![Dispatch pattern
{ <pattern>, <resource-mod>, <init-params>}
i.e.
{[“a”], module_a, []}.
matches http://host/a & calls module_a
{[“a”, varname], module_a, []}.
match http://host/a/Carl & calls module_a
with “varname” = “Carl”](https://image.slidesharecdn.com/arestfulinterfaceforerlangcodeusingwebmachine-140821090131-phpapp02/85/A-RESTful-Interface-for-Erlang-Code-using-Webmachine-15-320.jpg)
![A CRUD dispatch
• % Accounts
• {["account","add"], webui_resource_account,
[add, [{'POST', <<"accounts">>}]]},
• {["account","delete",id], webui_resource_account,
[delete, [{'POST', <<"accounts">>}]]},
• {["account","edit",id], webui_resource_account,
[edit, [{'POST', <<"accounts">>}]]},
• {["accounts"], webui_resource_account,
[account_many,[{'GET', <<"accounts">>}]]},
• {["json","accounts"], webui_resource_account,
[accounts, [{'GET', <<"accounts">>}]]},](https://image.slidesharecdn.com/arestfulinterfaceforerlangcodeusingwebmachine-140821090131-phpapp02/85/A-RESTful-Interface-for-Erlang-Code-using-Webmachine-17-320.jpg)
![content_types_provided
• This function defines the types of content
that the module can provide.
• It defaults to [{“text/html”,to_html}] .
• to_html is function name that creates the
results.
• You might want this to return
[{“text/html”,to_html}, {“json”,to_json}]](https://image.slidesharecdn.com/arestfulinterfaceforerlangcodeusingwebmachine-140821090131-phpapp02/85/A-RESTful-Interface-for-Erlang-Code-using-Webmachine-21-320.jpg)
A RESTful Interface for Erlang Code using Webmachine
- 1. A RESTful interface for Erlang code using Webmachine Copyright 2014 Carl Wright
- 2. RESTful interface • Exposes your app as resources on the Web. • Resources respond to 6 HTTP methods: GET, HEAD, POST, PUT, DELETE and OPTIONS
- 3. HTTP: interface to your erlang app • Start with an erlang app • add webmachine code • Write the dispatch table & web app start • Write the resource code indicated by the dispatch table Erlang app Webmachine HTTP:
- 4. A specific application Webui holds the code to respond to URIs Webmachine provides an HTTP server to handle URI requests on a specific channel.
- 5. Adding webmachine • Go to https://github.com/basho/webmachine/wiki • To see the documentation and to fork a copy of webmachine • Add it to your erlang application.
- 6. The others apps • To run webmachine, you need the following apps: – mochiweb • http interaction support library – crypto • Cryptographic functions to support secure web – inets • Base webservices (ftp, tftp, http, https, etc.)
- 7. Adding to your app definition • You have a “.rel” to define your application release.
- 8. Yes, you need mochiweb, too. Mochiweb is installed along webmachine and your “webui” folder. Crypto and inets are in the standard erlang libraries. You just include them in Your application definition.
- 9. Release configuration • Add “webmachine” to your release configuration files for “relx” or “rebar”. • These are the most common release managers for erlang systems.
- 10. Inside your web UI • OTP folder structure • ebin holds .app file and compiled binaries • priv holds the dispatch table. • src holds the application source code.
- 11. Webui.app (in ebin folder)
- 12. The src folder
- 14. A simple dispatch table 1. http://host/device/status/7348272000 2. http://host {anything else}
- 15. Dispatch pattern { <pattern>, <resource-mod>, <init-params>} i.e. {[“a”], module_a, []}. matches http://host/a & calls module_a {[“a”, varname], module_a, []}. match http://host/a/Carl & calls module_a with “varname” = “Carl”
- 16. Left side pattern • Is a list of any atom, string or star • Breaks the URL on slashes • Strings must match the URL contents • Atoms associate with the value so that you retrieve their value • Star is “*” and must be the last in the list when present.
- 17. A CRUD dispatch • % Accounts • {["account","add"], webui_resource_account, [add, [{'POST', <<"accounts">>}]]}, • {["account","delete",id], webui_resource_account, [delete, [{'POST', <<"accounts">>}]]}, • {["account","edit",id], webui_resource_account, [edit, [{'POST', <<"accounts">>}]]}, • {["accounts"], webui_resource_account, [account_many,[{'GET', <<"accounts">>}]]}, • {["json","accounts"], webui_resource_account, [accounts, [{'GET', <<"accounts">>}]]},
- 18. A real resource function
- 19. How does a resource function wire up to the web? • There is a mapping between 30+ functions that you can put in a resource module. • They map to states in the HTTP state machine that webmachine implements.
- 20. Resource functions • resource_exists • service_available • allowed_methods • content_types_provid ed • etcetera • These functions all have default values when absent. • You only write functions when you needs something more.
- 21. content_types_provided • This function defines the types of content that the module can provide. • It defaults to [{“text/html”,to_html}] . • to_html is function name that creates the results. • You might want this to return [{“text/html”,to_html}, {“json”,to_json}]
- 22. A real resource function
- 23. Actual results
- 24. Questions?