Erlang 聊天室程序(3) 数据交换格式-json的decode

Erlang 聊天室程序(三) 数据交换格式---json的decode

霸哥的blog中提到过Erlang服务器在通信中与客户端的数据交换方式：yufeng

为了简单起见这个聊天室程序采用json，要使用到rfc4627这个库

先定义一个Message类：

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public class Message {String id; //消息IDString type; //消息类型String from; //发送方String to; //接收方String subject; //主题String content; //内容Date creationDate; //时间public Message(String type,String from,String to,String subject,String content){this.id =MessageIdGenerator.nextId();this.type=type;this.from=from;this.to=to;this.subject=subject;this.content=content;this.creationDate=new Date();}public String getId() {return id;}public void setId(String id) {this.id = id;}public String getType() {return type;}public void setType(String type) {this.type = type;}public String getFrom() {return from;}public void setFrom(String from) {this.from = from;}public String getTo() {return to;}public void setTo(String to) {this.to = to;}public String getSubject() {return subject;}public void setSubject(String subject) {this.subject = subject;}public String getContent() {return content;}public void setContent(String content) {this.content = content;}public Date getCreationDate() {return creationDate;}public void setCreationDate(Date creationDate) {this.creationDate = creationDate;}} 再定义一个JSON的工具类：

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public class JSONParaser {public static JSONObject getJSON(Object content){try{JSONObject result = JSONObject.fromObject(content);return result;}catch(Exception ex){return null;}}public static Object getString(String json){try{JSONObject jobj=JSONObject.fromObject(json);return JSONObject.toBean(jobj);}catch(Exception ex){return null;}}} 再修改SOCKET 发送部分代码：

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public void sendMsg(Message msg){try {String data=(JSONParaser.getJSON(msg)).toString();oust.write(data.getBytes());oust.flush();} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}} 测试下发送后服务器端接收到的数据：

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client_session dwmsg recived {message,undefined,msg, [6], undefined,undefined, <<"{"content":"aaaaa","creationDate":{"date":27,"day":1,"hours":13,"minutes":10,"month":1,"seconds":26,"time":1330319426281,"timezoneOffset":-480,"year":112},"from":"client1","id":"x8yL-2","subject":"chat","to":"","type":"msg"}">>, undefined}client_session dwmsg sended

服务器端新建一个模块util_MessageParas，将收到的json数据转成内部可识的message：

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%% Author: Administrator%% Created: 2012-2-27%% Description: TODO: Add description to util_MessageParas-module(util_MessageParas).%%%% Include files%%%%-include("json.hrl").-include("message.hrl").%%%% Exported Functions%%<<"{"content":"aaa","creationDate":{"date":27,"day":1,"hours":18,"minutes":8,"month":1,"seconds":26,"time":1330337306984,"timezoneOffset":-480,"year":112},"from":"client1","id":"289n-2","subject":"chat","to":"","type":"msg"}">>-export([paraseDecode/1]).%%%% API Functions%%%%%% Local Functions%%%paras json data to messageparaseDecode(Bin)->case rfc4627:decode(Bin) of{ok,Obj,_Re}->paraElements(Obj);{error,Reason}->{error,Reason}end.%we get elements from decoded json,%it has to be 7 elementsparaElements(Obj)->{obj,List}=Obj,Data =#message{},%catch exception heretry paraEle(List,Data)catch{error,Reason,NewData}->io:format("Format"),{error,Reason,NewData}end.paraEle([Ele|Els],Data)->NewData=para(Ele,Data),paraEle(Els,NewData);paraEle([],Data)->Data.%length of content should not more than 1000para({"content",Val},Data) when is_binary(Val)->io:format("para content:~p~n",[Data]),Content=binary_to_list(Val),if length(Content)<1000 -> NewData=Data#message{content=Content}, io:format("paraed content:~p~n",[NewData]), NewData; true -> throw({error,"illegal Content value",Data})end;para({"to",Val},Data) when is_binary(Val)->io:format("para to:~p~n",[Data]),To =binary_to_list(Val),NewData=Data#message{to=To};para({"id",Val},Data) when is_binary(Val)->io:format("para id:~p~n",[Data]),Id=binary_to_list(Val),NewData=Data#message{id=Id};para({"subject",Val},Data) when is_binary(Val)->io:format("para subject:~p~n",[Data]),Sub=binary_to_list(Val),%we should validate subject here if Sub=:="chat" -> NewData=Data#message{subject=Sub}; true -> %throw exception throw({error,"illegal subject value",Data})end;para({"type",Val},Data) when is_binary(Val)->io:format("para type:~p~n",[Data]),Type = binary_to_list(Val),if Type=:="msg"-> NewData=Data#message{type=Type}; true -> %throw exception throw({error,"illegal type value",Data})end;para({"from",Val},Data) when is_binary(Val)->io:format("para from:~p~n",[Data]),From=binary_to_list(Val),NewData=Data#message{from=From};para({"creationDate",Val},Data)->Data;para({Key,Val},Data)->%no mache %throw exceptionthrow({error,"unkown element",Data}).paraseEncode()->ok.
做下测试：

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util_MessageParas:paraseDecode(<<"{"content":"aaa","creationDate":{"date":27,"day":1,"hours":18,"minutes":8,"month":1,"seconds":26,"time":1330337306984,"timezoneOffset":-480,"year":112},"from":"client1","id":"289n-2","subject":"chat","to":"","type":"msg"}">>).para content:{message,undefined,undefined,undefined,undefined,undefined, undefined,undefined}paraed content:{message,undefined,undefined,undefined,undefined,undefined, "aaa",undefined}para from:{message,undefined,undefined,undefined,undefined,undefined,"aaa", undefined}para id:{message,undefined,undefined,"client1",undefined,undefined,"aaa", undefined}para subject:{message,"289n-2",undefined,"client1",undefined,undefined,"aaa", undefined}para to:{message,"289n-2",undefined,"client1",undefined,"chat","aaa", undefined}para type:{message,"289n-2",undefined,"client1",[],"chat","aaa",undefined}{message,"289n-2","msg","client1",[],"chat","aaa",undefined}
OK，收到的数据可以正常地解析为message了。

注：

在此处只需要将json数据的外层转换为message消息。message消息针对不同的类型和作用会有不同的json内容，所以内层数据应该在具体的消息处理部分再调用相应的paras处理。

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