grails源码分析---之Filters机制(1)
grails提供了两种对请求的拦截机制，一是在Controller中定义beforeInterceptor和afterInterceptor两个方法，分别在执行action之前和之后调用，具体实现代码是在SimpleGrailsController和SimpleGrailsControllerHelper中，不再赘述。
还有一个是Filter，即在grails-app/conf目录下定义以Filters结尾的groovy文件既可，提供了三个拦截方法before，after，afterView，分别对应Spring MVC的HandlerInterceptor接口的preHandle(在处理请求前调用)，postHandle(在处理请求后生成View之前调用，提供了修改Model的机会)，afterCompletion(在请求处理完毕生成View之后调用)。
看看源码即可发现其实grails的MVC即是在Spring MVC框架上包装一层而成的，所以看来暂时不可能把核心框架修改为struts的可能。
下面看看grails是如何把Filters结尾的groovy文件变成Spring的HandlerInterceptor。
DefaultGrailsPlugin加载所有的plugin，当然也包含FiltersGrailsPlugin
DefaultGrailsPlugin.groovy

    //加载plugin,调用plugin的doWithApplicationContext方法    public void doWithRuntimeConfiguration(            RuntimeSpringConfiguration springConfig) {        if(this.pluginBean.isReadableProperty(DO_WITH_SPRING)) {            if(LOG.isDebugEnabled()) {                LOG.debug("Plugin " + this + " is participating in Spring configuration...");            }            //调用plugin的doWithSpring方法，加载plugin到spring的ApplicationContext，使用Spring DSL方式的BeanBuilder             Closure c = (Closure)this.plugin.getProperty(DO_WITH_SPRING);            BeanBuilder bb = new BeanBuilder(getParentCtx(), application.getClassLoader());            bb.setSpringConfig(springConfig);            Binding b = new Binding();            b.setVariable("application", application);            b.setVariable("manager", getManager());            b.setVariable("plugin", this);            b.setVariable("parentCtx", getParentCtx());            b.setVariable("resolver", getResolver());            bb.setBinding(b);            c.setDelegate(bb);            bb.invokeMethod("beans", new Object[]{c});        }    }    //动态配置plugin，调用plugin的doWithApplicationContext方法     public void doWithApplicationContext(ApplicationContext applicationContext)    

FiltersGrailsPlugin.groovy

    def watchedResources = "file:./grails-app/conf/**/*Filters.groovy"    //Spring bean DSL    static final BEANS = { filter ->            "${filter.fullName}Class"(MethodInvokingFactoryBean) {                targetObject = ref("grailsApplication", true)                targetMethod = "getArtefact"                arguments = [TYPE, filter.fullName]            }            "${filter.fullName}"(filter.clazz) { bean ->                bean.singleton = true                bean.autowire = "byName"            }    }    //生成了实现spring HandlerInterceptor接口的filterInterceptor    def doWithSpring = {filterInterceptor(org.codehaus.groovy.grails.plugins.web.filters.CompositeInterceptor) {        }        for(filter in application.getArtefacts(TYPE)) {            def callable = BEANS.curry(filter)            callable.delegate = delegate            callable.call()        }}def doWithApplicationContext = { applicationContext ->        reloadFilters(application, applicationContext)}//   把Filters groovy类变成CompositeInterceptor的handlers成员//  用FilterToHandlerAdapter适配器把preHandle==before，postHandle==after，afterCompletion==afterView对应起来private reloadFilters(GrailsApplication application, applicationContext) {        log.info "reloadFilters"        def filterConfigs = application.getArtefacts(TYPE)        def handlers = []        for(c in filterConfigs) {            def filterClass = applicationContext.getBean("${c.fullName}Class")            def bean = applicationContext.getBean(c.fullName)            for(filterConfig in filterClass.getConfigs(bean)) {                handlers << new FilterToHandlerAdapter(filterConfig:filterConfig, configClass:bean)            }        }        if (log.isDebugEnabled()) log.debug("resulting handlers: ${handlers}")        applicationContext.getBean('filterInterceptor').handlers = handlers    }