HTTP Methods

Describing the Format of HTTP Requests

  • An HTTP client sends an HTTP request to a server

  • An HTTP request maintains the following format:

    • A request line

    • Zero or more header lines

      • Including general, request, and entity fields
    • An empty line
    • Optional message body

Describing the Format of HTTP Responses

  • First, a server receives a HTTP request message
  • Then, that server responds with an HTTP response message
  • HTTP responses maintain a similar format as HTTP requests

  • They maintain the following format:

    • A request line
    • Zero or more header lines
    • An empty line
    • Optional message body

Components of HTTP Requests and Responses

  • Request Line: Contains:

    • A request method
    • A URL of the desired resource
  • General Header: General info about a request or response
  • Entity Header: Info about the resource of a request
  • Request Header: Information about the client
  • Response Header: Information about the server
  • Message Body: Data meant for the client or server recipient
  • An HTTP request has a request header
  • An HTTP response has a response header
  • A typical request looks like the following:

httprequest

Defining HTTP Request Methods

  1. GET Method

    • This method is given a server URI
    • This method is used to retrieve information from this server
    • Specifically, this method should only retrieve data
    • It should not have any other effect on the data

  2. HEAD Method

    • This method is also given a server URI
    • It is also used to retrieve information from this server
    • However, it returns the status line and header section only

  3. POST Method

    • This method is used to send date to a server
    • This method represents an addition of data

    • For example, this data could include:

      • Customer information
      • File uploads
      • Data from HTML files

  4. PUT Method

    • This method is used to replace data from a server
    • Specifically, it replaces this data with a given resource
    • The target resource is given by a URI
    • This method represents a replacement of data

  5. DELETE Method

    • This method is used to remove data from a server
    • Specifically, the target resource is given by a URI
    • The target resource is removed from the server

  6. CONNECT Method

    • This method is used to establish a tunnel to the server
    • Specifically, the server is identified by a given URI

  7. OPTIONS Method

    • This method is used to describe the options of communication for the target resource

  8. TRACE Method

    • This method is used to perform a message loop-back test to a target resource

Examples of HTTP Requests

  1. GET Method
GET /test.html HTTP/1.1
Host: www.test101.com
Accept: image/gif, image/jpeg, */*
Accept-Language: en-us
Accept-Encoding: gzip, deflate
User-Agent: Mozilla/4.0
Content-Length: 35

bookId=12345&author=Mike+Lane
  1. HEAD Method
HEAD /test.html HTTP/1.1
Host: www.test101.com
Accept: image/gif, image/jpeg, */*
Accept-Language: en-us
Accept-Encoding: gzip, deflate
User-Agent: Mozilla/4.0
Content-Length: 35

bookId=12345&author=Mike+Lane
  1. POST Method
POST /bin/login HTTP/1.1
Host: www.test101.com
Accept: image/gif, image/jpeg, */*
Accept-Language: en-us
Accept-Encoding: gzip, deflate
User-Agent: Mozilla/4.0
Content-Length: 35

User=Peter+Lee&pw=123456&action=login
  1. PUT Method
PUT /new.html HTTP/1.1
Host: www.test101.com
Accept: image/gif, image/jpeg, */*
Accept-Language: en-us
Accept-Encoding: gzip, deflate
User-Agent: Mozilla/4.0
Content-Length: 31
Content-type: text/html

<p>New File</p>
  1. DELETE Method
DELETE /file.html HTTP/1.1
  1. CONNECT Method
CONNECT server.example.com:80 HTTP/1.1
Host: server.example.com:80
Proxy-Authorization: basic aGVsbG86d29ybGQ=
  1. OPTIONS Method
OPTIONS /resources/post-here/ HTTP/1.1
Host: bar.other
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-us,en;q=0.5
Accept-Encoding: gzip,deflate
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7
Connection: keep-alive
Origin: http://foo.example
Access-Control-Request-Method: POST
Access-Control-Request-Headers: X-PINGOTHER, Content-Type
  1. TRACE Method
TRACE /index.html

Defining HTTP Response Codes

  • HTTP response codes indicate the status of an HTTP request

  • These responses are grouped into five classes:

    1. Informational Responses: 100-199 codes

      • The request was received and the process is continuing

    2. Successful Responses: 200-299 codes

      • The action was successfully received and understood

    3. Redirectional Responses: 300-399 codes

      • The action must be continued to complete the request

    4. Client Errors: 400-499 codes

      • The request contains incorrect syntax

    5. Server Errors: 500-599 codes

      • The server failed to fulfill any request

References

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