严重：处理请求期间发生异常：null java.lang.NullPointerException

时间：2015-09-17 11:34:51

标签： java xml validation struts2 nullpointerexception

我正在尝试在eclipse中的Struts2中创建一个基本的登录/注册。我得到的例外情况是我无法解决的，我正在尝试最近几个小时：

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC
   "-//Apache Software Foundation//DTD Struts Configuration 2.5//EN"
   "http://struts.apache.org/dtds/struts-2.5.dtd">

<struts>
    <include file="struts-default.xml"/>
    <package name="a" extends="struts-default">
        <action name="loginauth" class="com.project.loginreg.LoginAction" method="execute" >
           <result name="SUCCESS" type="redirect">
        <param name="location">/welcome.jsp</param>
        </result>
            <result name="ERROR">/login.jsp</result>
        </action>
    </package>
</struts>

Web.xml中

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
  <display-name>Login_Reg</display-name>

<filter>
    <filter-name>struts2</filter-name>
<filter-class>
       org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter                
</filter-class>
</filter>

<filter-mapping>
    <filter-name>struts2</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>

<welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>

以下是我正在制作的问题详情

Sep 17, 2015 4:54:41 PM org.apache.struts2.dispatcher.DefaultDispatcherErrorHandler error
SEVERE: Exception occurred during processing request: null
java.lang.NullPointerException
    at com.project.loginreg.LoginAction.execute(LoginAction.java:14)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at ognl.OgnlRuntime.invokeMethod(OgnlRuntime.java:870)
    at ognl.OgnlRuntime.callAppropriateMethod(OgnlRuntime.java:1293)
    at ognl.ObjectMethodAccessor.callMethod(ObjectMethodAccessor.java:68)
    at com.opensymphony.xwork2.ognl.accessor.XWorkMethodAccessor.callMethodWithDebugInfo(XWorkMethodAccessor.java:117)
    at com.opensymphony.xwork2.ognl.accessor.XWorkMethodAccessor.callMethod(XWorkMethodAccessor.java:108)
    at ognl.OgnlRuntime.callMethod(OgnlRuntime.java:1369)
    at ognl.ASTMethod.getValueBody(ASTMethod.java:90)
    at ognl.SimpleNode.evaluateGetValueBody(SimpleNode.java:212)
    at ognl.SimpleNode.getValue(SimpleNode.java:258)
    at ognl.Ognl.getValue(Ognl.java:494)
    at ognl.Ognl.getValue(Ognl.java:458)
    at com.opensymphony.xwork2.ognl.OgnlUtil$2.execute(OgnlUtil.java:309)
    at com.opensymphony.xwork2.ognl.OgnlUtil.compileAndExecute(OgnlUtil.java:340)
    at com.opensymphony.xwork2.ognl.OgnlUtil.getValue(OgnlUtil.java:307)
    at com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:423)
    at com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:287)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:250)
    at org.apache.struts2.interceptor.DeprecationInterceptor.intercept(DeprecationInterceptor.java:41)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244)
    at org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:256)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244)
    at com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:167)
    at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244)
    at com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:265)
    at org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:76)
    at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244)
    at com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:138)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244)
    at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:229)
    at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244)
    at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:229)
    at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244)
    at com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:191)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244)
    at org.apache.struts2.interceptor.MultiselectInterceptor.intercept(MultiselectInterceptor.java:73)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244)
    at org.apache.struts2.interceptor.DateTextFieldInterceptor.intercept(DateTextFieldInterceptor.java:125)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244)
    at org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:91)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244)
    at org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:253)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244)
    at com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:100)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244)
    at com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:141)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244)
    at com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:145)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244)
    at com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:171)
    at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244)
    at com.opensymphony.xwork2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:139)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244)
    at org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:164)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244)
    at com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:193)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244)
    at com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:189)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244)
    at org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:54)
    at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:564)
    at org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:81)
    at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:99)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:240)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:164)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:462)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:164)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:562)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:395)
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:250)
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:188)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:302)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)

继承LoginAction：

package com.project.loginreg;

import com.opensymphony.xwork2.ActionSupport;

public class LoginAction extends ActionSupport{

    private static final long serialVersionUID = 1L;
    private String userId;
    private String password;

    private Boolean error;

    public String execute(){
        if (userId.equals("")) {
            addActionError("Please Enter user id.");
            error = true;
        }
        else if(password.equals("")){
            addActionError("Please Enter Password.");
            error = true;
        }
         else if(!userId.equalsIgnoreCase(password)) {
             addActionError("Invalid userid or password.");
             error = true;
         } else {
             error = false;
         }
        if (error) {
            return ERROR;
        } else {
            return SUCCESS;
        }   
    }

    public String getUserId() {
        return userId;
    }

    public void setUserId(String userId) {
        this.userId = userId;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }
}

