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) 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 }