登錄期間Struts2空指針異常

Question

我是struts2框架的新手，當我單擊“提交”按鈕時，我得到了nullpointer的期望，寄存器表單值未傳遞給Bean類，我在Bean類中打印了表單值，但打印了null值，我找不到我的錯誤，請幫助我。

index.jsp

<%@ taglib uri="/struts-tags" prefix="s"%>
<s:form action="insert">
    <s:textfield name="uname" label="UserName " />
    <s:textfield name="age" label="age " />
    <s:textfield name="sex" label="sex" />
    <s:submit name="submit" label="submit" />
</s:form>

Struts.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE struts PUBLIC
"-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
"http://struts.apache.org/dtds/struts-2.0.dtd">

<struts>
    <package name="a" extends="struts-default">
        <action name="insert" class="com.infrasoft.login.action.UserRegistrationDAO">
            <result name="success">/success.jsp</result>
            <result name="error">/error.jsp</result>

        </action>
    </package>
</struts>

動作課

package com.infrasoft.login.action;
import com.opensymphony.xwork2.ActionSupport;
public class UserRegistrationDAO extends ActionSupport {
private String uname;
private String sex;
private int age;

public String getUname() {
    return uname;
}

public void setUname(String uname) {
    this.uname = uname;
}

public String getSex() {
    return sex;
}

public void setSex(String sex) {
    this.sex = sex;
}

public int getAge() {
    return age;
}

public void setAge(int age) {
    this.age = age;
}

private static final long serialVersionUID = 1L;

public UserRegistrationDAO() {
    System.out.println("dao");
}

@Override
public String execute() {
    System.out.println("username" + uname); // getting null value
    System.out.println("uname" + getUname());// getting null value

    if (uname != null) {
        return SUCCESS;
    } else {
        return ERROR;
    }
  }

