RequestHander类介绍

RequestHander是一个抽象类，是一个线程。它封装了一个Socket。代码不难；

package org.simpleHTTPServer;

import java.io.IOException;
import java.net.Socket;

/**
 * Handling Network Socket Requests.
 * This is "general-purpose" so far and could handle different protcols (i.e. it is NOT tied to HTTP).
 *
 * @author vorburger
 */
abstract class RequestHandler implements Runnable {
    private final Socket socket;

    public RequestHandler(Socket socket) {
        this.socket = socket;
    }

    /**
     * Handle a request given a Socket - read stuff from it - answer stuff back, etc!
     *
     * @param socket
     * @throws IOException
     * @throws SimpleWebServerException
     */
    protected abstract void handle(Socket socket) throws IOException, SimpleWebServerException;

    public void run() {
        try {
            handle(socket);
        }
        catch (Exception ex) {
            // TODO Real logging... (WARN here)
            ex.printStackTrace();
            // Note: No re-throwing here! "The show must go on..." - servers doesn't die just because we had a problem with one request.
        }
        finally {
            try {
                // Should never be null, but let's be on the safe side anyway
                if ( socket != null ) {
                    // Some options, faster & safer?
                    socket.setSoLinger(false, 0);
                    socket.shutdownInput();
                    socket.shutdownOutput();
                    socket.close();
                }
            } catch (IOException e) {
                // Ignore... OK.
            }
        }
    }
}

我们看到这种设计方法，可以称作是模板方法，整个逻辑框架已经写好，只有具体的handle()方法，可以通过重写不同的类重现不同的逻辑。

RequestHandlerHTTP10这个类，继承了RequestHandler类，重写了handle方法，在handler逻辑上写加上了对http协议的处理，但是依然是抽闲类，出现一个新的抽象方法

void handle(HTTPRequest request, HTTPResponse response)

 protected abstract void handle(HTTPRequest request, HTTPResponse response) throws IOException;

//该方法中创建了httpRequest对象，和HttpResponse队形，然后调用handle(request,responce)

    @Override
    protected void handle(Socket socket) throws IOException, SimpleWebServerException {

       //构建原始的HttpRequset信息
        HTTPRequest request = this.getHTTPRequest(socket);
    //构建响应信息
        HTTPResponse response = new HTTPResponse(socket);

        // "The Date general-header field represents the date and time at which the message was originated"
        // TODO Profile/research: Is DateFormat initialization an expensive operation?  Do this only once...
        DateFormat rfc1123_DateFormat = new SimpleDateFormat(RFC1123_DATE_PATTERN, Locale.US);
        rfc1123_DateFormat.setTimeZone(new SimpleTimeZone(0, "GMT"));
        String date = rfc1123_DateFormat.format(new Date());
        response.setHeader(HTTPResponse.Header.Date, date);

        response.setHeader(HTTPResponse.Header.Server, "SimpleHTTPServer/1.0");

        // This is Connection: close is probably not strictly neccessary as we are a HTTP/1.0 server so far here, but it can't work and seems to work well
        response.setHeader(HTTPResponse.Header.Connection, "close");
        if (HTTPRequest.Version.HTTP11.toString().equals(request.getHTTPVersion())) {
            // Until HTTP/1.1 is properly implemented here, simply "force" (?) response to 1.0 (http://www.ietf.org/rfc/rfc2145.txt)
            // I'm not 1000% sure if this is correct... but it seems to work well with HTTP/1.1 browsers...
            response.setHTTPVersion(HTTPRequest.Version.HTTP10);
        } else if (!HTTPRequest.Version.HTTP10.toString().equals(request.getHTTPVersion())) {
            throw new SimpleWebServerException("Don't know how to answer HTTP requests with this version header: " + request.getHTTPVersion());
        }

        this.handle(request, response);

        System.out.println(socket.getInetAddress().getHostAddress()+" [" + new Date().toString() + "] " + request.getMethod() + " " + request.getHTTPVersion() + " " + request.getURI() + " " + response.getStatusCode());

        // TODO HTTP/1.1 support, we probably don't want to close this response (ultimately, underlying socket) just yet and wait for more requests in this same Handler?
        response.close();
    }

//从http请求信息中抽取信息，封装成HTTPRequest对象
    private HTTPRequest getHTTPRequest(Socket socket) throws IOException, SimpleWebServerException {
        HTTPRequest r = new HTTPRequest();
        InputStream is = socket.getInputStream();
        // TODO Charset of IS?  Try an URL with an Umlaut..  UTF-8?
        Reader reader = new InputStreamReader(is /* charset??? */);
        BufferedReader bufferedReader = new BufferedReader(reader/*, size???  Default is 8k - leave that for now */);
        String httpRequestLine = "";
        // TODO Security: Use e.g. a custom BufferedReader subclass that limits characters per line and total lines to avoid DOS/exhaustion attacks.. (but take big file uploads via POST into account!)
        httpRequestLine = bufferedReader.readLine();
        // This could throw a SocketTimeoutException, which will propagate to the caller, as it should.
        // If null, this also indicates a timeout occured, and we are not dealing with the request either...
        if (httpRequestLine == null) {
            throw new SimpleWebServerException("No (or not enough) data received (within timeout)");
        }

