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
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" + "File Not Found
"; 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; }...}