Action filters

Before filters

Before filters are run before an action is run. If a before filter responds something, all filters after it and the action will not be run.

import xitrum.Action
import xitrum.annotation.GET

@GET("before_filter")
class MyAction extends Action {
  beforeFilter {
    log.info("I run therefore I am")
  }

  // This method is run after the above filters
  def execute() {
    respondInlineView("Before filters should have been run, please check the log")
  }
}

After filters

After filters are run after an action is run. They are functions that take no argument. Their return value will be ignored.

import xitrum.Action
import xitrum.annotation.GET

@GET("after_filter")
class MyAction extends Action {
  afterFilter {
    log.info("Run at " + System.currentTimeMillis())
  }

  def execute() {
    respondText("After filter should have been run, please check the log")
  }
}

Around filters

import xitrum.Action
import xitrum.annotation.GET

@GET("around_filter")
class MyAction extends Action {
  aroundFilter { action =>
    val begin = System.currentTimeMillis()
    action()
    val end   = System.currentTimeMillis()
    val dt    = end - begin
    log.info(s"The action took $dt [ms]")
  }

  def execute() {
    respondText("Around filter should have been run, please check the log")
  }
}

If there are many around filters, they will be nested.

Execution order of filters

• Before filters are run first, then around filters, then after filters.
• If one of the before filters returns false, the rest (including around and after filters) will not be run.
• After filters are always run if at least an around filter is run.
• If an around filter decide not to call action, the inner nested around filters will not be run.

before1 -true-> before2 -true-> +--------------------+ --> after1 --> after2
                                | around1 (1 of 2)   |
                                |   around2 (1 of 2) |
                                |     action         |
                                |   around2 (2 of 2) |
                                | around1 (2 of 2)   |
                                +--------------------+