OpenResty(Lua)笔记总结一

json 解析的异常捕获

local cjson = require "cjson"

local json_str = [[{"name":"ybl}]]

local tab = cjson.decode(json_str)

ngx.say(type(tab))

代码执行错误日志如下：

2016/12/11 11:51:58 [error] 8364#0: *2810371 lua entry thread aborted: runtime error: /web/lua/cc2_demo.lua:167: Expected value but found unexpected end of string at character 14

stack traceback:

coroutine 0:

[C]: in function 'decode'

/web/lua/cc2_demo.lua:167: in function , client: 127.0.0.1, server: localhost, request: "GET /demo HTTP/1.1", host: "127.0.0.1"

如果需要在Lua中处理错误，必须使用函数pcall（protected call）来包装需要执行的代码。pcall接收一个函数和要传递给后者的参数，并执行，执行结果：有错误、无错误；返回值true或者或false, errorinfo。pcall以一种"保护模式"来调用第一个参数，因此pcall可以捕获函数执行中的任何错误。

所以改良一下代码如下

function json_decode( str )

local cjson = require "cjson"

local json_value = nil

pcall(function (str) json_value = cjson.decode(str) end, str)

return json_value

end

local json_str_1 = [[{"name":"ybl}]]

local json_str_2 = [[{"name":"ybl"}]]

local tab1 = json_decode(json_str_1)

local tab2 = json_decode(json_str_2)

ngx.say(type(tab1))

ngx.say(type(tab2))

运行结果：nil 和 table

Lua 中 pairs 和 ipairs 的区别

这个新手很容易犯的错，标准库提供了集中迭代器，包括迭代文件每行的(io.lines)，迭代table元素的(pairs)，迭代数组元素的(ipairs)，迭代字符串中单词的，由于在 lua 内部实际采用哈希表保存键值对、数组保存普通值，table和数组还是有区别的，简单这样理解吧，哈希表是key value类型的，数组是索引数组，所以在lua中

pairs 可以迭代索引数组和哈希类型的数组

ipairs 可以迭代索引数组，哈希类型的数组不行

首先他们两个效率非常高，比for,while等高很多；ipairs比pairs效率还要高

举例：

local arr_1 = {1,2,3,4,5,6,7,8,9,0}

local arr_2 = {name = "ybl" , age = 22 , sex = "男" , likes = "篮球，跑步，健身"}

local arr_3 = { first="red", "blue", third="green", "yellow"}

针对arr_1，pairs和ipairs都可以迭代，推荐ipairs

针对arr_2，pairs迭代，ipairs空值

针对arr_3，pairs迭代，ipairs空值

非空判断

这里的ken狠多，用如下封装的方法就可以，如果你想了解更多，可查看OpenResty最佳实践

function isTableEmpty(t)

if t == nil or next(t) == nil then

return true

else

return false

end

end

lua获取GET 和 POST参数

function getpost()

local args = {}

local request_method = ngx.var.request_method

if "GET" == request_method then

args = ngx.req.get_uri_args()

elseif "POST" == ngx.req.get_method() then

ngx.req.read_body()

args = ngx.req.get_post_args()

end

return args

end

lua获取请求 body-适合获取http请求post和get参数【推荐】

ngx.req.get_body_data() 读请求体，会偶尔出现读取不到直接返回 nil 的情况。

所以得事先调用ngx.req.read_body(),强制本模块读取请求体

ngx.req.read_body()

local json_str = ngx.req.get_body_data()