  }

例外

 May 22, 2014 10:03:54 PM org.apache.catalina.core.AprLifecycleListener init
INFO: The APR based Apache Tomcat Native library which allows optimal performance in production environments was not found on the java.library.path: C:\Program Files (x86)\Java\jre7\bin;C:\Windows\Sun\Java\bin;C:\Windows\system32;C:\Windows;C:/Program Files (x86)/Java/jre7/bin/client;C:/Program Files (x86)/Java/jre7/bin;C:/Program Files (x86)/Java/jre7/lib/i386;C:\Windows\SYSTEM32;C:\Windows;C:\Windows\SYSTEM32\WBEM;C:\Windows\SYSTEM32\WINDOWSPOWERSHELL\V1.0\;;C:\Program Files (x86)\Java\jdk1.7.0\bin;E:\Language SW\KRISHSOFT\eclipse;;.
May 22, 2014 10:03:54 PM org.apache.tomcat.util.digester.SetPropertiesRule begin
WARNING: [SetPropertiesRule]{Server/Service/Engine/Host/Context} Setting property 'source' to 'org.eclipse.jst.jee.server:xmlvalidationdemo' did not find a matching property.
May 22, 2014 10:03:54 PM org.apache.tomcat.util.digester.SetPropertiesRule begin
WARNING: [SetPropertiesRule]{Server/Service/Engine/Host/Context} Setting property 'source' to 'org.eclipse.jst.jee.server:Com.LTS.Register' did not find a matching property.
May 22, 2014 10:03:54 PM org.apache.tomcat.util.digester.SetPropertiesRule begin
WARNING: [SetPropertiesRule]{Server/Service/Engine/Host/Context} Setting property 'source' to 'org.eclipse.jst.jee.server:Com.Demo.Javatpoint' did not find a matching property.
May 22, 2014 10:03:54 PM org.apache.tomcat.util.digester.SetPropertiesRule begin
WARNING: [SetPropertiesRule]{Server/Service/Engine/Host/Context} Setting property 'source' to 'org.eclipse.jst.jee.server:com.infrasoft.struts' did not find a matching property.
May 22, 2014 10:03:55 PM org.apache.coyote.AbstractProtocol init
INFO: Initializing ProtocolHandler ["http-bio-8080"]
May 22, 2014 10:03:55 PM org.apache.coyote.AbstractProtocol init
INFO: Initializing ProtocolHandler ["ajp-bio-8009"]
May 22, 2014 10:03:55 PM org.apache.catalina.startup.Catalina load
INFO: Initialization processed in 1279 ms
May 22, 2014 10:03:55 PM org.apache.catalina.core.StandardService startInternal
INFO: Starting service Catalina
May 22, 2014 10:03:55 PM org.apache.catalina.core.StandardEngine startInternal
INFO: Starting Servlet Engine: Apache Tomcat/7.0.29
May 22, 2014 10:03:56 PM org.apache.catalina.util.SessionIdGenerator createSecureRandom
INFO: Creation of SecureRandom instance for session ID generation using [SHA1PRNG] took [240] milliseconds.
May 22, 2014 10:03:56 PM com.opensymphony.xwork2.config.providers.XmlConfigurationProvider register
INFO: Parsing configuration file [struts-default.xml]
May 22, 2014 10:03:57 PM com.opensymphony.xwork2.config.providers.XmlConfigurationProvider register
INFO: Parsing configuration file [struts-plugin.xml]
May 22, 2014 10:03:57 PM com.opensymphony.xwork2.config.providers.XmlConfigurationProvider register
INFO: Parsing configuration file [struts.xml]
May 22, 2014 10:03:57 PM org.apache.struts2.config.Settings getLocale
WARNING: Settings: Could not parse struts.locale setting, substituting default VM locale
May 22, 2014 10:03:57 PM com.opensymphony.xwork2.util.ObjectTypeDeterminerFactory <clinit>
INFO: Setting DefaultObjectTypeDeterminer as default ...
May 22, 2014 10:03:57 PM org.apache.catalina.loader.WebappClassLoader validateJarFile
INFO: validateJarFile(F:\workspace\StrutsProject\.metadata\.plugins\org.eclipse.wst.server.core\tmp0\wtpwebapps\Com.LTS.Register\WEB-INF\lib\servlet-api.jar) - jar not loaded. See Servlet Spec 2.3, section 9.7.2. Offending class: javax/servlet/Servlet.class
May 22, 2014 10:03:58 PM com.opensymphony.xwork2.config.providers.XmlConfigurationProvider register
INFO: Parsing configuration file [struts-default.xml]
May 22, 2014 10:03:58 PM com.opensymphony.xwork2.config.providers.XmlConfigurationProvider register
INFO: Parsing configuration file [struts-plugin.xml]
May 22, 2014 10:03:58 PM com.opensymphony.xwork2.util.DomHelper$StartHandler error
SEVERE: Document is invalid: no grammar found. at (null:2:8)
org.xml.sax.SAXParseException; systemId: file:/F:/workspace/StrutsProject/.metadata/.plugins/org.eclipse.wst.server.core/tmp0/wtpwebapps/Com.LTS.Register/WEB-INF/classes/struts.xml; lineNumber: 2; columnNumber: 8; Document is invalid: no grammar found.
    at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.createSAXParseException(Unknown Source)
    at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.error(Unknown Source)
    at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(Unknown Source)
    at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(Unknown Source)
    at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(Unknown Source)
    at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.scanStartElement(Unknown Source)
    at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl$NSContentDriver.scanRootElementHook(Unknown Source)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(Unknown Source)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$PrologDriver.next(Unknown Source)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(Unknown Source)
    at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.next(Unknown Source)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(Unknown Source)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(Unknown Source)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(Unknown Source)
    at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(Unknown Source)
    at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(Unknown Source)
    at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(Unknown Source)
    at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl.parse(Unknown Source)
    at com.opensymphony.xwork2.util.DomHelper.parse(DomHelper.java:121)
    at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.loadConfigurationFiles(XmlConfigurationProvider.java:830)
    at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.loadDocuments(XmlConfigurationProvider.java:131)
    at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.init(XmlConfigurationProvider.java:100)
    at com.opensymphony.xwork2.config.impl.DefaultConfiguration.reload(DefaultConfiguration.java:130)
    at com.opensymphony.xwork2.config.ConfigurationManager.getConfiguration(ConfigurationManager.java:52)
    at org.apache.struts2.dispatcher.Dispatcher.init_PreloadConfiguration(Dispatcher.java:395)
    at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:452)
    at org.apache.struts2.dispatcher.FilterDispatcher.init(FilterDispatcher.java:201)
    at org.apache.catalina.core.ApplicationFilterConfig.initFilter(ApplicationFilterConfig.java:277)
    at org.apache.catalina.core.ApplicationFilterConfig.getFilter(ApplicationFilterConfig.java:258)
    at org.apache.catalina.core.ApplicationFilterConfig.setFilterDef(ApplicationFilterConfig.java:382)
    at org.apache.catalina.core.ApplicationFilterConfig.<init>(ApplicationFilterConfig.java:103)
    at org.apache.catalina.core.StandardContext.filterStart(StandardContext.java:4650)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5306)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1559)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1549)
    at java.util.concurrent.FutureTask.run(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)

