StandardWrapperValve[imgServlet]: Allocate exception for servlet imgServlet

[GWT]

Hi,
I have a problem with my servlet.
This servlet (ImageServlet) retrieves an image file from a fileupload
in a formPanel and sends it as a byte array (byte []) to the database.
Everything was working alright ! ... till I had this message in my gwt
console (hosted mode) :

[WARN] StandardWrapperValve[imgServlet]: Allocate exception for
servlet imgServlet
javax.servlet.ServletException: Error instantiating servlet class
bsc.wfp.ui.server.parametrage.site.ImageServlet
at
org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:
996)
at
org.apache.catalina.core.StandardWrapper.allocate(StandardWrapper.java:
687)
at
org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:
144)
at
org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:
104)
at
org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:
520)
at
org.apache.catalina.core.StandardContextValve.invokeInternal(StandardContextValve.java:
198)
at
org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:
152)
at
org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:
104)
at
org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:
520)
at
org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:
137)

Here is my web.xml :

<web-app>

<servlet>
<servlet-name>shell</servlet-name>
<servlet-class>
com.google.gwt.dev.shell.GWTShellServlet
</servlet-class>
</servlet>

<servlet>
<servlet-name>imgServlet</servlet-name>
<servlet-class>
bsc.wfp.ui.server.parametrage.site.ImageServlet
</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>shell</servlet-name>
<url-pattern>/*</url-pattern>
</servlet-mapping>

<servlet-mapping>
<servlet-name>imgServlet</servlet-name>
<url-pattern>/images/*</url-pattern>
</servlet-mapping>

</web-app>

Here is my gwt code :

final FormPanel form = new FormPanel();
form.setAction("../images/site/" + siteInfo.getIdSite() + "/plan");

form.setEncoding(FormPanel.ENCODING_MULTIPART);
form.setMethod(FormPanel.METHOD_POST);

AbsolutePanel panel = new AbsolutePanel();
form.setWidget(panel);
planFileUpload = new FileUpload();
planFileUpload.setName("formFileUpload");
planFileUpload.setStyleName("wfp-Button");
planFileUpload.setWidth("269px");

panel.add(planFileUpload);

there is also a button firing "form.submit()" when clicked !

I'm using maven. I added these dependencies in my pom.xml :
<dependency>
<groupId>commons-fileupload</groupId>
<artifactId>commons-fileupload</artifactId>
<version>1.2</version>
</dependency>
<dependency>
<groupId>commons-io</groupId>
<artifactId>commons-io</artifactId>
<version>1.3.1</version>
</dependency>

I don't see what's goingf wrong with my code !
Everything was working perfectly !
Can anyone help me with this !

Thanks

Marouene

[GWT]

Here's also the servlet declaration in my entrypoint xml file
<servlet path="/images"
class="bsc.wfp.ui.server.parametrage.site.ImageServlet"/>