作爲NullPointerException插入在struts2錯誤

在這裏，我帶來了一個問題，插入數據在struts2中，所以我已經嘗試與我的水平作爲初學者，但它顯示一些錯誤，我不能夠識別錯誤可能有人可以幫助這個？ ??作爲NullPointerException插入在struts2錯誤

錯誤

HTTP Status 500 - java.lang.NullPointerException 

type Exception report 

message java.lang.NullPointerException 

description The server encountered an internal error that prevented it from fulfilling this request. 

exception 

javax.servlet.ServletException: java.lang.NullPointerException 
    org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:515) 
    org.apache.struts2.dispatcher.FilterDispatcher.doFilter(FilterDispatcher.java:419) 
root cause 

java.lang.NullPointerException 
    Action.Testiue.add(Testiue.java:18) 
    sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
    sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) 
    sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) 
    java.lang.reflect.Method.invoke(Method.java:606) 
    com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:404) 
    com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:267) 
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:229) 
    com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:221) 
    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:86) 
    com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224) 
    com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223) 
    com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455) 
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221) 
    com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:150) 
    org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:48) 
    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:86) 
    com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224) 
    com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223) 
    com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455) 
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221)

Testiue.java

包動作;

import com.opensymphony.xwork2.ActionSupport; 
import dao.UserDao; 
import dbBean.UseBean; 

public class Testiue 
{ 
    private UserDao dao; 


    public String add() 
    { 

     UseBean bean = new UseBean(); 
     System.out.println(bean.getName()); 
     dao.addUser(bean); 
     return ActionSupport.SUCCESS; 

    } 

}

Userdao.java

package dao; 

import java.sql.Connection; 
import java.sql.PreparedStatement; 
import java.sql.ResultSet; 
import java.sql.SQLException; 
import java.sql.Statement; 
import java.util.ArrayList; 
import java.util.List; 

import dbBean.UseBean; 
import Dbconnect.*; 

public class UserDao 
{ 

    private Connection conn; 

    public UserDao() 
    { 
     conn=Dbconnect.getConnection(); 
    } 
    public void addUser(UseBean bean) 
    { 
     try 
     { 
      String sql="insert into senthil (name,pass,phoneno,emailid) values(?,?,?,?)"; 
      PreparedStatement ps=conn.prepareStatement(sql);  
      ps.setString(1,bean.getName()); 
      ps.setString(2,bean.getPassword()); 
      ps.setString(3,bean.getPhoneo()); 
      ps.setString(4,bean.getEmailID()); 
      ps.executeUpdate(); 

     } 
     catch (Exception e) 
     { 
      // TODO: handle exception 
     } 
    }

insert.jsp

<%@ taglib prefix="s" uri="/struts-tags" %> 
<html> 
<head> 
</head> 
<body> 
<a href="<s:url action="view.action"/>">Display Records</a> 
<br><br> 
<b><font color="#5d8122" face="verdana">Insert Details</font></b> 
    <s:form action="adduser"> 

      <s:textfield label="id" name="ID" cssClass="bord"/> 
      <s:textfield label="Name" name="Name" cssClass="bord"/> 
      <s:textfield label="Password" name="password" cssClass="bord"/> 
      <s:textfield label="phoneno" name="Phoneo"></s:textfield> 
      <s:textfield label="Emailid" name="Emailid"></s:textfield> 


    <s:submit value="Insert" /> 

</s:form> 
</body> 
</html>

的web.xml

<?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"> 
    <filter> 
    <filter-name>struts2</filter-name> 
    <filter-class>org.apache.struts2.dispatcher.FilterDispatcher</filter-class> 
    </filter> 
    <filter-mapping> 
    <filter-name>struts2</filter-name> 
    <url-pattern>/*</url-pattern> 
    </filter-mapping> 
    <welcome-file-list> 
    <welcome-file>insert.jsp</welcome-file> 
    </welcome-file-list> 
</web-app>

struct.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> 
    <include file="struts-default.xml" /> 
    <package name="a" extends="struts-default"> 

     <action name="adduser" class="Action.Testiue" method="add"> 
      <result name="success">insert.jsp</result> 
     </action> 

</package> 
</struts>

來源

2014-05-07 user3607180

http://stackoverflow.com/a/17488971/573032 –

剛纔所做這裏referrence UserDao dao但尚未初始化

做這樣

public class Testiue 
{ 
    private UserDao dao; 


    public String add() 
    { 
dao=new UserDao(); 
     UseBean bean = new UseBean(); 
     System.out.println(bean.getName()); 
     dao.addUser(bean); 
     return ActionSupport.SUCCESS; 

    } 

}

來源

2014-05-07 07:18:43 SpringLearner

其插入，但所有插入像空值不能插入用戶值？ – user3607180

抱歉不瞭解你 – SpringLearner

sry爲了遲到回覆它的工作 – user3607180

作爲NullPointerException插入在struts2錯誤

回答

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