关于#java#的问题：从数据库读取数据是发生错误信息

从数据库读取数据是发生错误信息，有点错误，一直服务器发生的错误信息，行处理 [/index.jsp] 时发生异常？

img


 
<%@ page import="java.util.List" %>
<%@ page import="com.NewsProject.model.TbNews" %>
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>



"UTF-8">
"pragma" CONTENT="no-cache">
欢迎访问喜迎二十大，庆建团百年网站
<%@include file="../userpublic/indexIncludeFile.jsp"%>


    include page="../userpublic/indexMenu.jsp">include>
    
class="contentDiv" >
        
class="Section_Content_Left" id="contentDiv">
            
class="Section_Left_Title">政声

            
class="Section_Left_NewsList">
                
            

            
class="Section_Left_Title">学习要闻

            
            
class="Section_Left_Title">大会内容

            
        

        
class="Section_Content_Right">
            include page="../userpublic/indexRightMenu.jsp">include>
        

    include page="../userpublic/indexFooter.jsp">include>


 
 
 
package com.NewsProject.controller;
 
import com.NewsProject.dao.DBUtils;
import com.NewsProject.model.TbNews;
 
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
import java.util.List;
 
@WebServlet(name = "Index_News", value = "/Index_News")
public class Index_News extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String sql="(select * from tb_news where ftypeid=1 order by id desc limit 5) union(select * from tb_news where ftypeid=2 order by id desc limit 5) union(select * from tb_news where ftypeid=3 order by id desc limit 5)";
        DBUtils dbUtils=new DBUtils();
        List list=(List) dbUtils.executeQueryBeans(sql,TbNews.class);
        request.setAttribute("listNews",list);
        request.getRequestDispatcher("home/Index.jsp").forward(request,response);
    }
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request,response);
    }
}
 
package com.NewsProject.model;
 
import java.sql.Timestamp;
import java.text.SimpleDateFormat;
 
public class TbNews {
    int id;
    String title;
    String content;
    String writer;
    String phoUrl;
    int ftypeid;
    Timestamp insertTime;
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getTitle() {
        return title;
    }
    public void setTitle(String title) {
        this.title = title;
    }
    public String getContent() {
        return content;
    }
    public void setContent(String content) {
        this.content = content;
    }
    public String getWriter() {
        return writer;
    }
    public void setWriter(String writer) {
        this.writer = writer;
    }
    public String getPhoUrl() {
        return phoUrl;
    }
    public void setPhoUrl(String phoUrl) {
        this.phoUrl = phoUrl;
    }
    public int getFtypeid() {
        return ftypeid;
    }
    public void setFtypeid(int ftypeid) {
        this.ftypeid = ftypeid;
    }
    public String getInsertTime(String fm) {
        if(this.insertTime!=null) {
            SimpleDateFormat df = new SimpleDateFormat(fm);
            return df.format(this.insertTime);
        }
        return "";
    }
    public void setInsertTime(Timestamp insertTime) {
        this.insertTime = insertTime;
    }
}

img


错误上说这个为null，那应该是这行代码有问题
List list=(List) dbUtils.executeQueryBeans(sql,TbNews.class);
你在这行代码下，加一个 System.out.println(list);
我看看输出

这里没获取到数据，空指针异常了，看下为什么没获取到数据，拿你的sql直接去数据库查询看能不能查询到数据，或者加个非空判断

if(listNews!=null&&listNews.size()>0){
  for (TbNews tbNews: listNews){.....
}

img