May 22, 2014 10:03:58 PM org.apache.catalina.core.StandardContext filterStart
SEVERE: Exception starting filter struts2
file:/F:/workspace/StrutsProject/.metadata/.plugins/org.eclipse.wst.server.core/tmp0/wtpwebapps/Com.LTS.Register/WEB-INF/classes/struts.xml:2:8
    at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.loadConfigurationFiles(XmlConfigurationProvider.java:835)
    at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.loadDocuments(XmlConfigurationProvider.java:131)
    at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.init(XmlConfigurationProvider.java:100)
    at com.opensymphony.xwork2.config.impl.DefaultConfiguration.reload(DefaultConfiguration.java:130)
    at com.opensymphony.xwork2.config.ConfigurationManager.getConfiguration(ConfigurationManager.java:52)
    at org.apache.struts2.dispatcher.Dispatcher.init_PreloadConfiguration(Dispatcher.java:395)
    at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:452)
    at org.apache.struts2.dispatcher.FilterDispatcher.init(FilterDispatcher.java:201)
    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$StartChild.call(ContainerBase.java:1559)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1549)
    at java.util.concurrent.FutureTask.run(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)
Caused by: Document is invalid: no grammar found. - file:/F:/workspace/StrutsProject/.metadata/.plugins/org.eclipse.wst.server.core/tmp0/wtpwebapps/Com.LTS.Register/WEB-INF/classes/struts.xml:2:8
    at com.opensymphony.xwork2.util.DomHelper.parse(DomHelper.java:123)
    at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.loadConfigurationFiles(XmlConfigurationProvider.java:830)
    ... 20 more
Caused by: org.xml.sax.SAXParseException; systemId: file:/F:/workspace/StrutsProject/.metadata/.plugins/org.eclipse.wst.server.core/tmp0/wtpwebapps/Com.LTS.Register/WEB-INF/classes/struts.xml; lineNumber: 2; columnNumber: 8; Document is invalid: no grammar found.
    at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.createSAXParseException(Unknown Source)
    at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.error(Unknown Source)
    at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(Unknown Source)
    at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(Unknown Source)
    at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(Unknown Source)
    at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.scanStartElement(Unknown Source)
    at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl$NSContentDriver.scanRootElementHook(Unknown Source)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(Unknown Source)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$PrologDriver.next(Unknown Source)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(Unknown Source)
    at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.next(Unknown Source)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(Unknown Source)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(Unknown Source)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(Unknown Source)
    at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(Unknown Source)
    at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(Unknown Source)
    at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(Unknown Source)
    at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl.parse(Unknown Source)
    at com.opensymphony.xwork2.util.DomHelper.parse(DomHelper.java:121)
    ... 21 more

