Transcript CP3024 – Lecture 4

CP3024 – Lecture 4
Further server side
scripting
CP3024 – Lecture 4
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PHP Further Features
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ASP/VB Script
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JSP (Java)
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Other techniques
PHP Further Features
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Arrays
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Functions
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Database access
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Miscellaneous
PHP Arrays
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Arrays do not require declaration
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Grow automatically
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Indexing syntax like Java/C
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E.g.
for($i=0;$i<10;$i++)
$x[$i] = $i * $i;
PHP Arrays
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Arrays can be initialised using the fucntion
array() with a value list as parameter
E.g.
$coins = array(1,2,5,10,20,50,100,200);
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A string is an array of characters
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E.g.
echo “CP3024”[2] outputs '3'
PHP Arrays
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Arrays are collections of name/value pairs
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The following are valid
$x[-23] = 44;
$uname[“cm1958”] = “Mary”;
$uname[“cm1901”] = “Peter”;
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Also known as key/value pairs
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“cm1958” is key, “Mary” is value
PHP Functions
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PHP functions are declared using syntax
function name(arg-list)
{
Code
}
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Value returned using
return value;
PHP Functions
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Can be recursive
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Declarations can be nested
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Function names can be stored in a
variable
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main() is “implicit” function
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Can have default parameters
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Parameters normally “call by value” (like
Java and C)
PHP Functions
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Example
function addup3($x,$y,$z)
{
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return $x+$y+$z; }
Usage
echo addup3(21,22,23);
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Outputs 66
Database Access
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Connect to server
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Select database
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Construct SQL query
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Send query to server
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Receive “result set”
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Convert result set to array (of strings)
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Repeat as required
Database Access
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Database connection uses the function
mysql_connect(hostname,username,
password)
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Returns a PHP “resource”.
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E.g.
$dbconn =
mysql_connect(“clun.scit.wlv.ac.uk”,”demo”);
Database Access
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MySQL keeps user tables in “areas” called
databases. You need to select the
relevant database.
Use mysql_select_db(dbname)
The most recently opened database
server connection is used
Database Access
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Before querying the database construct
the query in SQL and save in a string.
$sql="SELECT * FROM gazetteer WHERE
feature = ' " . $place ." ' ";
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Extra spaces to make quoting clear
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Double quotes enclose PHP strings.
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In the constructed SQL single quotes
enclose the value of $place.
Database Access
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The function mysql_query() sends the
SQL query to the server, a “result set”
resource is returned.
E.g.
$result = mysql_query($sql);
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Failure sets $result to “false”, not the
same as no matching data found.
Use mysql_num_rows($result) to
determine rows in result set.
Database Access
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The “result set” resource consists of a set
of rows of data.
mysql_fetch_array(result_set) returns an
array of strings, one for each column
(field) in the result set.
Array element keys are column names as
the names appeared in the SQL
Repeated calls yield successive rows
Global Variables
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PHP has a number of global arrays
sometimes called superglobals. The
values can be accessed within any
function
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$_SERVER – server provided information
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$_GET – values from GET request
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$_POST – values from POST request
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$_ENV – environment information
PHP packages
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PHP extensions are optional groups of
functions that may be included in a PHP
build and are part of the interpreter.
PHP packages are groups of PHP code
included at run time. They are managed
by a tool called “pear”.
PHP Resources
(local)
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Local on-line manual
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http://www.scit.wlv.ac.uk/appdocs/php
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Essential reading
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Examples and discussion
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http://www.scit.wlv.ac.uk/~jphb/sst/php
Numerous examples fully described,
discussions of image generation, LDAP,
security, session control, classes, XML,
SOAP and more.
ASP
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Micro$soft's Active Server Pages
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Server side scripting similar to PHP
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A variety of scripting languages
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VBScript (described here) and ASP.NET most
popular
Always available on IIS servers
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Versions available under Apache/Unix
ASP/VBscript
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Derived from Visual Basic
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Script enclosed in <% ... %> tags
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May start with
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<% @ language = vbscript %>
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<% option explicit %>
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Means all variables must be declared
<% .... code .... %>
ASP/VBscript
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Language Basics
Is object oriented but no user class
mechanism.
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I.e. You can only use “official” objects
Variables are typed, conversion routines
required
Control structures as VB
ASP/VBscript
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Basic example
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<table border=6><tr><td bgcolor=black>
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<font face = verdana color=green size=3>
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<% = time() %>
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</font></td></tr></table>
Shows time in a box
Syntax = function() means display
function value on standard output
channel
ASP/VBscript
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Getting values from WWW browser
HTTP request is parsed by IIS and results
are part of a “request” object.
total = cint(request("num1")) +
cint(request("num2"))
Adds up two numbers associated with
names “num1” and “num2”
cint() converts strings to integers
ASP/VBscript
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Output to the page is performed using
the write() method of the response
class/object.
