《HowTomcatWorks》读书笔记

第三章：连接器，涉及到的核心类包括：

• Bootstrap：启动类，目前只是调用HttpConnector的start()方法，为后文做铺垫，新增部分
• HttpConnector和HttpProcessor：连接器和处理器，第二章中的HttpServer在第三章被拆分了HttpConnector和HttpProcessor两个类，拆分成两个组件，为后文做铺垫，新增部分
• HttpRequest：实现HttpServletRequest接口，功能扩充
• HttpResponse：实现HttpServletResponse接口，功能扩充
• ServletProcessor：与第二章相同
• StaticResourceProcessor：与第二章相同

public final class Bootstrap {
  public static void main(String[] args) {
    HttpConnector connector = new HttpConnector();
    connector.start();
  }
}

public class HttpConnector implements Runnable {

  boolean stopped;
  private String scheme = "http";

  public String getScheme() {
    return scheme;
  }

  public void run() {
    ServerSocket serverSocket = null;
    int port = 8080;
    try {
      serverSocket =  new ServerSocket(port, 1, InetAddress.getByName("127.0.0.1"));
    }
    catch (IOException e) {
      e.printStackTrace();
      System.exit(1);
    }
    while (!stopped) {
      // Accept the next incoming connection from the server socket
      Socket socket = null;
      try {
        socket = serverSocket.accept();
      }
      catch (Exception e) {
        continue;
      }
      // Hand this socket off to an HttpProcessor
      HttpProcessor processor = new HttpProcessor(this);
      processor.process(socket);
    }
  }

  public void start() {
    Thread thread = new Thread(this);
    thread.start();
  }
}

功能：

• 创建服务器套接字
• 创建HttpProcessor，对应关系1:1，一次只能处理一个Http请求

public class HttpProcessor {

  public HttpProcessor(HttpConnector connector) {
    this.connector = connector;
  }
  
  private HttpConnector connector = null;
  private HttpRequest request;
  private HttpRequestLine requestLine = new HttpRequestLine();
  private HttpResponse response;

  protected String method = null;
  protected String queryString = null;

  
  protected StringManager sm =
    StringManager.getManager("ex03.pyrmont.connector.http");

  public void process(Socket socket) {
    SocketInputStream input = null;
    OutputStream output = null;
    try {
      input = new SocketInputStream(socket.getInputStream(), 2048);
      output = socket.getOutputStream();

      // create HttpRequest object and parse
      request = new HttpRequest(input);

      // create HttpResponse object
      response = new HttpResponse(output);
      response.setRequest(request);

      response.setHeader("Server", "Pyrmont Servlet Container");

      // 解析请求行，即Http请求的第一行内容
      parseRequest(input, output);
      parseHeaders(input);

      //check if this is a request for a servlet or a static resource
      //a request for a servlet begins with "/servlet/"
      if (request.getRequestURI().startsWith("/servlet/")) {
        ServletProcessor processor = new ServletProcessor();
        processor.process(request, response);
      }
      else {
        StaticResourceProcessor processor = new StaticResourceProcessor();
        processor.process(request, response);
      }

      // Close the socket
      socket.close();
      // no shutdown for this application
    }
    catch (Exception e) {
      e.printStackTrace();
    }
  }
  //省略parseHeader、parseRequest等方法
}

这一章除了新增Bootstrap组件，将HttpServer拆分成HttpConnector和HttpProcessor，还对第4步解析http报文做了较大的扩充，在解析uri之上，借助了tomcat4中已经被废弃的SocketInputStream来解析请求头、请求体等内容，并构造出更为完整的HttpRequest（看到它一下子变多的成员变量就直到了）。之前还打算手敲代码自己跑一遍，直到碰到了这个类，就放弃了这种想法，还是老老实实的写源码注释吧！