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。

 

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;
	}

	
}

 

 

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;
	}

}