Lua JSONRPC學習筆記

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JSON RPC

　　JSON RPC 為利用json資料格式來執行遠程調用方式，

作用同xmlrpc，不過與xmlrpc相比， jsonrpc更加輕量，json更加節省資料量，更加可讀性高。

 

官網網站：

http://www.json-rpc.org/

JSONRPC協議規範：

http://www.json-rpc.org/wiki/specification

 

lua實現的jsonrpc項目：

https://github.com/craigmj/json4lua

http://json.luaforge.net/

 

JSON

JSON為一種字串方式資料群組織的格式，以便於傳輸， 其文法同JAVASCRIPT對象寫法（JS Object Notation）。

官網：

http://www.json.org/ 

lua實現的json項目：

https://github.com/craigmj/json4lua

 

LUA JSON 編解碼

下載 json lua實現程式碼封裝， 解壓後，將json檔案夾放到lua path下，即lua安裝目錄下。

下載網址：

https://github.com/craigmj/json4lua

 

其中example檔案夾下有示範代碼 example.lua, 示範了如何將 一個 lua table編碼為JSON字串， 又如何將此字串，恢複為LUA table。

--[[JSON4Lua example script.Demonstrates the simple functionality of the json module.]]--json = require(‘json‘)-- Object to JSON encodetest = {  one=‘first‘,two=‘second‘,three={2,3,5}}jsonTest = json.encode(test)print(‘JSON encoded test is: ‘ .. jsonTest)-- Now JSON decode the json stringresult = json.decode(jsonTest)print ("The decoded table result:")table.foreach(result,print)print ("The decoded table result.three")table.foreach(result.three, print)

 

 

LUA JSON RPC

lua json的下載安裝包，已經包括 json rpc的實現， 只需要從example中測試 jsonrpc的 用戶端和 伺服器端例子即可。

 用戶端依賴 luasocket 來發起http請求。

 伺服器端代碼經過改造， 宿主與xavante， 有串連到來時， 觸發執行。

 

用戶端：

require ("json.rpc")result, error = json.rpc.call("http://localhost:12345","echo","Test echo!")print("echo call="..result)print("\n\n")result, error = json.rpc.call("http://localhost:12345","average", 1, 3)print("average="..result.average)

 

 

伺服器端代碼：

xavante = require("xavante")wsapi = require("wsapi")wsapi.xavante = require("wsapi.xavante")wsapi.request = require("wsapi.request")require (‘json‘)-- The Lua class that is to serve JSON RPC requestslocal myServer = {  echo = function (msg) return msg end,  average = function(...)    local total=0    local count=0    for i=1, table.getn(arg) do      total = total + arg[i]      count = count + 1    end    return { average= total/count, sum = total, n=count }  end}
-- JSON RPC 伺服器端處理主體程式local function serve(luaClass, packReturn, req)  local postData =  req.POST.post_data    -- SAPI.Request.getpostdata()  --[[{ "id":1, "method":"echo","params":["Hi there"]}]]  --  -- @TODO Catch an error condition on decoding the data  local jsonRequest = json.decode(postData)  local jsonResponse = {}  jsonResponse.id = jsonRequest.id  local method = luaClass[ jsonRequest.method ]  if not method then    jsonResponse.error = ‘Method ‘ .. jsonRequest.method .. ‘ does not exist at this server.‘  else    local callResult = { pcall( method, unpack( jsonRequest.params ) ) }    if callResult[1] then    -- Function call successfull      table.remove(callResult,1)      if packReturn and table.getn(callResult)>1 then        jsonResponse.result = callResult      else        jsonResponse.result = unpack(callResult)    -- NB: Does not support multiple argument returns      end    else      jsonResponse.error = callResult[2]    end  end     -- Output the result  -- TODO: How to be sure that the result and error tags are there even when they are nil in Lua?  -- Can force them by hand... ?  return json.encode( jsonResponse ) end---  WSAPI handler-- @param wsapi_env WSAPI environmentfunction wsapi_handler(wsapi_env)   local headers = { ["Content-type"] = "text/plain" }   local req = wsapi.request.new(wsapi_env)   local r = serve(myServer, nil, req)   print("r="..r)   headers["Content-length"] = tostring(#r)   local function xmlrpc_reply(wsapienv)      coroutine.yield(r)   end   return 200, headers, coroutine.wrap(xmlrpc_reply)endlocal rules = {{ match = ".", with = wsapi.xavante.makeHandler(wsapi_handler) }}local config = { server = {host = "*", port = 12345}, defaultHost = { rules = rules} }xavante.HTTP(config)xavante.start()

 

 

代碼實現了， 用戶端和服務通過JSONRPC調用，實現 echo 和 做平均計算的例子。