ä½¾|®ã€?/li>
- 在抽象上åQŒå¯ä»¥æ‰€æœ‰çš„逻辑都å°è£…在Processorä¸ï¼Œä¹Ÿå¯ä»¥å°†æ ¸å¿ƒé€»è¾‘使用Processor抽象åQŒè€Œå¤–围逻辑使用Filter抽象ã€?/li>
- 在浽E‹æŽ§åˆ¶ä¸ŠåQŒä¸€èˆ¬é€šè¿‡åœ¨Processor实现æ–ÒŽ(gu¨©)³•ä¸ç›´æŽ¥ä‹É用ProcessorChain实例(通过å‚数掺入)æ¥æŽ§åˆ¶æµ½E‹ï¼Œåˆ©ç”¨æ–ÒŽ(gu¨©)³•è°ƒç”¨çš„è¿›æ ˆå‡ºæ ˆçš„ç‰ÒŽ(gu¨©)€§å®žçŽ°preProcess()å’ŒpostProcess()处ç†ã€?/li>
Intercepting Filter模å¼åœ¨Servletçš„Filterä¸çš„实现åQˆJetty版本åQ?/h2>å…¶ä¸Servletçš„Filter在Jetty的实çŽîC¸ä½¿ç”¨æ•°ç»„å˜å‚¨FilteråQŒFilter末尾å¯ä»¥ä½¿ç”¨Servlet实例处ç†çœŸæ£çš„业务逻辑åQŒåœ¨‹¹ç¨‹æŽ§åˆ¶ä¸Šï¼Œä½¿ç”¨FilterChainçš„doFilteræ–ÒŽ(gu¨©)³•æ¥å®žçŽ°ã€‚如FilterChain在Jettyä¸çš„实现åQ?br />public void doFilter(ServletRequest request, ServletResponse response) throws IOException, ServletException
// pass to next filter
if (_filter < LazyList.size(_chain)) {
FilterHolder holder= (FilterHolder)LazyList.get(_chain, _filter++);
Filter filter= holder.getFilter();
filter.doFilter(request, response, this);
return;
}
// Call servlet
HttpServletRequest srequest = (HttpServletRequest)request;
if (_servletHolder != null) {
_servletHolder.handle(_baseRequest,request, response);
}
}˜q™é‡ŒåQŒ_chain实际上是一个Filterçš„ArrayListåQŒç”±FilterChain调用doFilter()å¯åŠ¨è°ƒç”¨½W¬ä¸€ä¸ªFilterçš„doFilter()æ–ÒŽ(gu¨©)³•åQŒåœ¨å®žé™…çš„Filter实现ä¸ï¼Œéœ€è¦æ‰‹åŠ¨çš„调用FilterChain.doFilter()æ–ÒŽ(gu¨©)³•æ¥å¯åŠ¨ä¸‹ä¸€ä¸ªFilter的调用，利用æ–ÒŽ(gu¨©)³•è°ƒç”¨çš„è¿›æ ˆå‡ºæ ˆçš„ç‰ÒŽ(gu¨©)€§å®žçŽ°Requestçš„pre-processå’ŒResponseçš„post-process处ç†ã€‚如果ä¸è°ƒç”¨FilterChain.doFilter()æ–ÒŽ(gu¨©)³•åQŒåˆ™è¡¨ç¤ºä¸éœ€è¦è°ƒç”¨ä¹‹åŽçš„FilteråQŒæµ½E‹ä»Žå½“å‰Filter˜q”回åQŒåœ¨å®ƒä¹‹å‰çš„Filterçš„FilterChain.doFilter()调用之åŽçš„逻辑åå‘处ç†ç›´åˆ°½W¬ä¸€ä¸ªFilter处ç†å®Œæˆè€Œè¿”回ã€?br />public class MyFilter implements Filter {
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
// pre-process ServletRequest
chain.doFilter(request, response);
// post-process Servlet Response
}
}整个Filteré“„¡š„处熋¹ç¨‹å¦‚下åQ?br />
// pass to next filter
if (_filter < LazyList.size(_chain)) {
FilterHolder holder= (FilterHolder)LazyList.get(_chain, _filter++);
Filter filter= holder.getFilter();
filter.doFilter(request, response, this);
return;
}
// Call servlet
HttpServletRequest srequest = (HttpServletRequest)request;
if (_servletHolder != null) {
_servletHolder.handle(_baseRequest,request, response);
}
}
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
// pre-process ServletRequest
chain.doFilter(request, response);
// post-process Servlet Response
}
}
Intercepting Filter模å¼åœ¨Netty3ä¸çš„实现
Netty3在DefaultChannelPipelineä¸å®žçŽîCº†Intercepting Filter模å¼åQŒå…¶ä¸ChannelHandler是它的Filter。在Netty3çš„DefaultChannelPipelineä¸ï¼Œä½¿ç”¨ä¸€ä¸ªä»¥ChannelHandlerContextä¸ø™Š‚点的åŒå‘链表æ¥å˜å‚¨ChannelHandleråQŒæ‰€æœ‰çš„横切é¢é€»è¾‘和实际业务逻辑都用ChannelHandler表达åQŒåœ¨æŽ§åˆ¶‹¹ç¨‹ä¸Šä‹É用ChannelHandlerContextçš„sendDownstream()å’ŒsendUpstream()æ–ÒŽ(gu¨©)³•æ¥æŽ§åˆ¶æµ½E‹ã€‚ä¸åŒäºŽServletçš„FilteråQŒChannelHandler有两个å接å£åQšChannelUpstreamHandlerå’ŒChannelDownstreamHandler分别用æ¥è¯äh±‚˜q›å…¥æ—¶çš„处熋¹ç¨‹å’Œå“应出åŽÀL—¶çš„处ç†æµ½E‹ã€‚对于Client的请求，从DefaultChannelPipelineçš„sendUpstream()æ–ÒŽ(gu¨©)³•å…¥å£åQ?br />public void sendDownstream(ChannelEvent e) {
