(c) 2006-2008 e.s.boese all rights reserved.1 internet applications chapter 15 - lecture slides

(c) 2006-2008 E.S.Boese All Rights Reserved. 1

Internet Applications

Chapter 15 - Lecture Slides


Internet Terminology

URL : full path

Protocol : set of rules (e.g. http, https, ftp, telnet, etc. )

Domain name : can purchase right to use

IP address : 4 numbers between 0 and 255 separated with . (e.g. 128.57.127.2 )

Internet address : English version of an IP address

Hyperlinks : link on a webpage that takes you to another page (or a different location within the same page)


JEditorPane


JEditorPane creation

Declare a JEditorPane component.

JEditorPane pane;

Check to see if it is null (first time we run the applet). If it is null, we instantiate it:

if( pane == null )

pane = new JEditorPane( );


JEditorPane Set the web page in to the JEditorPane.

NOTE: The URL MUST begin with http://

pane.setPage( url );

try...catch blocks are Java's way of handling errors which are thrown We need to put our code within a try…catch block in case there is a problem accessing the web page.

try {

pane.setPage( url ); }catch( IOException ioe ) {

pane.setText( "Error accessing web page: " + url ); }

If there is an error accessing the page we

want, we’ll print the error message inside the JEditorPane


JEditorPane – setupURL method Create a method setupURL to make it easier for us to change the

page being displayed:

public void setupURL( String url ) {

if( pane == null ) pane = new JEditorPane( );

try {

pane.setPage( url ); } catch( IOException ioe ) {

pane.setText( "Error accessing web page: " + url );

} }


JEditorPane

Store the JEditorPane inside a JScrollPane, to ensure users can access the whole page being displayed

JScrollPane scrollPane = new JScrollPane(pane);


JEditorPane Handle clicks on links inside the web page that is displayed.

To do this, there are four things we need to do (similar to other events we've worked with).

1. These events are inside the javax.swing.event package

import javax.swing.event.*;

2. Specify that we are listening for these type of events –

implements HyperlinkListener

3. Specify that we want to listen for HyperLinkEvents on our JEditorPane component:

pane.addHyperlinkListener( this );

4. Implement the required method for implementing the HyperlinkListener,

public void hyperlinkUpdate( HyperlinkEvent event ) {

if( event.getEventType() == HyperlinkEvent.EventType.ACTIVATED ) { setupURL( String.valueOf( event.getURL( )) ); }

}


Simple example

see JEditorPaneEx.java


Example with buttons

see JEditorPaneExBtn.java


Hosting applets on the Internet


Hosting your applet on the Web Get your applet up and running on a host somewhere. First you need to get your applet ready without using an IDE such as

Eclipse.

Setting up the HTML file Create a file (in your text editor). Enter the following line, changing the XYZ to the name of your class.

<HTML> <BODY> <APPLET CODE=XYZ.class WIDTH=500 HEIGHT=500>

</APPLET></BODY></HTML>

This needs to be saved a file named exactly: "index.html" in lower case letters.

Modify the width and height to what you want.


Hosting your applet on the Web Hosting for free (or buy a domain – see below)

University accounts http://www.doteasy.com/ http://members.freewebs.com/index.jsp

Another option: Buying a Domain Name (FYI, not necessary) Register.com Registar.com Aplus.net domainsInSeconds.com others...


Hosting your applet on the Web Uploading files

Upload the index.html, all the .class files, all the images and sound files necessary to make your applet work

Make sure your code referencing the image file names matches the actual file name (case sensitive!! This is important as Eclipse in Windows has been lazy, allowing any case to work)

NOTE: if your project read in from a local file (not a URL) or writes to a file, you need to remove that code before it will work on the Internet (see Security section).


Applet Parameters


Applet Parameters

Customize applet without changing the code Send preferences in HTML document as param tags Give a name and value

<HTML> <BODY> <APPLET CODE=XYZ.class WIDTH=500 HEIGHT=500>

<PARAM NAME=bkcolor VALUE=”0000FF”><PARAM NAME=textcolor VALUE=”AAAA00”><PARAM NAME=title VALUE=”Lizzie’s Playground”>

</APPLET>Use double-quotes for text with spaces in it.</BODY></HTML>

Use double-quotes for text

with spaces in it.


