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2023-06-26 17:30:52 +00:00
< ol class = "chapter" > < li class = "chapter-item expanded affix " > < a href = "../index.html" > Go语言圣经< / a > < / li > < li class = "chapter-item expanded affix " > < a href = "../preface-zh.html" > 译者序< / a > < / li > < li class = "chapter-item expanded affix " > < a href = "../preface.html" > 前言< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch1/ch1.html" > < strong aria-hidden = "true" > 1.< / strong > 入门< / a > < / li > < li > < ol class = "section" > < li class = "chapter-item expanded " > < a href = "../ch1/ch1-01.html" > < strong aria-hidden = "true" > 1.1.< / strong > Hello, World< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch1/ch1-02.html" > < strong aria-hidden = "true" > 1.2.< / strong > 命令行参数< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch1/ch1-03.html" > < strong aria-hidden = "true" > 1.3.< / strong > 查找重复的行< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch1/ch1-04.html" > < strong aria-hidden = "true" > 1.4.< / strong > GIF动画< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch1/ch1-05.html" > < strong aria-hidden = "true" > 1.5.< / strong > 获取URL< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch1/ch1-06.html" > < strong aria-hidden = "true" > 1.6.< / strong > 并发获取多个URL< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch1/ch1-07.html" class = "active" > < strong aria-hidden = "true" > 1.7.< / strong > Web服务< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch1/ch1-08.html" > < strong aria-hidden = "true" > 1.8.< / strong > 本章要点< / a > < / li > < / ol > < / li > < li class = "chapter-item expanded " > < a href = "../ch2/ch2.html" > < strong aria-hidden = "true" > 2.< / strong > 程序结构< / a > < / li > < li > < ol class = "section" > < li class = "chapter-item expanded " > < a href = "../ch2/ch2-01.html" > < strong aria-hidden = "true" > 2.1.< / strong > 命名< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch2/ch2-02.html" > < strong aria-hidden = "true" > 2.2.< / strong > 声明< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch2/ch2-03.html" > < strong aria-hidden = "true" > 2.3.< / strong > 变量< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch2/ch2-04.html" > < strong aria-hidden = "true" > 2.4.< / strong > 赋值< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch2/ch2-05.html" > < strong aria-hidden = "true" > 2.5.< / strong > 类型< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch2/ch2-06.html" > < strong aria-hidden = "true" > 2.6.< / strong > 包和文件< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch2/ch2-07.html" > < strong aria-hidden = "true" > 2.7.< / strong > 作用域< / a > < / li > < / ol > < / li > < li class = "chapter-item expanded " > < a href = "../ch3/ch3.html" > < strong aria-hidden = "true" > 3.< / strong > 基础数据类型< / a > < / li > < li > < ol class = "section" > < li class = "chapter-item expanded " > < a href = "../ch3/ch3-01.html" > < strong aria-hidden = "true" > 3.1.< / strong > 整型< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch3/ch3-02.html" > < strong aria-hidden = "true" > 3.2.< / strong > 浮点数< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch3/ch3-03.html" > < strong aria-hidden = "true" > 3.3.< / strong > 复数< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch3/ch3-04.html" > < strong aria-hidden = "true" > 3.4.< / strong > 布尔型< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch3/ch3-05.html" > < strong aria-hidden = "true" > 3.5.< / strong > 字符串< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch3/ch3-06.html" > < strong aria-hidden = "true" > 3.6.< / strong > 常量< / a > < / li > < / ol > < / li > < li class = "chapter-item expanded " > < a href = "../ch4/ch4.html" > < strong aria-hidden = "true" > 4.< / strong > 复合数据类型< / a > < / li > < li > < ol class = "section" > < li class = "chapter-item expanded " > < a href = "../ch4/ch4-01.html" > < strong aria-hidden = "true" > 4.1.< / strong > 数组< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch4/ch4-02.html" > < strong aria-hidden = "true" > 4.2.< / strong > Slice< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch4/ch4-03.html" > < strong aria-hidden = "true" > 4.3.< / strong > Map< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch4/ch4-04.html" > < strong aria-hidden = "true" > 4.4.< / strong > 结构体< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch4/ch4-05.html" > < strong aria-hidden = "true" > 4.5.<
2022-08-04 06:59:33 +00:00
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2023-06-26 17:46:27 +00:00
< li > < em > 凹语言(专为 WebAssembly 设计): < a href = "https://github.com/wa-lang/wa" > https://github.com/wa-lang/wa< / a > < / em > < / li >
< li > < em > KCL 配置语言(Rust): < a href = "https://github.com/kcl-lang/kcl" > https://github.com/kcl-lang/kcl< / a > < / em > < / li >
< / ul >
2022-08-04 06:59:33 +00:00
< hr >
< h2 id = "17-web服务" > < a class = "header" href = "#17-web服务" > 1.7. Web服务< / a > < / h2 >
< p > Go语言的内置库使得写一个类似fetch的web服务器变得异常地简单。在本节中， ， ， " hello" 。< / p >
< p > < u > < i > gopl.io/ch1/server1< / i > < / u > < / p >
< pre > < code class = "language-go" > // Server1 is a minimal " echo" server.
package main
import (
" fmt"
" log"
" net/http"
)
func main() {
http.HandleFunc(" /" , handler) // each request calls handler
log.Fatal(http.ListenAndServe(" localhost:8000" , nil))
}
// handler echoes the Path component of the request URL r.
