Solution for the Proxy Cache Lab

Solution for the Proxy Cache Lab

The following is one solution for the proxy cache lab. It contains code for all the three classes in the lab.

ProxyCache.java

/**
 * ProxyCache.java - Simple caching proxy
 *
 * $Id: ProxyCache.java,v 1.3 2004/02/16 15:22:00 kangasha Exp $
 *
 */
 
import java.net.*;
import java.io.*;
import java.util.*;
 
public class ProxyCache {
    /** Port for the proxy */
    private static int port;
    /** Socket for client connections */
    private static ServerSocket socket;
 
    /** Create the ProxyCache object and the socket */
    public static void init(int p) {
    port = p;
    try {
        socket = new ServerSocket(port);
    } catch (IOException e) {
        System.out.println("Error creating socket: " + e);
        System.exit(-1);
    }
    }
 
    public static void handle(Socket client) {
    Socket server = null;
    HttpRequest request = null;
    HttpResponse response = null;
 
    /* Process request. If there are any exceptions, then simply
     * return and end this thread. This unfortunately means the
     * client will hang for a while, until it timeouts. */
 
    /* Read request */
    try {
        BufferedReader fromClient = 
        new BufferedReader(new InputStreamReader(client.getInputStream()));
        System.out.println("Reading request...");
 
        request = new HttpRequest(fromClient);
        System.out.println("Got request...");
    } catch (IOException e) {
        System.out.println("Error reading request from client: " + e);
        return;
    }
    /* Send request to server */
    try {
        /* Open socket and write request to socket */
        server = new Socket(request.getHost(), request.getPort());
        DataOutputStream toServer = 
        new DataOutputStream(server.getOutputStream());
        toServer.writeBytes(request.toString());
    } catch (UnknownHostException e) {
        System.out.println("Unknown host: " + request.getHost());
        System.out.println(e);
        return;
    } catch (IOException e) {
        System.out.println("Error writing request to server: " + e);
        return;
    }
    /* Read response and forward it to client */
    try {
        DataInputStream fromServer = 
        new DataInputStream(server.getInputStream());
        //InputStream is = server.getInputStream();
 
        response = new HttpResponse(fromServer);
        //response = new HttpResponse(is);
        DataOutputStream toClient =
            new DataOutputStream(client.getOutputStream());
        toClient.writeBytes(response.toString());
        toClient.write(response.body);
        client.close();
        server.close();
        /* Insert object into the cache */
        /* Fill in (optional exercise only) */
    } catch (IOException e) {
        System.out.println("Error writing response to client: " + e);
    }
    }
 
 
    /** Read command line arguments and start proxy */
    public static void main(String args[]) {
    int myPort = 0;
 
    try {
        myPort = Integer.parseInt(args[0]);
    } catch (ArrayIndexOutOfBoundsException e) {
        System.out.println("Need port number as argument");
        System.exit(-1);
    } catch (NumberFormatException e) {
        System.out.println("Please give port number as integer.");
        System.exit(-1);
    }
 
    init(myPort);
 
    /** Main loop. Listen for incoming connections and spawn a new
     * thread for handling them */
    Socket client = null;
 
    while (true) {
        try {
        client = socket.accept();
        System.out.println("Got connection " + client);
        handle(client);
        //ProxyCacheThread request = new ProxyCacheThread(client);
        //request.run();
        } catch (IOException e) {
        System.out.println("Error reading request from client: " + e);
        /* Definitely cannot continue, so skip to next
         * iteration of while loop. */
        continue;
        }
    }
 
    }
}

HttpRequest.java

/**
 * HttpRequest - HTTP request container and parser
 *
 * $Id: HttpRequest.java,v 1.3 2004/02/16 15:21:14 kangasha Exp $
 *
 */
 
import java.io.*;
import java.net.*;
import java.util.*;
 
public class HttpRequest {
    /** Help variables */
    final static String CRLF = "\r\n";
    final static int HTTP_PORT = 80;
    /** Store the request parameters */
    String method;
    String URI;
    String version;
    String headers = "";
    /** Server and port */
    private String host;
    private int port;
 
    /** Create HttpRequest by reading it from the client socket */
    public HttpRequest(BufferedReader from) {
    String firstLine = "";
    try {
        firstLine = from.readLine();
    } catch (IOException e) {
        System.out.println("Error reading request line: " + e);
    }
 
    String[] tmp = firstLine.split(" ");
    method = tmp[0];
    URI = tmp[1];
    version = tmp[2];
 
