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;
}
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