《how tomcat work》 搬运工 chapter 1

charter 1

基本的服务端接收请求并处理

 

包和类

HttpServer  是主函数入口，通过await()方法新建ServerSock 对象实例来绑定端口，接收请求，通过请求来新建 Request 和 Response 对象实例，

package com.howtomcatwork.xy;

import java.net.Socket;
import java.net.ServerSocket;
import java.net.InetAddress;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.IOException;
import java.io.File;


public class HttpServer {

    
    public static final String WEB_ROOT = System.getProperty("user.dir")
            + File.separator + "webroot";

    // shutdown command
    private static final String SHUTDOWN_COMMAND = "/SHUTDOWN";

    // the shutdown command received
    private boolean shutdown = false;

    public static void main(String[] args) {
        HttpServer server = new HttpServer();
        server.await();
    }

    public void await() {
        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);
        }

        // Loop waiting for a request
        while (!shutdown) {
            Socket socket = null;
            InputStream input = null;
            OutputStream output = null;
            try {
                socket = serverSocket.accept();
                input = socket.getInputStream();
                output = socket.getOutputStream();

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

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

                // Close the socket and send outputstream to client
                socket.close();

                // check if the previous URI is a shutdown command
                shutdown = request.getUri().equals(SHUTDOWN_COMMAND);
            } catch (Exception e) {
                e.printStackTrace();
                continue;
            }
        }
    }
}

自定义的Request 类

自定义的Request 类主要接收 inputStream(接收的请求数据)的2进制数据如何进行处理，

parse()函数将inputstream转换为string，并通过parseUri函数将uri赋值, 

parseUri(String )函数将String 类型的请求中获取请求的url,

package com.howtomcatwork.xy;

import java.io.InputStream;
import java.io.IOException;

public class Request {
    private InputStream input;
    private String uri;

    public Request(InputStream input) {
        this.input = input;
    }

    public void parse() {
        // Read a set of characters from the socket
        StringBuffer request = new StringBuffer(2048);
        int i;
        byte[] buffer = new byte[2048];
        try {
            i = input.read(buffer);
        } catch (IOException e) {
            e.printStackTrace();
            i = -1;
        }
        for (int j = 0; j < i; j++) {
            request.append((char) buffer[j]);
        }
        System.out.print(request.toString());
        uri = parseUri(request.toString());
    }

    private String parseUri(String requestString) {
        int index1, index2;
        index1 = requestString.indexOf(' ');
        if (index1 != -1) {
            index2 = requestString.indexOf(' ', index1 + 1);
            if (index2 > index1)
                return requestString.substring(index1 + 1, index2);
        }
        return null;
    }

    public String getUri() {
        return uri;
    }

}

自定义的Response 类

sendStaticResource() 通过请求的uri  读取文件或返回404提示,将读取的内容或404提示的bit形式输出到响应的输出流

package com.howtomcatwork.xy;

import java.io.OutputStream;
import java.io.IOException;
import java.io.FileInputStream;
import java.io.File;

public class Response {

    private static final int BUFFER_SIZE = 1024;
    Request request;
    OutputStream output;

    public Response(OutputStream output) {
        this.output = output;
    }

    public void setRequest(Request request) {
        this.request = request;
    }

    public void sendStaticResource() throws IOException {
        byte[] bytes = new byte[BUFFER_SIZE];
        FileInputStream fis = null;
        try {
            File file = new File(HttpServer.WEB_ROOT, request.getUri());
            if (file.exists()) {
                fis = new FileInputStream(file);
                int ch = fis.read(bytes, 0, BUFFER_SIZE);
                while (ch != -1) {
                    output.write(bytes, 0, ch);
                    ch = fis.read(bytes, 0, BUFFER_SIZE);
                }
            } else {
                // file not found
                String errorMessage = "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>";
                output.write(errorMessage.getBytes());
            }
        } catch (Exception e) {
            // thrown if cannot instantiate a File object
            System.out.println(e.toString());
        } finally {
            if (fis != null)
                fis.close();
        }
    }
}

完整的目录结构

主要参考  https://www.gitbook.com/book/l-webx/how_tomcat_works/details