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6.6.2 过滤器的类型 - Reference Documentation

Authors: Graeme Rocher, Peter Ledbrook, Marc Palmer, Jeff Brown, Luke Daley, Burt Beckwith

Version: null

6.6.2 过滤器的类型

Within the body of the filter you can then define one or several of the following interceptor types for the filter:
  • before - Executed before the action. Return false to indicate that the response has been handled that that all future filters and the action should not execute
  • after - Executed after an action. Takes a first argument as the view model to allow modification of the model before rendering the view
  • afterView - Executed after view rendering. Takes an Exception as an argument which will be non-null if an exception occurs during processing. Note: this Closure is called before the layout is applied.

For example to fulfill the common simplistic authentication use case you could define a filter as follows:

class SecurityFilters {
   def filters = {
       loginCheck(controller: '*', action: '*') {
           before = {
              if (!session.user && !actionName.equals('login')) {
                  redirect(action: 'login')
                  return false
               }
           }
       }
   }
}

Here the loginCheck filter uses a before interceptor to execute a block of code that checks if a user is in the session and if not redirects to the login action. Note how returning false ensure that the action itself is not executed.

Here's a more involved example that demonstrates all three filter types:

import java.util.concurrent.atomic.AtomicLong

class LoggingFilters {

private static final AtomicLong REQUEST_NUMBER_COUNTER = new AtomicLong() private static final String START_TIME_ATTRIBUTE = 'Controller__START_TIME__' private static final String REQUEST_NUMBER_ATTRIBUTE = 'Controller__REQUEST_NUMBER__'

def filters = {

logFilter(controller: '*', action: '*') {

before = { if (!log.debugEnabled) return true

long start = System.currentTimeMillis() long currentRequestNumber = REQUEST_NUMBER_COUNTER.incrementAndGet()

request[START_TIME_ATTRIBUTE] = start request[REQUEST_NUMBER_ATTRIBUTE] = currentRequestNumber

log.debug "preHandle request #$currentRequestNumber : " + "'$request.servletPath'/'$request.forwardURI', " + "from $request.remoteHost ($request.remoteAddr) " + " at ${new Date()}, Ajax: $request.xhr, controller: $controllerName, " + "action: $actionName, params: ${new TreeMap(params)}"

return true }

after = { Map model ->

if (!log.debugEnabled) return true

long start = request[START_TIME_ATTRIBUTE] long end = System.currentTimeMillis() long requestNumber = request[REQUEST_NUMBER_ATTRIBUTE]

def msg = "postHandle request #$requestNumber: end ${new Date()}, " + "controller total time ${end - start}ms" if (log.traceEnabled) { log.trace msg + "; model: $model" } else { log.debug msg } }

afterView = { Exception e ->

if (!log.debugEnabled) return true

long start = request[START_TIME_ATTRIBUTE] long end = System.currentTimeMillis() long requestNumber = request[REQUEST_NUMBER_ATTRIBUTE]

def msg = "afterCompletion request #$requestNumber: " + "end ${new Date()}, total time ${end - start}ms" if (e) { log.debug "$msg \n\texception: $e.message", e } else { log.debug msg } } } } }

In this logging example we just log various request information, but note that the model map in the after filter is mutable. If you need to add or remove items from the model map you can do that in the after filter.

在过滤器的主体内,你可以定义下列过滤器中拦截器类型的一个或者几个:

  • before - 在操作之前执行。返回值false表示响应已经被符合条件的过滤器处理过,并且其操作不被执行
  • after - 在操作之后执行。其第一个参数为视图模型(view model),并且允许在渲染视图之前修改此模型
  • afterView - 在渲染视图之后执行。如果有异常发生,其第一个参数为一个非null的异常。注意:此闭包在应用布局以前被调用。

比如,要执行一个通用简单的验证,你可以定义如下所示的过滤器:

class SecurityFilters {
   def filters = {
       loginCheck(controller: '*', action: '*') {
           before = {
              if (!session.user && !actionName.equals('login')) {
                  redirect(action: 'login')
                  return false
               }
           }
       }
   }
}

此处的loginCheck过滤器使用了before拦截器来执行一个代码块,用以检查一个用户是否在会话当中,如果不在,就重定向到login操作。注意:如何通过返回false的方式来确保操作本身不被执行。

下面是一个更深入的示例来演示所有的三种过滤器类型:

import java.util.concurrent.atomic.AtomicLong

class LoggingFilters {

private static final AtomicLong REQUEST_NUMBER_COUNTER = new AtomicLong() private static final String START_TIME_ATTRIBUTE = 'Controller__START_TIME__' private static final String REQUEST_NUMBER_ATTRIBUTE = 'Controller__REQUEST_NUMBER__'

def filters = {

logFilter(controller: '*', action: '*') {

before = { if (!log.debugEnabled) return true

long start = System.currentTimeMillis() long currentRequestNumber = REQUEST_NUMBER_COUNTER.incrementAndGet()

request[START_TIME_ATTRIBUTE] = start request[REQUEST_NUMBER_ATTRIBUTE] = currentRequestNumber

log.debug "preHandle request #$currentRequestNumber : " + "'$request.servletPath'/'$request.forwardURI', " + "from $request.remoteHost ($request.remoteAddr) " + " at ${new Date()}, Ajax: $request.xhr, controller: $controllerName, " + "action: $actionName, params: ${new TreeMap(params)}"

return true }

after = { Map model ->

if (!log.debugEnabled) return true

long start = request[START_TIME_ATTRIBUTE] long end = System.currentTimeMillis() long requestNumber = request[REQUEST_NUMBER_ATTRIBUTE]

def msg = "postHandle request #$requestNumber: end ${new Date()}, " + "controller total time ${end - start}ms" if (log.traceEnabled) { log.trace msg + "; model: $model" } else { log.debug msg } }

afterView = { Exception e ->

if (!log.debugEnabled) return true

long start = request[START_TIME_ATTRIBUTE] long end = System.currentTimeMillis() long requestNumber = request[REQUEST_NUMBER_ATTRIBUTE]

def msg = "afterCompletion request #$requestNumber: " + "end ${new Date()}, total time ${end - start}ms" if (e) { log.debug "$msg \n\texception: $e.message", e } else { log.debug msg } } } } }

在这个日志示例中,我们只记录不同请求的信息,但要注意到after过滤器中的model是可变的。如果你需要增加或者移除model的内容,可以在after过滤器中实现。