上一篇文章说道, Web发展初期, 用户只能查看静态页面. 随着Web发展,只能显示静态页面的web显然已经不能满足大众的需求,所以出现了CGI和用Java编写的Servlet程序. Servlet可以根据用户的请求动态的生成html页面,然后发给浏览器.
下面模拟一下这个过程:
HttpServer2类
服务器类,负责启动Http服务.
import java.io.*;import java.net.*;{port = 8088;private ServerSocket serverSocket = null;public HttpServer2() throws IOException {serverSocket = new ServerSocket(port);System.out.println(“HTTPServer startup OK…”);}() throws IOException {while (true) {try {Socket socket = serverSocket.accept();ServletRequest request = new ServletRequest(socket.getInputStream());ServletResponse response = new ServletResponse(socket.getOutputStream());System.out.println(“Receive request:\n” + request.getRequest());String servletName = request.getServletName();//动态生成servletServlet servlet = (Servlet) Class.forName(servletName).newInstance();//调用servlet接口servlet.init();servlet.service(request, response);servlet.destroy();socket.close();} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();}}}(String[] args) throws IOException,InterruptedException {HttpServer2 httpServer = new HttpServer2();httpServer.work();}}Servlet接口
定义Servlet服务接口.
public interface Servlet {();(ServletRequest req, ServletResponse res) throws Exception;();}HelloServlet类
实现Servlet接口.用户提交请求时,HttpServer2将请求发给HelloServlet处理.处理完后动态生成页面返回给用户.
{() {// TODO Auto-generated method stubSystem.out.println(“servlet init “);}(ServletRequest req, ServletResponse res)throws Exception {// TODO Auto-generated method stubString contentType = req.getContentType();String param = req.getParam();//组装HTTP响应头String header = res.assembleResponseHeader(contentType);//组装HTTP响应正文String body = res.assembleResponseBody(param);//返回响应res.write(header + body);}() {// TODO Auto-generated method stubSystem.out.println(“servlet destroy “);}}ServletRequest类
封装用户的请求.交给HelloServlet处理.
import java.io.IOException;import java.io.InputStream;{private String request;private InputStream socketIn;private String URI;private String contentType;private String param;public ServletRequest(InputStream socketIn) throws IOException {// TODO Auto-generated constructor stubthis.socketIn = socketIn;this.request = _getRequest();this.URI = _getURI();this.contentType = _getContentType();this.param = _getParam();}public String getRequest() {return request;}public String getURI() {return URI;}public String getContentType() {return contentType;}public String getParam() {return param;}private String _getRequest() throws IOException {int size = socketIn.available();byte[] requestBuff = new byte[size];socketIn.read(requestBuff);return new String(requestBuff);}//获得要调用servlet的类名public String getServletName(){return URI.substring(URI.indexOf(“/”) + 1, URI.indexOf(“?”));}private String _getURI() {String firstLine = request.substring(0, request.indexOf(“\r\n”));String[] parts = firstLine.split(” “);return parts[1];}private String _getContentType() {;}//获得请求参数private String _getParam() {String paramString = URI.substring(URI.indexOf(“?”) + 1);String[] paramPairs = paramString.split(“=”);return paramPairs[1];}}ServletResponse类
封装返回的响应.由HelloServlet返回.
import java.io.IOException;import java.io.OutputStream;{private OutputStream outputStream;public ServletResponse(OutputStream outputStream) {// TODO Auto-generated constructor stubthis.outputStream = outputStream;}public String assembleResponseHeader(String contentType) {/* 创建HTTP响应结果 */// HTTP响应的第一行String responseFirstLine = “HTTP/1.1 200 OK\r\n”;// HTTP响应头String responseHeader = “Content-Type:” + contentType + “\r\n\r\n”;return responseFirstLine + responseHeader;}public String assembleResponseBody(String param) {String content = “<body><h1>Hello:” + param + “</h1></body>”;String title = “<head><title>HelloWorld</title></head>”;String body = “<html>” + title + content + “</html>”;return body;}(String res) throws IOException {outputStream.write(res.getBytes());}}测试
在chrome浏览器输入:8088/HelloServlet?username=tom. 即用户请求的参数是tom,要调用HelloServlet. (在实际的servlet实现中,是用一个web.xm配置文件实现URI到servlet的映射.)
servlet解析出来后组装成html返回给浏览器.显示为Hello:tom
，友谊之花、爱情之树、以及遗憾之泪！
