lua中使用json：table转json与json转table

直接上代码：

json.lua

------------------------------------------------------------------------------- JSON4Lua: JSON encoding / decoding support for the Lua language.-- json Module.-- Author: Craig Mason-Jones-- Homepage: http://json.luaforge.net/-- Version: 0.9.40-- This module is released under the MIT License (MIT).-- Please see LICENCE.txt for details.---- USAGE:-- This module exposes two functions:--   encode(o)--     Returns the table / string / boolean / number / nil / json.null value as a JSON-encoded string.--   decode(json_string)--     Returns a Lua object populated with the data encoded in the JSON string json_string.---- REQUIREMENTS:--   compat-5.1 if using Lua 5.0---- CHANGELOG--   0.9.20 Introduction of local Lua functions for private functions (removed _ function prefix). --          Fixed Lua 5.1 compatibility issues.--   Introduced json.null to have null values in associative arrays.--          encode() performance improvement (more than 50%) through table.concat rather than ..--          Introduced decode ability to ignore /**/ comments in the JSON string.--   0.9.10 Fix to array encoding / decoding to correctly manage nil/null values in arrays.------------------------------------------------------------------------------------------------------------------------------------------------------------ Imports and dependencies-----------------------------------------------------------------------------local math = require('math')local string = require("string")local table = require("table")local base = _G------------------------------------------------------------------------------- Module declaration-----------------------------------------------------------------------------module("json")-- Public functions-- Private functionslocal decode_scanArraylocal decode_scanCommentlocal decode_scanConstantlocal decode_scanNumberlocal decode_scanObjectlocal decode_scanStringlocal decode_scanWhitespacelocal encodeStringlocal isArraylocal isEncodable------------------------------------------------------------------------------- PUBLIC FUNCTIONS-------------------------------------------------------------------------------- Encodes an arbitrary Lua object / variable.-- @param v The Lua object / variable to be JSON encoded.-- @return String containing the JSON encoding in internal Lua string format (i.e. not unicode)function encode (v)  -- Handle nil values  if v==nil then    return "null"  end    local vtype = base.type(v)    -- Handle strings  if vtype=='string' then        return '"' .. encodeString(v) .. '"'    -- Need to handle encoding in string  end    -- Handle booleans  if vtype=='number' or vtype=='boolean' then    return base.tostring(v)  end    -- Handle tables  if vtype=='table' then    local rval = {}    -- Consider arrays separately    local bArray, maxCount = isArray(v)    if bArray then      for i = 1,maxCount do        table.insert(rval, encode(v[i]))      end    else-- An object, not an array      for i,j in base.pairs(v) do        if isEncodable(i) and isEncodable(j) then          table.insert(rval, '"' .. encodeString(i) .. '":' .. encode(j))        end      end    end    if bArray then      return '[' .. table.concat(rval,',') ..']'    else      return '{' .. table.concat(rval,',') .. '}'    end  end    -- Handle null values  if vtype=='function' and v==null then    return 'null'  end    base.assert(false,'encode attempt to encode unsupported type ' .. vtype .. ':' .. base.tostring(v))end--- Decodes a JSON string and returns the decoded value as a Lua data structure / value.-- @param s The string to scan.-- @param [startPos] Optional starting position where the JSON string is located. Defaults to 1.