Bài giảng Web technologies and e-Services - Bài 7, Phần 1: Soap and Restful web service - Nguyễn Bình Minh
29/04/2021
IT4409: Web Technologies and e-Services
2020-2
SOAP & RESTFUL Web service
Instructor: Dr. Thanh-Chung Dao
Slides by Dr. Binh Minh Nguyen
Department of Information Systems
School of Information and Communication Technology
Hanoi University of Science and Technology
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Three Most Common Styles of Use
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RPC (Remote Procedure Calls)
– A distributed function call interface
SOAP (Simple Object Access Protocol)
– The basic unit of communication is a message, rather than an
operation
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REST (Representational State Transfer)
– Standard operations in HTTP: GET, POST, PUT, DELETE
– Interacting with stateful resources, rather than messages or
operations
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RPC Web Services
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Basic unit: WSDL operation
Widely deployed and supported, but not loosely
coupled
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Other approaches: CORBA, DCE/RPC, Java RMI
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SOAP Web Services
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Basic unit: message
Envelope
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Supported by most
major vendors, loose
Header
coupling
Body
Message
Payload
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Representational State Transfer (REST)
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Interacting with stateful resources, rather than
messages or operations
Using HTTP standard operations such as GET,
POST, PUT, DELETE
WSDL 2.0 offers support for binding to all HTTP
request methods
– WSDL 1.1 only GET and POST
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SOAP web service
– HTTP-XML-based protocol
– Enables application to communicate over Internet
– Uses XML documents called messages
– SOAP message contains an envelope
– Describes message’s content and intended recipient
– Ability to make a Remote Procedure Call (RPC)
– Request to another machine to run a task
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SOAP
Using Web Services and SOAP, the request would look
something like this:
<?xml version="1.0"?>
<soap:Envelope
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xmlns:soap="http://www.w3.org/2001/12/soap-envelope"
soap:encodingStyle="http://www.w3.org/2001/12/soap-encoding">
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<soap:body pb="http://www.acme.com/phonebook">
<pb:GetUserDetails>
<pb:UserID>12345</pb:UserID>
</pb:GetUserDetails>
</soap:Body>
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</soap:Envelope>
7
Pros & cons
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Advantages
n
Disadvantages
n
S-L-O………………..-W
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–
–
–
–
Human readable XML
n
XML produces a lot of overhead for
small messages
Easy to debug
SOAP runs over HTTP
Firewalls not affected
n
n
Web Services speed relies on
Internet traffic conditions
Not strictly-typed XML
Services can be written
in any language,
platform or operating
system
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GET: fetch information
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To fetch a web page, the browser does a GET
on some URI and retrieves a representation
(HTML, plain text, JPEG, or whatever) of the
resource identified by that URI
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GET is fundamental to browsers
REST requires a few more verbs to allow taking
actions
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Four verbs for every noun
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GET to retrieve information
POST to add new information, showing its
relation to old information
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PUT to update information
DELETE to discard information
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What’s REST?
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So what's REST already?
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REpresentational State Transfer
An architectural style, not a toolkit
“We don't need no toolkits!”
A distillation of the way the Web already works
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REST defined
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Resources are identified by uniform resource
identifiers (URIs)
Resources are manipulated through their
representations
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Messages are self-descriptive and stateless
Multiple representations are accepted or sent
Hypertext is the engine of application state
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HTTP Request/Response As REST
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REST style
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Client-server
Stateless
Cached
Uniform interface
Layered system
(Code on demand)
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A web page is a resource?
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A web page is a representation of a resource
Resources are just concepts
URIs tell a client that there's a concept
somewhere
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Clients can then request a specific
representation of the concept from the
representations the server makes available
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State
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“State” means application/session state
Maintained as part of the content transferred
from client to server back to client
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Thus any server can potentially continue
transaction from the point where it was left off
State is never left in limbo
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Transfer of state
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Connectors (client, server, cache, resolver,
tunnel) are unrelated to sessions
State is maintained by being transferred from
clients to servers and back to clients
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What?
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REST and HTTP
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REST is a post hoc description of the Web
HTTP 1.1 was designed to conform to REST
Its methods are defined well enough to get
work done
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Unsurprisingly, HTTP is the most RESTful
protocol
But it's possible to apply REST concepts to
other protocols and systems
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Existing HTTP uses
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Web browsing (obviously)
Instant messaging
Content management
What's outside its scope?
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What do REST messages look like?
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Like what we already know: HTTP, URIs, etc.
REST can support any media type, but XML is
expected to be the most popular transport for
structured information.
●
Unlike SOAP and XML-RPC, REST does not
really require a new message format
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SOAP vs. REST
Using Web Services and SOAP, the request would look
something like this:
<?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:body pb="http://www.acme.com/phonebook">
<pb:GetUserDetails>
<pb:UserID>12345</pb:UserID>
</pb:GetUserDetails>
</soap:Body>
</soap:Envelope>
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SOAP vs. REST
And with REST? The query will probably look like this:
GET /phonebook/UserDetails/12345 HTTP/1.1
Accept: application/xml
Complex query:
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SOAP vs. REST
SOAP
REST
Meaning
Simple Object Access Protocol
Representational State Transfer
T
Design
Standardized protocol with pre-defined rules Architectural style with loose guidelines and
to follow.
recommendations.
Approach
Function-driven (data available as services,
e.g.: “getUser”)
Data-driven (data available as resources, e.g.
“user”).
Statefulness
Stateless by default, but it’s possible to
make a SOAP API stateful.
Stateless (no server-side sessions).
Caching
API calls cannot be cached.
API calls can be cached.
Security
WS-Security with SSL support. Built-in ACID
compliance.
Supports HTTPS and SSL.
Performance
Requires more bandwidth and computing
power.
Requires fewer resources.
Message format
Transfer protocol(s)
Recommended for
Only XML.
Plain text, HTML, XML, JSON, YAML, and
others.
HTTP, SMTP, UDP, and others.
Only HTTP
Enterprise apps, high-security apps,
distributed environment, financial services,
payment gateways, telecommunication
services.
Public APIs for web services, mobile services,
social networks.
Advantages
High security, standardized, extensibility.
Scalability, better performance, browser-
friendliness, flexibility.
Disadvantages
Poorer performance, more complexity, less
flexibility.
Less security, not suitable for distributed
environments.
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