Rust Web 全栈开发（二）：构建 HTTP Server

参考视频：https://www.bilibili.com/video/BV1RP4y1G7KF

Web Server 的消息流动图：

Server：监听 TCP 字节流

Router：接收 HTTP 请求，并决定调用哪个 Handler

Handler：处理 HTTP 请求，构建 HTTP 响应

HTTP Library：

• 解释字节流，把它转换为 HTTP 请求
• 把 HTTP 响应转换回字节流

构建步骤：

1. 解析 HTTP 请求消息
2. 构建 HTTP 响应消息
3. 路由与 Handler
4. 测试 Web Server

创建成员包/库：httpserver、http

在原项目下新建成员包 httpserver、成员库 http：

cargo new httpserver
cargo new --lib http

在工作区内运行 cargo new 会自动将新创建的包添加到工作区内 Cargo.toml 的 [workspace] 定义中的 members 键中，如下所示：

在 http 成员库的 src 目录下新建两个文件：httprequest.rs、httpresponse.rs。

此时，我们可以通过运行 cargo build 来构建工作区。项目目录下的文件应该是这样的：

├── Cargo.lock
├── Cargo.toml
├── httpserver
│   ├── Cargo.toml
│   └── src
│       └── main.rs
├── http
│   ├── Cargo.toml
│   └── src
│       └── lib.rs
│       └── httprequest.rs
│       └── httpresponse.rs
├── tcpclient
│   ├── Cargo.toml
│   └── src
│       └── main.rs
├── tcpserver
│   ├── Cargo.toml
│   └── src
│       └── main.rs
└── target

解析 HTTP 请求

HTTP 请求的构成

HTTP 请求报文由 3 部分组成：请求行、请求头、请求体。

构建 HttpRequest

3 个数据结构：

名称	类型	描述
HttpRequest	struct	表示 HTTP 请求
Method	enum	指定所允许的 HTTP 方法
Version	enum	指定所允许的 HTTP 版本

以上 3 个数据结构都需要实现的 3 个 trait：

名称	描述
From<&str>	用于把传进来的字符串切片转换为 HttpRequest
Debug	打印调试信息
PartialEq	用于解析和自动化测试脚本里做比较

打开 http 成员库中的 httprequest.rs，编写代码：

use std::collections::HashMap;#[derive(Debug, PartialEq)]
pub enum Method {Get,Post,Uninitialized,
}
impl From<&str> for Method {fn from(s: &str) -> Method {match s {"GET" => Method::Get,"POST" => Method::Post,_ => Method::Uninitialized,}}
}#[derive(Debug, PartialEq)]
pub enum Version {V1_1,V2_0,Uninitialized,
}impl From<&str> for Version {fn from(s: &str) -> Version {match s {"HTTP/1.1" => Version::V1_1,_ => Version::Uninitialized,}}
}#[derive(Debug, PartialEq)]
pub enum Resource {Path(String),
}#[derive(Debug)]
pub struct HttpRequest {pub method: Method,pub resource: Resource,pub version: Version,pub headers: HashMap<String, String>,pub body: String,
}impl From<String> for HttpRequest {fn from(request: String) -> HttpRequest {let mut parsed_method = Method::Uninitialized;let mut parsed_resource = Resource::Path("".to_string());let mut parsed_version =  Version::V1_1;let mut parsed_headers = HashMap::new();let mut parsed_body = "";for line in request.lines() {if line.contains("HTTP") {let (method, resource, version) = process_request_line(line);parsed_method = method;parsed_resource = resource;parsed_version = version;} else if line.contains(":") {let (key, value) = process_header_line(line);parsed_headers.insert(key, value);} else if line.len() == 0 {} else {parsed_body = line;}}HttpRequest {method: parsed_method,resource: parsed_resource,version: parsed_version,headers: parsed_headers,body: parsed_body.to_string(),}}
}fn process_header_line(s: &str) -> (String, String) {let mut header_items = s.split(":");let mut key = String::from("");let mut value = String::from("");if  let Some(k) = header_items.next() {key = k.to_string();}if let Some(v) = header_items.next() {value = v.to_string();}(key, value)
}fn process_request_line(s: &str) -> (Method, Resource, Version) {let mut words = s.split_whitespace();let method = words.next().unwrap();let resource = words.next().unwrap();let version = words.next().unwrap();(method.into(),Resource::Path(resource.to_string()),version.into())
}#[cfg(test)]
mod test {use super::*;#[test]fn test_method_into() {let method: Method = "GET".into();assert_eq!(method, Method::Get);}#[test]fn test_version_into() {let version: Version = "HTTP/1.1".into();assert_eq!(version, Version::V1_1);}#[test]fn test_read_http() {let s = String::from("GET /greeting HTTP/1.1\r\nHost: localhost:3000\r\nUser-Agent: curl/7.71.1\r\nAccept: */*\r\n\r\n");let mut headers_excepted = HashMap::new();headers_excepted.insert("Host".into(), " localhost".into());headers_excepted.insert("Accept".into(), " */*".into());headers_excepted.insert("User-Agent".into(), " curl/7.71.1".into());let request: HttpRequest = s.into();assert_eq!(request.method, Method::Get);assert_eq!(request.resource, Resource::Path("/greeting".to_string()));assert_eq!(request.version, Version::V1_1);assert_eq!(request.headers, headers_excepted);}
}