        try {
            String[] httpRequestLineSplitArray = httpRequestLine.split(" ");
            r.method = httpRequestLineSplitArray[0];
            r.URI = httpRequestLineSplitArray[1];
            r.HTTPVersion = httpRequestLineSplitArray[2];
        } catch (Exception ex) {
            throw new SimpleWebServerException("HTTP Request Line (1st line) invalid, should be 'VERB URI VERSION' and not '" + httpRequestLine + "'; see RFC 2616, Section 5", ex);
        }

        while (bufferedReader.ready()) {
            String line = bufferedReader.readLine();
            if (line.length() == 0) {
                break;
            }
            int httpRequestHeaderKeySeparatorPos = line.indexOf(':');
            String httpRequestHeaderKey = line.substring(0, httpRequestHeaderKeySeparatorPos);
            String httpRequestHeaderValue = line.substring(httpRequestHeaderKeySeparatorPos + 1, line.length());
            httpRequestHeaderValue = httpRequestHeaderValue.trim(); // RFC 2616 Section 4.2

            r.headers.put(httpRequestHeaderKey, httpRequestHeaderValue);
        }

        // TODO Test if Header/Body delimiter code here works
        StringBuffer bodySB = new StringBuffer(1024);
        while (bufferedReader.ready()) {
            String line = "";
            do {
                line = bufferedReader.readLine();
            } while (line.length() == 0);
            bodySB.append(line);
            bodySB.append('\n');
        }
        r.body = bodySB.toString();

        return r;
    }
}

RequestHandlerStaticSite代码就很简单了

/**
 *  Copyright 2006-2012 Michael Vorburger (http://www.vorburger.ch)
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

/*******************************************************************************
 * Copyright (c) 2006-2012 Michael Vorburger (http://www.vorburger.ch).
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *******************************************************************************/

package org.simpleHTTPServer;

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.net.Socket;
import java.net.URI;
import java.net.URISyntaxException;

import javax.activation.MimetypesFileTypeMap;

/**
 * Handle HTTP requests by serving fiels from the local filesystem.
 * Given a root directory, files corresponding to the URI are sent to the client.
 *
 * @author vorburger
 * @author romain
 */
// TODO TestCase for RequestHandlerStaticSite
class RequestHandlerStaticSite extends RequestHandlerHTTP10 {

    File siteRoot;

    public RequestHandlerStaticSite(Socket socket, File htDocsRootPath) {
        super(socket);
        siteRoot = htDocsRootPath;
    }

    protected void handleGet(HTTPRequest request, HTTPResponse response) throws IOException {
        // Note: The JDK URI class can do RFC 2396 encoding and decoding for us here...
        URI uri;
        try {
            uri = new URI(request.getURI());
        } catch (URISyntaxException e) {
            response.setStatusCode(400); // 400 is Bad Request, seems a suitable answer for this case
            handleException(request, response, "URISyntaxException", e);
            return;
        }
        // This wouldn't handle %20-like encoding/decoding:  String uri = request.getURI();
        File file = new File(siteRoot, uri.getPath());

        if (!file.exists()) {
            response.setStatusCode(404); // 404 is 'Not Found', the correct answer for this case
            handleError(request, response, "File Not Found for requested URI '" + uri + "' ");
            return;
        }
        if (!file.canRead()) {
            response.setStatusCode(403); // 403 is 'Forbidden', this seems appropriate here
            handleError(request, response, "Local file matched by requested URI is not readable");
            // SECURITY Note: It's better not to show the full local path to the client, let's just log it on the server to help debugging
            return;
        }

        // TODO Security: Check that no request can read "outside" (above) the siteRoot... using getCanonicalPath() ?
        // (E.g. of the form http://localhost/../java/ch/vorburger/simplewebserver/RequestHandlerStaticSite.java if siteroot is src/htdocs-test)

        // TODO Implement modified-since stuff handling... something like: always send Last-Modified in response, and if request has a If-Modified-Since then check file with file.lastModified() and answer with code 304 if match (and Expires? Also not sure how exactly to handle If-Unmodified-Since request header)

        if (file.isFile()) {
            handleFile(file, response);
        } else if (file.isDirectory()) {
            handleDir(file, response);
        } else {
            handleError(request, response, "Content not file, not directory. We don't know how to handle it.");
        }
    }

    private static void handleFile(File file, HTTPResponse response) throws IOException {
        String filename = file.getName().toLowerCase();
        String contentType = getContentType(filename);
        response.setContentType(contentType);

        long length = file.length();
        response.setHeader(HTTPResponse.Header.ContentLength, Long.toString(length));