May 22, 2014 10:03:58 PM org.apache.catalina.core.StandardContext startInternal
SEVERE: Error filterStart
May 22, 2014 10:03:58 PM org.apache.catalina.core.StandardContext startInternal
SEVERE: Context [/Com.LTS.Register] startup failed due to previous errors
May 22, 2014 10:03:58 PM com.opensymphony.xwork2.config.providers.XmlConfigurationProvider register
INFO: Parsing configuration file [struts-default.xml]
May 22, 2014 10:03:58 PM com.opensymphony.xwork2.config.providers.XmlConfigurationProvider register
INFO: Parsing configuration file [struts-plugin.xml]
May 22, 2014 10:03:58 PM com.opensymphony.xwork2.config.providers.XmlConfigurationProvider register
INFO: Parsing configuration file [struts.xml]
May 22, 2014 10:03:58 PM org.apache.struts2.config.Settings getLocale
WARNING: Settings: Could not parse struts.locale setting, substituting default VM locale
May 22, 2014 10:03:59 PM com.opensymphony.xwork2.util.ObjectTypeDeterminerFactory <clinit>
INFO: Setting DefaultObjectTypeDeterminer as default ...
May 22, 2014 10:03:59 PM com.opensymphony.xwork2.config.providers.XmlConfigurationProvider register
INFO: Parsing configuration file [struts-default.xml]
May 22, 2014 10:03:59 PM com.opensymphony.xwork2.config.providers.XmlConfigurationProvider register
INFO: Parsing configuration file [struts-plugin.xml]
May 22, 2014 10:03:59 PM com.opensymphony.xwork2.config.providers.XmlConfigurationProvider register
INFO: Parsing configuration file [struts.xml]
May 22, 2014 10:03:59 PM org.apache.struts2.config.Settings getLocale
WARNING: Settings: Could not parse struts.locale setting, substituting default VM locale
May 22, 2014 10:03:59 PM org.apache.struts2.config.BeanSelectionProvider register
INFO: Loading global messages from java4s
May 22, 2014 10:04:00 PM com.opensymphony.xwork2.util.ObjectTypeDeterminerFactory <clinit>
INFO: Setting DefaultObjectTypeDeterminer as default ...
May 22, 2014 10:04:00 PM org.apache.coyote.AbstractProtocol start
INFO: Starting ProtocolHandler ["http-bio-8080"]
May 22, 2014 10:04:00 PM org.apache.coyote.AbstractProtocol start
INFO: Starting ProtocolHandler ["ajp-bio-8009"]
May 22, 2014 10:04:00 PM org.apache.catalina.startup.Catalina start
INFO: Server startup in 4822 ms
May 22, 2014 10:04:08 PM org.apache.tomcat.util.http.Parameters processParameters
INFO: Invalid chunk starting at byte [0] and ending at byte [6] with a value of [=krish] ignored
 Note: further occurrences of Parameter errors will be logged at DEBUG level.
dao
May 22, 2014 10:04:08 PM com.opensymphony.xwork2.validator.ActionValidatorManagerFactory <clinit>
INFO: Detected AnnotationActionValidatorManager, initializing it...
usernamenull
unamenull

Answer 1

您在類路徑上某處的XML API庫與Struts框架版本不兼容。 如果不對XML API使用自定義實現，請嘗試檢查JDK（可能是ext文件夾）或WEB-INF/lib 。 JDK7使用內部實現，可以選擇安裝新的JDK7。

Answer 2

試試這個...很好用..

@Override
public String execute() {
    HttpServletRequest request=(HttpServletRequest) ActionContext.getContext().get(ServletActionContext.HTTP_REQUEST);
      logger.info("username" + request.getParameter("uname")); 
      logger.info("uname" + getUname());// getting null value

      if (uname != null) {
        return SUCCESS;
      } else {
        return ERROR;
      }
}

初始化記錄器文件之前

private static Logger logger = Logger.getLogger(UserRegistrationDAO.class);//Getter and Setter Method.