An Introduction to HTTP

Prepared for ThoughtWorks Junior Consultant group

Transcript

2. Networking  Layers  
3. Why  Should  We  Care?  
4. An  HTTP  Session  
5. HTTP  HEAD  Request   URI  
6. URIs   •  Uniform  Resource  IdenEfiers   •  What’s  the  difference  between  a  URI  and  a   URL?  
7. HTTP  HEAD  Request   Method  
8. Basic  HTTP  Methods   •  GET   •  POST   •  PUT   •  DELETE  
9. Safe  Methods   •  GET   •  POST   •  PUT   •  DELETE  
10. Methods  With  Side  Effects   •  GET   •  POST   •  PUT   •  DELETE  
11. Idempotent  Methods   •  GET   •  POST   •  PUT   •  DELETE  
12. HTTP  HEAD  Response   Status  Code  
13. Status  Codes   •  1xx  InformaEonal  (HTTP  1.1)   •  2xx  Success   –  200  Ok   –  201  Created   •  3xx  RedirecEon   –  302  Found   •  4xx  Client  Error   –  400  Bad  Request   –  404  Not  Found   •  5xx  Server  Error   –  500  Internal  Server  Error  
14. HTTP  HEAD  Response   Expires  
15. Expires   •  Date/Eme  a\er  which  the  response  is   considered  stale   •  What  does  a  value  of  “-­‐1”  mean?  
16. HTTP  HEAD  Response   Cache-­‐Control  
17. Cache-­‐Control   •  InstrucEon  to  all  recipients  along  the  request/ response  chain   •  What  does  “private”  mean?  
18. HTTP  HEAD  Response   Content-­‐Type  
19. Content-­‐Type   •  Indicates  content  type  of  the  body  sent  in  the   response  
20. HTTP  State   •  HTTP  is  stateless   •  What  challenges  does  this  present?  
21. Exercises  -­‐  Setup   •  Workspace  setup   – Tomcat   – Eclipse   – curl   – Chrome  (try  Cmd  +  Alt  +  I)  
22. Project  Setup   •  Go  to  ‘Java  EE’  perspecEve   •  Go  to  ‘Servers’  view  and  configure  a  Tomcat   server   •  Create  a  ‘Dynamic  Web  Project’   •  Create  a  ‘DemoServlet’  
23. I  -­‐  Hello  World  GET   •  Modify  the  servlet  to  print  ‘Hello  World’  in  the   response      
24. II  -­‐  GET  with  curl     •  Send  an  HTTP  GET  request  using  curl  
25. III  -­‐  What  is  my  UserAgent?     •  Print  the  UserAgent  informaEon  in  the   response   •  Use  a  browser  to  test  
26. IV  -­‐  UserAgent  is  ‘myself’     •  Use  curl  to  set  the  UserAgent  to  ‘myself’  and   print  it  in  the  response    
27. Hint   •  Use  ‘–user-­‐agent’  opEon  
28. V  -­‐  POST  with  curl     •  POST  a  request,  using  curl,  with  values     ‘name’:  ‘<your  name>’   ‘interest’:  ‘<your  interest>’   •  And  print  them  in  the  response  
29. Hint   •  Use  ‘—data’  opEon  
30. ApplicaEon  Flow   Session   Request   Response   Request   Response  
31. Servlet  API   •  HkpServlet   •  HkpServletRequest   •  HkpServletResponse   •  HkpSession   •  HkpServletContext  
32. Filters   •  Diagram:   hkp://docs.oracle.com/cd/B15904_01/web. 1012/b14017/invfilt.gif  
33. Scopes   •  Request   •  Session   •  ApplicaEon  
34. VI  –  Count  my  requests   •  Implement  a  Servlet  based  counter  that  on   each  invocaEon  prints   ‘Hello!  This  request  number  <number>’   •  Invoke  it  using  browser   •  And  now  invoke  it  using  curl  
35. Hint   •  Use  curl  with  ‘—cookie’  opEon  
36. Extra  Credit  J   •  Create  an  authenEcaEon  servlet  that  validates   users  based  on  form  parameters  ‘username’   and  ‘password’  against  hardcoded  values   •  Implement  the  previous  ‘counter’  example,   incremenEng  the  counter  only  if  the  user  is   authenEcated      
37. More  Credit..   •  InvesEgate  HTTP  Content  negoEaEon  
38. Further  Reading   •  Request  methods   – hkp://www.w3.org/Protocols/rfc2616/rfc2616-­‐ sec9.html   •  Status  codes   – hkp://www.w3.org/Protocols/rfc2616/rfc2616-­‐ sec10.html   •  Header  Fields   – hkp://www.w3.org/Protocols/rfc2616/rfc2616-­‐ sec14.html#sec14.9.1