DefaultChannelHandlerContext tail = getActualDownstreamContext(this.tail);
if (tail == null) {
try {
getSink().eventSunk(this, e);
return;
} catch (Throwable t) {
notifyHandlerException(e, t);
return;
}
}
sendDownstream(tail, e);
}
void sendDownstream(DefaultChannelHandlerContext ctx, ChannelEvent e) {
if (e instanceof UpstreamMessageEvent) {
throw new IllegalArgumentException("cannot send an upstream event to downstream");
}
try {
((ChannelDownstreamHandler) ctx.getHandler()).handleDownstream(ctx, e)
} catch (Throwable t) {
e.getFuture().setFailure(t);
notifyHandlerException(e, t);
}
}
如果有å“应消æ¯ï¼Œè¯¥æ¶ˆæ¯ä»ŽDefaultChannelPipelineçš„sendDownstream()æ–ÒŽ(gu¨©)³•ä¸ºå…¥å£ï¼š(x¨¬)DefaultChannelHandlerContext tail = getActualDownstreamContext(this.tail);
if (tail == null) {
try {
getSink().eventSunk(this, e);
return;
} catch (Throwable t) {
notifyHandlerException(e, t);
return;
}
}
sendDownstream(tail, e);
}
void sendDownstream(DefaultChannelHandlerContext ctx, ChannelEvent e) {
if (e instanceof UpstreamMessageEvent) {
throw new IllegalArgumentException("cannot send an upstream event to downstream");
}
try {
((ChannelDownstreamHandler) ctx.getHandler()).handleDownstream(ctx, e)
} catch (Throwable t) {
e.getFuture().setFailure(t);
notifyHandlerException(e, t);
}
}
public void sendUpstream(ChannelEvent e) {
DefaultChannelHandlerContext head = getActualUpstreamContext(this.head);
if (head == null) {
return;
}
sendUpstream(head, e);
}
void sendUpstream(DefaultChannelHandlerContext ctx, ChannelEvent e) {
try {
((ChannelUpstreamHandler) ctx.getHandler()).handleUpstream(ctx, e);
} catch (Throwable t) {
notifyHandlerException(e, t);
}
}
在实际实现ChannelUpstreamHandler或ChannelDownstreamHandleræ—Óž¼Œè°ƒç”¨ChannelHandlerContextä¸çš„sendUpstream或sendDownstreamæ–ÒŽ(gu¨©)³•ž®†æŽ§åˆ¶æµ½E‹äº¤¾l™ä¸‹ä¸€ä¸ªChannelUpstreamHandler或下一个ChannelDownstreamHandleråQŒæˆ–调用Channelä¸çš„writeæ–ÒŽ(gu¨©)³•å‘é€å“应消æ¯ã€?br />DefaultChannelHandlerContext head = getActualUpstreamContext(this.head);
if (head == null) {
return;
}
sendUpstream(head, e);
}
void sendUpstream(DefaultChannelHandlerContext ctx, ChannelEvent e) {
try {
((ChannelUpstreamHandler) ctx.getHandler()).handleUpstream(ctx, e);
} catch (Throwable t) {
notifyHandlerException(e, t);
}
}
public class MyChannelUpstreamHandler implements ChannelUpstreamHandler {
public void handleUpstream(ChannelHandlerContext ctx, ChannelEvent e) throws Exception {
// handle current logic, use Channel to write response if needed.
