这是我在struts2中插入数据时遇到的一个问题,因此我以初学者的水平进行了尝试,但是它显示了一些错误,我无法识别该错误,有人可以对此提供帮助吗???
错误
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
打包动作;
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>
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>
您刚刚在这里进行了引荐,UserDao dao
但尚未初始化
像这样
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;
}
}
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