Applet Parameters

In Eclipse


Applet Parameters

Inside your Java Code, call getParameter( keyName ) Example:

For HTML<PARAM NAME=title VALUE=”Lizzie’s Playground”>

Java Codelabel = new JLabel( getParameter( “title” ) );

Parameter for getParameter matches

the NAME in HTML PARAM tag


Applet Parameters Read in values within the applet

getParameter( name )

import java.awt.*;import javax.swing.*;public class AppParams extends JApplet{

JPanel bkgrnd;JLabel heading;public void init( ){

bkgrnd = new JPanel( );bkgrnd.setBackground( new Color( Integer.parseInt( getParameter( "bkcolor" ), 16 ) ) );heading = new JLabel( getParameter( "title" ) );heading.setForeground( new Color( Integer.parseInt( getParameter( "textcolor" ), 16 ) ) );bkgrnd.add( heading );setLayout( new BorderLayout( ) );add( bkgrnd, BorderLayout.CENTER );

}}


Configuration Files


Configuration Files

Another way to customize the applet without changing the source code

Store name/value pairs in a text file Example file:

title=My Favorite Playground

bkcolor=0000FF

textcolor=AAAA00


Configuration Files split method

Specify a delimiter Stores the separated tokens into an array Example: use \n as a delimiter to separate each line into a

separate String stored in an array

String dataFile = “cats and dogs\nJava goodness\nskiing”;String[ ] lines;lines = dataFile.split( "\n" );

Remove the newline at the endlines[0] = lines[0].substring( 0, lines[0].length( ) - 1 );

lines

cats and dogs\n

Java goodness\n

skiing

0

1

2


title=My Favorite Playground\n

bkcolor=0000FF\n

textcolor=AAAA00\n

0

1

2

Configuration Files Algorithm

Read in all the lines in the file and store in a String Use split method on \n to separate each line into a separate

String stored in an array

String[ ] lines;lines = configFile.split( "\n" );

Use split method again on = for each line to separate the name from the value lines[0].split(“=“)

title=My Favorite Playgroundbkcolor=0000FFtextcolor=AAAA00

lines

title=

My Favorite Playground\n

0

1

title=My Favorite Playground\n

bkcolor=0000FF\n

textcolor=AAAA00\n

0

1

2


Configuration Files public String readConfigFile( ) {

String content; try {

URL target = new URL( getCodeBase( ), configFilename ); URLConnection con = target.openConnection( ); con.connect( ); byte b[ ] = new byte[ 1024 ]; // byte array int nbytes; // num bytes read in String retVal = new String( ); BufferedInputStream in = new BufferedInputStream( con.getInputStream( ), 2048 ); while( (nbytes = in.read( b, 0, 1024 )) != -1 ) // while there's more data to read { content = new String( b, 0, nbytes ); // get 1024 bytes of data fr file retVal += content; } in.close( ); // close connection return retVal; // returns the whole config file as a String

} catch ( Exception e ) { return "Error reading config file"; } }

Read in the entire config file

You shouldn’t need to change this code

for reading in any file


Configuration Filespublic void parseConfig( String cfg ){

String[ ] lines, tokenkey;lines = cfg.split( "\n" );for( int i=0; i<lines.length; i++ ){

tokenkey = lines[i].split( "=" ); // remove newline at end

String value = tokenkey[1].substring( 0, tokenkey[1].length( ) -1 ); if ( tokenkey[0].equals( "bkcolor" ) )

backcolor = new Color( Integer.parseInt( value, 16 ) );else if ( tokenkey[0].equals( "textcolor" ) )

textcolor = new Color( Integer.parseInt( value, 16 ) );else if ( tokenkey[0].equals( "title" ) )

titletext = value;}

}

Method to parse the String

containing the contents of the

config file

Customize your applet based on the token and

value pairs

parseInt needs the value and the 16 for

the base. Colors use hex (base 16)


Applets and Email


Applets and Email

Applets cannot send email directly Need CGI program CGI

Common Gateway Interface Program executing on the server that allows an HTML web page

or Java applet to access/write info on the server Can be written in various programming languages: C, perl, php

Example: Requires access to code interpreter and either mail or sendmail

program


Applets and Email

CGI Programs

YourApplet

1 - Request to CGI program

Web Server

2 - Executes CGI program

Read/Write access to files

on server

3 - CGI programreturns info

Web server is where you ‘host’ your applet on

the Internet


Applets and Email

Perl CGI Example Store perl file (ends with .pl) in appropriate area on web site Change permissions on file

Unix/MacOS system: Run: chmod u+rwx CGIfile.pl Windows system: right-click on file, choose “Properties”

Depending on setup, may need to ask administrator: Full path to perl Full path to either mail or sendmail program Location for CGI files (e.g. in public_html/cgi-bin directory) Required filename postfix

