如何优雅地或有效地将地图写入http.ResponseWriter

Question

I was wondering what would be the most elegant way to write a Key Value Form encoded map to a http.ResponseWriter.

Respond(kv map[string]string) {
  for key, value := range kv {
    fmt.Fprintf(a.w, "%s:%s
", key, value)
  }  
}

I have to follow this Key-Value format:

Key-Value Form Encoding

A message in Key-Value form is a sequence of lines. Each line begins with a key, followed by a colon, and the value associated with the key. The line is terminated by a single newline (UCS codepoint 10, " "). A key or value MUST NOT contain a newline and a key also MUST NOT contain a colon.

Additional characters, including whitespace, MUST NOT be added before or after the colon or newline. The message MUST be encoded in UTF-8 to produce a byte string.

I thought about using encoding/csv but isn't that a bit overkill?

Edit: What I came up with so far. (Thanks for all the suggested answers)

http://godoc.org/github.com/kugutsumen/encoding/keyvalue

https://github.com/kugutsumen/encoding/tree/master/keyvalue

Answer 1

If you want to write strings to any Writer in Go (including an http.ResponseWriter) without using the fmt package, you can use the bytes package to read the strings and write them to the Writer.

The code below creates a Buffer from the key and value strings using bytes.NewBufferString and then writes them to the http.ResponseWriter using the WriteTo function.

package main

import (
    "bytes"
    "log"
    "net/http"
)

func main() {
    kv := map[string]string{"key1": "val1", "key2": "val2", "key3": "val3", "key4": "val4", "key5": "val5"}
    http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
        for key, value := range kv {
            kvw := bytes.NewBufferString(key + ":" + value + "
")
            if _, err := kvw.WriteTo(w); err != nil {
                log.Fatal("Error: ", err)
            }
        }
    })
    if err := http.ListenAndServe("localhost:8080", nil); err != nil {
        log.Fatal("ListenAndServe: ", err)
    }
}

Will output:

key1:val1
key2:val2
key3:val3
key4:val4
key5:val5

Hopefully that's close to what you're after.

EDIT: You can also use the strings.Reader Type and the corresponding WriteTo function from the strings package.