问题
I am making a streaming API which handles both RPC style calls as well as notifications from the server to the client (not the notifications in the JSON-RPC spec which are client to server). This last part unfortunately rules out JSON-RPC + persistent HTTP.
The API is based on the JSON and JSON-RPC specs.
JSON - http://www.ietf.org/rfc/rfc4627.txt
JSON-RPC - http://www.jsonrpc.org/specification
Typical session might be:
-> Sending to server
<- Receiving from server
-> {'id': 0, 'method':'login','params':{'token':'secret'}}
<- {'id': 0, 'method':'login','result':0}
-> {'id': 1, 'method':'subscribe','params':{'symbol':'VOD.L'}}
<- {'id': 1, 'method':'subscribe','result':0}
...
<- {'method':'notifyPrice','params':{'symbol':'VOD.L', 'bid':10.1, 'ask':10.03}}
<- {'method':'notifyPrice','params':{'symbol':'VOD.L', 'bid':10.2, 'ask':10.03}}
The above messages, particularly the notifications, could come in any order and in the same packet. Neither of the specs seem to include details of a message separator which makes it difficult to know when an entire JSON message has been received without using a SAX based JSON parser, which are rather rare compared to their DOM counterparts.
Am I missing something obvious, or is there genuinely no standard way to separate between multiple JSON messages coming in over the wire?
回答1:
You are missing something :-)
Each JSON-RPC message is a valid JSON value. A JSON value can by any of:
- an
Array - an
Object - a
String - a
Number
The JSON-RPC envelope is an Object.
If this were a raw socket (like Telnet), then...
Objects start with { and end with }.
If you're using the right kind of parser (pull, or event-oriented) at your receiver then it doesn't matter how nested the Objects and Arrays get, you'll still know when you hit that last }.
The above messages, particularly the notifications, could come in any order and in the same packet.
As long as the requests are not interlaved (one finishes before the next starts), then there's no problem at all. It's up to you whether you also require newline termination of the envelope (a.k.a line-oriented protocol).
However, as you're dealing with HTTP...
Why not just use batch messages per the JSON-RPC spec?
来源：https://stackoverflow.com/questions/24471689/reading-multiple-json-objects-on-a-json-rpc-connection