End with .pl or .cgi


Applets and EmailUnix Perl Script

#!/usr/bin/perl use CGI ':standard';my $outfile = "mailing.out";my $sendmail = "/usr/sbin/sendmail -t"; my $reply_to = "Reply-to: boese\@cs.colostate.edu\n"; my $subject = "Subject: Applet Message\n";my $to = "To: boese\@cs.colostate.edu\n";my $content = param('message');print header; # required first set of linesprint "Thanks!";open(SENDMAIL, "|$sendmail") or die "Cannot open $sendmail: $!";print SENDMAIL $reply_to;print SENDMAIL $subject;print SENDMAIL $to;print SENDMAIL "Content-type: text/plain\n\n";print SENDMAIL $content;close(SENDMAIL);

Change to the absolute path to the perl program on your system, and the

absolute path to the sendmail program

Change the Reply-to and To email

addresses to your own

The \ before the @ is required



The \ before the @ is required


Applets and Email

Inside your Java applet Write a method named sendMail takes as

parameters the URL to the CGI program and the message you want to send

URL ends with ? then the message string?message=String

Example:

String s = sendMail( "http://www.cs.colostate.edu/~boese/cgi-bin/mailer.cgi?message=",message );


Applets and Email public String sendMail( String fullPath, String msg ) { try { String enc = URLEncoder.encode(msg, "UTF-8"); URL target = new URL( fullPath + enc ); String content; URLConnection con = target.openConnection( ); // open connection con.setUseCaches( false ); con.setDefaultUseCaches( false ); byte b[ ] = new byte[ 1024 ]; // byte array int nbytes; // num bytes read in String retVal = new String(); BufferedInputStream in = new BufferedInputStream( con.getInputStream( ), 2048 ); while( (nbytes = in.read( b, 0, 1024 )) != -1 ) // while there's more data to read { content = new String( b, 0, nbytes ); // get 1024 bytes of data fr file retVal += content; } in.close( ); // close connection return retVal; } catch( Exception e ) { return "Error " + e.toString( ); } }

You shouldn’t need to change this

method, just call it


Applets and Email

PHP CGI Example Store php file (ends with .php) in appropriate area on web site Works the same on UNIX/Linux/MacOS and Windows Change permissions on file

Unix/MacOS system: Run: chmod u+rwx CGIfile.pl Windows system: right-click on file, choose “Properties”

Depending on setup, may need to ask administrator: Full path to either mail or sendmail program Location for PHP files (e.g. in public_html/cgi-bin directory) Required filename postfix

End with .php or .cgi


Applets and EmailUnix PHP Script

<?php $request_method = $_SERVER["REQUEST_METHOD"]; if ( $request_method == "GET“ )

{ $query_vars = $_GET; }

elseif ( $request_method == "POST“ ) {

$query_vars = $_POST; } reset ( $query_vars );

$emailbody = "New Form Submission: ";while ( list ($key, $val ) = each ( $query_vars ) ){

$emailbody = "$emailbody \n $key = $val" ;}$emailto = '[email protected]';

$emailfrom = '[email protected]'; $subject = "New Form Submission"; mail ( $emailto, $subject, $emailbody, "From: $emailfrom" );?>

Either use mail or sendmail

Depending on your system setup.






Applets and Email

Inside your Java applet Write the same method named sendMail as used

for the CGI program Example:

String s = sendMail( "http://www.cs.colostate.edu/~boese/mailer.php?message=",message );


Writing Files


Writing Files via Applets

Due to applet security restrictions, applets cannot write to files

To record information send information to a CGI program Examples:

Results from a poll User information High score Blogs


Writing Files via Applets

#!/usr/bin/perl use CGI ':standard';my $outfile = "mailing.out";print header; # required first set of lines

# Write to fileopen(OUT, ">>$outfile") or print( "Couldn't open $outfile: $!“ );if ( param( 'message‘ ) ) { print OUT param( 'message‘ ),"\n";}close( OUT );print "Thanks!";

“>>” appends to the file. Use “>” instead of “>>” if

you want to rewrite the file – e.g. store a new

“High Score”

message is the name we

specified in applet after CGI

in the URL

Perl CGI Program


Writing Files via Applets<?php $request_method = $_SERVER["REQUEST_METHOD"]; if ( $request_method == "GET“ ) { $query_vars = $_GET; } elseif ( $request_method == "POST“ ) { $query_vars = $_POST; } reset( $query_vars ); $file = $_SERVER['DOCUMENT_ROOT'] . "/formData"; $fp = fopen( $file, “a“ ); while ( list ( $key, $val ) = each ( $query_vars ) ) { fputs ( $fp, "$key = $val\n"); } fclose($fp);?>

Change formData to the name of the file

you want the values saved to

The a is for appending to a file.

If you want to overwrite it, use w

PHP CGI Program


Summary

JEditorPane Hosting Applets Applet Parameters Configuration Files Applets and Emails Writing to Files

(c) 2006-2008 e.s.boese all rights reserved.1 internet applications chapter 15 - lecture slides

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