由 dawei 副标题#e#
参考 http://www.cnblogs.com/yjl49/archive/2011/09/02/2371964.html
1.客户端连接服务器后，发送消息给服务器的xml数据处理在ejabberd_c2s中。
?? ejabberd_c2s 是一个gen_fsm 状态机，在socket连接建立之后创建。
?? 初始状态为 wait_for_stream，接受形为 {xmlstreamstart,_Name,Attrs} 的消息，其他任何消息都会导致stop。
?? 接受到连接请求，发送feature 请求后状态改为wait_for_feature_request 。
?? 接受到feature 再发送challenge 后，状态改为 wait_for_sasl_response。
?? 经过sasl鉴权后，状态改为 wait_for_stream， 此时 StateData#state.authenticated 已经不为false。
?? 客户端重新发起<stream> 连接请求，服务器发送bind 消息，状态改为 wait_for_bind 。
?? 客户端发送bind 与资源绑定，服务器按照策略验证是否允许相同的用户用不同的资源连接，通过后状态改为 wait_for_session。
?? 客户端发送<iq> 消息创建session，服务器调用 ejabberd_sm:open_session 后将状态改为 session_established。
?? 客户端发送普通的通信消息<iq>，<presence>，<message> 等，都通过session_established2/2 函数处理。
- %%?Process?packets?sent?by?user?(coming?from?user?on?c2s?XMPP??
- %%?connection)??
- session_established2(El,?StateData)?->??
- ??
- ????%%从变量El中取出Name,Attrs?两个参数,El必须是一个以xmlelement?为第一个元子的元组??
- ????{xmlelement,?Name,?Attrs,?_Els}?=?El,??
- ????%%从StateDate中取出user,server,jid???
- ????User?=?StateData#state.user,??
- ????Server?=?StateData#state.server,??
- ????FromJID?=?StateData#state.jid,??
- ??
- ????%%从Attrs属性变量中获取to(也就是发送给谁)??
- ????To?=?xml:get_attr_s("to",?Attrs),??
- ???????
- ????%%将To转换成一个标准的JID:??
- ????%%#jid{user,resource,luser,lserver,lresource},具体参见jlib.erl中的定义??
- ????ToJID?=?case?To?of??
- ????????""?->??
- ????????????jlib:make_jid(User,?Server,?"");??
- ????????_?->??
- ????????????jlib:string_to_jid(To)??
- ????????end,??
- ??
- ????%%这里的El里的Attrs应该是一个元组组成的列表[{key1,value1},{key2,value2},{key3,value3},{key4,value4}.....]??
- ????%%下面的语句会从Attrs中删除key?为xmlns的元组，并返回新的El存放到NewEl1中??
- ????NewEl1?=?jlib:remove_attr("xmlns",?El),??
- ????NewEl?=?case?xml:get_attr_s("xml:lang",?Attrs)?of??
- ????????""?->??
- ????????????case?StateData#state.lang?of??
- ????????????""?->?NewEl1;??
- ????????????Lang?->??
- ????????????????xml:replace_tag_attr("xml:lang",?Lang,?NewEl1)??
- ????????????end;??
- ????????_?->??
- ????????????NewEl1??
- ????????end,??
- ??
- ????%%这里根据消息类型进行不同的处理??
- ????NewState?=??
- ????case?ToJID?of??
- ????????error?->??
- ????????case?xml:get_attr_s("type",?Attrs)?of??
- ????????????"error"?->?StateData;??
- ????????????"result"?->?StateData;??
- ????????????_?->??
- ????????????Err?=?jlib:make_error_reply(NewEl,??ERR_JID_MALFORMED),??
- ????????????send_element(StateData,?Err),??
- ????????????StateData??
- ????????end;??
- ????????_?->??
- ????????case?Name?of??
- ????????????"presence"?->??
- ????????????????????????%%如果为一个presence?消息,使用函数回调c2s_updatepresence参见2??
- ????????????????PresenceEl?=?ejabberd_hooks:run_fold(??
- ???????????????????????c2s_update_presence,??
- ???????????????????????Server,??
- ???????????????????????NewEl,??
- ???????????????????????[User,?Server]),??
- ?????????????????
- ??????????????????????????%%将调用结果发送回客户端??
- ??????????????????????????ejabberd_hooks:run(??
- ??????????????user_send_packet,??
- ??????????????Server,??
- ??????????????[FromJID,?ToJID,?PresenceEl]),??
- ????????????case?ToJID?of??
- ????????????????#jid{user?=?User,??
- ?????????????????server?=?Server,??
