简单实现Java web服务器

一个简单的Java web服务器实现，比较简单，基于java.net.Socket和java.net.ServerSocket实现；
一、程序执行步骤
 1.创建一个ServerSocket对象；
 2.调用ServerSocket对象的accept方法，等待连接，连接成功会返回一个Socket对象，否则一直阻塞等待；
 3.从Socket对象中获取InputStream和OutputStream字节流，这两个流分别对应request请求和response响应；
 4.处理请求：读取InputStream字节流信息，转成字符串形式，并解析，这里的解析比较简单，仅仅获取uri(统一资源标识符)信息;
 5.处理响应：根据解析出来的uri信息，从WEB_ROOT目录中寻找请求的资源资源文件, 读取资源文件，并将其写入到OutputStream字节流中；
 6.关闭Socket对象；
 7.转到步骤2，继续等待连接请求；

二、代码实现

 服务器实现： 

package ex01.pyrmont;

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 {

 /**
 * WEB_ROOT是HTML和其它文件存放的目录. 这里的WEB_ROOT为工作目录下的webroot目录
 */
 public static final String WEB_ROOT = System.getProperty("user.dir") + File.separator + "webroot";

 // 关闭服务命令
 private static final String SHUTDOWN_COMMAND = "/SHUTDOWN";

 public static void main(String[] args) {
 HttpServer server = new HttpServer();
 //等待连接请求
 server.await();
 }

 public void await() {
 ServerSocket serverSocket = null;
 int port = 8080;
 try {
  //服务器套接字对象
  serverSocket = new ServerSocket(port, 1, InetAddress.getByName("127.0.0.1"));
 } catch (IOException e) {
  e.printStackTrace();
  System.exit(1);
 }

 // 循环等待一个请求
 while (true) {
  Socket socket = null;
  InputStream input = null;
  OutputStream output = null;
  try {
  //等待连接，连接成功后，返回一个Socket对象
  socket = serverSocket.accept();
  input = socket.getInputStream();
  output = socket.getOutputStream();

  // 创建Request对象并解析
  Request request = new Request(input);
  request.parse();
  // 检查是否是关闭服务命令
  if (request.getUri().equals(SHUTDOWN_COMMAND)) {
   break;
  }

  // 创建 Response 对象
  Response response = new Response(output);
  response.setRequest(request);
  response.sendStaticResource();

  // 关闭 socket 对象
  socket.close();

  } catch (Exception e) {
  e.printStackTrace();
  continue;
  }
 }
 }
}

Request类：

package ex01.pyrmont;

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

public class Request {

 private InputStream input;
 private String uri;

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

 //从InputStream中读取request信息，并从request中获取uri值
 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.print(request.toString());
 uri = parseUri(request.toString());
 }

 /**
 *
 * requestString形式如下：
 * GET /index.html HTTP/1.1
 * Host: localhost:8080
 * Connection: keep-alive
 * Cache-Control: max-age=0
 * ...
 * 该函数目的就是为了获取/index.html字符串
 */
 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;
 }

}

Response类：

 package ex01.pyrmont;

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

/*
 HTTP Response = Status-Line
 *(( general-header | response-header | entity-header ) CRLF)
 CRLF
 [ message-body ]
 Status-Line = HTTP-Version SP Status-Code SP Reason-Phrase CRLF
*/

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 {
  //将web文件写入到OutputStream字节流中
  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();
 }
 }
}

三、结果测试

访问存在的资源文件(注意存放在工程目录的webroot文件夹里)：

访问不存在的资源文件：

关闭服务器：

参考资料：《深入剖析Tomcat》

@author   风一样的码农

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