HTTP Status 500错误怎么解决呀？

[fumin1987]

HTTP Status 500 -

--------------------------------------------------------------------------------

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 /BBS/showReplyInfo.jsp at line 75

72: <td>内容</td>
73: </tr>
74: <tr>
75: <td><img src="../images/<%=udb.getHeadByUId(list.get(0).getUId()) %>"></img><a href="showUserInfo.jsp?id=<%=list.get(0).getUId() %>"><%=udb.getUNameByUId(list.get(0).getUId()) %></a></td>
76: <td><%=list.get(0).getTitle() %></td>
77: <td><%=list.get(0).getContent() %></td>
78: </tr>


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(Unknown Source)
java.util.ArrayList.get(Unknown Source)
org.apache.jsp.BBS.showReplyInfo_jsp._jspService(showReplyInfo_jsp.java:185)
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)


note The full stack trace of the root cause is available in the Apache Tomcat/6.0.18 logs.


--------------------------------------------------------------------------------

Apache Tomcat/6.0.18

上面的问题怎么解决呀？

[一步一个脚印]

你的错误类似一个数组的length是0,而我们非要取>length的下标所对应的值.仔细分析下面这段代码

import java.util.List;
import java.util.ArrayList;

public class ListTest{
 public static void main(String[] args) {
   List listObj = new ArrayList(); 
   System.out.println("ListObj\'s size:" + listObj.size());
   System.out.println("ListObjItem{" + listObj.get(0).toString() + "}");
 }
}

[Ami121]

75行 List取值有问题
List size应该为空 根本就取不到值

[mydeman]

从异常信息中已经看出问题所在了：

org.apache.jasper.JasperException: An exception occurred processing JSP page /BBS/showReplyInfo.jsp at line 75
发生异常的位置，75行，

java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
引发异常的原因，数组越界。


对于list取值之前不要假设已经有值，一定要加上下面的判断：
<%
if(list != null && list.size() > 0){
%>
<!-- 这样再使用list就比较安全一些 -->
<%
}
%>

楼主写程序不但要考虑成功的情况，还要考虑异常情况

[billhepeng]

数组越界