CMSC 433 - Project 1 - Java exercise
Due Feb. 13, 6:00PM

Part 1 - Counter

Write myCounter, a counter class. It should support the following functionality:

public class myCounter {
    Integer getNextID();
    }

• The values returned by getNextID() should start at 0, increase by 1 each time, and be distinct across all myCounter instances (i.e. all myCounter instances should share the same internal counter).
• If the value will exceed Integer.MAX_VALUE, return -1 on this and all future calls.

Part 2 - Timestamper

Write myTimestamper, a timestamping class. It should support the following functionality:

public class myTimestamper {
    java.util.Date getTimestamp();
    }

• The return value of getTimestamp() should indicate the time of day at which the function was called.

Part 3 - Logging server and Logging client

Write myLoggingServer and myLoggingClient, server and client classes that support the following functionality:

public class myLoggingServer {   
    myLoggingServer(int port, java.io.Writer outStream);
    void writeRecord(String record);           
    String getRecords(long windowSize);
    void flush();
}

• myLoggingServer opens a socket on localhost at port number port and establishes outStream as the place to which it writes its output. Once established, myLoggingServer loops forever, doing the following:

  • accepts a connection from a myLoggingClient on port,

  • reads a command name ("writeRecord" + "\n", "getRecords" + "\n", or "flush" + "\n") from the socket

  • reads one record ((ID + "\n" + timestamp + "\n" + event + "\n") or  (windowSize)) from the socket,

  • calls the appropriate method passing the data read from the socket, appropriately converted,

  • if command was getRecords returns records in original format (ID + "\n" + timestamp + "\n" + event + "\n")

  • closes the connection. 

• The field separator for all fields will be the newline (so newlines are not allowed in ID or event strings).
• For the purpose of passing a java.util.Date object (either way) between the logging client and server (i.e. as part of a record), the String representation of a Date object  should be a value of type long that represents the number of milliseconds since the beginning of Unix time, January 1, 1970, 00:00:00 GMT (see Date.getTime() and the wrapper class Long).  
• writeRecord stores record on server.
• getRecords returns all records that are no older than windowSize milliseconds that have not yet been flushed. Make sure you print out the records in ascending order of their timestamps with one blank line in between each record. The timestamps should be human-readable (use  java.util.Date.toString() ).
• flush writes all records to outStream and removes them from the server's stored records. Make sure you print out the records in ascending order of their timestamps with one blank line in between each record. The timestamps should be printed using the long format, as for passing them between the client and server.
• The public static main() method for your server should get the port number to listen on from the command line (e.g., start the server with java -Dport=portnum myLoggingServer).  The port number can be extracted in your server with the Integer.getInteger() method.  For testing purposes, so everyone uses different ports, test your server using port x33yy, where x is your section number and yy is your account number.

public class myLoggingClient {
    myLoggingClient(InetAddress host, int port);
    void writeRecord(String ID, String timestamp, String event);
    void viewRecords(long windowSize);
    void flush();
}

• myLoggingClient stores information needed to connect to the myLoggingServer instance (i.e. host host at port port).
• writeRecord() sends its parameters to the myLoggingServer instance previously associated with this myLoggingClient instance, with each parameter string followed by a newline ("\n").
• viewRecords() creates a new window on the host machine and displays all records whose timestamp is no older than windowSize milliseconds.  See file TestPane.java for a sample program using Swing that displays text in a scrolling window.
• flush() sends a flush command to the server.
• The driver for the client should get the host and port number of the server to connect to from the command line.  For the client driver we provide, ProducerConsumerTest, start with java -Dhost=hostname -Dport=portnum ProducerConsumerTest). As show in the driver, the hostname can be extracted with the System.getProperty() method.

Details

Here is driver code that we will use to test your classes: ProducerConsumerTest.java, Producer.java, Consumer.java, and CubbyHole.java .  For these drivers, sample contents for the client viewRecords() window is here , and sample output for the server flush() command is here .  Note that your output will not match exactly because of thread behavior and values of timestamps.

Submission details

Submission will be handled using the submit program as project 1 (i.e. submit 1 *.java).

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