Restful services. Part 1. Rest pattern. Example

Сентябрь 7, 2022

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Restful services. Part 1. Rest pattern. Example

Содержание

2. What is REST? Representational State Transfer between Resource REST is a design pattern. It is a
3. Example: Airline Reservation Service Suppose that an airline wants to create a telephone reservation system for
4. Approach 1 "Press 1 for Premier, Press 2 for…" The airline provides a single telephone number.
5. Approach 2 Telephone Numbers are Cheap! Use Them! The airline provides several telephone numbers - one
6. Discussion In Approach 1 the answering machine introduces an extra delay, which is particularly annoying to
7. Web-Based Reservation Service Suppose now the airline wants to provide a Web reservation service for customers
8. Approach 1 One-Stop Shopping The airline provides a single URL. The Web service is responsible for
9. Approach 1 Disadvantages There is currently no industry accepted practice (rules) for expressing priorities, so rules
10. Web Design, Axiom 0 (Tim Berners-Lee, director of W3C) Axiom 0: all resources on the Web
11. Approach 2: URLs are Cheap! Use Them! The airline provides several URLs - one URL for
12. Approach 2 Advantages The different URLs are discoverable by search engines and UDDI registries. It's easy
13. Recap We have looked at a reservation service. We have seen a telephone-based version and a
14. This Ain't the REST Design Pattern Premier Members Frequent Flyer Members Regular Members Airline Reservation Answering
15. This is the REST Design Pattern Premier Members Frequent Flyer Members Regular Members 1-800-Premier Premier Customer
16. This ain't the REST Design Pattern Premier Members Frequent Flyer Members Regular Members Reservation Web Service
17. This is the REST Design Pattern Premier Members Frequent Flyer Members Regular Members client client client
18. Two Fundamental Aspects of the REST Design Pattern Resources Every distinguishable entity is a resource. A
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Слайд 2

What is REST?
Representational State Transfer between Resource
REST is a design pattern.
It

is a certain approach to creating Web Services.
HTTP is the main and the best example of a REST style implementation

Слайд 3

Example: Airline Reservation Service
Suppose that an airline wants to create a

telephone reservation system for customers to call in and make flight reservations.
The airline wants to ensure that its premier members get immediate service, its frequent flyer members get expedited service and all others get regular service.
There are two main approaches to implementing the reservation service...

Слайд 4

Approach 1 "Press 1 for Premier, Press 2 for…"
The airline provides a

single telephone number.
Upon entry into the system a customer encounters an automated message, "Press 1 if you are a premier member, press 2 if you are a frequent flyer, press 3 for all others."

Слайд 5

Approach 2 Telephone Numbers are Cheap! Use Them!
The airline provides several telephone

numbers - one number for premier members, a different number for frequent flyers, and still another for regular customers.

Слайд 6

Discussion
In Approach 1 the answering machine introduces an extra delay, which

is particularly annoying to premier members. (Doesn't everyone hate those answering systems)
With Approach 2 there is no intermediate step. Premier members get instant pickup from a customer service representative. Others may have to wait for an operator.

Слайд 7

Web-Based Reservation Service
Suppose now the airline wants to provide a Web

reservation service for customers to make flight reservations through the Web.
Just as with the telephone service, the airline wants to ensure that its premier members get immediate service, its frequent flyer members get expedited service, all others get regular service.
There are two main approaches to implementing the Web reservation service. The approaches are analogous to the telephone service...

Слайд 8

Approach 1 One-Stop Shopping
The airline provides a single URL. The Web service

is responsible for examining incoming client requests to determine their priority and process them accordingly.

Слайд 9

Approach 1 Disadvantages
There is currently no industry accepted practice (rules) for

expressing priorities, so rules would need to be made. The clients must learn the rule, and the Web service application must be written to understand the rule.
This approach is based upon the incorrect assumption that a URL is "expensive" and that their use must be rationed.
The Web service is a central point of failure. It is a bottleneck. Load balancing is a challenge.
It violates Tim Berners-Lee Web Design, Axiom 0 (see next slide).

Слайд 10

Web Design, Axiom 0 (Tim Berners-Lee, director of W3C)
Axiom 0: all resources

on the Web must be uniquely identified with a URI.

resource1

URL1

resource2

URL2

resource3

URL3

Слайд 11

Approach 2: URLs are Cheap! Use Them!
The airline provides several URLs

- one URL for premier members, a different URL for frequent flyers, and still another for regular customers.

