Question

resultset 到 arraylist 出错

新手做毕设 显示前台分页效果 然后卡在这里了 其他的页面代码没问题
JSP代码
HwBeanBo hbb=new HwBeanBo();
//默认显示第一页
ArrayList al=hbb.getGoodsByPage(4,1);
%>
<table width="100%" height="600" border="1" align="center" cellspacing="0" class="mycss3">
<tr>
<td height="50" colspan="3"><img src="images/tabPanel_bg.gif" width="100%" height="50"></td>
</tr>
<%
int t=0;
for(int i=0;i<2;i++){

//2大行
%>
<tr>
<%

//1大行取三个元素

for(int j=0;j<3;j++){

HwBean hb=(HwBean)al.get(t);
t++;
%>
BEAN代码
public ArrayList getGoodsByPage(int pageSize,int pageNow){

ArrayList al=new ArrayList();

try {
ct=new ConnDb().getConn();
ps=ct.prepareStatement("select * from hw where goodsid limit "+pageSize+","+pageSize*(pageNow-1)+"");
//select * from hw where goodsid limit +"pageSize"+,"+pageSize*(pageNow-1)+"
rs=ps.executeQuery();

if(rs.next()){
HwBean hb=new HwBean();
hb.setGoodsid(rs.getInt(1));
hb.setGoodsname(rs.getString(2));
hb.setGoodsxinxi(rs.getString(3));
hb.setGoodsprice(rs.getInt(4));
hb.setGoodsphoto(rs.getString(5));
//加入到AL中
al.add(hb);
以下报的错误
type Exception report

message

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

exception

org.apache.jasper.JasperException: An exception occurred processing JSP page /right.jsp at line 28

25:
26: for(int j=0;j<3;j++){
27:
28: HwBean hb=(HwBean)al.get(t);
29: t++;
30: %>
31:

Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:505)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:416)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)

root cause

java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
java.util.ArrayList.RangeCheck(ArrayList.java:547)
java.util.ArrayList.get(ArrayList.java:322)
org.apache.jsp.right_jsp._jspService(right_jsp.java:86)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:374)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)

求解~~愁死

Answer 1

数组下标越界，你的getGoodsByPage方法返回的集合最多只有一个元素
if(rs.next()){
HwBean hb=new HwBean();
hb.setGoodsid(rs.getInt(1));
hb.setGoodsname(rs.getString(2));
hb.setGoodsxinxi(rs.getString(3));
hb.setGoodsprice(rs.getInt(4));
hb.setGoodsphoto(rs.getString(5));
//加入到AL中
al.add(hb);

这里的if应改成while

而你的循环无论集合中有没有值都会遍历前三个元素
int t=0;
for(int j=0;j<3;j++){

HwBean hb=(HwBean)al.get(t);
t++;}

你的循环可以加一个判断条件
for(int j=0;j<3&&t<al.size();j++){