《How Tomcat Works》学习笔记（二）

第二章主要是编写一个简单的servlet容器。

书中对Servlet中的一些接口和类进行了详细的解释。

通过书中的自己写一个可以访问静态资源和servlet的简单Servlet容器（从上一讲的拓展）

SocketTest 

Request

Response

StaticResourceProcessor

ServletProcessor1

Constants

项目目录结构：



SocketTest

package com.test.test;

import java.io.InputStream;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;

public class SocketTest
{
//获取文件路径

private static final String SHUTDOWN="/SHUTDOWN";
private boolean shutdown = false;
public static void main(String[] args)
{

SocketTest st = new SocketTest();
st.await();
}

public void await()
{
ServerSocket serverSocket = null;

int port = 8080;

try
{
serverSocket = new ServerSocket(port, 1, InetAddress.getByName("127.0.0.1"));
}catch(Exception e)
{
e.printStackTrace();
System.exit(1);
}
while(!shutdown)
{
Socket socket = null;

InputStream is = null;

OutputStream os = null;

try
{
socket  = serverSocket.accept();
is = socket.getInputStream();
os = socket.getOutputStream();

Request request = new Request(is);

request.parse();

Response response = new Response(os);

response.setRequest(request);

//判断请求的是静态资源还是servlet
//处理servlet
if(request.getUri().startsWith("/servlet/"))
{
ServletProcessor1 sp = new ServletProcessor1();
sp.process(request,response);
}//处理静态资源
else
{
StaticResourceProcessor srp = new StaticResourceProcessor();

srp.process(request,response);
}
socket.close();
shutdown = request.getUri().equals(SHUTDOWN);

}catch(Exception e)
{
e.printStackTrace();
System.exit(1);
}
}

}
}

Request:

package com.test.test;

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.AsyncContext;
import javax.servlet.DispatcherType;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletContext;
import javax.servlet.ServletInputStream;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class Request implements ServletRequest{

private InputStream is;

private String uri;

public Request(InputStream is)
{
this.is = is;
}

public String getUri()
{
return this.uri;
}

public void parse() {

StringBuffer sb = new StringBuffer(2048);
byte[] buff = new byte[2048];

int length = -1;
try
{

length = is.read(buff);

}catch(Exception e)
{
e.printStackTrace();
}
for(int i=0; i<length; i++)
{
sb.append((char)buff[i]);
}
System.out.println("request :  "+sb.toString());

//解析
uri = parseUri(sb.toString());
}

//请求头的格式GET /servlet/PrimitiveServlet HTTP/1.1
//返回的的是/servlet/PrimitiveServlet
private String parseUri(String source) {

int beginIndex,endIndex;
beginIndex = source.indexOf(" ");

if(-1 != beginIndex)
{
endIndex = source.indexOf(" ", beginIndex+1);

if(endIndex > beginIndex)
{
return source.substring(beginIndex+1, endIndex);
}
}

return null;
}

@Override
public Object getAttribute(String name) {
// TODO Auto-generated method stub
return null;
}

@Override
public Enumeration<String> getAttributeNames() {
// TODO Auto-generated method stub
return null;
}

@Override
public String getCharacterEncoding() {
// TODO Auto-generated method stub
return null;
}

@Override
public void setCharacterEncoding(String env) throws UnsupportedEncodingException {
// TODO Auto-generated method stub

}

@Override
public int getContentLength() {
// TODO Auto-generated method stub
return 0;
}

@Override
public String getContentType() {
// TODO Auto-generated method stub
return null;
}

@Override
public ServletInputStream getInputStream() throws IOException {
// TODO Auto-generated method stub
return null;
}

@Override
public String getParameter(String name) {
// TODO Auto-generated method stub
return null;
}

@Override
public Enumeration<String> getParameterNames() {
// TODO Auto-generated method stub
return null;
}

@Override
public String[] getParameterValues(String name) {
// TODO Auto-generated method stub
return null;
}

@Override
public Map<String, String[]> getParameterMap() {
// TODO Auto-generated method stub
return null;
}

@Override
public String getProtocol() {
// TODO Auto-generated method stub
return null;
}

@Override
public String getScheme() {
// TODO Auto-generated method stub
return null;
}

@Override
public String getServerName() {
// TODO Auto-generated method stub
return null;
}

@Override
public int getServerPort() {
// TODO Auto-generated method stub
return 0;
}

@Override
public BufferedReader getReader() throws IOException {
// TODO Auto-generated method stub
return null;
}

@Override
public String getRemoteAddr() {
// TODO Auto-generated method stub
return null;
}

@Override
public String getRemoteHost() {
// TODO Auto-generated method stub
return null;
}