// ctx.getChannel().write(message);
ctx.sendUpstream(e);
}
}
public class MyChannelDownstreamHandler implements ChannelDownstreamHandler {
public void handleDownstream(
ChannelHandlerContext ctx, ChannelEvent e) throws Exception {
// handle current logic
ctx.sendDownstream(e);
}
}
当ChannelHandlerå‘ChannelPipelineContextå‘é€äº‹ä»¶æ—¶åQŒå…¶å†…部从当å‰ChannelPipelineContext
节点出å‘扑ֈ°ä¸‹ä¸€ä¸ªChannelUpstreamHandler或ChannelDownstreamHandler实例åQŒåƈå‘å…¶å‘é€?
ChannelEventåQŒå¯¹äºŽDownstream链，如果到达铑ְ¾åQŒåˆ™ž®†ChannelEventå‘é€ç»™C(j¨©)hannelSinkåQ?br />public void handleUpstream(ChannelHandlerContext ctx, ChannelEvent e) throws Exception {
// handle current logic, use Channel to write response if needed.
// ctx.getChannel().write(message);
ctx.sendUpstream(e);
}
}
public class MyChannelDownstreamHandler implements ChannelDownstreamHandler {
public void handleDownstream(
ChannelHandlerContext ctx, ChannelEvent e) throws Exception {
// handle current logic
ctx.sendDownstream(e);
}
}
public void sendDownstream(ChannelEvent e) {
DefaultChannelHandlerContext prev = getActualDownstreamContext(this.prev);
if (prev == null) {
try {
getSink().eventSunk(DefaultChannelPipeline.this, e);
} catch (Throwable t) {
notifyHandlerException(e, t);
}
} else {
DefaultChannelPipeline.this.sendDownstream(prev, e);
}
}
public void sendUpstream(ChannelEvent e) {
DefaultChannelHandlerContext next = getActualUpstreamContext(this.next);
if (next != null) {
DefaultChannelPipeline.this.sendUpstream(next, e);
}
}
æ£æ˜¯å› äØ“(f¨´)˜q™ä¸ªå®žçŽ°åQŒå¦‚果在一个末ž®„¡š„ChannelUpstreamHandlerä¸å…ˆ¿U»é™¤è‡ªå·±åQŒåœ¨å‘末ž®¾æ·»åŠ 一个新的ChannelUpstreamHandleråQŒå®ƒæ˜¯æ— 效的åQŒå› 为它的nextå·²ç»åœ¨è°ƒç”¨å‰ž®±å›ºå®šè®¾¾|®äØ“(f¨´)null了ã€?br />DefaultChannelHandlerContext prev = getActualDownstreamContext(this.prev);
if (prev == null) {
try {
getSink().eventSunk(DefaultChannelPipeline.this, e);
} catch (Throwable t) {
