package code.tomcat.simpleWebServer;

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

public class HttpServer {

    // 项目放置的文件夹
    public static final String WEB_ROOT = System.getProperty("user.id") + File.separator + "webroot";
    // SHUTDOWN命令
    private static final String SHUTDOWN_COMMAND = "/SHUTDOWN";
    // 判断是否Shutdown标示符，控制程序运行
    private boolean isShutdown = false;
    // 主程序
    public static void main(String[] args) {
        HttpServer httpSever = new HttpServer();
        // 不能叫wait,你懂的
        httpSever.await();
    }
    
    private void await(){
        ServerSocket serverSocket = null;
        int port = 8080;
        
        try {
            // 用ServerSocket等待端口消息
            serverSocket = new ServerSocket(port, 1, InetAddress.getByName("127.0.0.1"));
        } catch (IOException e) {
            e.printStackTrace();
            System.exit(1);//异常后，把java虚拟机都关掉
        }
        while( ! isShutdown ){
            Socket socket = null; 
            InputStream input = null; 
            OutputStream output = null;
            try {
                // 建立socket
                socket = serverSocket.accept();
                // socket的输入
                input = socket.getInputStream();
                // socket的输出
                output = socket.getOutputStream();
                Request request = new Request(input);
                request.parse();//Request来解析出uri
                Response response = new Response(output);
                response.setRequest(request);//把Request放进去，是要用解析出来的uri
                response.sendStaticResource();//把产生的返回内容发送出去
                // 关闭socket
                socket.close();
                isShutdown = request.getUri().equals(SHUTDOWN_COMMAND);
            } catch (IOException e) {
                e.printStackTrace();
                continue;
            }
        }
    }
}

package code.tomcat.simpleWebServer;

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

public class Request {
    private InputStream input;
    private String uri;
    
    public Request(InputStream input) {
        this.input = input;
    }

    public void parse() {
        StringBuffer request = new StringBuffer(2048);
        int i;
        byte[] buffer = new byte[2048];
        try {
            // 把InputStream读出来，放进byte[2048]大小的buffer中
            i = input.read(buffer);
        } catch (IOException e) {
            e.printStackTrace();
            i = -1;
        }
        // 传化成StringBuffer
        for (int j = 0; j < i; j++) {
            request.append((char) buffer[j]);
        }
        // 然后再以String的形式传经解析方法中去
        uri = parseUri(request.toString());
    }

    // 真正解析uri出来的方法,相当于是解析request的第一行：GET /killbug/ HTTP/1.1 想要取出“/killbug/”这段，即两个空格之间那一段
    private String parseUri(String requestString) {
        int index1, index2;
        // 第一个空格位置
        index1 = requestString.indexOf(' ');
        if (index1 != -1) {
            // 第二个空格位置
            index2 = requestString.indexOf(' ', index1 + 1);
            if (index2 > index1)
                // 根据两个空格的位置截断出需要的一段
                return requestString.substring(index1 + 1, index2);
        }
        return null;
    }

    public String getUri() {
        return uri;
    }
}

package code.tomcat.simpleWebServer;

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

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];
        //文件输入流
        FileInputStream fis = null;
        // request.getUri()相当于：“/killbug/”，把路径和文件起来定位到具体的文件，可以是项目中的一个html文件
        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) {
                // 写进socket的output中去，就成了返回值了
                output.write(bytes, 0, ch);
                ch = fis.read(bytes, 0, BUFFER_SIZE);
            }
        }else { // 找不到文件的情况相当于404啦
                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()); 
                }
        }
    }