本文是阅读《深度解析Tomcat》的笔记。
源码：http://www.brainysoftware.com/source/9780975212806.zip
├── src
│ └── pyrmont
│ ├── Constants.java
│ ├── HttpServer1.java
│ ├── HttpServer2.java
│ ├── RequestFacade.java
│ ├── Request.java
│ ├── ResponseFacade.java
│ ├── Response.java
│ ├── ServletProcessor1.java
│ ├── ServletProcessor2.java
│ └── StaticResourceProcessor.java
└── webroot
├── images
│ └── logo.gif
├── index.html
├── PrimitiveServlet.class
└── PrimitiveServlet.java
1、HttpServer1监听在8080端口，等待客户端socket连接，一旦有客户端连接，就为此客户端新建一个Request、Response，并分别传递InputStream，OutputStream。
其实就是把客户端的输入和服务器的输出封装到Request、Response。
2、HttpServer1利用Request解析url，判断客户端是要请求静态资源还是一个Servlet(目前的HttpServer1只支持这两种简单的请求)。
如果是静态资源则交给StaticResourceProcessor处理，Servlert则交给ServletProcessor1处理。
StaticResourceProcessor：调用Response处理静态文件，即利用IO读写文件。
ServletProcessor1：解析url中Servlet的Name，找到该Servlet的class文件，加载Servlet。调用xxxServlet.service((ServletRequest)request,(ServletResponse)response)
优化分析：
xxxServlet.service((ServletRequest)request,(ServletResponse)response)，把我们web容器的request，response传给web程序，如果该程序员了解我们容器的实现，他就可以
向下转型为Request、Response。我们并不希望Request、Response的实现细节暴露给调用这，所以不能是public修饰方法，只能是默认修饰。为了更优雅的达到目的，可以用外观模式，新增外观类 RequestFacade，ResponseFacade。
xxxServlet.service((ServletRequest)request,(ServletResponse)response)里的request，response是RequestFacade，ResponseFacade。
启动HttpServer1，在项目下应该有webroot文件夹，里面有index.html ,和xxServlet.class
访问：http://127.0.0.1:8080/index.html
访问：http://127.0.0.1:8080/servlet/xxServlet
源码：
package pyrmont;
import java.io.File;
public class Constants {
public static final String WEB_ROOT =
System.getProperty("user.dir") + File.separator + "webroot";
}
package pyrmont; 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 { /**
* WEB_ROOT is the directory where our HTML and other files reside.
* For this package, WEB_ROOT is the "webroot" directory under the working
* directory.
* The working directory is the location in the file system
* from where the java command was invoked.
*/
// shutdown command
private static final String SHUTDOWN_COMMAND = "/SHUTDOWN"; // the shutdown command received
private boolean shutdown = false; public static void main(String[] args) {
HttpServer1 server = new HttpServer1();
server.await();
} public 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);
} // Loop waiting for a request
while (!shutdown) {
Socket socket = null;
InputStream input = null;
OutputStream output = null;
try {
socket = serverSocket.accept();
input = socket.getInputStream();
output = socket.getOutputStream(); // create Request object and parse
Request request = new Request(input);
request.parse(); // create Response object
Response response = new Response(output);
response.setRequest(request); // check if this is a request for a servlet or a static resource
// a request for a servlet begins with "/servlet/"
if (request.getUri().startsWith("/servlet/")) {
ServletProcessor1 processor = new ServletProcessor1();
processor.process(request, response);
} else {
StaticResourceProcessor processor = new StaticResourceProcessor();
processor.process(request, response);
} // Close the socket
socket.close();
//check if the previous URI is a shutdown command
shutdown = request.getUri().equals(SHUTDOWN_COMMAND);
} catch (Exception e) {
e.printStackTrace();
System.exit(1);
}
}
}
}
package pyrmont;
import java.io.IOException;
public class StaticResourceProcessor {
public void process(Request request, Response response) {
try {
response.sendStaticResource();
} catch (IOException e) {
e.printStackTrace();
}
}
}
package pyrmont; import javax.servlet.Servlet;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.net.URLClassLoader;
import java.net.URLStreamHandler; public class ServletProcessor1 { public void process(Request request, Response response) { String uri = request.getUri();
String servletName = uri.substring(uri.lastIndexOf("/") + 1);
URLClassLoader loader = null; try {
// create a URLClassLoader
URL[] urls = new URL[1];
URLStreamHandler streamHandler = null;
File classPath = new File(Constants.WEB_ROOT);
// the forming of repository is taken from the createClassLoader method in
// org.apache.catalina.startup.ClassLoaderFactory
String repository = (new URL("file", null, classPath.getCanonicalPath() + File.separator)).toString() ;
// the code for forming the URL is taken from the addRepository method in
// org.apache.catalina.loader.StandardClassLoader class.
urls[0] = new URL(null, repository, streamHandler);
loader = new URLClassLoader(urls);
}
catch (IOException e) {
System.out.println(e.toString() );
}
Class myClass = null;
try {
myClass = loader.loadClass(servletName);
}
catch (ClassNotFoundException e) {
System.out.println(e.toString());
} Servlet servlet = null; try {
servlet = (Servlet) myClass.newInstance();
servlet.service((ServletRequest) request, (ServletResponse) response);
}
catch (Exception e) {
System.out.println(e.toString());
}
catch (Throwable e) {
System.out.println(e.toString());
} }
}
package pyrmont; import javax.servlet.*;
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; public class Request implements ServletRequest { private InputStream input;
private String uri; public Request(InputStream input) {
this.input = input;
} public String getUri() {
return uri;
} 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 void parse() {
// Read a set of characters from the socket
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.print(request.toString());
uri = parseUri(request.toString());
} ...
