servlet接口

　　使用servlet编程需要实现或者继承实现了javax.servlet.Servlet接口的类,其中定义了5个签名方法：

1 public void init(ServletConfig config) throws ServletException2 public void service(ServletRequest req,ServletResponse res) throws ServletException,java.io.IOException3 public void destroy()4 public ServletConfig getServletConfig()5 public java.lang.String getServletInfo()

init(),service(),destroy对应着servlet的生命周期，init只在加载该servlet时执行且只此一次，容器根据用户请求调用对应servlet的service执行方法，当实例销毁移除前容器调用destroy处理后续操作。

模拟容器主要工作流程：

• 等待http请求
• 根据请求创建对应Request与Response对象
• 如果请求的是静态资源，则调用StaticResourceProcessor发送对应资源
• 如果请求是servlet，则加载该类并执行其service方法

简单servlet容器

 主要类信息如下：

1. HttpServer  与web服务器类似，不同的是加入了servlet请求判断，并调用ServletProcessor处理对应servlet
2. Request   与上一篇web服务器类似，但是实现了ServletRequest接口
3. Response   与上一篇web服务器类似，但是实现了ServletResponse接口
4. StaticResourceProcessor  用于处理请求静态资源时调用
5. ServletProcessor 用于当请求是servlet时调用
6. Constant 定义一些常量
7. MyLogger 自己定义在控制台打印日志信息，可以忽略
8. PrimitiveServlet 实现servlet接口，自定义servlet程序用于请求调用

说明：部分接口只是实现了需要用到的方法，并没有完全实现所有方法，使用默认即可，代码里面没有贴出来

(一）HttpServer 

 

1 public class HttpServer { 2     MyLogger logger = new MyLogger<>(HttpServer.class); 3     private static final String SHUTDOWN_COMMAND = "/SHUTDOWN"; 4     private boolean  shutdown = false; 5      6     public void await() { 7         ServerSocket serverSocket = null; 8         int port = 8080; 9         try {10             serverSocket = new ServerSocket(port, 1, InetAddress.getByName("127.0.0.1"));11             logger.log("server started......." + "at " + serverSocket.toString());12         } catch (IOException e) {13             // TODO Auto-generated catch block14             e.printStackTrace();15             System.exit(1);16         }17         while (!shutdown){18             Socket socket = null;19             InputStream inputStream = null;20             OutputStream outputStream = null;21             try {22                 socket = serverSocket.accept();23                 logger.log("accepted new request...");24                 inputStream = socket.getInputStream();25                 outputStream = socket.getOutputStream();26                 Request request = new Request(inputStream);27                 request.Parse();28                 Response response = new Response(outputStream);29                 response.setRequest(request);30                 logger.log("inition done,begin process.......");31                 if(request.getUri() == null){32                     logger.log("request uri is null...close socket");33                     socket.close();34                     continue;35                 }36                 else if(request.getUri().startsWith("/servlet/")){37                     logger.log("execute servlet...");38                     ServletProcessor servletProcessor = new ServletProcessor();39                     servletProcessor.process(request, response);40                 }41                 else {42                     logger.log("send staticResource...");43                     StaticResourceProcessor staticResourceProcessor = new StaticResourceProcessor();44                     staticResourceProcessor.process(request, response);45                 }46                 socket.close();47                 shutdown = request.getUri().equals(SHUTDOWN_COMMAND);48             } catch (IOException e) {49                 // TODO Auto-generated catch block50                 e.printStackTrace();51             }52         }53     }54 }

(二）Request 

 

1 public class Request implements ServletRequest{ 2      3     MyLogger logger = new MyLogger(ServletRequest.class); 4     private String uri; 5     private InputStream in; 6      7     public Request(InputStream in){ 8         this.in = in; 9     }10     11     public String parseUri(String request){12         int index1,index2;13         index1 = request.indexOf(" ");14         if (index1 != -1){15             index2 = request.indexOf(" ", index1+ 1);16             if (index1 < index2)17                 return request.substring(index1 + 1, index2);18         }19         return null;20     }21     22     public void Parse(){23         StringBuffer request = new StringBuffer(2048);24         byte[] bs = new byte[2048];25         int i;26         try {27             i = in.read(bs);28         } catch (IOException e) {29             e.printStackTrace();30             i = -1;31         }32         33         for(int j=0; j

 

(三）Response 

 