--如果是json，则可以转化为table等等。。。

lua发起http get和post请求

function http_post(url,table_par)

local http = require "http"

local httpc = http.new()

local res, err = httpc:request_uri(url,{

method = 'POST',

body = cjson.encode(table_par),

headers = {["Content-Type"] = "application/x-www-form-urlencoded",}

})

if not res then

return 100

end

return res.body

end

function comm_fun:http_get(url,table_par)

local http = require "http"

local httpc = http:new()

local res, err = httpc:request_uri(url, {

method = "GET",

query = table_par,

--ssl_verify = false, -- 需要关闭这项才能发起https请求

headers = {["Content-Type"] = "application/x-www-form-urlencoded" },

})

if not res then

return 100

end

return res.body

end

Lua获取请求者的ip，浏览器，系统等信息

function getBrowser()

local user_agent = ngx.req.raw_header()

local browser = "others"

if ngx.re.match(user_agent,"Chrome") then

browser = "Chrome"

elseif ngx.re.match(user_agent,"Firefox") then

browser = "Firefox"

elseif ngx.re.match(user_agent,"QQBrowser") then

browser = "QQBrowser"

elseif ngx.re.match(user_agent,"Safari") then

browser = "Safari"

elseif ngx.re.match(user_agent,"Opera") then

browser = "Opera"

elseif ngx.re.match(user_agent,"MSIE 11.0") or ngx.re.match(user_agent,"rv:11.0") then

browser = "IE 11.0"

elseif ngx.re.match(user_agent,"MSIE 10.0") or ngx.re.match(user_agent,"rv:10.0") then

browser = "IE 10.0"

elseif ngx.re.match(user_agent,"MSIE 9.0") or ngx.re.match(user_agent,"rv:9.0") then

browser = "IE 9.0"

elseif ngx.re.match(user_agent,"MSIE 8.0") or ngx.re.match(user_agent,"rv:8.0") then

browser = "IE 8.0"

elseif ngx.re.match(user_agent,"MSIE 7.0") or ngx.re.match(user_agent,"rv:7.0") then

browser = "IE 7.0"

elseif ngx.re.match(user_agent,"MSIE 6.0") or ngx.re.match(user_agent,"rv:6.0") then

browser = "IE 6.0"

else

browser = "others"

end

return browser

end

function getSystem()

local user_agent = ngx.req.raw_header()

local system = "others"

if ngx.re.match(user_agent,"Mac OS") then

system = "Mac OS"

elseif ngx.re.match(user_agent,"Mac") then

system = "Macintosh"

elseif ngx.re.match(user_agent,"Windows NT 10.0") then

system = "Windows 10"

elseif ngx.re.match(user_agent,"Windows NT 6.2") then

system = "Windows 8"

elseif ngx.re.match(user_agent,"Windows NT 6.1") then

system = "Windows 7"

elseif ngx.re.match(user_agent,"Windows NT 6.0") then

system = "Windows Vista"

elseif ngx.re.match(user_agent,"Windows NT 5.1") then

system = "Windows XP"

elseif ngx.re.match(user_agent,"Windows NT 5.0") then

system = "Windows 2000"

elseif ngx.re.match(user_agent,"linux") then

system = "Linux"

elseif ngx.re.match(user_agent,"unix") then

system = "Unix"

elseif ngx.re.match(user_agent,"FreeBSD") then

system = "FreeBSD"

elseif ngx.re.match(user_agent,"IRIX") then

system = "IRIX"

elseif ngx.re.match(user_agent,"OSF1") then

system = "OSF1"

elseif ngx.re.match(user_agent,"BSD") then

system = "BSD"

elseif ngx.re.match(user_agent,"NetBSD") then

system = "NetBSD"

elseif ngx.re.match(user_agent,"HPUX") then

system = "HPUX"

elseif ngx.re.match(user_agent,"AIX") then

system = "AIX"

elseif ngx.re.match(user_agent,"PowerPC") then

system = "PowerPC"

elseif ngx.re.match(user_agent,"sun") then

system = "SUN"

elseif ngx.re.match(user_agent,"ibm") then

system = "IBM"

end

return system

end

function getIP()

return ngx.var.remote_addr

end

通过FFI的方式加载其他C接口动态库来获取系统

local ffi = require("ffi")

if ffi.os == "Windows" then

ngx.say("windows")

elseif ffi.os == "OSX" then

ngx.say("MAC OS X")

else

ngx.say(ffi.os)

end