func handler(w http.ResponseWriter, r *http.Request) {
fmt.Fprintf(w, " URL.Path = %q\n" , r.URL.Path)
}
< / code > < / pre >
< p > 我们只用了八九行代码就实现了一个Web服务程序， ， ， ， ， ， ， ， ， < / p >
< p > 让我们在后台运行这个服务程序。如果你的操作系统是Mac OS X或者Linux， & 符号， ， < / p >
< pre > < code > $ go run src/gopl.io/ch1/server1/main.go &
< / code > < / pre >
< p > 现在可以通过命令行来发送客户端请求了：< / p >
< pre > < code > $ go build gopl.io/ch1/fetch
$ ./fetch http://localhost:8000
URL.Path = " /"
$ ./fetch http://localhost:8000/help
URL.Path = " /help"
< / code > < / pre >
< p > 还可以直接在浏览器里访问这个URL， ， ： < / p >
< p > < img src = "../images/ch1-02.png" alt = "" / > < / p >
< p > 在这个服务的基础上叠加特性是很容易的。一种比较实用的修改是为访问的url添加某种状态。比如， ， ； ， < / p >
< p > < u > < i > gopl.io/ch1/server2< / i > < / u > < / p >
< pre > < code class = "language-go" > // Server2 is a minimal " echo" and counter server.
package main
import (
" fmt"
" log"
" net/http"
" sync"
)
var mu sync.Mutex
var count int
func main() {
http.HandleFunc(" /" , handler)
http.HandleFunc(" /count" , counter)
log.Fatal(http.ListenAndServe(" localhost:8000" , nil))
}
// handler echoes the Path component of the requested URL.
func handler(w http.ResponseWriter, r *http.Request) {
mu.Lock()
count++
mu.Unlock()
fmt.Fprintf(w, " URL.Path = %q\n" , r.URL.Path)
}
// counter echoes the number of calls so far.
func counter(w http.ResponseWriter, r *http.Request) {
mu.Lock()
fmt.Fprintf(w, " Count %d\n" , count)
mu.Unlock()
}
< / code > < / pre >
< p > 这个服务器有两个请求处理函数， ： ， ， ， ， ， ， ； ： （ ） ， ， < / p >
< p > 下面是一个更为丰富的例子， ， ： < / p >
< p > < u > < i > gopl.io/ch1/server3< / i > < / u > < / p >
< pre > < code class = "language-go" > // handler echoes the HTTP request.
func handler(w http.ResponseWriter, r *http.Request) {
fmt.Fprintf(w, " %s %s %s\n" , r.Method, r.URL, r.Proto)
for k, v := range r.Header {
fmt.Fprintf(w, " Header[%q] = %q\n" , k, v)
}
fmt.Fprintf(w, " Host = %q\n" , r.Host)
fmt.Fprintf(w, " RemoteAddr = %q\n" , r.RemoteAddr)
if err := r.ParseForm(); err != nil {
log.Print(err)
}
for k, v := range r.Form {
fmt.Fprintf(w, " Form[%q] = %q\n" , k, v)
}
}
< / code > < / pre >
< p > 我们用http.Request这个struct里的字段来输出下面这样的内容： < / p >
< pre > < code > GET /?q=query HTTP/1.1
Header[" Accept-Encoding" ] = [" gzip, deflate, sdch" ]
Header[" Accept-Language" ] = [" en-US,en;q=0.8" ]
Header[" Connection" ] = [" keep-alive" ]
Header[" Accept" ] = [" text/html,application/xhtml+xml,application/xml;..." ]
Header[" User-Agent" ] = [" Mozilla/5.0 (Macintosh; Intel Mac OS X 10_7_5)..." ]
Host = " localhost:8000"
RemoteAddr = " 127.0.0.1:59911"
Form[" q" ] = [" query" ]
< / code > < / pre >
< p > 可以看到这里的ParseForm被嵌套在了if语句中。Go语言允许这样的一个简单的语句结果作为局部的变量声明出现在if语句的最前面， （ ） ： < / p >
< pre > < code class = "language-go" > err := r.ParseForm()
if err != nil {
log.Print(err)
}
< / code > < / pre >
< p > 用if和ParseForm结合可以让代码更加简单， ， < / p >
< p > 在这些程序中， ， ， ， ， < / p >
< p > 尽管三种具体的实现流程并不太一样， ， ， < / p >
< p > Go语言的接口机制会在第7章中讲解， ， ， ， < / p >
< pre > < code class = "language-Go" > handler := func(w http.ResponseWriter, r *http.Request) {
lissajous(w)
}
http.HandleFunc(" /" , handler)
< / code > < / pre >
< p > 或者另一种等价形式：< / p >
< pre > < code class = "language-Go" > http.HandleFunc(" /" , func(w http.ResponseWriter, r *http.Request) {
lissajous(w)
})
< / code > < / pre >
< p > HandleFunc函数的第二个参数是一个函数的字面值， < / p >
< p > 做完这些修改之后，在浏览器里访问 http://localhost:8000 。每次你载入这个页面都可以看到一个像图1.3那样的动画。< / p >
< p > < img src = "../images/ch1-03.png" alt = "" / > < / p >
< p > < strong > 练习 1.12： < / strong > 修改Lissajour服务， ， ， < / p >
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