# 15.5 确保网页应用健壮 当网页应用的处理函数发生 panic,服务器会简单地终止运行。这可不妙:网页服务器必须是足够健壮的程序,能够承受任何可能的突发问题。 首先能想到的是在每个处理函数中使用 `defer/recover`,不过这样会产生太多的重复代码。[13.5节](13.5.md) 使用闭包的错误处理模式是更优雅的方案。我们把这种机制应用到前一章的简单网页服务器上。实际上,它可以被简单地应用到任何网页服务器程序中。 为增强代码可读性,我们为页面处理函数创建一个类型: ```go type HandleFnc func(http.ResponseWriter, *http.Request) ``` 我们的错误处理函数应用了[13.5节](13.5.md) 的模式,成为 `logPanics` 函数: ```go func logPanics(function HandleFnc) HandleFnc { return func(writer http.ResponseWriter, request *http.Request) { defer func() { if x := recover(); x != nil { log.Printf("[%v] caught panic: %v", request.RemoteAddr, x) } }() function(writer, request) } } ``` 然后我们用 `logPanics` 来包装对处理函数的调用: ```go http.HandleFunc("/test1", logPanics(SimpleServer)) http.HandleFunc("/test2", logPanics(FormServer)) ``` 处理函数现在可以恢复 panic 调用,类似[13.5节](13.5.md) 中的错误检测函数。完整代码如下: 示例 15.11 [robust_webserver.go](examples/chapter_15/robust_webserver.go) ```go package main import ( "io" "log" "net/http" ) const form = `
` type HandleFnc func(http.ResponseWriter, *http.Request) /* handle a simple get request */ func SimpleServer(w http.ResponseWriter, request *http.Request) { io.WriteString(w, "

hello, world

") } /* handle a form, both the GET which displays the form and the POST which processes it.*/ func FormServer(w http.ResponseWriter, request *http.Request) { w.Header().Set("Content-Type", "text/html") switch request.Method { case "GET": /* display the form to the user */ io.WriteString(w, form) case "POST": /* handle the form data, note that ParseForm must be called before we can extract form data*/ //request.ParseForm(); //io.WriteString(w, request.Form["in"][0]) io.WriteString(w, request.FormValue("in")) } } func main() { http.HandleFunc("/test1", logPanics(SimpleServer)) http.HandleFunc("/test2", logPanics(FormServer)) if err := http.ListenAndServe(":8088", nil); err != nil { panic(err) } } func logPanics(function HandleFnc) HandleFnc { return func(writer http.ResponseWriter, request *http.Request) { defer func() { if x := recover(); x != nil { log.Printf("[%v] caught panic: %v", request.RemoteAddr, x) } }() function(writer, request) } } ``` ## 链接 - [目录](directory.md) - 上一节:[写一个简单的网页应用](15.4.md) - 下一节:[用模板编写网页应用](15.6.md)