unable to deploy the application on google app engine : appengine-web.xml does not contain a <threadsafe> element

Question

When i click to deploy the application on google app engine in netbeans ,these are the error messages produced. Let me tell you that initially, probably i entered the wrong password and the application failed to deploy. But now when i click to deploy the application it doesn't ask me the email or the password.

Anyway how can i resolve these errors ?

Reading application configuration data...
Bad configuration: appengine-web.xml does not contain a <threadsafe> element.
See http://code.google.com/appengine/docs/java/config/appconfig.html#Using_Concurrent_Requests for more information.
You probably want to enable concurrent requests.
Please see the logs [C:\Users\user\AppData\Local\Temp\appcfg6534187344911851576.log] for further information.
May 28, 2012 12:35:54 PM com.google.apphosting.utils.config.AppEngineWebXmlReader readAppEngineWebXml
INFO: Successfully processed W:/UnderTest/NetbeansCurrent/Guestbook/build/web\WEB-INF/appengine-web.xml
May 28, 2012 12:35:54 PM com.google.apphosting.utils.config.AppEngineWebXmlReader readAppEngineWebXml
SEVERE: Received exception processing W:/UnderTest/NetbeansCurrent/Guestbook/build/web\WEB-INF/appengine-web.xml
com.google.apphosting.utils.config.AppEngineConfigException: appengine-web.xml does not contain a <threadsafe> element.
See http://code.google.com/appengine/docs/java/config/appconfig.html#Using_Concurrent_Requests for more information.
You probably want to enable concurrent requests.
at com.google.apphosting.utils.config.AppEngineWebXmlReader.readAppEngineWebXml(AppEngineWebXmlReader.java:79)
at com.google.appengine.tools.admin.Application.<init>(Application.java:139)
at com.google.appengine.tools.admin.Application.readApplication(Application.java:225)
at com.google.appengine.tools.admin.AppCfg.<init>(AppCfg.java:145)
at com.google.appengine.tools.admin.AppCfg.<init>(AppCfg.java:69)
at com.google.appengine.tools.admin.AppCfg.main(AppCfg.java:65)

EDIT : I tried the same thing in linux and this time I entered the right password.Then also i am getting the exceptions which are :

May 28, 2012 1:26:51 PM com.google.apphosting.utils.config.AppEngineWebXmlReader readAppEngineWebXml
INFO: Successfully processed /home/non-admin/NetBeansProjects/Guestbook/build/web/WEB-INF/appengine-web.xml
May 28, 2012 1:26:51 PM com.google.apphosting.utils.config.AppEngineWebXmlReader readAppEngineWebXml
SEVERE: Received exception processing /home/non-admin/NetBeansProjects/Guestbook/build/web/WEB-INF/appengine-web.xml
com.google.apphosting.utils.config.AppEngineConfigException: appengine-web.xml does not contain a <threadsafe> element.
See http://code.google.com/appengine/docs/java/config/appconfig.html#Using_Concurrent_Requests for more information.
You probably want to enable concurrent requests.
at  com.google.apphosting.utils.config.AppEngineWebXmlReader.readAppEngineWebXml(AppEngineWebXmlReader.java:79)
at com.google.appengine.tools.admin.Application.<init>(Application.java:139)
at com.google.appengine.tools.admin.Application.readApplication(Application.java:225)
at com.google.appengine.tools.admin.AppCfg.<init>(AppCfg.java:145)
at com.google.appengine.tools.admin.AppCfg.<init>(AppCfg.java:69)
at com.google.appengine.tools.admin.AppCfg.main(AppCfg.java:65)
Bad configuration: appengine-web.xml does not contain a <threadsafe> element.
See http://code.google.com/appengine/docs/java/config/appconfig.html#Using_Concurrent_Requests for more information.
You probably want to enable concurrent requests.
Please see the logs [/tmp/appcfg6804971430427378027.log] for further information.
Reading application configuration data...
 May 28, 2012 1:41:52 PM com.google.apphosting.utils.config.AppEngineWebXmlReader readAppEngineWebXml
INFO: Successfully processed /home/non-admin/NetBeansProjects/Guestbook/build/web/WEB-INF/appengine-web.xml
May 28, 2012 1:41:52 PM com.google.apphosting.utils.config.AppEngineWebXmlReader readAppEngineWebXml
SEVERE: Received exception processing /home/non-admin/NetBeansProjects/Guestbook/build/web/WEB-INF/appengine-web.xml
com.google.apphosting.utils.config.AppEngineConfigException: appengine-web.xml does not contain a <threadsafe> element.
See http://code.google.com/appengine/docs/java/config/appconfig.html#Using_Concurrent_Requests for more information.
You probably want to enable concurrent requests.
at com.google.apphosting.utils.config.AppEngineWebXmlReader.readAppEngineWebXml(AppEngineWebXmlReader.java:79)
at com.google.appengine.tools.admin.Application.<init>(Application.java:139)
at com.google.appengine.tools.admin.Application.readApplication(Application.java:225)
at com.google.appengine.tools.admin.AppCfg.<init>(AppCfg.java:145)
at com.google.appengine.tools.admin.AppCfg.<init>(AppCfg.java:69)
at com.google.appengine.tools.admin.AppCfg.main(AppCfg.java:65)
 Bad configuration: appengine-web.xml does not contain a <threadsafe> element.
 See http://code.google.com/appengine/docs/java/config/appconfig.html#Using_Concurrent_Requests for more information.
 You probably want to enable concurrent requests.
 Please see the logs [/tmp/appcfg8910063489276425896.log] for further information.

Answer 1

To build on what @alex said....

You have in your first error log

Bad configuration: appengine-web.xml does not contain a <threadsafe> element. See http://code.google.com/appengine/docs/java/config/appconfig.html#Using_Concurrent_Requests for more information.

The first line

Bad configuration: appengine-web.xml does not contain a <threadsafe> element.

tells you what is wrong. The second line

See http://code.google.com/appengine/docs/java/config/appconfig.html#Using_Concurrent_Requests for more information.

indicates what part of the GAE documentation to study to fix your problem.

I must admit, the error log entries are very clear and helpful. I wish more could follow the example made for you here. If you are still stuck, please would you specify exactly what you are stuck on?

Answer 2

Simply add

<threadsafe>true</threadsafe>

to your war/WEB-INF/appengine-web.xml

Like this:

    <?xml version="1.0" encoding="UTF-8"?>
<appengine-web-app xmlns="http://appengine.google.com/ns/1.0">
<application></application>
<version>1</version>
<threadsafe>true</threadsafe>