notifyHandlerException(e, t);
}
} else {
DefaultChannelPipeline.this.sendDownstream(prev, e);
}
}
public void sendUpstream(ChannelEvent e) {
DefaultChannelHandlerContext next = getActualUpstreamContext(this.next);
if (next != null) {
DefaultChannelPipeline.this.sendUpstream(next, e);
}
}
在DefaultChannelPipelineçš„ChannelHandler链æ¡çš„处ç†æµ½E‹äØ“(f¨´)åQ?br />
在这个实çŽîC¸åQŒä¸åƒServletçš„Filter实现利用æ–ÒŽ(gu¨©)³•è°ƒç”¨æ ˆçš„˜q›å‡ºæ ˆæ¥å®Œæˆpre-processå’Œpost-processåQŒè€Œæ˜¯åœ¨è¿›åŽÈš„é“‘Ö’Œå‡ºæ¥çš„链å„自调用handleUpstream()å’ŒhandleDownstream()æ–ÒŽ(gu¨©)³•åQŒè¿™æ ·ä¼š(x¨¬)引è“vè°ƒç”¨æ ˆå…¶å®žæ˜¯ä¸¤æ¡é“„¡š„æ€Õd’ŒåQŒå› 而需è¦æ³¨æ„è¿™æ¡é“¾çš„æ€»é•¿åº¦ã€‚è¿™æ ·åšçš„好处是˜q™æ¡ChannelHandler的链ä¸ä¾èµ–于æ–ÒŽ(gu¨©)³•è°ƒç”¨æ ˆï¼Œè€Œæ˜¯åœ¨DefaultChannelPipeline内部本èín的链åQŒå› 而在handleUpstream()或handleDownstream()å¯ä»¥éšæ—¶ž®†æ‰§è¡Œæµ½E‹è{å‘给其他¾U¿ç¨‹æˆ–线½E‹æ± åQŒåªéœ€è¦ä¿ç•™C(j¨©)hannelPipelineContext引用åQŒåœ¨å¤„ç†å®ŒæˆåŽç”¨˜q™ä¸ªChannelPipelineContexté‡æ–°å‘è¿™æ¡é“¾çš„åŽä¸€ä¸ªèŠ‚点å‘é€ChannelEventåQŒç„¶è€Œç”±äºŽServletçš„Filterä¾èµ–äºŽæ–¹æ³•çš„è°ƒç”¨æ ˆï¼Œå› è€Œæ–¹æ³•è¿”å›žæ„味ç€æ‰€æœ‰æ‰§è¡Œå®Œæˆï¼Œ˜q™ç§é™åˆ¶åœ¨å¼‚æ¥ç¼–½E‹ä¸ä¼?x¨¬)å¼•èµ·é—®é¢˜ï¼Œå› è€ŒServletåœ?.0åŽå¼•å…¥äº†Async的支æŒã€?br />
Intercepting Filter模å¼çš„缺ç‚?/h2>½Ž€å•æ一下这个模å¼çš„¾~ºç‚¹åQ?br />1. ç›¸å¯¹ä¼ ç»Ÿçš„ç¼–½E‹æ¨¡åž‹ï¼Œ˜q™ä¸ªæ¨¡å¼æœ‰ä¸€å®šçš„å¦ä¹ (f¨¤n)曲线åQŒéœ€è¦å¾ˆå¥½çš„ç†è§£è¯¥æ¨¡å¼åŽæ‰èƒ½ç‰|´»çš„应用它æ¥ç¼–½E‹ã€?br />2. 需è¦åˆ’分ä¸åŒçš„逻辑åˆîC¸åŒçš„Filterä¸ï¼Œ˜q™æœ‰äº›æ—¶å€™åƈä¸æ˜¯é‚£ä¹ˆå®ÒŽ(gu¨©)˜“ã€?br />3. å„个Filter之间å…׃ín数殞®†å˜å¾—困难。在Netty3ä¸å¯ä»¥è‡ªå®šä¹‰è‡ªå·±çš„ChannelEventæ¥å®žçŽ°è‡ªå®šä¹‰æ¶ˆæ¯çš„ä¼ è¾“ï¼Œæˆ–è€…ä‹É用ChannelPipelineContextçš„Attachmentå—段æ¥å®žçŽ°æ¶ˆæ¯ä¼ 输，而Servletä¸çš„Filter则没有æ供类似的机制åQŒå¦‚æžœä¸æ˜¯å¯ä»¥é…¾|®çš„æ•°æ®åœ¨Configä¸ä¼ 递，其他时候的数æ®å…׃ín需è¦å…¶ä»–机刉™…åˆå®Œæˆã€?br />
å‚è€?/h2>Core J2EE Pattern - Intercepting Filter