@Override
public void setAttribute(String name, Object o) {
// TODO Auto-generated method stub

}

@Override
public void removeAttribute(String name) {
// TODO Auto-generated method stub

}

@Override
public Locale getLocale() {
// TODO Auto-generated method stub
return null;
}

@Override
public Enumeration<Locale> getLocales() {
// TODO Auto-generated method stub
return null;
}

@Override
public boolean isSecure() {
// TODO Auto-generated method stub
return false;
}

@Override
public RequestDispatcher getRequestDispatcher(String path) {
// TODO Auto-generated method stub
return null;
}

@Override
public String getRealPath(String path) {
// TODO Auto-generated method stub
return null;
}

@Override
public int getRemotePort() {
// TODO Auto-generated method stub
return 0;
}

@Override
public String getLocalName() {
// TODO Auto-generated method stub
return null;
}

@Override
public String getLocalAddr() {
// TODO Auto-generated method stub
return null;
}

@Override
public int getLocalPort() {
// TODO Auto-generated method stub
return 0;
}

@Override
public ServletContext getServletContext() {
// TODO Auto-generated method stub
return null;
}

@Override
public AsyncContext startAsync() {
// TODO Auto-generated method stub
return null;
}

@Override
public AsyncContext startAsync(ServletRequest servletRequest, ServletResponse servletResponse) {
// TODO Auto-generated method stub
return null;
}

@Override
public boolean isAsyncStarted() {
// TODO Auto-generated method stub
return false;
}

@Override
public boolean isAsyncSupported() {
// TODO Auto-generated method stub
return false;
}

@Override
public AsyncContext getAsyncContext() {
// TODO Auto-generated method stub
return null;
}

@Override
public DispatcherType getDispatcherType() {
// TODO Auto-generated method stub
return null;
}

}

Response:

package com.test.test;

import java.io.File;
import java.io.FileInputStream;
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 BUFF_SIZE = 1024;
private OutputStream os;

private Request request;

PrintWriter writer;

public Response(OutputStream os)
{
this.os = os;
}

public void setRequest(Request request) {
this.request = request;
}
public void sendStaticResource()
{
byte[] buff = new byte[BUFF_SIZE];

FileInputStream fis = null;
try
{
File file = new File(Constants.WebRoot, request.getUri());

fis = new FileInputStream(file);

int length = -1;
while(-1 != (length = fis.read(buff)))
{
os.write(buff, 0, length);
}

}catch(Exception 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>";;
try {
os.write(errorMessage.getBytes());
} catch (IOException e1) {
e1.printStackTrace();
}
}finally
{
try {
os.close();
} catch (IOException e) {
e.printStackTrace();
}
}

}

@Override
public String getCharacterEncoding() {
// TODO Auto-generated method stub
return null;
}

@Override
public String getContentType() {
// TODO Auto-generated method stub
return null;
}

@Override
public ServletOutputStream getOutputStream() throws IOException {
// TODO Auto-generated method stub
return null;
}

@Override
public PrintWriter getWriter() throws IOException {

writer = new PrintWriter(os, true);
return writer;
}

@Override
public void setCharacterEncoding(String charset) {
// TODO Auto-generated method stub

}

@Override
public void setContentLength(int len) {
// TODO Auto-generated method stub

}

@Override
public void setContentType(String type) {
// TODO Auto-generated method stub

}

@Override
public void setBufferSize(int size) {
// TODO Auto-generated method stub

}

@Override
public int getBufferSize() {
// TODO Auto-generated method stub
return 0;
}

@Override
public void flushBuffer() throws IOException {
// TODO Auto-generated method stub

}

@Override
public void resetBuffer() {
// TODO Auto-generated method stub

}

@Override
public boolean isCommitted() {
// TODO Auto-generated method stub
return false;
}

@Override
public void reset() {
// TODO Auto-generated method stub

}

@Override
public void setLocale(Locale loc) {
// TODO Auto-generated method stub

}

@Override
public Locale getLocale() {
// TODO Auto-generated method stub
return null;
}
}

StaticResourceProcessor

package com.test.test;

/**
* 静态资源
*
*/
public class StaticResourceProcessor {

public void process(Request request, Response response) {

try
{
response.sendStaticResource();

}catch(Exception e)
{
e.printStackTrace();
}

}

}

ServletProcessor

package com.test.test;

import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.net.URLClassLoader;
import java.net.URLStreamHandler;

import javax.servlet.Servlet;

public class ServletProcessor1 {

public void process(Request request, Response response)
{
String fullName = request.getUri();

String servletName = fullName.substring(fullName.lastIndexOf("/")+1);

System.out.println("servletName: "+servletName);

