Tomcat第一课--构建简单静态资源访问

最近在看《深入剖析TOMCAT》这本书，跟着书边看边学，试着搭搭tomcat,主要是试着了解思想~ 首先，单纯的只是访问静态资源————比如Html，只需要三个类就可以： HttpServer、Reuest、Response 其实单看架构跟一些互联网项目是有类似的地方的。

1.HttpServer

package com.draz.ex01; 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; /** * Created by Drazen on 2017/2/24. */ public class HttpServer { public static final String WEB_ROOT = System.getProperty("user.dir") + File.separator + "web"; // 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 = 8001; 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 socket.close(); //check if the previous URI is a shutdown command shutdown = request.getUri().equals(SHUTDOWN_COMMAND); } catch (Exception e) { e.printStackTrace(); continue; } } } } 这个类主要是通过一个main()方法启动一个关于本地的监听，有一个公有方法await(),主要作用是启动监听，设置端口号（后期可以修改成配置文件的形式），加工请求并相应。 WEB_ROOT的值是我存放html的目录，也就是web。 调用的ServerSocket对象的accept()方法，这个方法的执行将使Server端的程序处于等待状态，程序将一直阻塞直到捕捉到一个来自Client端的请求，并返回一个用于与该Client通信的Socket对象Link-Socket。此后Server程序只要向这个Socket对象读写数据，就可以实现向远端的Client读写数据。结束监听时，关闭ServerSocket对象： Socket类的构造函数有两个参数，第一个参数是欲连接到的Server计算机的主机地址，第二个参数是该Server机上提供服务的端口号。 Socket对象建立成功之后，就可以在Client和Server之间建立一个连接，并通过这个连接在两个端点之间传递数据。利用Socket类的方法getOutputStream()和getInputStream()分别获得向Socket读写数据的输入／输出流，最后将从Server端读取的数据重新返还到Server端。 当Server和Client端的通信结束时，可以调用Socket类的close()方法关闭Socket，拆除连接。 这样，在Request类中处理的访问请求会传给Response并指向要访问的资源

2.Request

package com.draz.ex01; 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; } }

一个公有的parse方法 Request 类里干的最主要的活就是加工！加工！加工 InputStream实例被拆分成字节数组的形式, 打印出来的request是这样的：

GET /index.html HTTP/1.1 Host: localhost:8001 Connection: keep-alive Cache-Control: max-age=0 Upgrade-Insecure-Requests: 1 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Safari/537.36 Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8 Accept-Encoding: gzip, deflate, sdch, br Accept-Language: zh-CN,zh;q=0.8 Cookie: logName=23700013181

最后

3.Response

package com.draz.ex01; 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 { 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(); } } }