英文:
HandleFunc being called twice
问题
我正在使用Go语言遵循一个简单的Web服务器示例。
我插入了一个log语句，所以最终的代码如下所示：
package mainimport ("io""log""net/http")func hello(w http.ResponseWriter, r *http.Request) {io.WriteString(w, "Hello world!")log.Println("hello.")}func main() {mux := http.NewServeMux()mux.HandleFunc("/", hello)http.ListenAndServe(":8000", mux)}
问题是，每当我在Web浏览器中加载端口8000时，这个函数会被调用两次。这是一个问题，因为我打算在每次访问页面时递增一个计数器。由于这种行为，计数器会被递增两次。另一方面，如果我使用curl localhost:8000命令，它只会被调用一次。
我觉得我在这里漏掉了一些非常愚蠢的东西。
英文:
I am following a simple web server example in Go.
I inserted a log statement so that the resulting code looks like below:
package mainimport ("io""log""net/http")func hello(w http.ResponseWriter, r *http.Request) {io.WriteString(w, "Hello world!")log.Println("hello.")}func main() {mux := http.NewServeMux()mux.HandleFunc("/", hello)http.ListenAndServe(":8000", mux)}
Problem is that whenever I load port 8000 in my web browser, this function is called twice. This is an issue because I intend to increment a counter on each page visit. With this behavior, counter gets incremented twice. OTOH, if I do curl localhost:8000, it is called only once.
I feel it's something really silly that I am missing here.
答案1
得分: 41
只需记录请求即可。您会发现您的浏览器也会请求 /favicon.ico。
有关更多信息，请参阅 https://en.wikipedia.org/wiki/Favicon。
英文:
Just log the requests. You will realize that your browser also requests /favicon.ico.
See https://en.wikipedia.org/wiki/Favicon for more information.
答案2
得分: 21
如果您是从服务中发出请求，那么没问题，但如果您是从浏览器进行测试，并且不是为了生产意图，您可以在Golang代码中执行以下操作以避免浏览器加载favicon：
http.HandleFunc("/favicon.ico", doNothing)func doNothing(w http.ResponseWriter, r *http.Request){}
对于投票给负面的人：这是有效的，抱歉在不需要favicon或其他内容的API中使用这段代码...
英文:
If you request from a service is fine, but if you test from a browser and is not the production intention you can do this in golang code for avoid browser load the favicon:
http.HandleFunc("/favicon.ico", doNothing)
And the function
func doNothing(w http.ResponseWriter, r *http.Request){}
For people voting negatives: this works, sorry for handle it with this code in an api that doesn't need favicon or whatever...
答案3
得分: 3
根据Didier的说法，这是你的浏览器尝试加载网站图标。你可以通过将以下代码添加到标签中来阻止这种情况发生：
<link rel="icon" type="image/png" href="data:image/png;base64,iVBORw0KGgo=">
英文:
As Didier says, it's your browser trying to load the favicon. You can prevent this by adding this code to the <head>:
<link rel="icon" type="image/png" href="data:image/png;base64,iVBORw0KGgo=">
答案4
得分: 3
根据Didier Spezia所说，"/"是一个子树路径的示例（因为它以斜杠结尾）。另一个示例可能是"/static/"。当请求的URL路径的开头与子树路径匹配时，子树路径模式将被匹配（并调用相应的处理程序）。如果有助于你的理解，你可以将子树路径视为在末尾有一个通配符，类似于"/**"或"/static/**"。这解释了为什么"/"模式充当了一个捕获所有的作用。该模式实际上意味着匹配一个斜杠，后面跟着任何内容（或根本没有内容）。
为了防止这种情况发生，只需在你的hello处理程序中添加一个检查，如下所示：
func hello(w http.ResponseWriter, r *http.Request) {if r.URL.Path != "/" {http.NotFound(w, r)return}io.WriteString(w, "Hello world!")log.Println("hello.")}
英文:
Building on what Didier Spezia said,
"/" is an example of a subtree path (because it ends in a trailing
slash). Another example would be something like "/static/". Subtree path patterns are
matched (and the corresponding handler called) whenever the start of a request URL path
matches the subtree path. If it helps your understanding, you can think of subtree paths as
acting a bit like they have a wildcard at the end, like "/**" or "/static/**" .
This helps explain why the "/" pattern is acting as a catch-all. The pattern essentially
means match a single slash, followed by anything (or nothing at all).
To prevent that from happening,
just add a check in your hello handler like so
func hello(w http.ResponseWriter, r *http.Request) {if r.URL.Path != "/" {http.NotFound(w, r)return}io.WriteString(w, "Hello world!")log.Println("hello.")}
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