1 public class Response implements ServletResponse{ 2      3     MyLogger logger = new MyLogger(Response.class); 4     private static final int BUFFER_SIZE = 1024; 5     private Request request; 6     private OutputStream out; 7     private PrintWriter writer; 8      9     public  Response(OutputStream out) {10         this.out = out;11     }12     13     public  void setRequest(Request request) {14         this.request = request;15     }16     //假设请求的是图片资源17     public void sendStaticResource() throws IOException{18         byte[] buffer = new byte[BUFFER_SIZE];19         FileInputStream fis = null;20         File file = new File(Constant.WEB_ROOT, request.getUri());21         try {22             logger.log("Begin read file + " + file.toString());23             fis = new FileInputStream(file);24             String headerMsg = "HTTP/1.1 200 OK\r\n" + 25                     "Content-Type: image/jpg\r\n" + 26                     "Content-Length: " + file.length() + "\r\n" +27                     "\r\n" ;28             logger.log("headerMsg->\r\n" + headerMsg);29             out.write(headerMsg.getBytes());30             int ch = fis.read(buffer, 0, BUFFER_SIZE);31             while (ch != -1){32                 out.write(buffer, 0, BUFFER_SIZE);33                 ch = fis.read(buffer, 0, BUFFER_SIZE);34             }35         } catch (FileNotFoundException e) {36             String html = "
file not found
";37             logger.log("FileNotFoundException");38             String errorMsg = "HTTP/1.1 404 file not found\r\n" + 39                     "Content-Type: text/html\r\n" + 40                     "Content-Length: " + html.getBytes().length + "\r\n" +41                     "\r\n" +42                     html;43             out.write(errorMsg.getBytes());44             logger.log("errorMsg->" + errorMsg);45         }46         finally {47             if(fis != null){48                 fis.close();49             }50         }51     }52 }

 

(四）StaticResourceProcessor 

 

1 public class StaticResourceProcessor {2     public void process(Request request,Response response) {3         try {4             response.sendStaticResource();5         } catch (IOException e) {6             e.printStackTrace();7         }8     }9 }

 

(五）ServletProcessor 

 

1 public class ServletProcessor { 2     public void process(Request request,Response response){ 3         String uri = request.getUri(); 4         String servletName = uri.substring(uri.lastIndexOf("/") + 1); 5         URLClassLoader loader = null; 6          7         URL[] urls = new URL[1]; 8         URLStreamHandler urlStreamHandler = null; 9         File classPath = new File(Constant.WEB_ROOT);10         try {11             String repository = (new URL("file",null,classPath.getCanonicalPath() + 12                     File.separator)).toString();13             urls[0] = new URL(null,repository,urlStreamHandler);14             loader = new URLClassLoader(urls);15         } catch (IOException e) {16             // TODO Auto-generated catch block17             e.printStackTrace();18         }19         Class myClass = null;20         try {21             myClass = loader.loadClass(servletName);22         } catch (ClassNotFoundException e) {23             e.printStackTrace();24         }25         26         Servlet servlet = null;27         try {28             servlet = (Servlet) myClass.newInstance();29             servlet.service((ServletRequest)request, (ServletResponse) response);30         31         } catch (InstantiationException | IllegalAccessException e) {32             // TODO Auto-generated catch block33             e.printStackTrace();34         } catch (ServletException e) {35             // TODO Auto-generated catch block36             e.printStackTrace();37         } catch (IOException e) {38             // TODO Auto-generated catch block39             e.printStackTrace();40         }41         42     }43 }

 

(六）MyLogger 

 

1 public  class MyLogger
     
       { 2     private String classStr = ""; 3      4     public  void log(T msg){ 5         System.out.println(classStr + "(" +  6                 (new SimpleDateFormat("yyyy-MM-dd HH:mm:ss")).format(new Date()) + ")" + ": " + msg); 7     } 8     public MyLogger(Class classz){ 9         classStr = classz.getName();10     }11 }
     

 

(七）PrimitiveServlet 

 

1 public class PrimitiveServlet implements Servlet{ 2     MyLogger Logger = new MyLogger<>(PrimitiveServlet.class); 3     @Override 4     public void destroy() { 5         // TODO Auto-generated method stub 6          7     } 8  9     @Override10     public ServletConfig getServletConfig() {11         // TODO Auto-generated method stub12         return null;13     }14 15     @Override16     public String getServletInfo() {17         // TODO Auto-generated method stub18         return null;19     }20 21     @Override22     public void init(ServletConfig arg0) throws ServletException {23         // TODO Auto-generated method stub24         25     }26 27     @Override28     public void service(ServletRequest request, ServletResponse response) throws ServletException, IOException {29         Logger.log("service execute.....");30         PrintWriter writer = response.getWriter();31         writer.println("Hey,welcome on board!");32         writer.println("lets rock!");33     }34 35 }

(八）Constant 

 

public class Constant {    public static final String WEB_ROOT =             System.getProperty("user.dir") + File.separator + "bin";}