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[Java教程]一个简单的Java web服务器实现


  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;

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;

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();    }  }}

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》