3 个答案:

答案 0 :(得分：2)

你的

private String userId

未初始化。它是NULL。 如果你想匹配一个空字符串，你必须先将它初始化。

所以将其改为

private String userId = "";

答案 1 :(得分：2)

你在深水中...：|顺便说一下，简而言之：

  

防止NPE

要在比较字符串时阻止NPE，请将其与已知字符串进行比较：

if (userId.equals("")) { // throws NPE
if ("".equals(userId)) { // it's ok

在你的代码中你应该检查null，所以两者都可以：

if (userId==null || userId.equals("")) {
  

正确的地方：验证

现在它们正常运行，删除所有这些检查并将它们in the validate() method, or in a validation.xml file放入，或使用注释进行验证。 Struts支持所有这些方法，returns the INPUT result when things go south。

永远不要在行动方法中使用这种检查，这是错误的地方。

  

正确处理身份验证的Struts2方法：拦截器

不要使用操作来执行此操作，而是创建一个身份验证拦截器，将其应用于除登录/注销之外的所有操作。

有full working example here。

答案 2 :(得分：0)

您的私有变量<svg class="main-logo" width="980" height="598" viewBox="0 0 1500 650" version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"> <title>Logo</title> <desc>Main Logo</desc> <g id="Canvas" transform="translate(-20990 -1876)"> <clipPath id="clip-0" clip-rule="evenodd"> <path d="M 20990 1876L 21970 1876L 21970 2474L 20990 2474L 20990 1876Z" fill="#FFFFFF"/> </clipPath> <g id="Frame" clip-path="url(#clip-0)"> <g id="Group 2.3"> <g id="Group"> <g id="Subtract"> <a class = "about-me-logo-link" href = "about-me.html"><use xlink:href="#yellow" transform="translate(21507.5 1874)" fill="#F2C94C"/></a> </g> <g id="Vector"> <a class = "resume-logo-link" href="resume.html"><use xlink:href="#green" transform="translate(21439.6 1934.83)" fill="#27AE60"/></a> </g> <g id="Vector"> <a class = "media-logo-link" href="media.html"><use xlink:href="#grey" transform="translate(21196.4 1934.82)" fill="#4F4F4F"/></a> </g> </g> <g id="Subtract"> <a class = "blog-logo-link" href="blog.html"><use xlink:href="#blue" transform="translate(20990 1874)" fill="#2F80ED"/></a> </g> </g> <g id="FEHRNSTROM"> <use xlink:href="#path4_fill" transform="matrix(0.459551 -0.888151 0.888151 0.459551 21601 2423.85)"/> </g> </g> </g> <defs> <path id="yellow" fill-rule="evenodd" d="M 221.328 0L 0 415.462L 93.4941 550.935L 381.551 0L 221.328 0Z"/><!--Yellow--> <path id="green" fill-rule="evenodd" d="M 161.675 490.11L 0 256.658L 0.0265208 0L 245.883 328.391L 161.675 490.11Z"/><!--Green--> <path id="grey" fill-rule="evenodd" d="M 243.115 0L 0 333.587L 81.3885 490.182L 335.524 123.363L 243.171 0.0759988L 243.115 0Z"/><!--Gray--> <path id="blue" fill-rule="evenodd" d="M 0 0L 288.092 551L 385.535 409.802L 162.213 0L 0 0Z"/> <!--Blue--> <path id="text" d="M 47.1377 60.3789L 21.1592 60.3789L 21.1592 87L 5.04883 87L 5.04883 20.1719L 49.7539 20.1719L 49.7539 32.6104L 21.1592 32.6104L 21.1592 47.9863L 47.1377 47.9863L 47.1377 60.3789ZM 97.9014 58.6807L 72.5654 58.6807L 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496.942 37.9346 496.483 50.0518L 496.438 54.9629C 496.438 61.5111 497.524 66.5446 499.696 70.0635C 501.869 73.5824 505.097 75.3418 509.381 75.3418C 513.451 75.3418 516.587 73.613 518.79 70.1553C 520.993 66.6976 522.11 61.7253 522.141 55.2383L 522.141 52.1631ZM 567.993 20.1719L 582.91 66.667L 597.781 20.1719L 618.986 20.1719L 618.986 87L 602.83 87L 602.83 71.3945L 604.391 39.4492L 588.234 87L 577.586 87L 561.384 39.4033L 562.944 71.3945L 562.944 87L 546.834 87L 546.834 20.1719L 567.993 20.1719Z"/> </defs> </svg>未初始化。这个评论是正确的。 但是，您应该编写一个set函数

userId

初始化您的变量而不是

public void setUserId(String userId){
    this.userId =userId;
}

我和你的问题一样，这是我的解决方案。

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