Add some robustness against bogus parameters.

lib/MyApp/Controller/Book.pm

@@ -5,39 +5,70 @@ use MyModel::Author;
 
 sub books ($self) {
    my $page_number = $self->param('page_number') // 1;
+   if ($page_number < 1) {
+      $self->redirect_to('not_found');
+      return;
+   }
    my $book_model = MyModel::Book->new(rows_per_page => $self->rpp);
    my $book_page = $book_model->get_page(
       $page_number,
       $self->param('title_like'),
    );
+   my $pager = $book_page->pager;
+   if ($page_number > $pager->last_page) {
+      $self->redirect_to('not_found');
+      return;
+   }
    $self->render(
       book_page => $book_page,
-      pager => $book_page->pager,
+      pager => $pager,
    );
 }
 
 sub authors ($self) {
    my $page_number = $self->param('page_number') // 1;
+   if ($page_number < 1) {
+      $self->redirect_to('not_found');
+      return;
+   }
    my $author_model = MyModel::Author->new(rows_per_page => $self->rpp);;
    my $author_page = $author_model->get_page(
       $page_number,
       $self->param('name_like'),
    );
+   my $pager = $author_page->pager;
+   if ($page_number > $pager->last_page) {
+      $self->redirect_to('not_found');
+      return;
+   }
    $self->render(
       author_page => $author_page,
-      pager => $author_page->pager,
+      pager => $pager,
    );
 }
 
 sub author ($self) {
    my ($id, $page_number) = ($self->param('id'), $self->param('page_number'));
+   if ($page_number < 1) {
+      $self->redirect_to('not_found');
+      return;
+   }
    my ($author, $book_page) = MyModel::Author->new(
       rows_per_page => $self->rpp
    )->find_by_id($id, $page_number);
+   if (!defined $author) {
+      $self->redirect_to('not_found');
+      return;
+   }
+   my $pager = $book_page->pager;
+   if ($page_number > $pager->last_page) {
+      $self->redirect_to('not_found');
+      return;
+   }
    $self->render(
       author => $author,
       book_page => $book_page,
-      pager => $book_page->pager,
+      pager => $pager,
    );
 }
 

lib/MyModel/Author.pm

@@ -21,6 +21,7 @@ sub get_page ($self, $page_number = 1, $name_like = undef) {
 
 sub find_by_id ($self, $id, $page_number = 1) {
    my $author = $self->schema->resultset('Author')->find({ id => $id });
+   return (undef, undef) if (!defined $author);
    my $book_page = $author->books_rs->search(
       undef,
       {  order_by => [ "me.title" ],