Navigation to call action for bean class - jsf

Question

I am using JSF 2.0 and PrimeFaces 3.0. I have uploaded the images and have to crop the image. The images are uploaded and successfully displayed in the upload pages.
When I select the images and click the crop button the corresponding crop bean is not called. If I don't select the image and click the crop button the corresponding crop bean class is called but a NullPointerException occurred. What is the problem?
The Facelet view is:
<h:form>
<p:panel header="FILE UPLOAD WITH CROPPER" style="width:900px; margin: 0 auto; margin-top:0px">
<p:fileUpload fileUploadListener="#{photoUploadAction.handleImageUpload}"
mode="advanced"
update="getImageId,messages" auto="false"
allowTypes="/(\.|\/)(gif|jpe?g|png)$/"/>
<p:growl id="messages" showDetail="true"/>
<p:growl id="uploadMessages" showSummary="true" showDetail="true"/>
<h:panelGrid columns="2" >
<p:imageCropper value="#{photoUploadAction.croppedImage}" id="getImageId"
image="images/#{photoUploadVO.imageName}"/>
</h:panelGrid>
<p:commandButton value="Crop" update="getImageId" action="#{imageCropperBean.crop}" />
</p:panel>
</h:form>
BACKING BEAN for ImageCropper:
#ManagedBean(name="imageCrop")
#RequestScoped
public class ImageCropperBean {
private CroppedImage croppedImage;
private String newFileName;
private String imageName;
public String getImageName() {
return imageName;
}
public void setImageName(String imageName) {
System.out.println("TEH IMAGE NAME ===="+imageName);
this.imageName = imageName;
}
public String getNewFileName() {
return newFileName;
}
public void setNewFileName(String newFileName) {
System.out.println("AAAAAAAAAAAAAA"+this.newFileName);
this.newFileName = newFileName;
}
public CroppedImage getCroppedImage() {
return croppedImage;
}
public void setCroppedImage(CroppedImage croppedImage) {
System.out.println("cRRRRRRRRRRRRR"+croppedImage);
this.croppedImage = croppedImage;
}
public ImageCropperBean(){
}
public String crop() {
System.out.println("WELCOMEMMMMMMMMMMMMMM");
FacesContext context = FacesContext.getCurrentInstance();
ImageCropperBean imageCropperBean = (ImageCropperBean) context.getApplication().evaluateExpressionGet(context, "#{imageCropperBean}", ImageCropperBean.class);
ServletContext servletContext = (ServletContext) FacesContext.getCurrentInstance().getExternalContext().getContext();
newFileName = servletContext.getRealPath("") + File.separator + "cropImage" + File.separator+ "croppedImage.jpg";
System.out.println("FILE NAME NAME NAME NAME "+newFileName);
String file = new File(newFileName).getName();
System.out.println("DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD"+file);
imageCropperBean.setImageName(file);
File fileFolder = new File("e:/Mecherie_project/image_web/WebContent/cropImages",file);
System.out.println("FILE ANE"+file);
// String target=null;
FileImageOutputStream imageOutput;
try {
imageOutput = new FileImageOutputStream(fileFolder);
System.out.println("HHHHHHHHHH=="+imageOutput);
imageOutput.write(croppedImage.getBytes(), 0, croppedImage.getBytes().length);
imageOutput.close();
FacesMessage msg = new FacesMessage("Succesful", file
+ " is cropped.");
FacesContext.getCurrentInstance().addMessage(null, msg);
} catch (FileNotFoundException e) {
FacesMessage error = new FacesMessage(FacesMessage.SEVERITY_ERROR,
"The files were not Cropped!", "");
FacesContext.getCurrentInstance().addMessage(null, error);
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
FacesMessage error = new FacesMessage(FacesMessage.SEVERITY_ERROR,
"The files were not Cropped!", "");
FacesContext.getCurrentInstance().addMessage(null, error);
}
// System.out.println("ghfhgfghgh"+target);
return "success";
}
}