E.g.
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response.write(“number is “ & num1)
& is ASP/VBscript's string concatenation
operator
Database access
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Accessing a MySQL database
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Create a database connection object
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Execute connect method
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Construct SQL query
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Construct result object
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Execute query method
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Examine result object
Database Access
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Basic database connection object
set myconn =
server.createobject("adodb.connection")
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Before executing connection method need
connection specification string
connection =
"driver={MySQL};server=134.220.4.130;uid
=demo;database=mydatabase"
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Connection method
myconn.open (connection)
Database Access
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Create a “result” object
set result =
server.createobject("adodb.recordset")
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Construct SQL query
sql = "SELECT * FROM gazetteer WHERE
feature ='" & request("place") & "'"
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Execute query
set result = myconn.execute(sql)
Database Access
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Unlike PHP, ASP/VBScript does not
provide a method to count the rows in a
result set
Need to loop until “EOF” encountered
while not result.EOF
....
....
wend
JSP
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Originally Java Server Pages
Allows Java code to be used as server
side script
Either free-standing Java server
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Tricky to handle anything other than JSP
Or via Apache and Tomcat
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A separate process that communicates with
Apache
JSP
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Apache server forwards requests for JSP
to Tomcat process
Tomcat process (written in Java) looks for
JSP document, converts it to Java code
(wrapping HTML in Java output methods),
compiles the Java and sends the output
back to Apache.
Compiled Java is cached for efficiency
JSP
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Code is enclosed within <% ... %>
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Inspired by ASP
Tomcat provides main() method etc.,
Tomcat provides a request object with a
getParameter() method to retrieve user
entered data (as a String)
JSP
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Adding up two numbers
Stringsn1,sn2;
int n1,n2;
sn1 = request.getParameter("n1");
sn2 = request.getParameter("n2");
n1 = Integer.parseInt(sn1);
n2 = Integer.parseInt(sn2);
out.println("<br>The sum is " +
(n1+n2));
Database Access
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For database access some standard class
packages need to be imported.
Syntax is similar to Java
<%@ page
import = "java.io.*"
import = "java.lang.*"
import = "java.sql.*"
%>
Database Access
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Before creating any connection objects it
is necessary to load the driver class for
the specific database server
Class.forName("org.gjt.mm.mysql.Driver");
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This could fail and must be enclosed in a
try catch construct
Database Access
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Set up a database connection using
dbconn =
DriverManager.getConnection("jdbc:m
ysql://clun.scit.wlv.ac.uk/mydataba
se","demo","");
String syntax is specific to the particular
driver
JDBC = Java Data Base Connector
Database Access
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Query is prepared in SQL as a string.
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This is then prepared for processing.
String sql = .......
sql = dbconn.prepareStatement(sql);
results = sql.executeQuery();
Database Access
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There is no way of discovering number of
rows in a result set.
Scan result set until no more results
while(results.next())
{
Lat = results.getInt(“Lat”);
}
Comparison
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PHP
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Advantages
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Popular, Simple, Extensive Libraries, Free
(Open Source), Most platforms, Good
debugging, Designed for the purpose
Disadvantages
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Security niggles, Interpretation overhead
Comparison
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ASP
Actually several languages(.NET more
recent than VBScript)
Advantages
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Good support, popular, integrates with other
products
Disadvantages
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Single supplier
Comparison
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JSP
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Advantages
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Strength of Java language and standard
libraries, security
Disadvantages
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Complexity, performance, difficult to set up,
Comparison
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C
Powerful general purpose close to system
language.
Advantages
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Can do anything (almost), performance
Disadvantages
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Development costs, not specifically designed
for WWW backends
Comparison
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Perl
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Powerful general purpose
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Advantages
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Widespread support, lots of quality packages
Disadvantages
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Obscure syntax
Local Resources
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Checkttp://www.scit.wlv.ac.uk/~jphb/sst
for a substantial collection of information
on server side issues.
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Slides prepared by Peter Burden using
Open Office version 1.9.79
Background image was taken from a web
cam on the Isle of Skye on 21/11/2003
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http://www.uhi.ac.uk/webcams/index.php?cam=smo&mode=large
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Slides in 44/66 point Verdana and 36 point Courier New Bold
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Notes in 14 point Gill Sans and Courier New Bold