URLClassLoader loader = null;

try
{
URL[] urls = new URL[1];

URLStreamHandler streamHandler = null;

File classPath = new File(Constants.WebRoot);

//			System.out.println("absolution: "+classPath.getAbsolutePath());
//
//			System.out.println("canon: "+classPath.getCanonicalPath());

String reposity = (new URL("file",null, classPath.getCanonicalPath()+File.pathSeparator)).toString();

urls[0] = new URL(null,reposity, streamHandler);

loader = new URLClassLoader(urls);

}catch(Exception e)
{
e.printStackTrace();
}

try {

Class<?> servletClass = loader.loadClass(servletName);

Object obj = servletClass.newInstance();

Servlet servlet = (Servlet)obj;

servlet.service(request, response);

} catch (Exception e) {
e.printStackTrace();

try {
response.getWriter().println("<h1>Not Find Servlet</h1>");
} catch (IOException e1) {
e1.printStackTrace();
}

}

}

}

PrimitiveServlet(注意写在默认包内)

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.Servlet;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class PrimitiveServlet implements Servlet{

@Override
public void init(ServletConfig config) throws ServletException {

System.out.println("*******init******");
}

@Override
public ServletConfig getServletConfig() {
// TODO Auto-generated method stub
return null;
}

@Override
public void service(ServletRequest request, ServletResponse response) throws ServletException, IOException {

System.out.println("from service");
PrintWriter out = response.getWriter();
//System.out.println(out+".....");
out.println("Hello. Roses are red.");
out.println("Violets are blue.");

}

@Override
public String getServletInfo() {
// TODO Auto-generated method stub
return null;
}

@Override
public void destroy() {
System.out.println("destroy....");
}

}

Constants

package com.test.test;

import java.io.File;

public class Constants {

public static final String WebRoot=System.getProperty("user.dir")+File.separator+"WebContent";
}

运行效果：







有没有觉得ServletProcessor类中看着有点晕，其实是用java中的反射调用PrimitiveServlet中的service方法

改写成下面的也可以：（主要是里面URLClassLoader,URLStreamHandler等等没有弄明白）

package com.test.test;

import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.net.URLClassLoader;
import java.net.URLStreamHandler;

import javax.servlet.Servlet;

public class ServletProcessor1 {

public void process(Request request, Response response)
{
String fullName = request.getUri();

String servletName = fullName.substring(fullName.lastIndexOf("/")+1);

System.out.println("servletName: "+servletName);

try {

Class<?> clazz = Class.forName(servletName);

Servlet servlet = (Servlet)clazz.newInstance();

servlet.service(request, response);

} catch (Exception e) {
e.printStackTrace();

try {
response.getWriter().println("<h1>Not Find Servlet</h1>");
} catch (IOException e1) {
e1.printStackTrace();
}
}

}

}

第一个应用程序有一个严重的问题。在ServletProcessor1类的process方法，你向上转换ex02.pyrmont.Request实例为javax.servlet.ServletRequest，并作为第一个参数传递给servlet的service方法。你也向下转换ex02.pyrmont.Response实例为javax.servlet.ServletResponse，并作为第二个参数传递给servlet的service方法这会危害安全性。知道这个servlet容器的内部运作的Servlet程序员可以分别把ServletRequest和ServletResponse实例向下转换为ex02.pyrmont.Request和ex02.pyrmont.Response，并调用他们的公共方法。拥有一个Request实例，它们就可以调用parse方法。拥有一个Response实例，就可以调用sendStaticResource方法。

添加二个类：

RequestFacade:

package com.test.test;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.util.Enumeration;
import java.util.Locale;
import java.util.Map;

import javax.servlet.AsyncContext;
import javax.servlet.DispatcherType;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletContext;
import javax.servlet.ServletInputStream;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class RequestFacade implements ServletRequest{

private ServletRequest request = null;

public RequestFacade(Request request)
{
this.request = request;
}

@Override
public Object getAttribute(String name) {
return request.getAttribute(name);
}

@Override
public Enumeration<String> getAttributeNames() {

return request.getAttributeNames();
}

@Override
public String getCharacterEncoding() {

return null;
}

@Override
public void setCharacterEncoding(String env) throws UnsupportedEncodingException {
// TODO Auto-generated method stub

}

@Override
public int getContentLength() {
// TODO Auto-generated method stub
return 0;
}

@Override
public String getContentType() {
// TODO Auto-generated method stub
return null;
}

@Override
public ServletInputStream getInputStream() throws IOException {
// TODO Auto-generated method stub
return null;
}

@Override
public String getParameter(String name) {
// TODO Auto-generated method stub
return null;
}

