6,一个简单的servlet容器
总的来说，一个全功能的servlet容器会为servlet的每个HTTP请求做下面一些工作：
当第一次调用servlet的时候，加载该servlet类并调用servlet的init方法(仅仅一次)。
?对每次请求，构造一个javax.servlet.ServletRequest实例和一个javax.servlet.ServletResponse实例。
调用servlet的service方法，同时传递ServletRequest和ServletResponse对象。
当servlet类被关闭的时候，调用servlet的destroy方法并卸载servlet类。
下面这个简单的servlet容器不能做上面的工作，相反，做了下面的几件事
1，等待HTTP请求。
2，构造一个ServletRequest对象和一个ServletResponse对象。
3，假如该请求需要一个静态资源的话，调用StaticResourceProcessor实例的process方法，同时传递ServletRequest和ServletResponse对象。
4，假如该请求需要一个servlet的话，加载servlet类并调用servlet的service方法，同时传递ServletRequest和ServletResponse对象。
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Servlet由Servlet容器来管理，当客户请求到来时，容器创建一个ServletRequest对象，封装请求数据，同时创建一个ServletResponse对象，封装响应数据。这两个对象将被容器作为service（）方法的参数传递给Servlet，Serlvet利用ServletRequest对象获取客户端发来的请求数据，利用ServletRequest对象发送响应数据。
所以，我们的容器应构造一个ServletRequest和ServletResponse，即实现这俩个接口即可。
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核心代码如下：
package org.tomcat;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;import java.net.InetAddress;import java.net.ServerSocket;import java.net.Socket;public class HttpServer1 {private static final String SHUTDOWN_COMMAND= "/SHUTDOWN";private boolean shutdown =false;public static void main(String[] args){HttpServer1 server = new HttpServer1();server.await();}private void await() {ServerSocket serverSocket = null;int port =8080;try{serverSocket = new ServerSocket(port,1,InetAddress.getByName("127.0.0.1"));}catch(IOException e){e.printStackTrace();System.exit(-1);}while(!shutdown){Socket socket = null;InputStream input = null;OutputStream output = null;try{socket = serverSocket.accept();input = socket.getInputStream();output = socket.getOutputStream();Request request = new Request(input);request.parse();Response response = new Response(output);response.setRequest(request);if (request.getUri().startsWith("/servlet/")) {ServletProcessor1 processor = new ServletProcessor1(); processor.proess(request, response);}else{StaticResourceProcessor processor = new StaticResourceProcessor(); processor.process(request, response);}socket.close();shutdown = request.getUri().equals(SHUTDOWN_COMMAND);}catch(Exception e){e.printStackTrace();System.exit(-1);}}}}?
package org.tomcat;import java.io.BufferedReader;import java.io.IOException;import java.io.InputStream;import java.io.UnsupportedEncodingException;import java.util.Enumeration;import java.util.Locale;import java.util.Map;import javax.servlet.RequestDispatcher;import javax.servlet.ServletInputStream;import javax.servlet.ServletRequest;public class Request implements ServletRequest{private InputStream input;private String uri;public Request(InputStream input){this.input = input;}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.println(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 Object getAttribute(String arg0) {return null;}public Enumeration getAttributeNames() {return null;}public String getCharacterEncoding() {return null;}public int getContentLength() {return 0;}public String getContentType() {return null;}public ServletInputStream getInputStream() throws IOException {return null;}public String getLocalAddr() {return null;}public Locale getLocale() {return null;}public Enumeration getLocales() {return null;}public String getLocalName() {return null;}public int getLocalPort() {return 0;}public String getParameter(String arg0) {return null;}public Map getParameterMap() {return null;}public Enumeration getParameterNames() {return null;}public String[] getParameterValues(String arg0) {return null;}public String getProtocol() {return null;}public BufferedReader getReader() throws IOException {return null;}public String getRealPath(String arg0) {return null;}public String getRemoteAddr() {return null;}public String getRemoteHost() {return null;}public int getRemotePort() {return 0;}public RequestDispatcher getRequestDispatcher(String arg0) {return null;}public String getScheme() {return null;}public String getServerName() {return null;}public int getServerPort() {return 0;}public boolean isSecure() {return false;}public void removeAttribute(String arg0) {}public void setAttribute(String arg0, Object arg1) {}public void setCharacterEncoding(String arg0)throws UnsupportedEncodingException {}public String getUri() {return uri;}}?
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package org.tomcat;import java.io.File;import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.IOException;import java.io.OutputStream;import java.io.PrintWriter;import java.util.Locale;import javax.servlet.ServletOutputStream;import javax.servlet.ServletResponse;public class Response implements ServletResponse {private static final int BUFFER_SIZE=1024;Request request;OutputStream output;PrintWriter writer;public Response(OutputStream output){this.output = output;}public void sendStaticResource()throws IOException{byte[] bytes= new byte[BUFFER_SIZE];FileInputStream fis = null;try{File file = new File(Constants.WEB_ROOT,request.getUri());fis = new FileInputStream(file);int ch = fis.read(bytes,0,BUFFER_SIZE);while(ch!=-1){output.write(bytes,0,BUFFER_SIZE);ch = fis.read(bytes,0,BUFFER_SIZE);}}catch(FileNotFoundException e){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());}finally{if(fis!=null)fis.close();}}public void flushBuffer() throws IOException {}public int getBufferSize() {return 0;}public String getCharacterEncoding() {return null;}public String getContentType() {return null;}public Locale getLocale() {return null;}public ServletOutputStream getOutputStream() throws IOException {return null;}public PrintWriter getWriter() throws IOException {writer = new PrintWriter(output,true);return writer;}public boolean isCommitted() {return false;}public void reset() {}public void resetBuffer() {}public void setBufferSize(int arg0) {}public void setCharacterEncoding(String arg0) {}public void setContentLength(int arg0) {}public void setContentType(String arg0) {}public void setLocale(Locale arg0) {}public void setRequest(Request request) {this.request = request;}}?