    System.out.println("URI is: " + URI);
 
    if (!method.equals("GET")) {
        System.out.println("Error: Method not GET");
    }
    try {
        String line = from.readLine();
        while (line.length() != 0) {
        headers += line + CRLF;
        /* We need to find host header to know which server to
         * contact in case the request URI is not complete. */
        if (line.startsWith("Host:")) {
            tmp = line.split(" ");
            if (tmp[1].indexOf(':') > 0) {
            String[] tmp2 = tmp[1].split(":");
            host = tmp2[0];
            port = Integer.parseInt(tmp2[1]);
            } else {
            host = tmp[1];
            port = HTTP_PORT;
            }
        }
        line = from.readLine();
        }
    } catch (IOException e) {
        System.out.println("Error reading from socket: " + e);
        return;
    }
    System.out.println("Host to contact is: " + host + " at port " + port);
    }
 
    /** Return host for which this request is intended */
    public String getHost() {
    return host;
    }
 
    /** Return port for server */
    public int getPort() {
    return port;
    }
 
    /**
     * Convert request into a string for easy re-sending.
     */
    public String toString() {
    String req = "";
 
    req = method + " " + URI + " " + version + CRLF;
    req += headers;
    /* This proxy does not support persistent connections */
    req += "Connection: close" + CRLF;
    req += CRLF;
 
    return req;
    }
}

HttpResponse.java

/**
 * HttpResponse - Handle HTTP replies
 *
 * $Id: HttpResponse.java,v 1.3 2004/02/16 15:21:46 kangasha Exp $
 *
 */
 
import java.io.*;
import java.net.*;
import java.util.*;
 
public class HttpResponse {
    final static String CRLF = "\r\n";
    /** How big is the buffer used for reading the object */
    final static int BUF_SIZE = 8192;
    /** Maximum size of objects that this proxy can handle. For the
     * moment set to 100 KB */
    final static int MAX_OBJECT_SIZE = 100000;
    /** Reply status and headers */
    String version;
    int status;
    String statusLine = "";
    String headers = "";
    /* Body of reply */
    byte[] body = new byte[MAX_OBJECT_SIZE];
 
    /** Read response from server. */
    public HttpResponse(DataInputStream fromServer) {
    //public HttpResponse(InputStream is) {
        /* Length of the object */
    int length = -1;
    boolean gotStatusLine = false;
 
    // Test code
    //BufferedReader fromServer = 
    //    new BufferedReader(new InputStreamReader(is));
 
    /* First read status line and response headers */
    try {
        String line = fromServer.readLine();
        while (line.length() != 0) {
        if (!gotStatusLine) {
            statusLine = line;
            gotStatusLine = true;
        } else {
            headers += line + CRLF;
        }
 
        /* Note length of content as indicated by
         * Content-Length header. Unfortunately this is not
         * present in every response. */
        if (line.startsWith("Content-Length:") ||
            line.startsWith("Content-length:")) {
            String[] tmp = line.split(" ");
            length = Integer.parseInt(tmp[1]);
        }
        line = fromServer.readLine();
        }
    } catch (IOException e) {
        System.out.println("Error reading headers from server: " + e);
        return;
    }
 
    try {
        int bytesRead = 0;
        byte buf[] = new byte[BUF_SIZE];
        boolean loop = false;
 
        /* If we didn't get Content-Length header, just loop until
         * the connection is closed. */
        if (length == -1) {
        loop = true;
        }
 
        /* Read the body in chunks of BUF_SIZE and copy the chunk
         * into body. Usually replies come back in smaller chunks
         * than BUF_SIZE. The while-loop ends when either we have
         * read Content-Length bytes or when the connection is
         * closed (when there is no Connection-Length in the
         * response. */
        while (bytesRead < length || loop) {
        /* Read it in as binary data */
        int res = fromServer.read(buf, 0, BUF_SIZE);
        //int res = is.read(buf, 0, BUF_SIZE);
        if (res == -1) {
            break;
        }
        /* Copy the bytes into body. Make sure we don't exceed
         * the maximum object size. */
        for (int i = 0; 
             i < res && (i + bytesRead) < MAX_OBJECT_SIZE; 
             i++) {
            body[bytesRead + i] = buf[i];
        }
        bytesRead += res;
        }
     } catch (IOException e) {
         System.out.println("Error reading response body: " + e);
         return;
     }
 
 
    }
 
    /**
     * Convert response into a string for easy re-sending. Only
     * converts the response headers, body is not converted to a
     * string.
     */
    public String toString() {
    String res = "";
 
    res = statusLine + CRLF;
    res += headers;
    res += CRLF;
 
    return res;
    }
}