On 2/1/2016 6:50 AM, Subhro Paul wrote:
Hi Team,
Our web application has a "header.jsp" which has 2 Arraylist on it. Each
ArrayList has more than 50 items inside. The code is to identify the
mobile device and requested page and transfer the call to mobile page
accordingly.
This code works fine once we restart the server and can continue running 2
months without any issue. But day by day it starts showing 500 error with
exception in log "ConcurrentModificationException". Below is the code
snippet of JSP code. My Question is why this issue is happening around 2
months? If we clear the temp file created by the server in work folder
then that will run for some time( 2- 3 days) and then again the same
exception starts occurring. I have identified one solution by moving the
JAVA code from JSP to JAVA file which worked good while perform testing
but client wants to know the root cause of the issue.
FYI, earlier we had Vector in place of Arraylist which gave trouble of
thread blocking due to synchronization. So, converting from Arraylist to
Vector will not be a good idea.
Exception:
java.util.ConcurrentModificationException
at
java.util.ArrayList$Itr.checkForComodification(ArrayList.java:859)
at java.util.ArrayList$Itr.next(ArrayList.java:831)
at
org.apache.jsp.includes.header_jsp.isHomePage(header_jsp.java:97)
Code Snippet:
<%!
private Set uas = new HashSet();
ArrayList<String> urlnames = new ArrayList<String>();
ArrayList<String> excludePathList = new ArrayList<String>();
Hi, Subhro-
Fields declared in a declarations section (<%! ... %>) are class
variables. If Tomcat uses a single JSP object to serve multiple
requests, which I believe it does, access to these fields should be made
thread safe. A simple solution would be to move the declarations of
these fields to a scriptlet section (<% ... %>) which would result in
them being local to the JSP service method. It isn't the most efficient
way to go about it but it should solve the concurrent access problem
you're seeing.
-Terence Bandoian
/http://www.tmbsw.com/
/
private boolean haveToRedirect(HttpServletRequest request,
String stopMobiCookie) {
boolean doRedirect = false;
String userAgent = request.getHeader("User-Agent");
if (! stopMobiCookie.equals("yes") && userAgent != null &&
userAgent.length()!=0 && (userAgent.indexOf("UsableNet")==-1))
{
Iterator iter = uas.iterator();
while (iter.hasNext()) {
if (userAgent.indexOf((String)iter.next())!=-1) {
doRedirect = true;
break;
}
}
}
return doRedirect;
}
private boolean isHomePage(HttpServletRequest request){
Iterator<String> itr = urlnames.iterator();
String path = "";
while (itr.hasNext()) {
path = itr.next();
if
(request.getRequestURI().toString().equalsIgnoreCase(path)){
return true;
}
}
return false;
}
private boolean isExcludePath(HttpServletRequest request){
Iterator<String> itr = excludePathList.iterator();
String path = "";
while (itr.hasNext()) {
path = itr.next();
if (request.getRequestURI().startsWith(path) &&
!request.getRequestURI().startsWith("/info/contact.jsp")){
return true;
}
}
return false;
}
%>
<%
uas.add("Blazer");
uas.add("Danger hiptop");
uas.add("DoCoMo/");
uas.add("Ericsson");
uas.add("Googlebot-Mobile");
uas.add("MSN Mobile Proxy");
uas.add("Handheld");
uas.add("HTC_HD2_T58585 Opera");
uas.add("iPhone");
uas.add("iPod");
uas.add("Klondike");
uas.add("LG-");
uas.add("LGE-");
....... Arround 40 items
excludePathList.add("/business/my_account");
excludePathList.add("/business/save_energy");
excludePathList.add("/business/services");
excludePathList.add("/business/small_large_business");
excludePathList.add("/info/environment");
excludePathList.add("/info/about");
excludePathList.add("/info/index.jsp");
excludePathList.add("/info/ambassador.jsp");
........ more than 50 items
stopMobiCookie = some cookie code
boolean doRedirect = haveToRedirect((HttpServletRequest)request,
stopMobiCookie);
if(doRedirect){
boolean isHomePage =
isHomePage((HttpServletRequest)request);
boolean isExcludePath =
isExcludePath((HttpServletRequest)request);
session.setAttribute("mobile_agent", "yes");
if(!isHomePage && !isExcludePath){
String mobileServer = "mobile.server.com";
try{
mobileServer = mobileServer +
request.getRequestURI().toString();
}catch(Exception e){}
%>
<script type="text/javascript">
window.location
="<%=mobileServer%>";
</script>
<%
}
}
%>
Thanks & Regards
Subhro Paul
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