1. Building
Web
Services
Jussi
Pohjolainen

2. Communica9on
between
Apps
• Implemen9ng
RPCs
can
be
a
difficult
task
• DCOM,
CORBA,
RMI
…
firewalls
and
proxy
servers
can
block
binary
• Using
HTTP
for
RPCs
you
can
bypass
this
problem

3. Web
Service
• Communica9on
between
devices
over
Web
– W3C
defines
"Web
Service"
as
a
technology
that
uses
WSDL,
SOAP,
HTTP
and
XML
to
create
the
communica9on
• Two
types
– XML
Web
Services
– Web
API

4. XML
Web
Services
• XML
Web
services
uses
XML
messages
that
follow
SOAP
standard
for
crea9ng
the
communica9on
• Services
are
wriRen
using
WSDL
– Web
Services
Descrip9on
Language
(WSDL)
• Web
Services
are
integrated
very
well
to
.NET
and
Java
(6
-­‐>)

5. Web
API
(Rest)
• Emphasis
to
simpler
communica9on
– Representa)onal
state
transfer
(REST)
• Do
not
require
SOAP,
WSDL
• Simple
Web
API
– hRp://www.something.com/twiRerthis.php?
msg=hello!
• If
the
Web
API
is
implemented
using
certain
constraints,
it's
rest
API
– hRp://www.something.com/clients/client17

6. XML
WEB
SERVICE

7. SOAP?
• SOAP
is
a
XML-­‐based
protocol
to
let
apps
exchange
informa9on
over
HTTP
• SOAP
is
language
independent
and
it's
W3C
recommenda9on
• Since
SOAP
is
XML
and
it's
text,
it
can
be
send
easily
through
firewalls

8. SOAP
Building
Blocks
<?xml version="1.0"?>
<soap:Envelope
xmlns:soap="http://www.w3.org/2001/12/soap-envelope"
soap:encodingStyle="http://www.w3.org/2001/12/soap-encoding">
<soap:Header>
...
</soap:Header>
<soap:Body>
...
<soap:Fault>
...
</soap:Fault>
</soap:Body>
</soap:Envelope>

9. SOAP
Request
<?xml version="1.0" encoding="UTF-8"?>
<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/
envelope/" xmlns:ns1="http://hello/">
<SOAP-ENV:Body>
<ns1:getArea><arg0>5.6</arg0></ns1:getArea>
</SOAP-ENV:Body>
</SOAP-ENV:Envelope>

10. SOAP
Response
<?xml version="1.0" ?>
<S:Envelope xmlns:S="http://schemas.xmlsoap.org/soap/envelope/">
<S:Body>
<ns2:getAreaResponse xmlns:ns2="http://hello/">
<return>98.5203456165759</return>
</ns2:getAreaResponse>
</S:Body>
</S:Envelope>

11. Client
and
Server
• "Soap
Server"
provides
a
WSDL
–
file
to
client
• Client
opens
the
WSDL
file
and
discovers
the
methods
and
arguments
of
given
service
• Client
makes
a
invoca9on
to
server.
The
invoka9on
is
a
soap
message
• Server
receives
the
soap
message,
parses
it
and
invocates
the
method.
Result
is
send
back
in
SOAP
envelope

13. Java
6:
XML
&
Web
Services
• Easy
way
of
crea9ng
Web
Services
• Expose
web
service
with
a
simple
annota9on

14. Web
Service
package hello;
import javax.jws.WebService;
@WebService
public class CircleFunctions {
public double getArea(double r) {
return java.lang.Math.PI * (r * r);
}
public double getCircumference(double r) {
return 2 * java.lang.Math.PI * r;
}
}

15. Server
package hello;
import javax.xml.ws.Endpoint;
class Publish {
public static void main(String[] args) {
Endpoint.publish(
"http://localhost:8080/circlefunctions",
new CircleFunctions());
}
}

16. Generate
Stub
Files
• Generate
stub
files:
– wsgen –classpath . hello.CircleFunctions

18. PHP
Client
<?php
$arguments = array (
"arg0" => "5.6",
);
// URI delivered to web service
$soapclient = new SoapClient("http://localhost:8080/
circlefunctions?wsdl");
$result = $soapclient->getArea($arguments);
print($result->return);
?>

20. REST

21. REST
Constraints
• Client
Server
– Interface
separates
clients
from
servers.
Server
and
client
can
be
replaced
and
developed
independently
– Client?
Browser,
PHP
script,
Desktop
app,
Command
line
…
• Statelessness
– Each
request
from
any
client
contains
all
the
informa9on
necessary
• Cacheable
– Clients
can
cache
responses.
Response
indicate
whether
it
is
cacheable
or
not
• Uniform
interface
– Uniform
interface
between
clients
and
servers.
Four
guiding
principles
• Layered
System
– Client
does
not
know
is
it
connected
directly
to
server
or
some
middleware

22. Guidelines
for
the
Interface
• Iden9fica9on
of
resources
– Resources
are
iden9fied
via
request
using
URIs
– Server
sends
to
client
HTML,
XML
or
JSON
as
result
(does
not
send
the
database)
• Manipula9on
of
resources
– Client
can
delete
or
modify
a
resource
when
it
holds
a
representa9on
of
the
resource
• Self-­‐descrip9ve
messages
– Message
includes
enough
informa9on
to
describe
how
to
process
the
message
• Hypermedia
as
the
engine
of
applica9on
state
– Client
enters
REST
app
using
simple
fixed
URL.
All
future
ac9ons
the
client
may
take
can
be
discovered
from
the
returned
representa9on

23. Resources
• Resource
can
be
anything:
ar9cle,
comment,
user
…
• Resources
are
accessed
by
URI
– hRp://example.com/ar9cle/1
– hRp://example.com/comments/

24. RESTful
Web
APIs

25. PHP
REST
IMPLEMENTATION

26. Rewrite
engine
• Rewrite
engine
is
a
sohware
that
modifies
web
URL's
appearance
– URL
rewri9ng
• Usage
– hRp://example.com/index.php?clien9d=123
• Can
be
altered
– hRp://example.com/clients/client/123
• Apache
HTTP
Server
has
URL
rewri9ng
provided
by
mod_rewrite
module

27. .htaccess
# Let's use the mod_rewrite module
RewriteEngine On
# Set's the base URL for per-directory rewrites
RewriteBase /
# Defines a condition under which rewriting will
# take place
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
# Make the rule
RewriteRule ^(.*)$ /xampp/rest/index.php/$1 [L]

28. XAMPP
windows
• Open
apache/conf/extra/hRpd-­‐xampp.conf
– set
AllowOverride
All

29. Gekng
info
about
Request
and
Path
<?php
$requestMethod = $_SERVER['REQUEST_METHOD'];
print("Request method: " . $requestMethod . "nn");
$urlPaths = $_SERVER['REQUEST_URI'] ;
print("Path: " . $urlPaths);
?>

32. Modifica9on
<?php
$requestMethod = $_SERVER['REQUEST_METHOD'];
$urlPaths = $_SERVER['REQUEST_URI'] ;
$paths = explode("/", $urlPaths);
$paths = array_splice($paths, 3);
print_r($paths);
?>

33. Encoding
and
decoding
• Encode
data
to
and
decode
from
JSON
– json_encode()
– json_decode()

34. Tes9ng:
Advanced
REST
Client
Chrome
App

35. Tes9ng
• PHP
Script
that
makes
hRp
requests
• CURL
• Telnet…