Java 在struts2中上载文件时出现NullPointerException异常

我正在开发struts2应用程序，我必须上传文件并将其保存到数据库中。 但是每次它显示NullPointerException我的代码都在这里

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;
}

}

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;

}
}

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>

---

实现ModelDriven接口，并将重写方法的对象返回给动作类中的模型类

实现ModelDriven接口，并将重写方法的对象返回给动作类中的模型类

异常在哪里？操作类在哪里？在任何情况下都不能这样做，

文件

只是一个文件系统指针。您需要实际读取该文件。异常的堆栈跟踪是什么？对我来说这似乎是一个真正的问题（至少现在是这样），投票赞成重新打开。顺便说一句，您的问题是，根据您的数据库和用于执行插入的库，您需要读取文件以获取字节并将其注入查询中（我在Spring中使用LobHandler，您需要找到另一种更经典的方式…在google上搜索）异常在哪里？操作类在哪里？在任何情况下都不能这样做，

文件

只是一个文件系统指针。您需要实际读取该文件。异常的堆栈跟踪是什么？对我来说这似乎是一个真正的问题（至少现在是这样），投票赞成重新打开。顺便说一句，您的问题是，根据您的数据库和用于执行插入的库，您需要读取文件以获取字节并将其注入查询中（我在Spring中使用LobHandler，您需要找到另一种更经典的方式…在google上搜索）

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;

}
}