-- @param Lua object, number The object that was scanned, as a Lua table / string / number / boolean or nil,-- and the position of the first character after-- the scanned JSON object.function decode(s, startPos)  startPos = startPos and startPos or 1  startPos = decode_scanWhitespace(s,startPos)  base.assert(startPos<=string.len(s), 'Unterminated JSON encoded object found at position in [' .. s .. ']')  local curChar = string.sub(s,startPos,startPos)  -- Object  if curChar=='{' then    return decode_scanObject(s,startPos)  end  -- Array  if curChar=='[' then    return decode_scanArray(s,startPos)  end  -- Number  if string.find("+-0123456789.e", curChar, 1, true) then    return decode_scanNumber(s,startPos)  end  -- String  if curChar==[["]] or curChar==[[']] then    return decode_scanString(s,startPos)  end  if string.sub(s,startPos,startPos+1)=='/*' then    return decode(s, decode_scanComment(s,startPos))  end  -- Otherwise, it must be a constant  return decode_scanConstant(s,startPos)end--- The null function allows one to specify a null value in an associative array (which is otherwise-- discarded if you set the value with 'nil' in Lua. Simply set t = { first=json.null }function null()  return null -- so json.null() will also return null ;-)end------------------------------------------------------------------------------- Internal, PRIVATE functions.-- Following a Python-like convention, I have prefixed all these 'PRIVATE'-- functions with an underscore.-------------------------------------------------------------------------------- Scans an array from JSON into a Lua object-- startPos begins at the start of the array.-- Returns the array and the next starting position-- @param s The string being scanned.-- @param startPos The starting position for the scan.-- @return table, int The scanned array as a table, and the position of the next character to scan.function decode_scanArray(s,startPos)  local array = {}-- The return value  local stringLen = string.len(s)  base.assert(string.sub(s,startPos,startPos)=='[','decode_scanArray called but array does not start at position ' .. startPos .. ' in string:\n'..s )  startPos = startPos + 1  -- Infinite loop for array elements  repeat    startPos = decode_scanWhitespace(s,startPos)    base.assert(startPos<=stringLen,'JSON String ended unexpectedly scanning array.')    local curChar = string.sub(s,startPos,startPos)    if (curChar==']') then      return array, startPos+1    end    if (curChar==',') then      startPos = decode_scanWhitespace(s,startPos+1)    end    base.assert(startPos<=stringLen, 'JSON String ended unexpectedly scanning array.')    object, startPos = decode(s,startPos)    table.insert(array,object)  until falseend--- Scans a comment and discards the comment.-- Returns the position of the next character following the comment.-- @param string s The JSON string to scan.-- @param int startPos The starting position of the commentfunction decode_scanComment(s, startPos)  base.assert( string.sub(s,startPos,startPos+1)=='/*', "decode_scanComment called but comment does not start at position " .. startPos)  local endPos = string.find(s,'*/',startPos+2)  base.assert(endPos~=nil, "Unterminated comment in string at " .. startPos)  return endPos+2  end--- Scans for given constants: true, false or null-- Returns the appropriate Lua type, and the position of the next character to read.-- @param s The string being scanned.-- @param startPos The position in the string at which to start scanning.-- @return object, int The object (true, false or nil) and the position at which the next character should be -- scanned.function decode_scanConstant(s, startPos)  local consts = { ["true"] = true, ["false"] = false, ["null"] = nil }  local constNames = {"true","false","null"}  for i,k in base.pairs(constNames) do    --print ("[" .. string.sub(s,startPos, startPos + string.len(k) -1) .."]", k)    if string.sub(s,startPos, startPos + string.len(k) -1 )==k then      return consts[k], startPos + string.len(k)    end  end  base.assert(nil, 'Failed to scan constant from string ' .. s .. ' at starting position ' .. startPos)end--- Scans a number from the JSON encoded string.-- (in fact, also is able to scan numeric +- eqns, which is not-- in the JSON spec.)-- Returns the number, and the position of the next character-- after the number.-- @param s The string being scanned.-- @param startPos The position at which to start scanning.