Premier Members

Frequent Flyer Members

Regular Members

client

http://www.kings-air/reservations/premier

http://www.kings-air/reservations/frequent-flyer

http://www.kings-air/reservations/regular

Premier
Member
Reservation
Service

Frequent
Flyer
Reservation
Service

Regular
Member
Reservation
Service

Слайд 12

Approach 2 Advantages
The different URLs are discoverable by search engines and

UDDI registries.
It's easy to understand what each service does simply by examining the URL, i.e., it exploits the Principle of Least Surprise.
There is no need to introduce rules. Priorities are elevated to the level of a URL. "What you see is what you get."
It's easy to implement high priority - simply assign a fast machine at the premier member URL.
There is no bottleneck. There is no central point of failure.
Consistent with Axiom 0.

Слайд 13

Recap
We have looked at a reservation service.
We have seen a telephone-based

version and a Web-based version of the reservation service.
With each version we have seen two main approaches to implementing the service.
Which approach is the REST design pattern and which isn't? See the following slides.

Слайд 14

This Ain't the REST Design Pattern
Premier Members
Frequent Flyer Members
Regular Members
Airline Reservation
Answering
Machine
Premier
Customer
Representative
F.F.
Customer
Representative
Regular
Customer
Representative

Слайд 15

This is the REST Design Pattern
Premier Members
Frequent Flyer Members
Regular Members
1-800-Premier
Premier
Customer
Representative
F.F.
Customer
Representative
Regular
Customer
Representative
1-800-Frequent
1-800-Reservation

Слайд 16

This ain't the REST Design Pattern
Premier Members
Frequent Flyer Members
Regular Members
Reservation
Web
Service
Determine
Priority
Premier
Customer
F.F.
Customer
Regular
Customer
client
client
client

Слайд 17

This is the REST Design Pattern
Premier Members
Frequent Flyer Members
Regular Members
client
client
client
http://www.kings-air/reservations/premier
http://www.kings-air/reservations/frequent-flyer
http://www.kings-air/reservations/regular
Premier
Member
Reservation
Service
Frequent
Flyer
Reservation
Service
Regular
Member
Reservation
Service

Слайд 18

Two Fundamental Aspects of the REST Design Pattern
Resources Every distinguishable entity is

a resource. A resource may be a Web site, an HTML page, an XML document, a Web service, a physical device, etc.
URLs Identify Resources Every resource is uniquely identified by a URL. This is Tim Berners-Lee Web Design, Axiom 0.

Restful services. Part 1. Rest pattern. Example

Содержание

What is REST?Representational State Transfer between ResourceREST is a design pattern.It

Example: Airline Reservation ServiceSuppose that an airline wants to create a

Approach 1 "Press 1 for Premier, Press 2 for…"The airline provides a

Approach 2 Telephone Numbers are Cheap! Use Them!The airline provides several telephone

DiscussionIn Approach 1 the answering machine introduces an extra delay, which

Web-Based Reservation ServiceSuppose now the airline wants to provide a Web

Approach 1 One-Stop ShoppingThe airline provides a single URL. The Web service

Approach 1 DisadvantagesThere is currently no industry accepted practice (rules) for

Web Design, Axiom 0 (Tim Berners-Lee, director of W3C)Axiom 0: all resources

Approach 2: URLs are Cheap! Use Them!The airline provides several URLs

Approach 2 AdvantagesThe different URLs are discoverable by search engines and

RecapWe have looked at a reservation service.We have seen a telephone-based

This Ain't the REST Design PatternPremier MembersFrequent Flyer MembersRegular MembersAirline ReservationAnsweringMachinePremierCustomerRepresentativeF.F.CustomerRepresentativeRegularCustomerRepresentative

This is the REST Design PatternPremier MembersFrequent Flyer MembersRegular Members1-800-PremierPremierCustomerRepresentativeF.F.CustomerRepresentativeRegularCustomerRepresentative1-800-Frequent1-800-Reservation

This ain't the REST Design PatternPremier MembersFrequent Flyer MembersRegular MembersReservationWeb ServiceDeterminePriorityPremierCustomerF.F.CustomerRegularCustomerclientclientclient

Two Fundamental Aspects of the REST Design PatternResources Every distinguishable entity is

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