Extension

You can add additional logic using Gohan Extension. Extensions has properties:

• id identity of the code
• code contents of a code
• code_type javascript, goext, go and Gohan script (DSL) are supported
• URL placement of code. Currently, file://, http:// and https:// schemes are supported
• path resource path to execute code

Example Code

  extensions:
  - code: console.log(Object.keys(context));
    id: test
    path: /v2.0/.*

Gohan supports four types of extensions:

• gohanscript
• javascript
• golang (as a callback, built-in)
• golang (as a plugin, loadable at runtime)

Comparison of different types of extensions:

Event

pre_list

list event before DB operation

context.response contains response data. You can also update response here

Note you can skip DB operation if you set context response in here

pre_list_in_transaction

Same as pre_list but executed in the DB transaction context.transaction contains transaction object for DB operation

id : request id

context.response contains response data. You can also update response here

post_list_in_transaction

Same as post_list but executed in the DB transaction context.transaction contains transaction object for DB operation

id : request id context.response contains response data. You can also update response here

post_list

list event after DB operation.

context.response contains response data. You can also update response here

pre_show

show event before DB access

id : request id context.response contains response data. You can also update response here

Note you can skip DB operation if you set context response in here

pre_show_in_transaction

Same as pre_show but executed in the DB transaction context.transaction contains transaction object for DB operation

id : request id context.response contains response data. You can also update response here

post_show_in_transaction

Same as post_show but executed in the DB transaction context.transaction contains transaction object for DB operation

id : request id context.response contains response data. You can also update response here

post_show

show event after DB operation

id : request id context.response contains response data. You can also update response here

pre_create

executed before creation Mainly used for validation purpose

context.resource contains user input data

Note you can skip DB operation if you set context response in here

pre_create_in_transaction

Same as pre_create but executed in the DB transaction context.transaction contains transaction object for DB operation

post_create_in_transaction

after creation in the transaction

post_create

after create context.response contains response data. context.transaction contains transaction object for db operation

pre_update

executed before an update Mainly used for validation purpose

context.resource contains user input data

Note you can skip DB operation if you set context response in here

pre_update_in_transaction

same as pre_update but executed in the db transaction context.transaction contains transaction object for db operation

post_update_in_transaction

after creation in transaction

post_update

after update context.response contains response data. context.transaction contains transaction object for db operation

pre_delete

executed before delete Mainly used for validation purpose

context.id contains resource id we are trying to delete context.transaction contains transaction object for db operation

pre_delete_in_transaction

same as pre_delete but executed in the db transaction context.transaction contains transaction object for db operation

post_delete_in_transaction

after creation in transaction

post_delete

after delete

pre_state_update_in_transaction

executed before a state update triggered by a backend event

context.resource contains the resource associated with the update, context.state contains the state changes, context.config_version contains the current config version

post_state_update_in_transaction

as above, but after the state update

pre_monitoring_update_in_transaction

executed before a monitoring update triggered by a backend event

context.resource contains the resource associated with the update, context.monitoring contains the new monitoring information

post_monitoring_update_in_transaction

as above, but after the monitoring update

notification

executed when you receive amqp/snmp/cron notification

Go extension (callback)

You can implement Gohan extension by native go. You can use "go" for code_type and specify your callback id in code. Also, you can register go struct & call it from javascript.

  extensions:
  - code: exampleapp_callback
    code_type: go
    id: example
    path: .*

  //Register go callback
  extension.RegisterGoCallback("exampleapp_callback",
      func(event string, context map[string]interface{}) error {
          fmt.Printf("callback on %s : %v", event, context)
          return nil
  })

We have exampleapp with comments in exampleapp directory. You can also, import github.com/cloudwan/server module and have your own RunServer method to have whole custom route written in go.