运行命令 cargo test -p http，测试 http 成员库。

3 个测试都通过了：

构建 HTTP 响应

HTTP 响应的构成

HTTP 响应报文由 3 部分组成：响应行、响应头、响应体。

构建 HttpResponse

HttpResponse 需要实现的方法或 trait：

名称	描述
Default trait	指定成员的默认值
From trait	将 HttpResponse 转化为 String
new()	使用默认值创建一个新的 HttpResponse 结构体
getter 方法	获取 HttpResponse 成员变量的值
send_response()	构建响应，将原始字节通过 TCP 传送

打开 http 成员库中的 httpresponse.rs，编写代码：

use std::collections::HashMap;
use std::io::{Result, Write};#[derive(Debug, PartialEq, Clone)]
pub struct HttpResponse<'a> {version: &'a str,status_code: &'a str,status_text: &'a str,headers: Option<HashMap<&'a str, &'a str>>,body: Option<String>,
}impl<'a> Default for HttpResponse<'a> {fn default() -> Self {Self {version: "HTTP/1.1".into(),status_code: "200".into(),status_text: "OK".into(),headers: None,body: None,}}
}impl<'a> From<HttpResponse<'a>> for String {fn from(response: HttpResponse) -> String {let res = response.clone();format!("{} {} {}\r\n{}Content-Length: {}\r\n\r\n{}",&res.version(),&res.status_code(),&res.status_text(),&res.headers(),&response.body.unwrap().len(),&res.body(),)}
}impl<'a> HttpResponse<'a> {pub fn new(status_code: &'a str,headers: Option<HashMap<&'a str, &'a str>>,body: Option<String>,) -> HttpResponse<'a> {let mut response: HttpResponse<'a> = HttpResponse::default();if status_code != "200" {response.status_code = status_code.into();}response.status_text = match response.status_code {// 消息"100" => "Continue".into(),"101" => "Switching Protocols".into(),"102" => "Processing".into(),// 成功"200" => "OK".into(),"201" => "Created".into(),"202" => "Accepted".into(),"203" => "Non-Authoritative Information".into(),"204" => "No Content".into(),"205" => "Reset Content".into(),"206" => "Partial Content".into(),"207" => "Multi-Status".into(),// 重定向"300" => "Multiple Choices".into(),"301" => "Moved Permanently".into(),"302" => "Move Temporarily".into(),"303" => "See Other".into(),"304" => "Not Modified".into(),"305" => "Use Proxy".into(),"306" => "Switch Proxy".into(),"307" => "Temporary Redirect".into(),// 请求错误"400" => "Bad Request".into(),"401" => "Unauthorized".into(),"402" => "Payment Required".into(),"403" => "Forbidden".into(),"404" => "Not Found".into(),"405" => "Method Not Allowed".into(),"406" => "Not Acceptable".into(),"407" => "Proxy Authentication Required".into(),"408" => "Request Timeout".into(),"409" => "Conflict".into(),"410" => "Gone".into(),"411" => "Length Required".into(),"412" => "Precondition Failed".into(),"413" => "Request Entity Too Large".into(),"414" => "Request-URI Too Long".into(),"415" => "Unsupported Media Type".into(),"416" => "Requested Range Not Satisfiable".into(),"417" => "Expectation Failed".into(),"421" => "Misdirected Request".into(),"422" => "Unprocessable Entity".into(),"423" => "Locked".into(),"424" => "Failed Dependency".into(),"425" => "Too