模擬Servlet容器管理Servlet

實現Servlet容器（Servlet容器根據web.xml文件調用對應的Servlet類）

Servlet（狹義解釋是Servlet介面，但更常見的解釋是實現Servlet的所有類）

介紹：Servlet容器是用來管理Servlet，

過程：瀏覽器輸入URL地址，伺服器接收到這個地址，根據瀏覽器的訪問方式，響應消息發送給瀏覽器，併在瀏覽器上顯示。

Servlet的工作過程：

1.瀏覽器提交請求（通常是URL或超鏈接或表單提交）

2.伺服器接收到請求後，判斷請求的Servlet如果是第一次請求就實例化一個Servlet

3.調用Servlet的service（）方法

4.伺服器把產生的響應內容發送給客戶端

5.瀏覽器根據自己的解析方式對響應內容進行解析

代碼實現：

編寫各類的功能：

HttpServletRequest解析URL，得到請求方式和地址等信息

HttpServletResponse封裝Http響應消息

HttpServlet抽象類，doService（）方法根據請求的方式執行相應的子類方法

Service類有主函數，伺服器Socket設置埠號，接收客戶端的socket對象，這裡讀取一個屬性文件web.properties來模擬配置文件Web.xml,實現URL到類的映射

MyServlet和MyServlet2繼承自HttpServlet，相應的方法把html通過httpServletResponse發送給瀏覽器

  1 package com.wj;
  2 
  3 import java.io.BufferedReader;
  4 import java.io.IOException;
  5 import java.io.InputStreamReader;
  6 import java.net.Socket;
  7 
  8 /*
  9  * 解析瀏覽器的請求，得到請求的方式和地址等信息
 10  */
 11 public class HttpServletRequest {
 12 
 13     private Socket socket;
 14     private String[] items;
 15     public HttpServletRequest(Socket socket) throws IOException {
 16         this.socket = socket;
 17         BufferedReader br=new BufferedReader(new InputStreamReader(socket.getInputStream()));
 18         String cmd=br.readLine();
 19         items=cmd.split(" ");
 20         
 21     }
 22     public String getMethod(){
 23         return items[0];
 24     }
 25     public String getURI(){
 26         return items[1];
 27     }
 28     
 29 }
 30 package com.wj;
 31 
 32 import java.io.IOException;
 33 import java.io.OutputStream;
 34 import java.io.PrintWriter;
 35 import java.net.Socket;
 36 
 37 public class HttpServletResponse {
 38 
 39     private Socket socket;
 40     public HttpServletResponse(Socket socket){
 41         this.socket=socket;
 42     }
 43     public OutputStream getOutputStream() throws IOException{
 44         return socket.getOutputStream();
 45     }
 46     public PrintWriter getWriter() throws IOException{
 47         return new PrintWriter(this.socket.getOutputStream());
 48     }
 49 }
 50 package com.wj;
 51 
 52 import java.io.IOException;
 53 
 54 
 55 public abstract class HttpServlet{
 56 
 57 
 58     public abstract void doPost(HttpServletRequest request,HttpServletResponse response) throws IOException;
 59 
 60     public abstract void doGet(HttpServletRequest request,HttpServletResponse response)throws IOException;
 61 
 62     public void doService(HttpServletRequest req, HttpServletResponse res)
 63             throws IOException {
 64         String me=req.getMethod();
 65         if(me.equalsIgnoreCase("get")){
 66             doGet(req, res);
 67         }else{
 68             doPost(req, res);
 69         }
 70     }
 71 }
 72 package com.wj;
 73 
 74 import java.io.BufferedReader;
 75 import java.io.FileInputStream;
 76 import java.io.IOException;
 77 import java.net.ServerSocket;
 78 import java.net.Socket;
 79 import java.util.Properties;
 80 
 81 public class Service {
 82     public static void main(String[] args) throws IOException {
 83         // TODO Auto-generated method stub
 84         ServerSocket server = null;
 85         BufferedReader br = null;
 86 
 87         server = new ServerSocket(11111);
 88         Socket socket = null;
 89         while (true) {// loop
 90             try {
 91                 socket = server.accept();
 92                 HttpServletRequest request = new HttpServletRequest(socket);
 93                 HttpServletResponse response = new HttpServletResponse(socket);
 94                 Properties prop = new Properties();
 95                 prop.load(new FileInputStream("src/web.properties"));  //Java讀取配置文件信息
 96                 String className = prop.getProperty(request.getURI());
 97                 HttpServlet servlet = (HttpServlet)Class.forName(className).newInstance();
 98                 servlet.doService(request, response);
 99             } catch (Exception ex) {
100                 System.out.println(ex.getMessage());
101             } finally {
102                 if(socket != null){
103                     socket.close();
104                 }
105             }
106         }
107     }
108 
109 }
110 package com.wj2;
111 
112 import java.io.IOException;
113 import java.io.PrintWriter;
114 
115 import com.wj.HttpServlet;
116 import com.wj.HttpServletRequest;
117 import com.wj.HttpServletResponse;
118 
119 public class MyServlet extends HttpServlet{
120 
121     @Override
122     public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
123         // TODO Auto-generated method stub
124         String html = "<html><head><title>hello</title></head><body><h1>Hello</h1></body></html>";
125         PrintWriter out=response.getWriter();
126         out.print(html);
127         out.flush();
128         out.close();
129         
130     }
131 
132     @Override
133     public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException {
134         // TODO Auto-generated method stub
135         this.doGet(request, response);
136     }
137     
138 
139 }
140 package com.wj2;
141 
142 import java.io.IOException;
143 import java.io.PrintWriter;
144 
145 import com.wj.HttpServlet;
146 import com.wj.HttpServletRequest;
147 import com.wj.HttpServletResponse;
148 
149 public class MyServlet2 extends HttpServlet{
150 
151     @Override
152     public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
153         // TODO Auto-generated method stub
154         String html = "<html><head><title>hello2</title></head><body><h1>Hello2</h1></body></html>";
155         PrintWriter out=response.getWriter();
156         out.println(html);
157         out.flush();
158         out.close();
159         
160     }
161 
162     @Override
163     public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException {
164         // TODO Auto-generated method stub
165         this.doGet(request, response);
166     }
167     
168 
169 }

web.properties內容：（URL，映射到對應的Servlet類）

/testServlet/servlet/SvTest com.wj2.MyServlet
/testServlet/SvTest2 com.wj2.MyServlet2

Java工程目錄樹為：

瀏覽器可以和訪問Tomcat伺服器一樣，我們直接訪問：http://localhost:11111/testServlet/Servlet/SvTest

 (ps:如果顯示localhost未發送任何數據的結果，可以換一個瀏覽器進行操作)