-- @return number, int The extracted number and the position of the next character to scan.function decode_scanNumber(s,startPos)  local endPos = startPos+1  local stringLen = string.len(s)  local acceptableChars = "+-0123456789.e"  while (string.find(acceptableChars, string.sub(s,endPos,endPos), 1, true)and endPos<=stringLen) do    endPos = endPos + 1  end  local stringValue = 'return ' .. string.sub(s,startPos, endPos-1)  local stringEval = base.loadstring(stringValue)  base.assert(stringEval, 'Failed to scan number [ ' .. stringValue .. '] in JSON string at position ' .. startPos .. ' : ' .. endPos)  return stringEval(), endPosend--- Scans a JSON object into a Lua object.-- startPos begins at the start of the object.-- Returns the object and the next starting position.-- @param s The string being scanned.-- @param startPos The starting position of the scan.-- @return table, int The scanned object as a table and the position of the next character to scan.function decode_scanObject(s,startPos)  local object = {}  local stringLen = string.len(s)  local key, value  base.assert(string.sub(s,startPos,startPos)=='{','decode_scanObject called but object does not start at position ' .. startPos .. ' in string:\n' .. s)  startPos = startPos + 1  repeat    startPos = decode_scanWhitespace(s,startPos)    base.assert(startPos<=stringLen, 'JSON string ended unexpectedly while scanning object.')    local curChar = string.sub(s,startPos,startPos)    if (curChar=='}') then      return object,startPos+1    end    if (curChar==',') then      startPos = decode_scanWhitespace(s,startPos+1)    end    base.assert(startPos<=stringLen, 'JSON string ended unexpectedly scanning object.')    -- Scan the key    key, startPos = decode(s,startPos)    base.assert(startPos<=stringLen, 'JSON string ended unexpectedly searching for value of key ' .. key)    startPos = decode_scanWhitespace(s,startPos)    base.assert(startPos<=stringLen, 'JSON string ended unexpectedly searching for value of key ' .. key)    base.assert(string.sub(s,startPos,startPos)==':','JSON object key-value assignment mal-formed at ' .. startPos)    startPos = decode_scanWhitespace(s,startPos+1)    base.assert(startPos<=stringLen, 'JSON string ended unexpectedly searching for value of key ' .. key)    value, startPos = decode(s,startPos)    object[key]=value  until false-- infinite loop while key-value pairs are foundend-- START SoniEx2-- Initialize some things used by decode_scanString-- You know, for efficiencylocal escapeSequences = {  ["\\t"] = "\t",  ["\\f"] = "\f",  ["\\r"] = "\r",  ["\\n"] = "\n",  ["\\b"] = "\b"}base.setmetatable(escapeSequences, {__index = function(t,k)  -- skip "\" aka strip escape  return string.sub(k,2)end})-- END SoniEx2--- Scans a JSON string from the opening inverted comma or single quote to the-- end of the string.-- Returns the string extracted as a Lua string,-- and the position of the next non-string character-- (after the closing inverted comma or single quote).-- @param s The string being scanned.-- @param startPos The starting position of the scan.-- @return string, int The extracted string as a Lua string, and the next character to parse.function decode_scanString(s,startPos)  base.assert(startPos, 'decode_scanString(..) called without start position')  local startChar = string.sub(s,startPos,startPos)  -- START SoniEx2  -- PS: I don't think single quotes are valid JSON  base.assert(startChar == [["]] or startChar == [[']],'decode_scanString called for a non-string')  --base.assert(startPos, "String decoding failed: missing closing " .. startChar .. " for string at position " .. oldStart)  local t = {}  local i,j = startPos,startPos  while string.find(s, startChar, j+1) ~= j+1 do    local oldj = j    i,j = string.find(s, "\\.", j+1)    local x,y = string.find(s, startChar, oldj+1)    if not i or x < i then      base.print(s, startPos, string.sub(s,startPos,oldj))      i,j = x,y-1      if not x then base.print(s, startPos, string.sub(s,startPos,oldj)) end    end    table.insert(t, string.sub(s, oldj+1, i-1))    if string.sub(s, i, j) == "\\u" then      local a = string.sub(s,j+1,j+4)      j = j + 4      local n = base.tonumber(a, 16)      base.assert(n, "String decoding failed: bad Unicode escape " .. a .. " at position " .. i .. " : " .. j)      -- math.floor(x/2^y) == lazy right shift      -- a % 2^b == bitwise_and(a, (2^b)-1)      -- 64 = 2^6      -- 4096 = 2^12 (or 2^6 * 2^6)      local x      if n < 0x80 then        x = string.char(n % 0x80)      elseif n < 0x800 then        -- [110x xxxx] [10xx xxxx]        x = string.char(0xC0 + (math.floor(n/64) % 0x20), 0x80 + (n % 0x40))      else        -- [1110 xxxx] [10xx xxxx] [10xx xxxx]        x = string.char(0xE0 + (math.floor(n/4096) % 0x10), 0x80 + (math.floor(n/64) % 0x40), 0x80 + (n % 0x40))      end      table.insert(t, x)    else      table.insert(t, escapeSequences[string.sub(s, i, j)])    end  end  table.insert(t,string.sub(j, j+1))  base.assert(string.find(s, startChar, j+1), "String decoding failed: missing closing " .. startChar .. " at position " .. j .. "(for string at position " .. startPos .. ")")  return table.concat(t,""), j+2  -- END SoniEx2end--- Scans a JSON string skipping all whitespace from the current start position.-- Returns the position of the first non-whitespace character, or nil if the whole end of string is reached.-- @param s The string being scanned-- @param startPos The starting position where we should begin removing whitespace.-- @return int The first position where non-whitespace was encountered, or string.len(s)+1 if the end of string-- was reached.function decode_scanWhitespace(s,startPos)  local whitespace=" \n\r\t"  local stringLen = string.len(s)  while ( string.find(whitespace, string.sub(s,startPos,startPos), 1, true)  and startPos <= stringLen) do    startPos = startPos + 1  end  return startPosend--- Encodes a string to be JSON-compatible.-- This just involves back-quoting inverted commas, back-quotes and newlines, I think ;-)-- @param s The string to return as a JSON encoded (i.e. backquoted string)-- @return The string appropriately escaped.local escapeList = {    ['"']  = '\\"',    ['\\'] = '\\\\',    ['/']  = '\\/',     ['\b'] = '\\b',    ['\f'] = '\\f',    ['\n'] = '\\n',    ['\r'] = '\\r',    ['\t'] = '\\t'}function encodeString(s) return s:gsub(".", function(c) return escapeList[c] end) -- SoniEx2: 5.0 compatend-- Determines whether the given Lua type is an array or a table / dictionary.-- We consider any table an array if it has indexes 1..n for its n items, and no-- other data in the table.-- I think this method is currently a little 'flaky', but can't think of a good way around it yet...-- @param t The table to evaluate as an array-- @return boolean, number True if the table can be represented as an array, false otherwise. If true,-- the second returned value is the maximum-- number of indexed elements in the array. function isArray(t)  -- Next we count all the elements, ensuring that any non-indexed elements are not-encodable   -- (with the possible exception of 'n')  local maxIndex = 0  for k,v in base.pairs(t) do    if (base.type(k)=='number' and math.floor(k)==k and 1<=k) then-- k,v is an indexed pair      if (not isEncodable(v)) then return false end-- All array elements must be encodable      maxIndex = math.max(maxIndex,k)    else      if (k=='n') then        if v ~= table.getn(t) then return false end  -- False if n does not hold the number of elements      else -- Else of (k=='n')        if isEncodable(v) then return false end      end  -- End of (k~='n')    end -- End of k,v not an indexed pair  end  -- End of loop across all pairs  return true, maxIndexend--- Determines whether the given Lua object / table / variable can be JSON encoded. The only-- types that are JSON encodable are: string, boolean, number, nil, table and json.null.-- In this implementation, all other types are ignored.-- @param o The object to examine.-- @return boolean True if the object should be JSON encoded, false if it should be ignored.function isEncodable(o)  local t = base.type(o)  return (t=='string' or t=='boolean' or t=='number' or t=='nil' or t=='table') or (t=='function' and o==null) end

测试代码：

--[[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)      --table转jsonprint('JSON encoded test is: ' .. jsonTest)-- Now JSON decode the json stringresult = json.decode(jsonTest)   --json转tableprint ("The decoded table result:")table.foreach(result,print)print ("The decoded table result.three")table.foreach(result.three, print)

代码参考：https://github.com/craigmj/json4lua