DefaultIoFilterChainBuilder chain = acceptor.getFilterChain();

    MdcInjectionFilter mdcInjectionFilter = new MdcInjectionFilter();
    chain.addLast("mdc", mdcInjectionFilter);

3.源碼解讀_DefaultIoFilterChainBuilder

        1.DefaultIoFilterChainBuilder內(nèi)部維護(hù)一個(gè)Entry的列表
                List<Entry> entries = new CopyOnWriteArrayList<Entry>();

        2.public synchronized void addLast(String name, IoFilter filter) 內(nèi)部調(diào)用register方法:register(entries.size(), new EntryImpl(name, filter))
                其核心代碼為:entries.add(index, e);
          同理其內(nèi)部addFirst/addBore/addAfter,均是將filter-pair(Entry)加入到list的不同位置.
       
        3.其實(shí)現(xiàn)IoFilterChainBuilder接口內(nèi)的方法:buildFilterChain(IoFilterChain chain)
                for (Entry e : entries) {
                        chain.addLast(e.getName(), e.getFilter());
                 }
            即調(diào)用IoFilerChain的方法組裝filter
       
        ->所以IoFilterChainBuilder是IoFilerChain的構(gòu)建接口.

4.源碼解讀_DefaultIoFilterChain

        1.其整體內(nèi)部實(shí)現(xiàn)了一個(gè)雙向鏈表.
                這里從head,tail以及EntryImpl的定義prevEntry/nextEntry可見一斑.

        2.public synchronized void addLast(String name, IoFilter filter)->內(nèi)部調(diào)用register方法:register(tail.prevEntry, name, filter)
                將尾部指針的前驅(qū)節(jié)點(diǎn)(tail.prevEntry)傳入作為新節(jié)點(diǎn)的前驅(qū)節(jié)點(diǎn)->
                ->將tail.prevEntry.nextEntry這里即tail作為新節(jié)點(diǎn)的后繼節(jié)點(diǎn)

        3.private void register(EntryImpl prevEntry, String name, IoFilter filter)
                1.新建節(jié)點(diǎn)newEntry
                2.調(diào)用filter.onPreAdd
                3.調(diào)整鏈表的前驅(qū)后繼關(guān)系并將newEntry加入Map<String, Entry> name2entry
                4.調(diào)用filter.onPostAdd

5.源碼解讀_NextFilter

        1.DefaultIoFilterChain中節(jié)點(diǎn)EntryImpl中有一個(gè)private final NextFilter nextFilter
                ->其表示當(dāng)前節(jié)點(diǎn)filter的下一個(gè)IoFilter

        2.EntryImp初始化nextFiler是用一個(gè)匿名內(nèi)部類初始化并覆寫接口方法
                1.messageReceived(IoSession session, Object message)
                        ->調(diào)用callNextMessageReceived(nextEntry,session,message),其中nextEntry為當(dāng)前節(jié)點(diǎn)的后繼節(jié)點(diǎn)
                        ->后繼節(jié)點(diǎn)執(zhí)行filter.messageReceived(nextFilter, session, message),其中nextFiler為后繼節(jié)點(diǎn)的NextFiler對(duì)象.

                也就是說(shuō)每個(gè)Filter的實(shí)現(xiàn)類如果在messageReceived(NextFilter nextFilter, IoSession session, Object message)中調(diào)用了nextFiler.messageReceive方法，則表示沿著過(guò)濾鏈繼續(xù)forward>>>>>>.而IoFilterAdapter的默認(rèn)實(shí)現(xiàn)則是這樣.

                2.filterWrite(IoSession session, WriteRequest writeRequest)
                        ->調(diào)用callPreviousFilterWrite(nextEntry, session, writeRequest),其中nextEntry為當(dāng)前節(jié)點(diǎn)的前驅(qū)節(jié)點(diǎn)
                        ->前驅(qū)節(jié)點(diǎn)執(zhí)行filter.filterWrite(nextFilter, session, writeRequest),其中nextFiler為前驅(qū)節(jié)點(diǎn)的NextFiler對(duì)象.

                同上,即每個(gè)Filer的實(shí)現(xiàn)類如果在filterWrite(NextFilter nextFilter, IoSession session, WriteRequest writeRequest)中調(diào)用了nextFilter.filterWrite方法，則表示沿著過(guò)濾鏈繼續(xù)forward<<<<<<<.

6.源碼解讀_HeadFilter

     1.此為DefaultIoFilterChain中頭結(jié)點(diǎn)的過(guò)濾器.

     2.此過(guò)濾器繼承了IoFilterAdapter,所以其messageReceived方法默認(rèn)調(diào)用了nextFiler.messageReceived方法,即收到消息不處理，直接轉(zhuǎn)發(fā)后繼節(jié)點(diǎn)進(jìn)行過(guò)濾處理.

     3.其主要覆寫了filterWrite(NextFilter nextFilter, IoSession session, WriteRequest writeRequest) 方法
      ->由processor處理write.

7.源碼解讀_TailFilter

     1.此為DefaultIoFilterChain中尾節(jié)點(diǎn)的過(guò)濾器.

     2.其繼承了IoFilterAdapter并覆寫了所有方法:
      其中sessionCreated/sessionOpened/sessionIdle/exceptionCaught/messageReceived/messageSent均調(diào)用了session.getHandler()的相關(guān)方法,即IoHandler,這個(gè)我們經(jīng)常用到且經(jīng)常寫的IoHandler.
     而filterWrite/filterClose則直接調(diào)用nextFilter.相關(guān)方法,即繼續(xù)沿著過(guò)濾鏈<<<<<forward.

8源碼解讀_ProtocolCodecFilter
     1.此為編解碼過(guò)濾器,用來(lái)編碼為二進(jìn)制數(shù)據(jù)或者將特定協(xié)議的數(shù)據(jù)解碼成消息對(duì)象.

     2.其覆寫了messageReceived:
          1.一個(gè)while循環(huán),直到buffer沒有數(shù)據(jù).while(in.hasRemaining)
          2.循環(huán)內(nèi)業(yè)務(wù)為調(diào)用decoder.decode方法進(jìn)行解碼
          3.調(diào)用decoderOut.flush完成解碼->{@link ProtocolDecoderOutputImpl #flush}->調(diào)用nextFilter.messageReceived,即繼續(xù)在過(guò)濾鏈進(jìn)行forward>>>>>>

     3.其覆寫了filterWrite
          1.調(diào)用encoder.encoder進(jìn)行編碼
          2.調(diào)用nextFilter.filterWrite,即繼續(xù)沿著過(guò)濾鏈進(jìn)行<<<<<<forward

8.總結(jié)
    mina的內(nèi)部采用filer_chain模式進(jìn)行消息的流轉(zhuǎn)(雙向)處理

    以讀寫消息來(lái)簡(jiǎn)單的說(shuō)明一下filter_chain過(guò)程:

       1.processor...binary_msg-->>HeadFilter#messageReceived-->>....-->>XXXFilter#messageReceived...-->>TailFilter#messageReceived-->>調(diào)用IoHandler#messageReceived
 在HeadFilter和TailFilter之間自定義過(guò)濾器,如firewall,log,decoder等

      2.procotol_msg-->>TailFilter#filterWrite-->>....-->>XXXFilter#FilterWrite....-->>HeaderFilter-->>由processor處理write
 在TailFilter和HeadFiler之間可自定義過(guò)濾器,如encoder等.