java - struts2上传文件时出现NullPointerException异常

Question

我正在开发 struts2 应用程序，我必须在其中上传文件并将其保存到数据库中。但每次它都显示 NullPointerException 我的代码在这里

堆栈跟踪是-

java.lang.NullPointerException
    dao.Clientdao.registration(Clientdao.java:31)
    action.client.Clientaction.execute(Clientaction.java:18)
    sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    java.lang.reflect.Method.invoke(Unknown Source)
    com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:452)
    com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:291)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:254)
    com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:176)
    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:263)
    org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:68)
    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:207)
    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:314)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    com.opensymphony.xwork2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:176)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:187)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:52)
    org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:485)
    org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:77)
    org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:91)

模型类是

import java.io.File;
public class Clientmodel {
private String Aggrement;
private String  date;
private String rate;
private String maturitydate;
private String detail;
private String taxno;
private File imagefile;
public File getImagefile() {
    return imagefile;
}

public void setImagefile(File imagefile) {
    this.imagefile = imagefile;
}

public String getRate() {
    return rate;
}

public void setRate(String rate) {
    this.rate = rate;
}

public String getDetail() {
    return detail;
}

public void setDetail(String detail) {
    this.detail = detail;
}

public String getTaxno() {
    return taxno;
}

public void setTaxno(String taxno) {
    this.taxno = taxno;
}

public String getAggrement() {
    return Aggrement;
}

public void setAggrement(String aggrement) {
    Aggrement = aggrement;
}



public String getMaturitydate() {
    return maturitydate;
}

public void setMaturitydate(String maturitydate) {
    this.maturitydate = maturitydate;
}

public String getDate() {
    return date;
}

public void setDate(String date) {
    this.date = date;
}

}

struts.xml

  <?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC
    "-//Apache Software Foundation//DTD Struts Configuration 2.3//EN"
    "http://struts.apache.org/dtds/struts-2.3.dtd">
<struts>
       <constant name="struts.enable.DynamicMethodInvocation" value="true"/>
             <constant name="struts.devmode" value="true"/>
             <package name="loginmodel" extends ="struts-default">

        <action name="clientlogin"  class="action.client.Clientaction" >
           <interceptor-ref name="exception"/>
            <interceptor-ref name="i18n"/>
            <interceptor-ref name="fileUpload">
            <param name="allowedTypes">text/plain</param>
            <param name="maximumSize">10240</param>
        </interceptor-ref> 
            <interceptor-ref name="params">
                <param name="excludeParams">dojo\..*,^struts\..*</param>
            </interceptor-ref>
            <interceptor-ref name="validation">
                <param name="excludeMethods">input,back,cancel,browse</param>
            </interceptor-ref>
            <interceptor-ref name="workflow">
                <param name="excludeMethods">input,back,cancel,browse</param>
            </interceptor-ref>

            <result name="input">/Registration/clientregistration.jsp </result>
           <result name ="success">/Registration/success.jsp  </result>

          </action>

         </package>
</struts>

客户端注册.jsp

<%@ page language ="java" contentType ="text/html; charset=ISO-8859-1" pageEncoding ="ISO-8859-1"%>
<%@ taglib uri ="/struts-tags" prefix="s"%>
<%@ taglib uri ="/struts-dojo-tags" prefix="sx" %>
<%@ taglib prefix="sj" uri="/struts-jquery-tags"%>
<html>
<head>
<sj:head jqueryui="true" jquerytheme="redmond" />
<style>
   div.ui-datepicker {
      font-size: 82.5%;
       }
</style>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>CLIENT</title>
<link rel="stylesheet" type="text/css" href="css/emp.css">
</head>
<body >

<div id ="did" align="center"> <h1 style="color: red">  CLIENT REGISTRATION FORM</h1>
  <s:form action ="clientlogin" method="post" enctype="multipart/form-data">

<s:select  name="Aggrement" label ="Type of Aggrement" list ="{'ORAL', 'written'}  "/>
<sj:datepicker  name="date" label="Aggrement DATE" changeMonth="true" changeYear="true"/>

 <s:select name ="rate" list="{'1','2','3'}" label ="Aggrement rate"/>
<s:textarea  name ="detail" label ="Aggrement Detail"></s:textarea>
 <s:textfield name ="taxno" label="Tax No "></s:textfield>
 <s:file name ="imagefile" label ="Upload Document"  />
<tr><td>&nbsp;</td></tr>
        <tr>
    <td>&nbsp;</td>

 <s:submit align="center"></s:submit>
</s:form>
   </div>
  </body>
</html>

客户端是

package dao;

import java.sql.Blob;
import java.sql.SQLException;
import model.Clientmodel;
import com.mysql.jdbc.PreparedStatement;
import com.mysql.jdbc.ResultSet;

public class Clientdao {

java.sql.Connection connection =null;   
PreparedStatement pst = null;   
ResultSet rs =null;

private java.sql.Connection getConnection() throws SQLException{
    java.sql.Connection conn;
conn = Connectionfactory.getInstance().getConntection();    
return conn;

}

public int registration(Clientmodel model){

    int i= 0;
   try{
      String str  = "insert into " + "clientdata(Aggrement,aggrementDate,rate,maturitydate,detail,taxno,image)"+
                     "values(?,?,?,?,?,?)";

       connection =getConnection();   

   pst =(PreparedStatement) connection.prepareStatement(str);
     pst.setString(1, model.getAggrement());
     pst.setString(2, model.getDate());
     pst.setString(3, model.getRate());
     pst.setString(4, model.getMaturitydate());
     pst.setString(5, model.getDetail());
     pst.setString(6, model.getTaxno());
     pst.setBlob(7,(Blob) model.getImagefile());    

     i = pst.executeUpdate();
     System.out.println("Result " +i);
   }
  catch (SQLException se){
    se.printStackTrace();  
   }
   return i;

}
}

Answer 1

实现ModelDriven 接口(interface)并将覆盖方法的对象返回给您的Action 类中的模型类。