DLevin 2015-09-03 22:14 å‘表评论]]>Reactor模å¼è¯¦è§£ http://www.aygfsteel.com/DLevin/archive/2015/09/02/427045.htmlDLevin DLevin Wed, 02 Sep 2015 07:14:00 GMT http://www.aygfsteel.com/DLevin/archive/2015/09/02/427045.html http://www.aygfsteel.com/DLevin/comments/427045.html http://www.aygfsteel.com/DLevin/archive/2015/09/02/427045.html#Feedback 2 http://www.aygfsteel.com/DLevin/comments/commentRss/427045.html http://www.aygfsteel.com/DLevin/services/trackbacks/427045.html å‰è®°
½W¬ä¸€‹Æ¡å¬åˆ°Reactor模å¼æ˜¯ä¸‰òq´å‰çš„æŸä¸ªæ™šä¸Šï¼Œä¸€ä¸ªå®¤å‹çªç„¶è·‘˜q‡æ¥é—®æˆ‘什么是Reactor模å¼åQŸæˆ‘上网查了一下，很多人都是给出NIOä¸çš„
Selector的例å，而且ž®±æ˜¯NIO里Selector多èµ\å¤ç”¨æ¨¡åž‹åQŒåªæ˜¯ç»™å®ƒè“v了一个比较fancyçš„åå—而已åQŒè™½ç„¶å®ƒå¼•å…¥äº†EventLoopæ¦?
念，˜q™å¯¹æˆ‘æ¥è¯´æ˜¯æ–°çš„概念åQŒä½†æ˜¯ä»£ç 实现å´æ˜¯ä¸€æ ïL(f¨¥ng)š„åQŒå› 而我òq¶æ²¡æœ‰å¾ˆåœ¨æ„˜q™ä¸ªæ¨¡å¼ã€‚然而最˜q‘开始读Nettyæºç åQŒè€ŒReactor模å¼æ˜¯å¾ˆå¤šä»‹¾lNettyçš„æ–‡ç« ä¸è¢«å¤§è‚†å®£ä¼ 的模å¼åQŒå› 而我å†æ¬¡é—®è‡ªå·±ï¼Œä»€ä¹ˆæ˜¯Reactor模å¼åQŸæœ¬æ–‡å°±æ˜¯å¯¹˜q™ä¸ªé—®é¢˜å…³äºŽæˆ‘的一些ç†è§£å’Œž®è¯•ç€æ¥è§£½{”ã€?br />
什么是Reactor模å¼
è¦å›ž½{”这个问题，首先当然是求助Google或WikipediaåQŒå…¶ä¸Wikipedia上说åQ?#8220;The reactor design pattern is an event handling pattern for handling service requests delivered concurrently by one or more inputs. The service handler then demultiplexes the incoming requests and dispatches them synchronously to associated request handlers.”。从˜q™ä¸ªæè¿°ä¸ï¼Œæˆ‘们知é“Reactor模å¼é¦–å…ˆæ˜?strong>事äšg驱动的，有一个或多个òq¶å‘输入æºï¼Œæœ‰ä¸€ä¸ªService HandleråQŒæœ‰å¤šä¸ªRequest Handlers
从结构上åQŒè¿™æœ‰ç‚¹¾cÖM¼¼ç”Ÿäñ”者消费者模å¼ï¼ŒåÏxœ‰ä¸€ä¸ªæˆ–多个生äñ”者将事äšg攑օ¥ä¸€ä¸ªQueueä¸ï¼Œè€Œä¸€ä¸ªæˆ–多个消费者主动的从这个Queueä¸Poll事äšgæ¥å¤„ç†ï¼›è€ŒReactor模å¼åˆ™åƈ没有Queueæ¥åš¾~“冲åQŒæ¯å½“一个Event输入到Service Handler之åŽåQŒè¯¥Service Handlerä¼?x¨¬)主动的æ Ò?gu¨©)®ä¸åŒçš„Event¾cÕdž‹ž®†å…¶åˆ†å‘¾l™å¯¹åº”çš„Request Handleræ¥å¤„ç†ã€?br />
