CSC 569 WINTER 13 GRADUATE PROJECT: NETWORK-BASED IMAGE REPOSITORY

Transcription

1 CSC 569 WINTER 13 GRADUATE PROJECT: NETWORK-BASED IMAGE REPOSITORY PROFESSOR GODFREY MUGANDA 1. Multi-Threaded Network Photo Server You are going to write a system that allows users to store photos on a servers. The project is loosely modelled after the operation of the Internet s FTP protocol. The server is a TCP multi-threaded server that functions as a network-based photo repository. A client connecting to the server must first register, or, if previously registered, must log in. Upon registration of a new user, the server creates a directory or folder for that user. All photos uploaded by the user will be stored in the directory assigned to that user. The server rejects a new registration if a person tries to register with a name that is already taken. Here is a list of protocol messages sent from the client to the server, followed by the server s response, if any. (1) register name. The client wants to register a new account under the given name. The parameter name is a string with the same syntax as a Java identifier. Upon receipt of this message, the server creates a folder with the given name if the folder does not already exist, and returns the string Ok: name registered to the client. If a folder of the same name already exists, the server returns the string Failure: name already in use to the client. A newly registered user is considered to be automatically logged in. (2) login name. The client wants to log in as the specified user. If there is no registered user by that name, the server returns the message Failure: unregistered user name to the client. Otherwise, the client gets logged in and the server returns the message Ok to the client. The server will reply with a Failure: not logged in message to any message that is received before the user has logged in. (3) logout. The client is done using the server. At the receipt of this message, the server closes the connection and de-allocates resources being used to maintain client-state information. (4) list. The client wants a list of names of all files previously stored by the logged-in user. 1

2 2 PROFESSOR GODFREY MUGANDA Upon receipt of this message, the server sends back a message consisting of n + 1 lines, where n is the number of files currently stored in the user s folder. The first line will be the number n. This line will be followed by n lines, with each line containing the name of a file. (5) store filename. The client wants to store a file of that name in the directory associated with the logged-in user. Upon receipt of this message the server will check to see if a file of that name already exists in the user s directory. If such a file exists, the server returns a message Failure: file already exists. Otherwise, the server returns a message of Ok: send file and moves into a state where it is expecting a connect store port message from the client. (6) connect store port. The client will only send this message after it has received an Ok: send file message from the server. Immediately after sending this message, the client sets up a server socket at the specified port to wait for a data connection request from the server. After a data connection request has been accepted, the client sends the contents of the file through the data connection and shuts down the output stream of the data connection. The server should only receive this message after it has sent an Ok: send file to the client. Upon receipt of this message, the server opens a data connection to the client at the specified port, reads the data stream, and stores the contents into a file of the specified name in the directory associated with the logged-in user. The server then sends an Ok: file stored message to the client. Upon receipt of this message, the client closes the active and passive sockets associated with the data connection. (7) retrieve filename. The client wants to retrieve a file of that name from the directory associated with the logged-in user. Upon receipt of this message the server will check to see if a file of that name exists in the user s directory. If such a file does not exists the server returns a message Failure: file does not exist. Otherwise, the server returns a message of Ok: receive file and moves into a state where it is expecting a connect retrieve port message from the client. (8) connect retrieve port. The client will only send this message after it has received an Ok: retrieve file message from the server. Immediately after sending this message, the client sets up a server socket at the specified port to wait for a data connection request from the server. After a data connection request has been accepted, the client reads the contents of the file the data connection and processes them. The client then sends a Ok: file retrieved

3 CSC 569 WINTER 13 GRADUATE PROJECT: NETWORK-BASED IMAGE REPOSITORY 3 message to the server, and closes two sockets associated with the data connection. The server should only receive this message after it has sent an Ok: retrieve file to the client. Upon receipt of this message, the server opens a data connection to the client at the specified port and copies the contents of the file into the output stream of the data connection. The server then shuts down the output stream. At this point, the server waits for an Ok: file retrieved message from the client, and then closes its data socket. 2. What to do with unknown commands If the server receives any other command, it will return an message Failure: unknown command to the client and close the connection. 3. The Client User Interface Next we need to specify the user interface on the user agent, that is, the application that interfaces with the user and runs the client-side protocol. When starting up, the user agent asks the user to enter the IP address of the server. (The server will be running at the usual port number of 50000). The client then connects to the server. The user can enter the following commands at the command line: (1) register name. The client will read the command and forward it to the server. The client then reads the server s response and displays it. (2) login name. The client forwards the command to the server. The client then reads the server s response and displays it. (3) list. The client will forward the command to the server and display the server s response. (4) get filename. The client will send a corresponding retrieve filename to the server. The client then reads the server s response and displays it. If the server s response was Ok, the client reads the file sent by the server and displays the image to the user. Details of how this is done are given later. (5) put filename. The user agent will pop up a JFileChooser dialog to allow the user to navigate the local file system and select a file. The client will then send a corresponding store filename to the server. If everything goes OK and the specified file name does not already exist in the user s folder on the server, the client sends the contents of the file selected by the user using the file chooser. Notice the file selected with the file chooser does not have to have the name specified by the user. However, it will be stored on the server under the name specified by the user.