}
package pyrmont; import javax.servlet.ServletOutputStream;
import javax.servlet.ServletResponse;
import java.io.*;
import java.util.Locale; 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 setRequest(Request request) {
this.request = request;
} /* This method is used to serve a static page */
public void sendStaticResource() throws IOException {
byte[] bytes = new byte[BUFFER_SIZE];
FileInputStream fis = null;
try {
/* request.getUri has been replaced by request.getRequestURI */
File file = new File(Constants.WEB_ROOT, request.getUri());
fis = new FileInputStream(file);
/*
HTTP Response = Status-Line
*(( general-header | response-header | entity-header ) CRLF)
CRLF
[ message-body ]
Status-Line = HTTP-Version SP Status-Code SP Reason-Phrase CRLF
*/
int ch = fis.read(bytes, 0, BUFFER_SIZE);
while (ch!=-1) {
output.write(bytes, 0, ch);
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 PrintWriter getWriter() throws IOException {
// autoflush is true, println() will flush,
// but print() will not.
writer = new PrintWriter(output, true);
return writer;
} ...
}
优化：
package pyrmont; 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 HttpServer2 { // shutdown command
private static final String SHUTDOWN_COMMAND = "/SHUTDOWN"; // the shutdown command received
private boolean shutdown = false; public static void main(String[] args) {
HttpServer2 server = new HttpServer2();
server.await();
} public 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);
} // Loop waiting for a request
while (!shutdown) {
Socket socket = null;
InputStream input = null;
OutputStream output = null;
try {
socket = serverSocket.accept();
input = socket.getInputStream();
output = socket.getOutputStream(); // create Request object and parse
Request request = new Request(input);
request.parse(); // create Response object
Response response = new Response(output);
response.setRequest(request); //check if this is a request for a servlet or a static resource
//a request for a servlet begins with "/servlet/"
if (request.getUri().startsWith("/servlet/")) {
ServletProcessor2 processor = new ServletProcessor2();
processor.process(request, response);
}
else {
StaticResourceProcessor processor = new StaticResourceProcessor();
processor.process(request, response);
} // Close the socket
socket.close();
//check if the previous URI is a shutdown command
shutdown = request.getUri().equals(SHUTDOWN_COMMAND);
}
catch (Exception e) {
e.printStackTrace();
System.exit(1);
}
}
}
}
package pyrmont; import javax.servlet.Servlet;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.net.URLClassLoader;
import java.net.URLStreamHandler; public class ServletProcessor2 { public void process(Request request, Response response) { String uri = request.getUri();
String servletName = uri.substring(uri.lastIndexOf("/") + 1);
URLClassLoader loader = null; try {
// create a URLClassLoader
URL[] urls = new URL[1];
URLStreamHandler streamHandler = null;
File classPath = new File(Constants.WEB_ROOT);
// the forming of repository is taken from the createClassLoader method in
// org.apache.catalina.startup.ClassLoaderFactory
String repository = (new URL("file", null, classPath.getCanonicalPath() + File.separator)).toString() ;
// the code for forming the URL is taken from the addRepository method in
// org.apache.catalina.loader.StandardClassLoader class.
urls[0] = new URL(null, repository, streamHandler);
loader = new URLClassLoader(urls);
}
catch (IOException e) {
System.out.println(e.toString() );
}
Class myClass = null;
try {
myClass = loader.loadClass(servletName);
}
catch (ClassNotFoundException e) {
System.out.println(e.toString());
} Servlet servlet = null;
RequestFacade requestFacade = new RequestFacade(request);
ResponseFacade responseFacade = new ResponseFacade(response);
try {
servlet = (Servlet) myClass.newInstance();
servlet.service((ServletRequest) requestFacade, (ServletResponse) responseFacade);
}
catch (Exception e) {
System.out.println(e.toString());
}
catch (Throwable e) {
System.out.println(e.toString());
} }
}
package pyrmont; import javax.servlet.*;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.util.Enumeration;
import java.util.Locale;
import java.util.Map; public class RequestFacade implements ServletRequest { private ServletRequest request = null; public RequestFacade(Request request) {
this.request = request;
}
... }
package pyrmont; import javax.servlet.ServletOutputStream;
import javax.servlet.ServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Locale; public class ResponseFacade implements ServletResponse { private ServletResponse response;
public ResponseFacade(Response response) {
this.response = response;
} ... }