The Java – JSTL FMT library throws a 500 error. Do you need to enable the session?

• Java

I am developing a simple servlet / JSP, data - driven website on Google App Engine I have started using the JSTL FMT library on some of my data entry forms and get the following session related errors < FMT: dateformat > and < FMT: numberformat > when using tags:

[java] java. lang.RuntimeException：appengine-web. Session support is not enabled in XML To enable the session, enter true in the file Without it, getsession () is allowed, but the operation of sessionattributes is not

The code in my JSP is, for example:

<c:forEach var="item" items="${dayList}" >
 <option><fmt:formatNumber value="${item}" pattern="00"/></option>
</c:forEach>

or

<jsp:useBean id="Now" scope="page" class="java.util.Date" />
Now: ${Now}<br/>
Year: <fmt:formatDate value="${Now}" pattern="yyyy" />

When I comment out these lines, the page will render, and when I reopen, there will be an error result

I didn't enable sessions because I don't need them for this web application, and it's best not to read them if you don't need them I have confirmed that no attribute is session scoped, and the only "session" in my NetBeans project is on the web In XML:

<session-config>
    <session-timeout>
        30
    </session-timeout>
</session-config>

Once I'm in App Engine web Enable session on XML, everything is normal

My research points out some things that can be found on the web Locale related context parameters set in XML, namely:

<context-param>
    <param-name>javax.servlet.jsp.jstl.fmt.fallbackLocale</param-name>
    <param-value>en-US</param-value>
</context-param>
<context-param>
    <param-name>javax.servlet.jsp.jstl.fmt.locale</param-name>
    <param-value>en-US</param-value>
</context-param>
<context-param>
<param-name>javax.servlet.jsp.jstl.fmt.timeZone</param-name>
    <param-value>EDT</param-value>
</context-param>

I have used these parameter sets to redeploy (and close the session) and get the same error

The JSTL FMT library seems to be very used to using dates, numbers, etc. on web forms. Although I may need to enable the session and move on at the end of the day - I missed something. Here is the locale setting that causes the default reference of the session? May this be unique to App Engine?

thank you

Note: This is the stack trace obtained when the session is disabled:

[java] Aug 17,2010 2:41:26 AM com.google.apphosting.utils.jetty.JettyLogger warn
 [java] WARNING: /manage/events/new
 [java] java.lang.RuntimeException: Session support is not enabled in appengine-web.xml.  To enable sessions,put <sessions-enabled>true</sessions-enabled> in that file.  Without it,getSession() is allowed,but manipulation of sessionattributes is not.
 [java]         at com.google.apphosting.utils.jetty.StubSessionManager$StubSession.throwException(StubSessionManager.java:67)
 [java]         at com.google.apphosting.utils.jetty.StubSessionManager$StubSession.setAttribute(StubSessionManager.java:63)
 [java]         at org.apache.jasper.runtime.PageContextImpl.doSetAttribute(PageContextImpl.java:340)
 [java]         at org.apache.jasper.runtime.PageContextImpl.access$300(PageContextImpl.java:64)
 [java]         at org.apache.jasper.runtime.PageContextImpl$4.run(PageContextImpl.java:314)
 [java]         at java.security.AccessController.doPrivileged(Native Method)
 [java]         at org.apache.jasper.runtime.PageContextImpl.setAttribute(PageContextImpl.java:312)
 [java]         at org.apache.taglibs.standard.tag.common.fmt.SetLocaleSupport.setResponseLocale(SetLocaleSupport.java:209)
 [java]         at org.apache.taglibs.standard.tag.common.fmt.SetLocaleSupport.doEndTag(SetLocaleSupport.java:108)
 [java]         at org.apache.jsp.WEB_002dINF.update_005fevent_jsp._jspx_meth_fmt_setLocale_0(update_005fevent_jsp.java:362)
 [java]         at org.apache.jsp.WEB_002dINF.update_005fevent_jsp._jspService(update_005fevent_jsp.java:117)
 [java]         at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:94)
 [java]         at javax.servlet.http.HttpServlet.service(HttpServlet.java:806)
 [java]         at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:324)
 [java]         at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:292)
 [java]         at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:236)
 [java]         at com.google.appengine.tools.development.PrivilegedJspServlet.access$101(PrivilegedJspServlet.java:23)
 [java]         at com.google.appengine.tools.development.PrivilegedJspServlet$2.run(PrivilegedJspServlet.java:59)
 [java]         at java.security.AccessController.doPrivileged(Native Method)
 [java]         at com.google.appengine.tools.development.PrivilegedJspServlet.service(PrivilegedJspServlet.java:57)
 [java]         at javax.servlet.http.HttpServlet.service(HttpServlet.java:806)
 [java]         at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
 [java]         at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
 [java]         at com.cj.trim.trimFilter.doFilter(UnkNown Source)
 [java]         at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
 [java]         at com.queerartfilm.web.JSTLConfigFilter.doFilter(JSTLConfigFilter.java:114)
 [java]         at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
 [java]         at com.google.appengine.api.blobstore.dev.ServeBlobFilter.doFilter(ServeBlobFilter.java:51)
 [java]         at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
 [java]         at com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java:43)
 [java]         at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
 [java]         at com.google.appengine.tools.development.StaticFileFilter.doFilter(StaticFileFilter.java:122)
 [java]         at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
 [java]         at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
 [java]         at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
 [java]         at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
 [java]         at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
 [java]         at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
 [java]         at com.google.apphosting.utils.jetty.DevAppEngineWebAppContext.handle(DevAppEngineWebAppContext.java:70)
 [java]         at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
 [java]         at com.google.appengine.tools.development.JettyContainerService$ApiProxyHandler.handle(JettyContainerService.java:349)
 [java]         at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
 [java]         at org.mortbay.jetty.Server.handle(Server.java:326)
 [java]         at org.mortbay.jetty.httpconnection.handleRequest(httpconnection.java:542)
 [java]         at org.mortbay.jetty.httpconnection$RequestHandler.headerComplete(httpconnection.java:923)
 [java]         at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:547)
 [java]         at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:212)
 [java]         at org.mortbay.jetty.httpconnection.handle(httpconnection.java:404)
 [java]         at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:409)
 [java]         at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)

Solution

That's very unfortunate Looks like you can't get around this Then your best way is to create custom El functions The following is an example of how to replace FMT: formatdate

First, create an EL function class (just a simple static class):

package com.example;

import java.text.SimpleDateFormat;
import java.util.Date;

public final class Functions {

    private Functions() {
        //
    }

    public static String formatDate(Date date,String pattern) {
        return new SimpleDateFormat(pattern).format(date);
    }

}

Then create a / WEB-INF / functions TLD (Note: JSP 2.1 is targeted. I'm not sure what your gae supports. It may be servlet 2.4. If so, you need to declare it as JSP 2.0 taglib):

<?xml version="1.0" encoding="UTF-8" ?>

<taglib 
    xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-jsptaglibrary_2_1.xsd"
    version="2.1">

    <display-name>Custom Functions</display-name>    
    <tlib-version>1.0</tlib-version>
    <uri>http://example.com/functions</uri>

    <function>
        <name>formatDate</name>
        <function-class>com.example.Functions</function-class>
        <function-signature>java.lang.String formatDate(java.util.Date,java.lang.String)</function-signature>
    </function>
</taglib>

You can then use the following in jsp:

<%@taglib uri="http://example.com/functions" prefix="f" %>
<jsp:useBean id="date" class="java.util.Date" />
...
<p>Current year: ${f:formatDate(date,'yyyy')}</p>
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