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[EN]中文

write a middleware

Middleware based on request body（ http.Request ）And return body（ http.Response ）Because both structures contain buf, such as the body of request and response body.

Therefore, in order to prevent superlcx read body, so that the client or server can't receive the real request body or response body, we need to do some operations.

The standard middleware stdout of the example write follows:

func handleRequest(over chan bool, req *http.Request) {
	content, err := httputil.DumpRequest(req, true)
	over <- true
	if err != nil {
		panic(err)
	}
...

The request body(if exists) will be read out by httputil.DumpRequest, and a copy of the request body will be assign to origin req. If we write a middleware by ourselves, we should do the same.

If you can't handle the body in the request and response well, you may have serious consequences:

  • Body is empty, which can cause EOF error during reading.
  • The body has been closed, panic when you read it.

In order to prevent the program from crashing for these reasons, it is recommended to write the middleware in the following way.

content, err := httputil.DumpRequest(req, true)
newReq, err := http.ReadRequest(bufio.NewReader(bytes.NewReader(content)))

In this way, it can completely avoid the influence of req request body and send it to the server to receive the reply.

Built-in middleware documentation

stdout

The middleware simply dumps a copy of the request and response to stdout as a sample template.

c_header

This middleware can add or modify headers in requests and returns based on configuration files, you can Edit config.toml to get what you want by referring to Configuration Description.

# c_header config
[CustomHeaders]
    [CustomHeaders.req1] # start with req -> means adding or modifying the request header
    Key="X-REAL-IP"
    Value="111.111.111.111"

    [CustomHeaders.resp1] # start with resp -> means adding or modifying the response header
    Key="Server"
    Value="ASP.NET"

sub_filter

The middleware is the same as the sub_filter function in NGINX. For the specified path (regular matching is supported), the response value of a specified path request will be modified referring to configration.

[SubFilter]
    [SubFilter.test] # name is temporarily useless
    Old="</head>" # original text
    Repl='<script src="/js/jquery.min.js"></script></head>' # what will be replace if matched
    Path="/" # specific url（Support for regular expressions）

js_lua

Using interpreted languages to conservatively extend functionality is another alternative for frequent updates. The program USES the following two libraries to implement invoke of Lua and Js.

"github.com/robertkrimen/otto"
"github.com/yuin/gopher-lua"

Configuration is as follows

Middleware = "js_lua"
LuaPath="./middlewares/js_lua/sub_custom.lua"
JsPath="./middlewares/js_lua/sub_custom.js"

This two scripts will be added as middleware only when LuaPath and JsPath are not empty and middleware js_lua was added.