问题内容
我需要请求、处理数据并将其格式化为 csv，然后根据请求通过 web 服务发送它们。
假设请求和处理的数据位于下面的 data 中，我设法使用中间临时文件来做到这一点：
package main
import (
"encoding/csv"
"io/ioutil"
"net/http"
"os"
"strconv"
"github.com/go-chi/chi/v5"
)
type data struct {
name string
age int
}
func main() {
data := []data{
{"john", 30},
{"jane", 20},
}
tempfilename := "temp.csv"
// create temporary intermediate file
file, err := os.create(tempfilename)
defer file.close()
if err != nil {
panic(err)
}
w := csv.newwriter(file)
var csvdata [][]string
for _, record := range data {
row := []string{record.name, strconv.itoa(record.age)}
csvdata = append(csvdata, row)
}
w.writeall(csvdata)
// read temporary intermediate file to send it via http
filebytes, err := ioutil.readfile(tempfilename)
if err != nil {
panic(err)
}
// send the file on request
router := chi.newrouter()
router.get("/data", func(w http.responsewriter, r *http.request) {
w.header().set("content-type", "application/octet-stream")
w.writeheader(http.statusok)
w.write(filebytes)
})
http.listenandserve(":8087", router)
}
请求成功：
PS C:\temp> wget http://localhost:8087/data --2023-06-13 15:34:00-- http://localhost:8087/data Resolving localhost (localhost)... ::1, 127.0.0.1 Connecting to localhost (localhost)|::1|:8087... connected. HTTP request sent, awaiting response... 200 OK Length: 16 [application/octet-stream] Saving to: 'data' data 100%[=================================================>] 16 --.-KB/s in 0s 2023-06-13 15:34:00 (523 KB/s) - 'data' saved [16/16] PS C:\temp> cat data John,30 Jane,20
到目前为止一切顺利 - 现在我想通过
删除中间文件- 使用内存“容器”来写入 csv 数据
- 将其内容以字节形式写入 http 编写器
我还是不太明白如何使用io.*和bufio.*来登陆所需的类型：
-
csv.newwriter()需要*os.file并返回*csv.writer - 这个
*csv.writer内容需要以某种方式提取为byte... - ...为了提供
http.responsewriter.write()
解决不同类型的内存文件操作问题的一般机制（以及特定于本例的机制）是什么？
正确答案
csv.newwriter 采用 io.writer，因此您可以将 http.responsewriter 的实例传递给它，而无需将内容写入文件或内存。
这是演示：
package main
import (
"encoding/csv"
"fmt"
"net/http"
"strconv"
"github.com/go-chi/chi/v5"
)
type Data struct {
Name string
Age int
}
func main() {
router := chi.NewRouter()
router.Get("/data", func(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Content-Type", "application/octet-stream")
w.WriteHeader(http.StatusOK)
data := []Data{
{"John", 30},
{"Jane", 20},
}
csvWriter := csv.NewWriter(w)
var csvData [][]string
for _, record := range data {
row := []string{record.Name, strconv.Itoa(record.Age)}
csvData = append(csvData, row)
}
if err := csvWriter.WriteAll(csvData); err != nil {
// handle the error
fmt.Println(err)
}
})
http.ListenAndServe(":8087", router)
}
