Preheat oven to 350 degrees.Peel, core and medium-dice the pears. Toss them in a large bowl with the granulated sugar, cornstarch, salt, both juices, vanilla, cinnamon, nutmeg and ginger. Mix well.In separate bowl, combine the flour, oats, brown sugar, cinnamon and salt. Add the melted butter and use you hands to mix and clump it with the dry ingredients. Pour the filling into a 9 x 13 inch glass pan that has been sprayed with cooking spray. Use a rubber spatula to spread it evenly.Crumble the topping evenly. over the filling with your hands.Bake for 45 minutes. Allow to cool slightly before serving.