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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"lens, traverse and validate question","articleBody":"I have deep hierarchal object that I need to validate. My question is how to accumulate and validate all validations in the data structure in one traversal?\r\n\r\nIn the below example, suppose I want to vaildate OrderDocument and OrderItem in one traversal, how to compose, traverse and add multiple validation in lens composition?\r\n\r\n```\r\n        final Lens\u003cOrder, List\u003cOrderDocument\u003e\u003e orderDocumentsLens =\r\n                Lens.lens(Order::getOrderDocuments, ds -\u003e cr -\u003e cr.withOrderDocuments(ds));\r\n        final Lens\u003cOrderDocument, List\u003cOrderItem\u003e\u003e orderItemsLens =\r\n                Lens.lens(OrderDocument::getOrderItems, is -\u003e crd -\u003e crd.withOrderItems(is));\r\n\r\n        final Lens\u003cOrderItem, List\u003cOrderItemProperties\u003e\u003e orderItemPropertiesLens =\r\n                Lens.lens(OrderItem::getOrderItemProperties, sls -\u003e i -\u003e i.withOrderItemProperties(sls));\r\n\r\n        final List\u003cString\u003e fail = orderDocumentsLens.composeTraversal(List.Optic.traversal())\r\n                .composeLens(orderItemsLens).composeTraversal(List.Optic.traversal())\r\n                .composeLens(orderItemPropertiesLens).composeTraversal(List.Optic.traversal())\r\n                .modifyValidationF(Semigroup.stringSemigroup, this::validateItemProperties)\r\n                .f(order)\r\n                .accumulate().fail();\r\n\r\n\r\n    private Validation\u003cString, OrderItemProperties\u003e validateItemProperties(OrderItemProperties properties) {\r\n        return Validation.success(properties);\r\n    }\r\n\r\n```","author":{"url":"https://github.com/prabhu-madanagopal","@type":"Person","name":"prabhu-madanagopal"},"datePublished":"2022-02-02T01:49:02.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":0},"url":"https://github.com/435/functionaljava/issues/435"}