        FileInputStream in;
        try {
            in = new FileInputStream(file);

            // TOD Charset conversion for text/* potentially needed?  Do I need to use InputStreamReader(in, Charset/CharsetDecoder/String charsetName) here in some cases?
            OutputStream os = response.getOutputStream();

            int c;
            while ((c = in.read()) != -1) {
                os.write(c);
            }

            in.close();
            os.close();
        } catch (FileNotFoundException ex) {
            throw new IOException("File " + file + " not found.", ex);
        }
    }

    private static String getContentType(String filename) {
        if (filename.endsWith(".js")) {
            return "application/javascript";
        } else if (filename.endsWith(".css")) {
            return "text/css";
        } else {
            return new MimetypesFileTypeMap().getContentType(filename);
        }
    }

    private void handleDir(File dir, HTTPResponse response) throws IOException {
        File indexFile = new File(dir.getAbsolutePath() + File.separator + "index.html");
        if (indexFile.exists()) {
            redirect(indexFile, response);
        } else {
            StringBuilder builder = new StringBuilder("<!DOCTYPE html PUBLIC \"-//W3C//DTD HTML 3.2 Final//EN\"><html> \n"
                    + "<title>Directory listing for /</title>\n"
                    + "<body>\n"
                    + "<h2>Directory listing</h2>\n"
                    + "<hr>\n"
                    + "<ul>");

            File[] files = dir.listFiles();
            for (File file : files) {
                String link = "<li><a href=\"" + getWebPath(file) + "\">" + file.getName() + "<a/></li>\n";
                builder.append(link);
            }
            builder.append("</ul>\n"
                    + "<hr>\n"
                    + "</body>\n"
                    + "</html>");
            String content = builder.toString();
            response.setHeader(HTTPResponse.Header.ContentLength, Long.toString(content.length()));
            response.setContentType("text/html");
            OutputStream os = response.getOutputStream();
            os.write(content.getBytes("utf-8"));
            os.close();
        }
    }

    private String getWebPath(File file) throws IOException {
        return file.getCanonicalPath().replace(siteRoot.getCanonicalPath(), "");
    }

    private void redirect(File file, HTTPResponse response) throws IOException {
        response.setStatusCode(302);
        response.setHeader("Location", getWebPath(file));
    }

    @Override
    protected void handle(HTTPRequest request, HTTPResponse response) throws IOException {
        try {
            if (!HTTPRequest.Method.GET.toString().equals(request.getMethod())) {
                response.setStatusCode(501); // 501 is "Not Implemented"
                return;
            } else {
                handleGet(request, response);
            }

        } catch (Exception ex) {
            handleException(request, response, "Server Error (Unexpected '" + ex.getMessage() + "' while handling request)", ex);
        }
    }

    private void handleError(HTTPRequest request, HTTPResponse response, String message) throws IOException {
        this.handleException(request, response, message, null);
    }

    private void handleException(HTTPRequest request, HTTPResponse response, String message, Exception ex) throws IOException {
        try {
            // If earlier code has already set a more precise HTTP error then
            // leave that, make it a generic 500 only if its still the default 200
            if (response.getStatusCode() == 200) {
                response.setStatusCode(500);
            }
            PrintWriter pw;
            response.setContentType("text/html");
            pw = response.getPrintWriter();

            pw.println("<html><head><title>Server Error</title></head><body><h1>Server Error</h1><p>");
            pw.println(message);
            pw.println("</p><pre>");
            if (ex != null) {
                ex.printStackTrace(pw);
            }
            pw.println("</pre></body></html>");
        } catch (IllegalStateException e) {
            // Oh, too late to getPrintWriter()? Well... log it but otherwise
            // ignore it; at least the setStatusCode() worked if we're here.
            System.out.println("Can't send stack trace to client because OutputStream was already open for something else: " + e.toString()); // TODO Real logging...
            System.out.println("Stack trace of where the IllegalStateException occured:");
            e.printStackTrace();
            return;
        }
    }
}

以下就是实现文件下载功能的核心代码，没啥稀奇的，

1.获得文件输入流

private static void handleFile(File file, HTTPResponse response) throws IOException {
        String filename = file.getName().toLowerCase();
        String contentType = getContentType(filename);
        response.setContentType(contentType);

        long length = file.length();
        // 设置
        response.setHeader(HTTPResponse.Header.ContentLength, Long.toString(length));

        FileInputStream in;
        try {
//获得文件输入流
            in = new FileInputStream(file);

            // TOD Charset conversion for text/* potentially needed?  Do I need to use InputStreamReader(in, Charset/CharsetDecoder/String charsetName) here in some cases?
  //王柳响应流
            OutputStream os = response.getOutputStream();

            int c;
            while ((c = in.read()) != -1) {
                os.write(c);
            }

            in.close();
            os.close();
        } catch (FileNotFoundException ex) {
            throw new IOException("File " + file + " not found.", ex);
        }
    }