- ?????????????????resource?=?""}?->??
- ?????????????????DEBUG("presence_update(~p,~n\t~p,~n\t~p)",??
- ???????????????????????[FromJID,?PresenceEl,?StateData]),??
- ????????????????presence_update(FromJID,??
- ????????????????????????StateData);??
- ????????????????_?->??
- ????????????????presence_track(FromJID,??
- ???????????????????????????StateData)??
- ????????????end;??
- ????????????"iq"?->??
- ??????????????????????????%%iq?消息的处理.注册,添加好友等都是通过iq消息来发送的??
- ??????????????????????????case?jlib:iq_query_info(NewEl)?of??
- ????????????????#iq{xmlns?=?Xmlns}?=?IQ??
- ????????????????when?Xmlns?==??NS_PRIVACY;??
- ?????????????????Xmlns?==??NS_BLOCKING?->??
- ????????????????process_privacy_iq(??
- ??????????????????FromJID,?IQ,?StateData);??
- ????????????????_?->??
- ????????????????ejabberd_hooks:run(??
- ??????????????????user_send_packet,??
- ??????????????????Server,??
- ??????????????????[FromJID,?NewEl]),??
- ????????????????check_privacy_route(FromJID,?StateData,?FromJID,?NewEl),??
- ????????????????StateData??
- ????????????end;??
- ????????????"message"?->??
- ????????????????????????io:format("message?arrvied~n",[]),??
- ????????????ejabberd_hooks:run(user_send_packet,??
- ???????????????????????[FromJID,??
- ????????????check_privacy_route(FromJID,??
- ????????????????????????ToJID,??
- ????????????StateData;??
- ????????????_?->??
- ????????????StateData??
- ????????end??
- ????end,??
- ????ejabberd_hooks:run(c2s_loop_debug,?[{xmlstreamelement,?El}]),??
- ????fsm_next_state(session_established,?NewState).??
#p#副标题#e##p#分页标题#e#
2.下面是比较关键的ejabberd中函数调用的分析:
- ?????????????run_fold(Hook,?Host,?Val,?Args)?->??
- ??????????????????case?ets:lookup(hooks,?{Hook,?Host})?of??
- ?????????????????????????[{_,?Ls}]?->run_fold1(Ls,?Hook,?Args);??
- ?????????????????????????[]?->Val??
- ??????????????????end.??
- e="code"?class="plain">PresenceEl?=?ejabberd_hooks:run_fold(??
- c2s_update_presence,??
- Server,??
- NewEl,??
- [User,?Server])??
在系统的ets库(内存中的一个数据库)中存有一个名为hooks的表,通过ets:lookup(hooks,{Hook,Host}) 可以找到一个 {_,Ls}的元组 (找不到就直接返回预定义的Val了),然后调用run_fold1(Ls,Hook,Val,Args).
Ls变量实际上是一个包含多个要具体调用的函数定义的列表,列表里面的元组分为两类:[{_Seq,Node,Moudle,Function} | Ls2]? [{_Seq,Module,Function} | Ls2],
run_fold1/4 的作用就是使用Args参数依次调用这个Ls列表里的方法.
run_fold1/4 最终会返回调用的结果出来.
所以从最终结果来看 ejabberd_hooks:run_fold/4? 方法就是去表hooks查找并调用所需的函数返回调用结果.
- PresenceEl?=?ejabberd_hooks:run_fold(??
- ???????????????????????c2s_update_presence,??
- ???????????????????????Server,??
- ???????????????????????NewEl,??
- ???????????????????????[User,?Server])??
针对上面的代码就是:
??????? 使用{c2s_update_presence,Server}作为key 在表hooks 中查找 要调用的方法列表,并使用[User,Server] 作为参数进行调用.
这个key具体找到什么样的方法呢? 我们可以在源码中查找下:
- root@ubuntu:??grep?*.erl?-e?c2s_update_presence??
查找结果中可以看到
mod_vcard_xupdate.erl?????????????? ejabberd_hooks:add(c2s_update_presence,Host
我们在mod_vcard_xupdate.erl中找到这段代码:
- start(Host,?_Opts)?->??
- ????mnesia:create_table(vcard_xupdate,??
- ????????????????????????[{disc_copies,?[node()]},??
- ?????????????????????????{attributes,?record_info(fields,?vcard_xupdate)}]),??
- ????ejabberd_hooks:add(c2s_update_presence,??
- ????????????????MODULE,?update_presence,?100),??
- ????ejabberd_hooks:add(vcard_set,?vcard_set,??
- ????ok.??
update_presence就所我们所要找的方法了.