ICT 4361 — Java Programming Exercise 7

Purpose

This exercise familiarizes you with the basic methods of the networking APIs in Java, and simple tasks such as reading the contents of a URL, and writing on a socket. This will also exercise your knowledge of Exceptions.

What To Hand In:

Please hand in a listing for each program requested, formatted in an easy-to-read style.

Ensure your name, and the name of the file is available in a comment at the top of the file.

Also, ensure that you have a sample of the output from the program.

If your program fails to compile, hand in your error listing as your output.

For each question asked, provide one or two sentences summarizing your answer. Please be both complete and succinct.

Problems

For the last problem, you will want to download hw7.jar This file contains the class files and source for a server process.

1. Create a class called ReadURL which has the following features:
   • A private field of type URL which stores a URL
   • A constructor which takes a String as a parameter, from which the URL is created
   • A constructor which takes a URL as a parameter, from which the URL is assigned
   • A constructor which takes a URI as a parameter, assigning to the URL with the toURL() method
   Note that there are exceptions which may be created as a result of these assigments, which you should handle in the constructor
   • A method called getContent() which returns a String, and performs the following:
     1. Creates and assigns URLConnection by invoking openConnection() on the URL
     2. Creates an InputStream from the URLConnection
     3. Creates a BufferedReader on a new InputStreamReader built from the InputStream
     4. Reads one line from the BufferedReader and stores it as the return value
     5. Closes the BufferedReader
     6. Returns the contents of the line
   • A method called getContentAsURI which returns a URI, by calling getContent() and using the line of text to construct a URI for return.
   Note that Exception handling is necessary in these methods as well.
   • Create a main method that creates a new ReadURL from the URL http://www.du.edu/~mschwart/ICT4361/hw7.problem1, gets its content, and then prints the URL, and its content.
   • Run the program
2. Create a new class with just a main method to do the following:
   • Creates a new ReadURL from the first parameter on the command line, or read from the user
   • Uses that ReadURL object to get the contents at that location as a URI
   • Converts that URI to a URL (using the toURL method)
   • Creates another ReadURL object using that URL
   • Uses the new ReadURL object to get the contents at that location as a String
   • Prints the first URL, second URL, and the contents of the second URL
   • Runs the program for the URL http://www.du.edu/~mschwart/ICT4361/hw7.problem2
3. Create a new class called WriteURI with the following features:
   • A private field of type URI
   • A private field of type Socket
   • A private field of type BufferedReader
   • A private field of type PrintWriter
   • A constructor that takes a URI parameter, sets the URI field with it, and calls method openConnection
   • A constructor that takes a String parameter, constructs the URI field with it, and calls method openConnection
   • A method called openConnection that:
     1. Sets the field of type Socket by opening a new Socket using the URI field's host and port
     2. Sets the field of type BufferedReader to a new InputStreamReader constructed from the Socket field's getInputStream() method
     3. Sets the field of type PrintWriter to a new PrintWriter constructed from the Socket field's getOutputStream() method, and supplying true for autoflush
   • A method called sendMessage that takes a String parameter, and uses println to send it on the PrintWriter object.
   • A method called receiveMessage that returns a String which it gets by calling readLine() on the BufferedReader
   • A main method that creates a WriteURI from the URI found in hw7server.uri

   Run the SimpleServer (provided in the hw7.jar) before doing the last step

   • Runs the program, sending your name as the message to sendMessage, and printing the reply from receiveMessage

Notes

1. Exception handling is an important part of this exercise
2. To run the SimpleServer from the command line in Windows, do the following:
   • Open a command prompt window
   • Ensure you can run Java by entering the command java -version
   • Run the command line java -cp hw7.jar hw7.SimpleServer hw7server.uri
     This will make the server run, placing its URI into the file hw7server.uri
   • The file hw7.log contains the record of connections to the server
3. You may use your ReadURL class to get the server host and port information, or you may examine the file, and then code its contents into your program
4. Note that hw7.jar contains the source for the server, as well as the class files, so you may examine this if you wish

Evaluation Criteria: