Japanese Auto Reloading Plugins

Last updated by admin 4 years ago

????????????????????{excerpt:hidden=true}Handling Auto Reload Events with Plugins{excerpt}

?????????????{excerpt:hidden=true}Monitoring Resources for Changes{excerpt}

???????????????????????????????????????????????????Grails?????????????????????????????????????Grails?????????? {{ServicesPlugin}} ??????????????????:{excerpt:hidden=true} Often it is valuable to monitor resources for changes and then reload those changes when they occur. This is how Grails implements advanced reloading of application state at runtime. For example, consider the below snippet from the {{ServicesPlugin}} that Grails comes with:{excerpt} 

code: null

class ServicesGrailsPlugin {
    …
    def watchedResources = "/grails-app/services/*Service.groovy"
    …
  def onChange = { event ->
    if(event.source) {
      def serviceClass = application.addServiceClass(event.source)
      if(serviceClass.transactional) {
        log.warning "Transactional services classes cannot be reloaded. Skipping $serviceClass"
      }
      else {
        def serviceName = "${serviceClass.propertyName}"
        def beans = beans {
           "$serviceName"(serviceClass.getClazz()) { bean ->
               bean.autowire =  true
        }
      }
      if(event.ctx) {
        event.ctx.registerBeanDefinition(serviceName,
                                       beans.getBeanDefinition(serviceName))
      }
    }
  }
}

code: null

??????????????????????????????????????????? {{watchedResources}} ???????????????????????Groovy???????????????????????? {{event}} ???????? {{onChange}} ????????????{excerpt:hidden=true}
Firstly it defines a set of {{watchedResources}} as either a String or a List of strings that contain either the references or patterns of the resources to watch. If the watched resources is a Groovy file, when it is changed it will automatically be reloaded and passed into the {{onChange}} closure inside the {{event}} object.{excerpt}
{{event}} ??????????????????????????:

    

  • event.source - ???????????Spring?Resource??????????????
    • 

  • event.ctx - Spring ApplicationContext???????
    • 

  • event.plugin - ????(????? {{this}} )????????????????
    • 

  • event.application - GrailsApplication???????{excerpt:hidden=true}
    • 

The {{event}} object defines a number of useful properties:

    

      

        

      • event.source - The source of the event which is either the reloaded class or a Spring Resource
        • 

      • event.ctx - The Spring ApplicationContext instance
        • 

      • event.plugin - The plugin object that manages the resource (Usually {{this}})
        • 

      • event.application - The GrailsApplication instance{excerpt}
        • 

??????????????????????????ApplicationContext????????????????????????Services???????????????????????????????bean?ApplicationContext????????????{excerpt:hidden=true}
From these objects you can evaluate the conventions and then apply the appropriate changes to the ApplicationContext and so forth based on the conventions, etc.  In the "Services" example above, a new services bean is re-registered with the ApplicationContext when one of the service classes changes.{excerpt}
???????????{excerpt:hidden=true}Influencing Other Plugins{excerpt}
?????????????????????????????????????????????????????????????????????????{excerpt:hidden=true}
As well as being able to react to changes that occur when a plugin changes, sometimes one plugin needs to "influence" another plugin.{excerpt}
???????????????????????????????????????????????????????????????????????????????????????????(auto-wire)?????????????????{excerpt:hidden=true}
Take for example the Services & Controllers plugins. When a service is reloaded, unless you reload the controllers too, problems will occur when you try to auto-wire the reloaded service into an older controller Class.{excerpt}
???????????????????????????????????influences??????????????????????????????????????????????????????????????????????????????????? {{ServicesGrailsPlugin}} ???????????????:{excerpt:hidden=true}
To get round this, you can specify which plugins another plugin "influences". What this means is that when one plugin detects a change, it will reload itself and then reload all influenced plugins. See this snippet from the {{ServicesGrailsPlugin}}:{excerpt}

def influences = ['controllers']