Question

JSP中前台点击按钮报错500，后台报错空指针，求大神帮忙！！！

这是后台报的错
java.lang.NullPointerException
at java.lang.Class.isAssignableFrom(Native Method)
at org.apache.struts.util.RequestUtils.rationalizeMultipleFileProperty(RequestUtils.java:506)
at org.apache.struts.util.RequestUtils.populate(RequestUtils.java:459)
at org.apache.struts.chain.commands.servlet.PopulateActionForm.populate(PopulateActionForm.java:50)
at org.apache.struts.chain.commands.AbstractPopulateActionForm.execute(AbstractPopulateActionForm.java:60)
at org.apache.struts.chain.commands.ActionCommandBase.execute(ActionCommandBase.java:51)
at org.apache.commons.chain.impl.ChainBase.execute(ChainBase.java:191)
at org.apache.commons.chain.generic.LookupCommand.execute(LookupCommand.java:305)
at org.apache.commons.chain.impl.ChainBase.execute(ChainBase.java:191)
at org.apache.struts.chain.ComposableRequestProcessor.process(ComposableRequestProcessor.java:283)
at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1913)
at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:462)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
at com.lbs.brick.web.filter.ApplicationFilter.doFilter(Unknown Source)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:215)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
at com.lbs.brick.sys.webcontroller.OperateLogFilter.doFilter(OperateLogFilter.java:65)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:215)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
at com.lbs.brick.sys.webcontroller.SafetyFilter.doFilter(SafetyFilter.java:108)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:215)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)

Answer 1

看一下你的struts的的执行方法。这里面你调用了一个空对象，或者是未实例化，或者是已不存在的对象。

追问

我debug的时候进不了后台，没发现里面引用了空对象…

追答

空指针就是引用了空对象。

追问

可是就是找不到，debug都进不去，怎么破

Answer 2

解决了吗？我这也是，多刷新就此就正常了，不知道什么原因！