语法: ngx.exec(uri, args?)
环境: rewrite_by_lua, access_by_lua*, content_by_lua**
使用 uri、args 参数执行一个内部跳转，与 echo-nginx-module 的 echo_exec 指令有些相似。
ngx.exec('/some-location');
ngx.exec('/some-location', 'a=3&b=5&c=6');
ngx.exec('/some-location?a=3&b=5', 'c=6');可选第二个参数 args 可被用来指名额外的 URI 查询参数，例如：
ngx.exec("/foo", "a=3&b=hello%20world")另外，对于 args 参数可使用一个 Lua 表，内部通过 ngx_lua 完成 URI 转义和字符串的连接。
ngx.exec("/foo", { a = 3, b = "hello world" })该结果和上一个示例是一样的。
作为 args 参数的 Lua 表格式化结果，与使用 ngx.encode_args 方法格式化结果是相同的。
命名 location 也是支持的，但是第二个 args 参数将被忽略（如果存在的话），并且对新目标地址的查询字符串会从引用 location （如果有）中继承。
下面的例子中， GET /foo/file.php?a=hello 将返回 "hello" ，而不是 "goodbye" ：
location /foo {
content_by_lua '
ngx.exec("@bar", "a=goodbye");
';
}
location @bar {
content_by_lua '
local args = ngx.req.get_uri_args()
for key, val in pairs(args) do
if key == "a" then
ngx.say(val)
end
end
';
}注意，ngx.exec 方法与 ngx.redirect 是完全不同的，前者是个纯粹的内部跳转并且没有引入任何额外 HTTP 信号。
注意，此方法的调用终止当前请求的处理，并且它 必须 在 ngx.send_headers 或明确有响应体应答（比如 ngx.print 或 ngx.say 之一）之前调用。
该方法调用与 return 语句联合使用，是推荐的代码样式，例如，通过return ngx.redirect(...)，可使用在 header_filter_by_lua 之外的环境中加强处理该请求被终止。
English source:
syntax: ngx.exec(uri, args?)
context: rewrite_by_lua, access_by_lua*, content_by_lua**
Does an internal redirect to uri with args and is similar to the echo_exec directive of the echo-nginx-module.
ngx.exec('/some-location');
ngx.exec('/some-location', 'a=3&b=5&c=6');
ngx.exec('/some-location?a=3&b=5', 'c=6');The optional second args can be used to specify extra URI query arguments, for example:
ngx.exec("/foo", "a=3&b=hello%20world")Alternatively, a Lua table can be passed for the args argument for ngx_lua to carry out URI escaping and string concatenation.
ngx.exec("/foo", { a = 3, b = "hello world" })The result is exactly the same as the previous example.
The format for the Lua table passed as the args argument is identical to the format used in the ngx.encode_args method.
Named locations are also supported but the second args argument will be ignored if present and the querystring for the new target is inherited from the referring location (if any).
GET /foo/file.php?a=hello will return "hello" and not "goodbye" in the example below
location /foo {
content_by_lua '
ngx.exec("@bar", "a=goodbye");
';
}
location @bar {
content_by_lua '
local args = ngx.req.get_uri_args()
for key, val in pairs(args) do
if key == "a" then
ngx.say(val)
end
end
';
}Note that the ngx.exec method is different from ngx.redirect in that
it is purely an internal redirect and that no new external HTTP traffic is involved.
Also note that this method call terminates the processing of the current request and that it must be called before ngx.send_headers or explicit response body outputs by either ngx.print or ngx.say.
It is recommended that a coding style that combines this method call with the return statement, i.e., return ngx.exec(...) be adopted when this method call is used in contexts other than header_filter_by_lua to reinforce the fact that the request processing is being terminated.