Early".into(),"426" => "Upgrade Required".into(),"449" => "Retry With".into(),"451" => "Unavailable For Legal Reasons".into(),// 服务器错误"500" => "Internal Server Error".into(),"501" => "Not Implemented".into(),"502" => "Bad Gateway".into(),"503" => "Service Unavailable".into(),"504" => "Gateway Timeout".into(),"505" => "HTTP Version Not Supported".into(),"506" => "Variant Also Negotiates".into(),"507" => "Insufficient Storage".into(),"509" => "Bandwidth Limit Exceeded".into(),"510" => "Not Extended".into(),"600" => "Unparseable Response Headers".into(),_ => "Not Found".into(),};response.headers = match &headers {Some(_h) => headers,None => {let mut header = HashMap::new();header.insert("Content-Type", "text/html");Some(header)}};response.body = body;response}fn version(&self) -> &str {self.version}fn status_code(&self) -> &str {self.status_code}fn  status_text(&self) -> &str {self.status_text}fn headers(&self) -> String {let map = self.headers.clone().unwrap();let mut headers_string = "".into();for (key, value) in map.iter() {headers_string = format!("{headers_string}{}:{}\r\n", key, value);}headers_string}fn body(&self) -> &str {match &self.body {Some(b) => b.as_str(),None => "",}}pub fn send_response(&self, write_stream: &mut impl Write) -> Result<()> {let response = self.clone();let response_string: String = String::from(response);let _ = write!(write_stream, "{}", response_string);Ok(())}
}#[cfg(test)]
mod test {use super::*;#[test]fn test_response_struct_creation_200() {let response_actual = HttpResponse::new("200",None,Some("xxxx".into()),);let response_excepted = HttpResponse {version: "HTTP/1.1",status_code: "200",status_text: "OK",headers: {let mut h = HashMap::new();h.insert("Content-Type", "text/html");Some(h)},body: Some("xxxx".into()),};assert_eq!(response_actual, response_excepted);}#[test]fn test_response_struct_creation_404() {let response_actual = HttpResponse::new("404",None,Some("xxxx".into()),);let response_excepted = HttpResponse {version: "HTTP/1.1",status_code: "404",status_text: "Not Found",headers: {let mut h = HashMap::new();h.insert("Content-Type", "text/html");Some(h)},body: Some("xxxx".into()),};assert_eq!(response_actual, response_excepted);}#[test]fn test_http_response_creation() {let response_excepted = HttpResponse {version: "HTTP/1.1",status_code: "404",status_text: "Not Found",headers: {let mut h = HashMap::new();h.insert("Content-Type", "text/html");Some(h)},body: Some("xxxx".into()),};let http_string: String = response_excepted.into();let actual_string = "HTTP/1.1 404 Not Found\r\nContent-Type:text/html\r\nContent-Length: 4\r\n\r\nxxxx";assert_eq!(http_string, actual_string);}
}

运行命令 cargo test -p http，测试 http 成员库。

现在一共有 6 个测试，都通过了：

lib

打开 http 成员库中的 lib.rs，编写代码：

pub mod httprequest;
pub mod httpresponse;