我的验证器表单出现 nullPointer 异常

Question

你好，我有一个类 Form，我在其中实现了这样的验证器，

public class LoginForm extends ActionForm {
    private String login;
    private String password;
    public void setLogin(String login) {
        this.login = login;
    }
    public string getLogin() {
        return login;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    public string getPassword() {
        return password;
    }
    public ActionErrors validate(ActionMapping mapping,HttpServletRequest request) {
        ActionErrors errors = new ActionErrors();
        if ( login==null || login.lenght()<=8) {
            errors.add("error",new ActionMessage ("error.login"));
        }
        if ( password==null || password.lenght()<=8) {
            errors.add("error",new ActionMessage ("error.password"));
        }
        return errors;
    }
}

问题是我在这一行

errors.add("error",new ActionMessage ("error.login"));

StackTrace 中有一个 nullPointerException：

Etat HTTP 500 - 

--------------------------------------------------------------------------------

type Rapport d'exception

message 

description Le serveur a rencontré une erreur interne () qui l'a empèché de satisfaire la requête.

exception 

java.lang.NullPointerException
    at fr.xxxx.xxxxx.xxxxx.forms.LoginForm.validate(AdministrationSaisieTarifsForm.java:77)
    at org.apache.struts.action.RequestProcessor.processValidate(RequestProcessor.java:950)
    at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:207)
    at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
    at org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:414)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:697)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:810)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:199)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:145)
    at org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:264)
    at org.acegisecurity.intercept.web.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:107)
    at org.acegisecurity.intercept.web.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:72)
    at org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:274)
    at org.acegisecurity.ui.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:110)
    at org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:274)
    at org.acegisecurity.providers.anonymous.AnonymousProcessingFilter.doFilter(AnonymousProcessingFilter.java:125)
    at org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:274)
    at org.acegisecurity.ui.rememberme.RememberMeProcessingFilter.doFilter(RememberMeProcessingFilter.java:142)
    at org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:274)
    at org.acegisecurity.wrapper.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:81)
    at org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:274)
    at org.acegisecurity.ui.AbstractProcessingFilter.doFilter(AbstractProcessingFilter.java:217)
    at org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:274)
    at org.acegisecurity.ui.logout.LogoutFilter.doFilter(LogoutFilter.java:106)
    at org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:274)
    at org.acegisecurity.context.HttpSessionContextIntegrationFilter.doFilter(HttpSessionContextIntegrationFilter.java:229)
    at org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:274)
    at org.acegisecurity.util.FilterChainProxy.doFilter(FilterChainProxy.java:148)
    at org.acegisecurity.util.FilterToBeanProxy.doFilter(FilterToBeanProxy.java:98)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:165)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:145)
    at org.springframework.orm.hibernate3.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:196)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:77)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:165)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:145)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:210)
    at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:596)
    at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:433)
    at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:955)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:139)
    at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:596)
    at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:433)
    at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:955)
    at org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2460)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:133)
    at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:596)
    at org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:119)
    at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:594)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
    at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:594)
    at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:433)
    at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:955)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:127)
    at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:596)
    at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:433)
    at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:955)
    at org.apache.coyote.tomcat4.CoyoteAdapter.service(CoyoteAdapter.java:157)
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:874)
    at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665)
    at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528)
    at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81)
    at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:685)
    at java.lang.Thread.run(Thread.java:534)

Answer 1

我决定根据您对堆栈跟踪的更新打开另一个答案。

以下行

errors.add("error",new ActionMessage ("error.login"));

仅当错误变量为 null 或在您粘贴的代码中该变量在之前通过以下方式初始化时，

ActionErrors errors = new ActionErrors();

才会导致 NullPointerException：因此，行号 77 不是您认为的行号。不可能是这个。

Answer 2

您提供的堆栈报告的异常不在您提到的类/行中，而是在以下行中：

fr.xxxx.xxxxx.xxxxx.forms.AdministrationSaisieTarifsForm.validate(AdministrationSaisieTarifsForm.java:77)

看一下AdministrationSaisieTarifsForm.validate(...)，根据您提供的堆栈，问题就在那里。