如何在Grails 3中使用过滤器而不是拦截器？

Question

The documentation for Grails 3 under Interceptors vs Filters says:

In versions of Grails prior to Grails 3.0, Grails supported the notion of filters. These are still supported for backwards compatibility but are considered deprecated.

I have a big Grails 2.5 application migrating to Grails 3.2 and would like to keep using filters.

How to make filters work in Grails 3.*?

As per [ http://docs.grails.org/latest/guide/upgrading.html] , I added compile 'org.grails:grails-plugin-filters:3.0.12' and moved the filter class from grails-app/conf to grails-app/controllers , but then I get the following exception:

java.lang.NullPointerException: null
    at java.beans.Introspector.getPublicDeclaredMethods(Introspector.java:1337)
    at java.beans.Introspector.getTargetMethodInfo(Introspector.java:1197)
    at java.beans.Introspector.getBeanInfo(Introspector.java:426)
    at java.beans.Introspector.getBeanInfo(Introspector.java:173)
    at groovy.lang.MetaClassImpl$15.run(MetaClassImpl.java:3318)
    at java.security.AccessController.doPrivileged(Native Method)
    at groovy.lang.MetaClassImpl.addProperties(MetaClassImpl.java:3316)
    at groovy.lang.MetaClassImpl.initialize(MetaClassImpl.java:3293)
    at org.codehaus.groovy.reflection.ClassInfo.getMetaClassUnderLock(ClassInfo.java:260)
    at org.codehaus.groovy.reflection.ClassInfo.getMetaClass(ClassInfo.java:302)
    at org.grails.plugins.web.filters.FilterToHandlerAdapter.$getStaticMetaClass(FilterToHandlerAdapter.groovy)
    at org.grails.plugins.web.filters.FilterToHandlerAdapter.<init>(FilterToHandlerAdapter.groovy:63)
    at org.grails.plugins.web.filters.FiltersGrailsPlugin.reloadFilters(FiltersGrailsPlugin.groovy:195)
    at org.grails.plugins.web.filters.FiltersGrailsPlugin.doWithApplicationContext(FiltersGrailsPlugin.groovy:72)
    at org.grails.plugins.DefaultGrailsPlugin.doWithApplicationContext(DefaultGrailsPlugin.java:523)
    at org.grails.plugins.AbstractGrailsPluginManager.doPostProcessing(AbstractGrailsPluginManager.java:224)
    at grails.boot.config.GrailsApplicationPostProcessor.onApplicationEvent(GrailsApplicationPostProcessor.groovy:246)
    at grails.boot.config.GrailsApplicationPostProcessor.onApplicationEvent(GrailsApplicationPostProcessor.groovy)
    at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:167)
    at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:139)
    at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:383)
    at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:337)
    at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:882)
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.finishRefresh(EmbeddedWebApplicationContext.java:144)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:545)
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:122)
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:762)
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:372)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:316)
    at grails.boot.GrailsApp.run(GrailsApp.groovy:83)
    at grails.boot.GrailsApp.run(GrailsApp.groovy:388)
    at grails.boot.GrailsApp.run(GrailsApp.groovy:375)
    at grails.boot.GrailsApp$run.call(Unknown Source)
    at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:48)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:113)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:133)
    at app6.Application.main(Application.groovy:8)

Answer 1

The very same documentations sez:

These are still supported

which means you can still use them as-is. Deprecation means, that you should start considering to replace them with interceptors.