How to use

FileExistsValidator

in

org.geoserver.web.wicket

  protected FileParamPanel buildFileParamPanel(final IModel paramsModel) {
    FileParamPanel file =
        new FileParamPanel(
            "url",
            new MapModel(paramsModel, URLP.key),
            new ParamResourceModel("shapefile", this),
            true);
    file.setFileFilter(new Model(new ExtensionFileFilter(".shp")));
    file.getFormComponent().add(new FileExistsValidator());
    return file;
  }
}

      is = connection.getInputStream();
    } catch(Exception e) {
      error(validatable, "FileExistsValidator.unreachable", 
          Collections.singletonMap("file", uriSpec));
    } finally {
error(validatable, "FileExistsValidator.fileNotFoundError", 
    Collections.singletonMap("file", uriSpec));

protected FileParamPanel buildFileParamPanel(final IModel paramsModel) {
  FileParamPanel file = new FileParamPanel("url", new MapModel(paramsModel, URLP.key),
      new ParamResourceModel("shapefile", this), true);
  file.setFileFilter(new Model(new ExtensionFileFilter(".shp")));
  file.getFormComponent().add(new FileExistsValidator());
  return file;
}

public DefaultCoverageStoreEditPanel(final String componentId, final Form storeEditForm) {
  super(componentId, storeEditForm);
  final IModel formModel = storeEditForm.getModel();
  // url
  TextParamPanel url = new TextParamPanel("urlPanel", new PropertyModel(formModel, "URL"),
      new ResourceModel("url", "URL"), true);
  url.getFormComponent().add(new FileExistsValidator());
  add(url);
}

  public DefaultCoverageStoreEditPanel(final String componentId, final Form storeEditForm) {
    super(componentId, storeEditForm);

    final IModel formModel = storeEditForm.getModel();
    // url
    TextParamPanel url =
        new TextParamPanel(
            "urlPanel",
            new PropertyModel(formModel, "URL"),
            new ResourceModel("url", "URL"),
            true);
    url.getFormComponent().add(new FileExistsValidator());
    add(url);
  }
}

fc.add(new FileExistsValidator());

public AbstractRasterFileEditPanel(final String componentId, final Form storeEditForm,
    boolean useDirectoryChooser, String... fileExtensions) {
  super(componentId, storeEditForm);
  final IModel model = storeEditForm.getModel();
  setDefaultModel(model);
  final IModel paramsModel = new PropertyModel(model, "connectionParameters");
  FileParamPanel file;
  if (useDirectoryChooser) {
    file = new DirectoryParamPanel("url", new PropertyModel(model, "URL"), 
        new ResourceModel("url", "URL"), true);
  } else {
    file = new FileParamPanel("url", new PropertyModel(model, "URL"), 
        new ResourceModel("url", "URL"), true);
  }
  
  file.getFormComponent().add(new FileExistsValidator());
  if (fileExtensions != null && fileExtensions.length > 0) {
    file.setFileFilter(new Model(new ExtensionFileFilter(fileExtensions)));
  }
  add(file);
}

fc.add(new FileExistsValidator());

file.getFormComponent().add(new FileExistsValidator());
if (fileExtensions != null && fileExtensions.length > 0) {
  file.setFileFilter(new Model(new ExtensionFileFilter(fileExtensions)));

        true);
final FormComponent urlFormComponent = url.getFormComponent();
urlFormComponent.add(new FileExistsValidator());
add(url);

        "watermark.uRL",
        new FileModel(new PropertyModel<String>(form.getModel(), "watermark.URL")));
watermarkUrlField.add(new FileExistsValidator(true));
watermarkUrlField.setOutputMarkupId(true);
form.add(watermarkUrlField);

form.add(new TextField("watermark.uRL").add(new FileExistsValidator(true)));
TextField<Integer> transparency = new TextField<Integer>("watermark.transparency");
transparency.add(new RangeValidator<Integer>(0,100));