æ›´å¦æœ¯çš„åQŒè¿™½‹‡æ–‡ç« （Reactor An Object Behavioral Pattern for Demultiplexing and Dispatching Handles for Synchronous EventsåQ‰ä¸Šè¯ß_(d¨¢)¼š(x¨¬)“The Reactor design pattern handles service requests that are delivered concurrently to an application by one or more clients. Each service in an application may consistent of several methods and is represented by a separate event handler that is responsible for dispatching service-specific requests. Dispatching of event handlers is performed by an initiation dispatcher, which manages the registered event handlers. Demultiplexing of service requests is performed by a synchronous event demultiplexer. Also known as Dispatcher, Notifier”。这ŒD‰|˜q°å’ŒW(xu¨¦)ikipedia上的æè¿°¾cÖM¼¼åQŒæœ‰å¤šä¸ªè¾“å…¥æºï¼Œæœ‰å¤šä¸ªä¸åŒçš„EventHandleråQˆRequestHandleråQ‰æ¥å¤„ç†ä¸åŒçš„请求，Initiation Dispatcher用于½Ž¡ç†EventHanderåQŒEventHandler首先è¦æ³¨å†Œåˆ°Initiation Dispatcherä¸ï¼Œç„¶åŽInitiation Dispatcheræ ÒŽ(gu¨©)®è¾“入的Event分呾l™æ³¨å†Œçš„EventHandleråQ›ç„¶è€ŒInitiation Dispatcheròq¶ä¸ç›‘å¬Event的到æ¥ï¼Œ˜q™ä¸ªå·¥ä½œäº¤ç»™Synchronous Event Demultiplexeræ¥å¤„ç†ã€?br />
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在解决了什么是Reactor模å¼åŽï¼Œæˆ‘们æ¥çœ‹çœ‹Reactor模å¼æ˜¯ç”±ä»€ä¹ˆæ¨¡å—æž„æˆã€‚图是一¿U比较简‹zåŞ象的表现方å¼åQŒå› è€Œå…ˆä¸Šä¸€å¼ å›¾æ¥è¡¨è¾‘ք个模å—çš„å称和他们之间的关系åQ?br />
HandleåQ?/strong>åÏx“作系¾lŸä¸çš„å¥æŸ„，是对资æºåœ¨æ“作系¾lŸå±‚é¢ä¸Šçš„一¿U抽象，它å¯ä»¥æ˜¯æ‰“开的文件ã€ä¸€ä¸ªè¿žæŽ?Socket)ã€Timer½{‰ã€‚由于Reactor模å¼ä¸€èˆ¬ä‹É用在¾|‘络¾~–程ä¸ï¼Œå› 而这里一般指Socket HandleåQŒå³ä¸€ä¸ªç½‘¾lœè¿žæŽ¥ï¼ˆConnectionåQŒåœ¨Java NIOä¸çš„ChannelåQ‰ã€‚这个Channel注册到Synchronous Event Demultiplexerä¸ï¼Œä»¥ç›‘å¬Handleä¸å‘生的事äšgåQŒå¯¹ServerSocketChannnelå¯ä»¥æ˜¯CONNECT事äšgåQŒå¯¹SocketChannelå¯ä»¥æ˜¯READã€WRITEã€CLOSE事äšg½{‰ã€?br />Synchronous Event DemultiplexeråQ?/strong>é˜Õd¡ž½{‰å¾…一¾pÕdˆ—çš„Handleä¸çš„事äšg到æ¥åQŒå¦‚果阻塞ç‰å¾…返回，匙¡¨½Cºåœ¨˜q”回的Handleä¸å¯ä»¥ä¸é˜Õd¡žçš„执行返回的事äšg¾cÕdž‹ã€‚这个模å—一般ä‹É用æ“作系¾lŸçš„selectæ¥å®žçŽ°ã€‚在Java NIOä¸ç”¨Selectoræ¥å°è£…，当Selector.select()˜q”回æ—Óž¼Œå¯ä»¥è°ƒç”¨Selectorçš„selectedKeys()æ–ÒŽ(gu¨©)³•èŽ·å–Set<SelectionKey>åQŒä¸€ä¸ªSelectionKey表达一个有事äšgå‘生的Channel以åŠ(qi¨¢ng)该Channel上的事äšg¾cÕdž‹ã€‚上囄¡š„“Synchronous Event Demultiplexer ---notifies--> Handle”çš„æµ½E‹å¦‚果是对的åQŒé‚£å†…部实现应该是select()æ–ÒŽ(gu¨©)³•åœ¨äº‹ä»¶åˆ°æ¥åŽä¼?x¨¬)先讄¡½®Handle的状æ€ï¼Œç„¶åŽ˜q”回。