@Override
public Enumeration<String> getParameterNames() {
// TODO Auto-generated method stub
return null;
}

@Override
public String[] getParameterValues(String name) {
// TODO Auto-generated method stub
return null;
}

@Override
public Map<String, String[]> getParameterMap() {
// TODO Auto-generated method stub
return null;
}

@Override
public String getProtocol() {
// TODO Auto-generated method stub
return null;
}

@Override
public String getScheme() {
// TODO Auto-generated method stub
return null;
}

@Override
public String getServerName() {
// TODO Auto-generated method stub
return null;
}

@Override
public int getServerPort() {
// TODO Auto-generated method stub
return 0;
}

@Override
public BufferedReader getReader() throws IOException {
// TODO Auto-generated method stub
return null;
}

@Override
public String getRemoteAddr() {
// TODO Auto-generated method stub
return null;
}

@Override
public String getRemoteHost() {
// TODO Auto-generated method stub
return null;
}

@Override
public void setAttribute(String name, Object o) {
// TODO Auto-generated method stub

}

@Override
public void removeAttribute(String name) {
// TODO Auto-generated method stub

}

@Override
public Locale getLocale() {
// TODO Auto-generated method stub
return null;
}

@Override
public Enumeration<Locale> getLocales() {
// TODO Auto-generated method stub
return null;
}

@Override
public boolean isSecure() {
// TODO Auto-generated method stub
return false;
}

@Override
public RequestDispatcher getRequestDispatcher(String path) {
// TODO Auto-generated method stub
return null;
}

@Override
public String getRealPath(String path) {
// TODO Auto-generated method stub
return null;
}

@Override
public int getRemotePort() {
// TODO Auto-generated method stub
return 0;
}

@Override
public String getLocalName() {
// TODO Auto-generated method stub
return null;
}

@Override
public String getLocalAddr() {
// TODO Auto-generated method stub
return null;
}

@Override
public int getLocalPort() {
// TODO Auto-generated method stub
return 0;
}

@Override
public ServletContext getServletContext() {
// TODO Auto-generated method stub
return null;
}

@Override
public AsyncContext startAsync() {
// TODO Auto-generated method stub
return null;
}

@Override
public AsyncContext startAsync(ServletRequest servletRequest, ServletResponse servletResponse) {
// TODO Auto-generated method stub
return null;
}

@Override
public boolean isAsyncStarted() {
// TODO Auto-generated method stub
return false;
}

@Override
public boolean isAsyncSupported() {
// TODO Auto-generated method stub
return false;
}

@Override
public AsyncContext getAsyncContext() {
// TODO Auto-generated method stub
return null;
}

@Override
public DispatcherType getDispatcherType() {
// TODO Auto-generated method stub
return null;
}

}


ResponseFacade:
package com.test.test;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Locale;

import javax.servlet.ServletOutputStream;
import javax.servlet.ServletResponse;

public class ResponseFacade implements ServletResponse{

private ServletResponse response;

public ResponseFacade(Response response)
{
this.response = response;
}

@Override
public String getCharacterEncoding() {

return response.getCharacterEncoding();
}

@Override
public String getContentType() {
// TODO Auto-generated method stub
return null;
}

@Override
public ServletOutputStream getOutputStream() throws IOException {
// TODO Auto-generated method stub
return null;
}

@Override
public PrintWriter getWriter() throws IOException {
// TODO Auto-generated method stub
return null;
}

@Override
public void setCharacterEncoding(String charset) {
// TODO Auto-generated method stub

}

@Override
public void setContentLength(int len) {
// TODO Auto-generated method stub

}

@Override
public void setContentType(String type) {
// TODO Auto-generated method stub

}

@Override
public void setBufferSize(int size) {
// TODO Auto-generated method stub

}

@Override
public int getBufferSize() {
// TODO Auto-generated method stub
return 0;
}

@Override
public void flushBuffer() throws IOException {
// TODO Auto-generated method stub

}

@Override
public void resetBuffer() {
// TODO Auto-generated method stub

}

@Override
public boolean isCommitted() {
// TODO Auto-generated method stub
return false;
}

@Override
public void reset() {
// TODO Auto-generated method stub

}

@Override
public void setLocale(Locale loc) {
// TODO Auto-generated method stub

}

@Override
public Locale getLocale() {
// TODO Auto-generated method stub
return null;
}

}
ServletProcessor修改一下：
Servlet servlet = null;
RequestFacade requestFacade = new RequestFacade(request);
ResponseFacade responseFacade = new ResponseFacade(response);
try {

servlet = (Servlet) myClass.newInstance();
servlet.service((ServletRequest) requestFacade,(ServletResponse)responseFacade);
}