Introduction to HTTP Requests AND Responses

Overview of Section - HTTP Requests and Responses

• HTTP Verbs - GET, POST, DELETE
• Headers
• Responses
  • Status Codes - e.g. 200, 404, 500
• This is the foundation for most web, HTTP, REST testing and automating.

HTTP GET Request sent from cURL

Command:

curl http://apichallenges.herokuapp.com/heartbeat ^
-H "accept: application/xml" ^
--proxy 127.0.0.1:8888

Sends a GET Request:

GET http://apichallenges.herokuapp.com/heartbeat HTTP/1.1
User-Agent: curl/7.39.0
Host: apichallenges.herokuapp.com
Connection: Keep-Alive
accept: application/xml

• GET requests retrieve information from the Web Application
• important stuff:
  • Verb (GET),
  • Http version (1.1),
  • User-Agent,
  • Accept,
  • Host,
  • endpoint

HTTP Response to GET /heartbeat request

HTTP/1.1 204 OK
Date: Thu, 17 Aug 2017 10:34:32 GMT
Content-Type: application/json
Transfer-Encoding: chunked
Server: Jetty(9.4.4.v20170414)

• cURL response was same but content-type was application/xml
• important stuff: Status Code (204 OK), Http version (1.1), Date, Content-Type

Raw HTTP Requests and Responses

• we need to be able to read them
• we will rarely have to create them by hand
• lookup headers you don't know
  • https://en.wikipedia.org/wiki/List_of_HTTP_header_fields
• some fields are for the server some are for the application some are documentation

Basic HTTP Verbs

• GET - retrieve data
• POST amend/create from partial information
• PUT - create or replace from full information
• DELETE - delete items
• OPTIONS - verbs available on this url

References

• W3c Standard
• IETF standard
• httpstatuses.com
• http://www.restapitutorial.com/lessons/httpmethods.html

HTTP Status Codes

• 1xx Informational
  • 100 Continue
• 2xx Success
  • e.g. 200 OK
• 3xx Redirection
  • e.g. 301 Moved Permanently
• 4xx Client Error
  • e.g. 404 Not Found
• 5xx Server Error
  • e.g. 500 Internal Server Error

Common HTTP Status Codes

HTTP Status code references

• https://httpstatuses.com/
• https://moz.com/blog/response-codes-explained-with-pictures
• https://http.cat/
• https://httpstatusdogs.com/

HTTP Message Body Format - JSON

• JSON - JavaScript Object Notation
• an actual Object in JavaScript
• common data transfer and marshalling format for other languages
• https://en.wikipedia.org/wiki/JSON
• http://json.org
• http://countwordsfree.com/jsonviewer
• schema exists for JSON http://json-schema.org/

JSON Example Explained

{
 "lists":
  [
   {
    "guid":"f8134dd6-a573-4cf5-a6c6-9d556118ed0b",
    "title":"a list title",
    "description":"",
    "createdDate":"2017-08-17-13-11-12",
    "amendedDate":"2017-08-17-13-11-12"
   }
  ]
}

• An object, which has an array called "lists".
• the lists array contains an object with fields: guid, title, description, createdDate, amendedDate - all String fields.

HTTP Message Body Format - XML

• XML - eXtended Markup Language
• HTML is often XML
• another common marshalling format
• can be validated against XML schema
• http://countwordsfree.com/xmlviewer

XML Example Explained

<?xml version="1.0" encoding="UTF-8" ?>
<lists>
  <list>
    <guid>f8134dd6-a573-4cf5-a6c6-9d556118ed0b</guid>
    <title>a list title</title>
    <description></description>
    <createdDate>2017-08-17-13-11-12</createdDate>
    <amendedDate>2017-08-17-13-11-12</amendedDate>
  </list>
</lists>

• elements, nested elements
• tags, values

URI - Universal Resource Identifier

scheme:[//[user[:password]@]host[:port]][/path][?query][#fragment]

• http://compendiumdev.co.uk/apps/api/mock/reflect
  • scheme = http
  • host = compendiumdev.co.uk
  • path = apps/api/mock/reflect

wikipedia.org/wiki/Uniform_Resource_Identifier

A URL is a URI

URI vs URL vs URN

• URI - Universal Resource Identifier
  • 'generic' representation - might not include the 'scheme'
  • http://compendiumdev.co.uk/apps/api/mock/reflect
  • compendiumdev.co.uk/apps/api/mock/reflect
  • /apps/api/mock/reflect
• URL - Universal Resource Locator
  • http://compendiumdev.co.uk/apps/api/mock/reflect
  • defines how to locate the identified resource
• URN - Universal Resource Name
  • not often used - uses scheme urn

Scheme(s)

• http
• https
• ftp
• mailto
• file

Query Strings

GET /lists/{guid}?without=title,description
GET http://apichallenges.herokuapp.com/lists/f13?without=title,description

Query String:

?without=title,description

• starts with ?
• params separated with &

More About Query Strings

GET /lists/{guid}?without=title,description

• usually name=value pairs separate by '&'
  • convention since anything after the ? is the Query string
  • app then parses as required
• can be used with any verb
• GET request - all params are send as query strings

https://en.wikipedia.org/wiki/Query_string

HTTP Standards?

• rfc7231 (HTTP/1.1): Semantics and Content
• rfc7230 (HTTP/1.1): Message Syntax and Routing

How to test with this information

• Read the standards for the verbs and the status codes.
• Projects often argue about interpretations.
• Some of the standards are exact enough that it is possible to say "I observed X" it does not match the standard - include links and quotes to the standards.

HTTP Headers

• Headers are Key: value pair attributes in the request
• Headers are not counted as the payload
• Headers help configure the response from the server and tell the server how to process this request
• e.g. a GET request with an accept: application/xml header is asking the server to respond with the information in XML format

User-Agent Header

• Often not sent when accessing an API
• Marks request as coming from a browser

User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64)
AppleWebKit/537.36 (KHTML, like Gecko)
Chrome/60.0.3112.90 Safari/537.36

Accept Header

• Defines the payload types that the receiver will accept
• If this was an API call it would likely return XML

Accept: text/html,application/xhtml+xml,application/xml;
q=0.9,image/webp,image/apng,*/*;q=0.8

Common values:

• text/html
• application/json
• application/xml

Basic Auth Header

• An application might use Basic Auth Authentication to control access to the API
• Authorization Header

e.g. Authorization: Basic dXNlcjpwYXNzd29yZA==

dXNlcjpwYXNzd29yZA== is base64 encoded "user:password"

see base64decode.org

• cURL you need to add the header
• Postman & Insomnia use the Authorization and Auth tabs