英文:
Go HTTP will not set header for SVG
问题
我正在生成一个SVG（它将在一个单独的浏览器窗口中加载，检测到头部错误时），将内容类型设置为"image/svg+xml"，然后写入SVG，但是当它发送到浏览器时，它以text/xml的形式显示。
我首先写入头部（这是这个问题的问题所在），在几个小时内毫无目的地移动代码后，我已经没有任何想法了。
这是我的代码：
const circlesize = 2.5// http.HandleFunc("/rendermap.svg", rendermapw)func rendermapw(w http.ResponseWriter, r *http.Request) {if r.Method != "GET" {w.WriteHeader(405)return}fmt.Println("Received request " + r.URL.String())var mapstring string// 已经渲染过if mapcache.valid {mapstring = mapcache.cache} else {// 获取模板contentb, err := ioutil.ReadFile("src/maptemplate.svg")if err != nil {fmt.Println("Error with request:", r)fmt.Println(err)w.WriteHeader(500)return}content := strings.Split(string(contentb), "<!--template-->")// 从数据库中获取数据alldata := *pullall()mapstring = content[0] // 头部for _, e := range alldata {newcircle := content[1]// 将uint64转换为字符串（将uint16转换为int64）newcircle = strings.Replace(newcircle, "{ulat}", strconv.FormatInt(int64(e.Ulat), 10), 1)newcircle = strings.Replace(newcircle, "{ulon}", strconv.FormatInt(180-int64(e.Ulon), 10), 1)newcircle = strings.Replace(newcircle, "{size}", strconv.FormatFloat(circlesize, 'f', 4, 64), 1)mapstring += newcircle}mapstring += content[2]// 保存缓存并发送mapcache = mapcached{valid: true,cache: mapstring,}}// 上面的所有代码都是有效的，我只是为了完整性而贴出来w.WriteHeader(200)w.Header().Set("content-type", "image/svg+xml")_, err := fmt.Fprint(w, mapstring) // 我也尝试过 w.Write([]byte(mapstring))if err != nil {fmt.Println("Error with request:", r)fmt.Println(err)w.WriteHeader(500)return}}
这是发送到浏览器的内容：
Content-Type: text/xml; charset=utf-8
maptemplate.svg的内容如下：
<?xml version="1.0" encoding="utf-8"?><!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd"><svg xmlns="http://www.w3.org/2000/svg" version="1.1" viewBox="0 0 360 180" fill-rule="evenodd" stroke-linejoin="round" stroke-miterlimit="2" fill="#0098ff"><!--template--><circle cx="{ulat}" cy="{ulon}" r="{size}" fill-opacity=".5"/><!--template--></svg>
如果我删除"<?xml version..."这一行，浏览器将收到text/plain类型的内容。
英文:
I'm generating an SVG (that will load in a separate browser window where it detects that the header is wrong), setting the content-type to "image/svg+xml", then writing the SVG, but when it is sent to the browser, it comes out as text/xml.
I'm writing the header first (which was the problem in this issue) and I'm out of ideas after moving stuff around aimlessly for a few hours.
Here is my code:
const circlesize = 2.5// http.HandleFunc("/rendermap.svg", rendermapw)func rendermapw(w http.ResponseWriter, r *http.Request) {if r.Method != "GET" {w.WriteHeader(405)return}fmt.Println("Received request " + r.URL.String())var mapstring string// already renderedif mapcache.valid {mapstring = mapcache.cache} else {// get templatecontentb, err := ioutil.ReadFile("src/maptemplate.svg")if err != nil {fmt.Println("Error with request:", r)fmt.Println(err)w.WriteHeader(500)return}content := strings.Split(string(contentb), "<!--template-->")// pull from databasealldata := *pullall()mapstring = content[0] // headerfor _, e := range alldata {newcircle := content[1]// string from uint64 (int64 from uint16)newcircle = strings.Replace(newcircle, "{ulat}", strconv.FormatInt(int64(e.Ulat), 10), 1)newcircle = strings.Replace(newcircle, "{ulon}", strconv.FormatInt(180-int64(e.Ulon), 10), 1)newcircle = strings.Replace(newcircle, "{size}", strconv.FormatFloat(circlesize, 'f', 4, 64), 1)mapstring += newcircle}mapstring += content[2]// save cache & sendmapcache = mapcached{valid: true,cache: mapstring,}}// everything above this works, I'm just posting it for completion's sakew.WriteHeader(200)w.Header().Set("content-type", "image/svg+xml")_, err := fmt.Fprint(w, mapstring) // I also tried w.Write([]byte(mapstring))if err != nil {fmt.Println("Error with request:", r)fmt.Println(err)w.WriteHeader(500)return}}
This is what gets sent to the browser:
Content-Type: text/xml; charset=utf-8
Here is maptemplate.svg looks like:
<?xml version="1.0" encoding="utf-8"?><!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd"><svg xmlns="http://www.w3.org/2000/svg" version="1.1" viewBox="0 0 360 180" fill-rule="evenodd" stroke-linejoin="round" stroke-miterlimit="2" fill="#0098ff"><!--template--><circle cx="{ulat}" cy="{ulon}" r="{size}" fill-opacity=".5"/><!--template--></svg>
If I remove the "<?xml version..." line, the browser gets sent text/plain.
答案1
得分: 1
我已经修复了。在w.WriteHeader(200)之前，你必须添加w.Header().Set("content-type", "image/svg+xml")。
修复后的代码：
// ...w.Header().Set("content-type", "image/svg+xml")w.WriteHeader(200)_, err := fmt.Fprint(w, mapstring)if err != nil {fmt.Println("请求错误：", r)fmt.Println(err)w.WriteHeader(500)return}
英文:
I fixed it. You have to have w.Header().Set("content-type", "image/svg+xml") before w.WriteHeader(200).
Working code:
// ...w.Header().Set("content-type", "image/svg+xml")w.WriteHeader(200)_, err := fmt.Fprint(w, mapstring)if err != nil {fmt.Println("Error with request:", r)fmt.Println(err)w.WriteHeader(500)return}
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