Chapter 47 - Understanding REST and JSON

Question 1

What is a library?

Answer 1

• Prebuilt index of data that can be used instead of writing the equivalent from scratch

Question 2

What are the attributes that define REST APIs?

Answer 2

• Client/server architecture - Uses API calls (E.g. HTTP requests) to access data on the REST server
• Stateless operation - Does not use information from previous API exchanges to influence future API exchanges
• Clear statement of cacheable and uncacheable - Marks data that should or should not be cached for better performance (if cached, the server does not have to retrieve a resource for the client after already retrieving it within a certain timeframe)
• Uniform interface
• Layered
• Code-on-demand

Question 3

What are Simple Variables?

Answer 3

• Variables with a single data name and a single attributed value

Question 4

What are Array Data Structures?

Answer 4

• Data Structure with a single data key but multiple attributed values

Question 5

What are Object Data Structures?

Answer 5

• Data structures that contain multiple key:value pairs
• Sometimes called a Dictionary

Question 6

Why do a lot of REST APIs use HTTP as their networking protocol?

Answer 6

• Very similar (e.g. both client/server, both stateless, both clearly mark cacheable and uncacheable data)
• REST APIs can also use URIs to specify in HTTP what data it needs to perform an action on

Question 7

What is CRUD?

Answer 7

• An acronym for the four primary actions of an application:
  - Create - Allows users to create variables and data structures at a server and set their initial values
  - Read - Allows users to retrieve the current value of variables that exist at a server
  - Update - Allows the client to update variables and data structures at a server
  - Delete - Allows the client to delete variables from a server

Question 8

List HTTP verbs and their corresponding CRUD terms

Answer 8

• POST - Create
• GET - Read
• PATCH/PUT - Update
• DELETE - Delete

Question 9

What are the different parts of a URI?

Answer 9

HTTPS://google.com/path/to/resource?specific=query

• Before the :// - Protocol (Scheme)
• Immediately after the :// - The hostname of the server (authority)
• Immediately after the / - The path to the resource on the server
• Immediately after the ? - A query that specifies the variable that the client is querying at a given destination

Question 10

What is JSON?

Answer 10

• JavaScript Object Notation
• Open standard file format and data interchange format that stores and transmits data in human readable text
• Data serialisation language
• Commonly used in REST APIs
• Whitespace is insignificant

Question 11

What is a Data Serialisation Language?

Answer 11

• Provides a standardised method of representing data between programs. Useful when programs are written in different languages as they may interpret/represent variables differently
• An example is JSON, XML, YAML
• Sometimes known as a Data Modelling Language

Question 12

What is XML?

Answer 12

• eXtensible Markup Language
• Data serialisation language
• A successor to HTML that improves on the ability for variables to be changed dynamically
• Commonly used in REST APIs and web pages
• Whitespace does not change the meaning of data
• key value pairs are written as <key> value </key>

Question 13

What is YAML?

Answer 13

• YAML Ain’t Markup Language
• Data serialisation language
• Unlike XML focuses more on data model details than markup
• Commonly used in Ansible
• White space does change the meaning of data
• Files start with ‘—’
• Lists start with ‘-‘
• Key value pairs are defined as key:value

Question 14

What is markup in the context of programming?

Answer 14

• The ability for a programming language to add more information to variables to define how they are displayed

Question 15

JSON syntax rules

Answer 15

• Key:Value Pair - Every colon identifies one key:value pair with the key before the colon and the value after.
• Key - Text inside double quotes, before a colon that is used as a name that references a value
• Value - Item after the colon that represents the value of the key. These can be:
  - string
  - number
  - null
  - boolean
  - Array
  - Object - An unordered list of key:value pairs
• Multiple Pairs - Separate each pair with a comma at the end of each pair apart from the last one
• Curly brackets - Begin and end a JSON object. A series of key:value pairs enclosed in curly brakcets. Python knows them as dictionaries.
• Square brackets - Begin and end a JSON array. A series of values (not key:value pairs) enclosed in square brackets. Python knows them as lists.
• Objects and arrays can be nested within each other
• Whitespace does not change the meaning of data

Question 16

What are JSON data types?

Answer 16

• null- Represents the intentional lack of a value. Just the word null in no quotes.
• string - Text value. Surrounded by quotes.
• boolean - True/False value. Not surrounded by quotes.
• number - Numeric value. Not surrounded by quotes.

Question 16

What are variables?

Answer 16

• A data container that stores a value

Question 17

How many key:value pairs are in the below?

{
“Identity”:{
“Interface”:”G0/1”,
“Enabled”:true
}
}

Answer 17

• 3
• However, “Identity” is a key and then everything inside the second set of curly brackets is the value.

Question 18

What are nested objects?

Answer 18

• Objects within objects
• An example is:
  {
  “Identity”:{
  “Interface”:”G0/1”,
  “Enabled”:true
  }
  }

Question 19

True or False. In JSON, having a comma at the end of the last key:value pair in an object is fine.

Answer 19

False. There should only be a comma between key:value pairs and not after the last key:value pair.

Question 20

What are HTTP response codes?

Answer 20

• 3 digit numbers that define the response from a HTTP server:
  - 1xx - Informational (e.g. 102 - Processing)
  - 2xx - Successful (e.g. 200 - OK, 201 - Created)
  - 3xx - Redirection (e.g. 301 - Moved permanently)
  - 4xx - Client error (e.g. 403 - Unauthorised, 404 - Not found)
  - 5xx - Server error (e.g. 500 - Internal server error)