目标
实现一个简单的Web服务器，能够根据HTTP请求的URL响应对应的静态资源，如果静态资源不存在则响应404。
HttpServer
使用ServerSocket实现的一个服务器，request根据socket.getInputStream()获取HTTP报文，response将响应写入socket.getOutputStream()中。
public class HttpServer {
public static final String WEB_ROOT = System.getProperty("user.dir") + File.separator + "webroot";
private static final String SHUTDOWN_COMMAND = "/SHUTDOWN";
private static final int PORT = 8899;
public HttpServer() {
}
public static void main(String[] args) throws IOException {
HttpServer httpServer = new HttpServer();
httpServer.service();
}
public void service() throws IOException {
ServerSocket serverSocket = new ServerSocket(PORT);
System.out.println("服务器启动：" + serverSocket);
while (true) {
try (Socket socket = serverSocket.accept()) {
System.out.println("客户端建立连接：" + socket);
Request request = new Request(socket.getInputStream());
if (Objects.isNull(request.getUri())) {
continue;
}
if (isShutdownComment(request)) { //如果是shutdown命令，则关闭服务器
break;
}
Response response = new Response(request, socket.getOutputStream());
response.sendStaticResource(); // 返回静态资源
System.out.println("客户端关闭连接：" + socket);
} catch (Exception e) {
e.printStackTrace();
}
}
}
private boolean isShutdownComment(Request request) {
return Objects.equals(SHUTDOWN_COMMAND, request.getUri());
}
}
Request
读取输入流，获取HTTP报文，并从中解析出URL，Response会根据这个URL去读取对应的静态资源
public class Request {
private InputStream inputStream;
/**
* HTTP 报文
*/
private String message;
/**
* HTTP 请求 URI
*/
private String uri;
public Request(InputStream inputStream) throws IOException {
parse(inputStream);
}
/**
* 从 inputStream 中读取出报文
*/
private void parse(InputStream inputStream) throws IOException {
StringBuilder sb = new StringBuilder();
BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
String line = null;
while (Objects.nonNull(line = reader.readLine())) {
sb.append(line).append("\n");
}
this.message = sb.toString();
this.uri = parseURI();
System.out.println("-------------------------------------------");
System.out.println(message);
System.out.println("-------------------------------------------");
}
/**
* 从报文中解析出请求 uri
*
* @return
*/
private String parseURI() {
int beginIndex = message.indexOf(" ");
int endIndex = message.indexOf(" ", beginIndex + 1);
if (beginIndex == -1 || endIndex == -1) {
return null;
}
return message.substring(beginIndex + 1, endIndex);
}
public String getUri() {
return uri;
}
public String getMessage() {
return message;
}
}
Response
调用 File staticResource = new File(HttpServer.WEB_ROOT, request.getUri()); 拿到对应的静态资源。
比如请求的url是 http://localhost:8899/index.html，则会去webRoot下面寻找index.html文件，如果文件不存在则返回404
public class Response {
private static final String RETURN_404 = "HTTP/1.1 404 File Not Found\r\n" +
"Content-Type: text/html\r\n" +
"Content-Length: 23\r\n" +
"\r\n" +
"<h1>File Not Found</h1>";
private OutputStream outputStream;
private Request request;
public Response(Request request, OutputStream outputStream) {
this.request = request;
this.outputStream = outputStream;
}
/**
* 发送静态资源
*/
public void sendStaticResource() throws IOException {
File staticResource = new File(HttpServer.WEB_ROOT, request.getUri()); //请求的静态资源路径
if (staticResource.exists()) { //静态资源存在则返回给客户端
try (FileInputStream fileInputStream = new FileInputStream(staticResource)) {
int b = 0;
while ((b = fileInputStream.read()) != -1) {
outputStream.write(b);
}
}
} else { //不存在返回404
outputStream.write(RETURN_404.getBytes());
}
outputStream.flush();
}
}
参考
1.《How Tomcat Works》 - Budi Kurniawan