ä¸äº†è§£å†…部实现机制åQŒå› 而ä¿ç•™åŽŸå›¾ã€?br />Initiation DispatcheråQ?/strong>用于½Ž¡ç†Event HandleråQŒå³EventHandler的容器，用以注册ã€ç§»é™¤EventHandler½{‰ï¼›å¦å¤–åQŒå®ƒ˜q˜ä½œä¸ºReactor模å¼çš„å…¥å£è°ƒç”¨Synchronous Event Demultiplexerçš„selectæ–ÒŽ(gu¨©)³•ä»¥é˜»å¡žç‰å¾…事件返回，当阻塞ç‰å¾…返回时åQŒæ ¹æ®äº‹ä»¶å‘生的Handlež®†å…¶åˆ†å‘¾l™å¯¹åº”çš„Event Handler处ç†åQŒå³å›žè°ƒEventHandlerä¸çš„handle_event()æ–ÒŽ(gu¨©)³•ã€?br />Event HandleråQ?/strong>定义事äšg处ç†æ–ÒŽ(gu¨©)³•åQšhandle_event()åQŒä»¥ä¾›InitiationDispatcher回调使用ã€?br />Concrete Event HandleråQ?/strong>事äšgEventHandler接å£åQŒå®žçŽ°ç‰¹å®šäº‹ä»¶å¤„ç†é€»è¾‘ã€?br />
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1. åˆå§‹åŒ–InitiationDispatcheråQŒåƈåˆå§‹åŒ–一个Handle到EventHandlerçš„Mapã€?br />2. 注册EventHandler到InitiationDispatcherä¸ï¼Œæ¯ä¸ªEventHandler包å«å¯¹ç›¸åº”Handle的引用，从而å¾ç«‹Handle到EventHandlerçš„æ˜ ž®„（MapåQ‰ã€?br />3. 调用InitiationDispatcherçš„handle_events()æ–ÒŽ(gu¨©)³•ä»¥å¯åŠ¨Event Loop。在Event Loopä¸ï¼Œè°ƒç”¨select()æ–ÒŽ(gu¨©)³•åQˆSynchronous Event DemultiplexeråQ‰é˜»å¡žç‰å¾…Eventå‘生ã€?br />4. 当æŸä¸ªæˆ–æŸäº›Handleçš„Eventå‘生åŽï¼Œselect()æ–ÒŽ(gu¨©)³•˜q”回åQŒInitiationDispatcheræ ÒŽ(gu¨©)®˜q”回的Handle扑ֈ°æ³¨å†Œçš„EventHandleråQŒåƈ回调该EventHandlerçš„handle_events()æ–ÒŽ(gu¨©)³•ã€?br />5. 在EventHandlerçš„handle_events()æ–ÒŽ(gu¨©)³•ä¸è¿˜å¯ä»¥å‘InitiationDispatcherä¸æ³¨å†Œæ–°çš„EventhandleråQŒæ¯”如对AcceptorEventHandleræ¥ï¼Œå½“有新的client˜qžæŽ¥æ—Óž¼Œå®ƒä¼š(x¨¬)产生新的EventHandler以处ç†æ–°çš„连接，òq¶æ³¨å†Œåˆ°InitiationDispatcherä¸ã€?br />
