A Simple Web Server

HTTP：Http允许Web服务器和浏览器通过Internet发送并接收数据，是一种基于“请求 - 响应”的协议。

一、HTTP 请求

• 请求方法  - URI - 协议/版本
• 请求头
• 实体

二、HTTP 响应

• 协议 - 状态码 - 描述
• 响应头
• 响应实体段

package org.http;

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

public class HttpServer
{
    public static final String WEB_ROOT = System.getProperty("user.dir")
            + File.separator + "WebContent";

    private static final String SHUTDOWN_COMMAND = "/SHUTDOWN";

    private final int PORT = 8080;

    private boolean shutdown = false;

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

    public void await()
    {
        ServerSocket serverSocket = null;
        try
        {
            serverSocket = new ServerSocket(PORT);
        }
        catch (IOException e)
        {
            e.printStackTrace();
            System.exit(1);
        }
        // Loop waitting 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();
                shutdown = request.getUri().equals(SHUTDOWN_COMMAND);
            }
            catch (IOException e)
            {
                e.printStackTrace();
            }
            finally
            {
                try
                {
                    socket.close();
                }
                catch (IOException e)
                {
                    e.printStackTrace();
                }
            }

        }
    }
}

package org.http;

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
        {
            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.println(request.toString());
        uri = parseUri(request.toString());
    }

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

    public String getUri()
    {
        return uri;
    }
}

package org.http;

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;
    private Request request;
    private OutputStream output;

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

    public void sendStaticResource()
    {
        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
            {
                String errorMessage = "HTTP/1.1 404 File Not Found\r\n"
                        + "Content-Type : text/html\r\n" + "\r\n"
                        + "<h1>File Not Found</h1>";
                output.write(errorMessage.getBytes());
            }
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }
        finally
        {
            if (fis != null)
                try
                {
                    fis.close();
                }
                catch (IOException e)
                {
                    e.printStackTrace();
                }
        }

    }

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

打印HTTP响应： 

package org.http;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;

public class Client
{
    public static void main(String[] args) throws Exception
    {
        Socket socket = new Socket("127.0.0.1", 8080);
        OutputStream os = socket.getOutputStream();
        InputStream is = socket.getInputStream();
        boolean autoFlush = true;
        PrintWriter out = new PrintWriter(os, autoFlush);
        BufferedReader in = new BufferedReader(new InputStreamReader(is));
        out.println("Get /index.jsp HTTP/1.1");
        out.println("Host: localhost:8080");
        out.println("Connection: close");
        out.println();

        boolean loop = true;
        StringBuffer sb = new StringBuffer(8096);
        while (loop)
        {
            if (in.ready())
            {
                int i = 0;
                do
                {
                    i = in.read();
                    sb.append((char) i);
                }
                while (i != -1);
                loop = false;
            }
            Thread.sleep(1000);
        }
        System.out.println(sb.toString());
        socket.close();
    }
}