Struts2 JSON Parameter Mystery

Question

Having a bit of trouble with this tomcat deployment. Deploying a complex webapp (not authored by me) and have gotten rid of most of the errors, but can't figure out this one for the life of me. It seems to be causing a shutdown of the servlet after initiating a debug itself. I've looked everywhere, but I can't find mention of a 'default parameter' anywhere in the coding.

DEBUG localhost-startStop-1 com.opensymphony.xwork2.util.fs.DefaultFileManagerFactory - Using default implementation of FileManager provided under name [system]: DefaultFileManager
DEBUG localhost-startStop-1 com.opensymphony.xwork2.config.providers.XmlConfigurationProvider - Loaded [BUILDER] {PackageConfig Name:default namespace: parents:[{PackageConfig Name:struts-default namespace: parents:[]}]}
DEBUG localhost-startStop-1 com.opensymphony.xwork2.config.providers.XmlConfigurationProvider - The result type [org.ambraproject.struts2.JsonResult] doesn't have a default param [DEFAULT_PARAM] defined!
java.lang.NoSuchFieldException: DEFAULT_PARAM
    at java.lang.Class.getField(Class.java:1579)
    at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.addResultTypes(XmlConfigurationProvider.java:578)
    at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.addPackage(XmlConfigurationProvider.java:530)
    at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.loadPackages(XmlConfigurationProvider.java:292)
    at org.apache.struts2.config.StrutsXmlConfigurationProvider.loadPackages(StrutsXmlConfigurationProvider.java:112)
    at com.opensymphony.xwork2.config.impl.DefaultConfiguration.reloadContainer(DefaultConfiguration.java:250)
    at com.opensymphony.xwork2.config.ConfigurationManager.getConfiguration(ConfigurationManager.java:67)
    at org.apache.struts2.dispatcher.Dispatcher.init_PreloadConfiguration(Dispatcher.java:446)
    at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:490)
    at org.ambraproject.struts2.AmbraStruts2Dispatcher.init(AmbraStruts2Dispatcher.java:116)
    at org.apache.catalina.core.ApplicationFilterConfig.initFilter(ApplicationFilterConfig.java:277)
    at org.apache.catalina.core.ApplicationFilterConfig.getFilter(ApplicationFilterConfig.java:258)
    at org.apache.catalina.core.ApplicationFilterConfig.setFilterDef(ApplicationFilterConfig.java:382)
    at org.apache.catalina.core.ApplicationFilterConfig.<init>(ApplicationFilterConfig.java:103)
    at org.apache.catalina.core.StandardContext.filterStart(StandardContext.java:4650)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5306)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:901)
    at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:877)
    at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:633)
    at org.apache.catalina.startup.HostConfig.deployWAR(HostConfig.java:977)
    at org.apache.catalina.startup.HostConfig$DeployWar.run(HostConfig.java:1655)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
    at java.util.concurrent.FutureTask.run(FutureTask.java:262)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at java.lang.Thread.run(Thread.java:744)

Answer 1

It's just a DEBUG message, nothing to worry about - basically each Result in Struts must provide DEFAULT_PARAM definition, at least it can be null.