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åœ?a >Reactor An Object Behavioral Pattern for Demultiplexing and Dispatching Handles for Synchronous Eventsä¸ï¼Œä¸€ç›´ä»¥Logging Serveræ¥åˆ†æžReactor模å¼åQŒè¿™ä¸ªLogging Server的实现完全éµå¾ªè¿™é‡Œå¯¹Reactoræè¿°åQŒå› 而放在这里以åšå‚考。Logging Serverä¸çš„Reactor模å¼å®žçŽ°åˆ†ä¸¤ä¸ªéƒ¨åˆ†ï¼š(x¨¬)Client˜qžæŽ¥åˆ°Logging Serverå’ŒClientå‘Logging Server写Logã€‚å› è€Œå¯¹å®ƒçš„æ述分战q™ä¸¤ä¸ªæ¥éª¤ã€?br />Client˜qžæŽ¥åˆ°Logging Server
1. Logging Server注册LoggingAcceptor到InitiationDispatcherã€?br />2. Logging Server调用InitiationDispatcherçš„handle_events()æ–ÒŽ(gu¨©)³•å¯åŠ¨ã€?br />3. InitiationDispatcher内部调用select()æ–ÒŽ(gu¨©)³•åQˆSynchronous Event DemultiplexeråQ‰ï¼Œé˜Õd¡ž½{‰å¾…Client˜qžæŽ¥ã€?br />4. Client˜qžæŽ¥åˆ°Logging Serverã€?br />5. InitiationDisptcherä¸çš„select()æ–ÒŽ(gu¨©)³•˜q”回åQŒåƈ通知LoggingAcceptor有新的连接到æ¥ã€?
6. LoggingAcceptor调用acceptæ–ÒŽ(gu¨©)³•accept˜q™ä¸ªæ–°è¿žæŽ¥ã€?br />7. LoggingAcceptor创å¾æ–°çš„LoggingHandlerã€?br />8. æ–°çš„LoggingHandler注册到InitiationDispatcherä¸?åŒæ—¶ä¹Ÿæ³¨å†Œåˆ°Synchonous Event Demultiplexerä¸?åQŒç‰å¾…Clientå‘è“v写logè¯äh±‚ã€?br />Clientå‘Logging Server写Log
1. Clientå‘é€log到Logging serverã€?br />2. InitiationDispatcher监测到相应的Handleä¸æœ‰äº‹äšgå‘生åQŒè¿”回阻塞ç‰å¾…，æ ÒŽ(gu¨©)®˜q”回的Handle扑ֈ°LoggingHandleråQŒåƈ回调LoggingHandlerä¸çš„handle_event()æ–ÒŽ(gu¨©)³•ã€?br />3. LoggingHandlerä¸çš„handle_event()æ–ÒŽ(gu¨©)³•ä¸è¯»å–Handleä¸çš„logä¿¡æ¯ã€?br />4. ž®†æŽ¥æ”¶åˆ°çš„log写入到日志文件ã€æ•°æ®åº“½{‰è®¾å¤‡ä¸ã€?br />3.4æ¥éª¤å¾ªçŽ¯ç›´åˆ°å½“å‰æ—¥å¿—处ç†å®Œæˆã€?br />5. ˜q”回到InitiationDispatcher½{‰å¾…下一‹Æ¡æ—¥å¿—写è¯äh±‚ã€?br />
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Java NIO对Reactor的实çŽ?/h2>在Javaçš„NIOä¸ï¼Œå¯¹Reactor模å¼æœ‰æ— ¾~的支æŒåQŒå³ä½¿ç”¨Selector¾cÕd°è£…了æ“作¾pÈ»Ÿæ供的Synchronous Event Demultiplexer功能。这个Doug Leaå·²ç»åœ?a >Scalable IO In Javaä¸æœ‰éžå¸¸æ·±å…¥çš„解释了åQŒå› 而ä¸å†èµ˜˜qŽÍ¼Œå¦å¤–˜q™ç¯‡æ–‡ç« 对Doug Leaçš?a >Scalable IO In Java有一些简å•è§£é‡Šï¼Œè‡›_°‘它的代ç æ ¼å¼æ¯”Doug Leaçš„PPTè¦æ•´‹z一些ã€?br />
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