4 4 PROFESSOR GODFREY MUGANDA 4. Working With Images You will need to display images that are received from the server. To do this, you need to know how to work with images. Here is an example program that works with images. It uses a JFileChooser to allow the user to select a file that contains an image from the local file system. The program also uses the read method of the ImageIO class to read the image from the file and return an Image object, and it uses the drawimage method of the Graphics object to draw an image on the surface of a JPanel object. To understand how images display works, you need to know that every Java user interface component has a void paintcomponent(graphics g) that is automatically called by the runtime system to draw the image and /or text that is to appear on the component whenever that component need to be displayed. If you want to draw an image on a component, you need to subclass the component and override the paintcomponent method to draw what you want. We do this in the ImagePanel class. We need to set the size of the panel showing the image to the pixel dimensions of the image. This is done by calling the getwidth and getheight methods of the image. We use the width and height to create a Dimension object which is in turn used to set the preferred size of the image panel to the exact dimensions of the image. We need a top level component to display the image panel. For this, we use a JDialog object. We define a subclass of JDialog that takes an image panel to display, and a title to display along with the image, and adds it to the dialog. When the dialog is made visible, the paintcomponent method of the enclosed image panel will be called, and that method will draw the image. package imagedemo; import java.awt.dimension; import java.awt.graphics; import java.awt.image; import java.awt.event.windowadapter; import java.awt.event.windowevent; import java.io.file; import java.io.ioexception; import javax.imageio.imageio; import javax.swing.jdialog; import javax.swing.jfilechooser; import javax.swing.jpanel; public class ImageDemo public static void main(string[] args) throws IOException // Ask user for the name of a file that contains an image JFileChooser inputchooser = new JFileChooser(); int result = inputchooser.showopendialog(null); if (result!= JFileChooser.APPROVE_OPTION)

5 CSC 569 WINTER 13 GRADUATE PROJECT: NETWORK-BASED IMAGE REPOSITORY 5 System.out.println("You did not select a file. " + "Program is ending."); System.exit(1); File inputfile = inputchooser.getselectedfile(); // Read the image in the file Image myimage = ImageIO.read(inputFile); // Create a panel that displays the image ImagePanel imagepanel = new ImagePanel(myImage); // Create an ImageDialog to display the image JDialog imagedialog = new ImageDialog(imagePanel, "Pretty Little Flowers"); // Show the image dialog imagedialog.setvisible(true); // Exit the program System.exit(0); /** * This class defines a panel that displays an image Administrator */ class ImagePanel extends JPanel private Image image; public ImagePanel(Image image) this.image = image; // get size of image and use it to set preferred size of panel int width = image.getwidth(this); int height = image.getheight(this); this.setpreferredsize(new Dimension(width, public void paintcomponent(graphics g) g.drawimage(image, 0, 0, this); /** * This class is a dialog for displaying a panel that has an image Administrator */ class ImageDialog extends JDialog

6 6 PROFESSOR GODFREY MUGANDA public ImageDialog(ImagePanel imagepanel, String title) // Make the dialog modal and set title this.setmodal(true); this.settitle(title); // Add the image panel and pack the size of the dialog this.add(imagepanel); this.pack(); // Make invisible when it is closed this.setdefaultcloseoperation(jdialog.hide_on_close); 5. Working With Directories and Files This section shows you how to work with files and directories. You need some knowledge of the Java File class. Look up the Java 7 documentation on this class. Some of the methods of this class you will need are File [] listfiles boolean mkdir() boolean isfile() boolean isdirectory() boolean exists() Path topath() You should also look at the constructors for the File class. You should also look at the Files class in the package java.nio. The Files class is new with Java 7. It offers some copy methods that provide very efficient means of copying an entire file to an output stream, (You can use this when the client is sending a file to the server) and an efficient means of copying an output stream to a file (You can use this when the server is receiving a file from the client). Here is an example. package directoriesprogram; import java.io.bytearrayinputstream; import java.io.bytearrayoutputstream; import java.io.file; import java.io.ioexception; import java.nio.file.files; import java.nio.file.path; import java.util.arrays; public class DirectoriesProgram public static void main(string[] args) throws IOException File dir = new File("c:/temp"); // List the contents of the director

7 CSC 569 WINTER 13 GRADUATE PROJECT: NETWORK-BASED IMAGE REPOSITORY 7 if (dir.isdirectory()) System.out.println("Directory " + dir + " has contents: "); System.out.println(Arrays.toString(dir.listFiles())); else System.out.println(dir + "is not a directory."); // Create two directories in the directory dir String [] subdirs = "Alan", "Beth"; for (String d : subdirs) File newdir = new File(dir, d); newdir.mkdir(); // List all the contents of dir System.out.println("Contents of " + dir + " are: "); System.out.println(Arrays.toString(dir.listFiles())); // The following code shows how to copy the content of an inputstream // into a target file. First you create an File object that represents // the target file, then you get a Path object that represents the // target file from the File object. Then you use the Files.copy // method to copy the contents of the input stream into the target file. // We use a ByteArrayInputStream for the input stream here, but you // could use a TCP socket input stream. Note that you cannot use an // existing file for the target file. If you run this more than once, // Delete the c:/temp/alan/file1.data file before running again. // Create a path name for a file1.data in the subdirectory Alan File parent = new File(dir, "Alan"); File datafile = new File(parent, "file1.data"); // Get a Path object to represent the file file1.data Path file1path = datafile.topath(); // Create a byte array input stream that has data to write to file1.data ByteArrayInputStream byteinstream = new ByteArrayInputStream("Hello".getBytes()); // Copy the byte array input stream to the file Files.copy(byteInStream, file1path); // The following code shows how to copy a source file into an output stream. // You can use this to copy a file into the output stream of a TCP socket. // Here we just use a ByteArrayOutputStream // Create a File object for the source file, and then get the Path // object from the File object. Here we already have the Path object // file1path, so we just use that. // Create a ByteArrayOutputStream

8 8 PROFESSOR GODFREY MUGANDA ByteArrayOutputStream byteoutstream = new ByteArrayOutputStream(); // Use Files.copy to copy the source file into the target output stream Files.copy(file1Path, byteoutstream); // Convert the bytes in the ByteOutputStream to String and display System.out.println(byteOutStream.toString()); This is due Friday of Week 10.