jackson 对象动态嵌套过滤代码

以下是一个基于 Jackson 的对象动态嵌套过滤代码示例：

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.node.ObjectNode;

import java.util.*;

public class JacksonDynamicFilter {

    private static final ObjectMapper objectMapper = new ObjectMapper();

    public static void main(String[] args) throws JsonProcessingException {
        String json = "{\n" +
                "  \"id\": 1,\n" +
                "  \"name\": \"John\",\n" +
                "  \"age\": 30,\n" +
                "  \"address\": {\n" +
                "    \"street\": \"123 Main St\",\n" +
                "    \"city\": \"New York\",\n" +
                "    \"state\": \"NY\",\n" +
                "    \"zip\": \"10001\"\n" +
                "  },\n" +
                "  \"phone\": [\n" +
                "    {\n" +
                "      \"type\": \"home\",\n" +
                "      \"number\": \"212-555-1234\"\n" +
                "    },\n" +
                "    {\n" +
                "      \"type\": \"work\",\n" +
                "      \"number\": \"646-555-5678\"\n" +
                "    }\n" +
                "  ]\n" +
                "}";

        JsonNode rootNode = objectMapper.readTree(json);
        Set<String> fields = new HashSet<>(Arrays.asList("id", "name", "address.city", "phone.number"));
        JsonNode filteredNode = filterFields(rootNode, fields);
        String filteredJson = objectMapper.writeValueAsString(filteredNode);
        System.out.println(filteredJson);
    }

    private static JsonNode filterFields(JsonNode node, Set<String> fields) {
        if (node.isObject()) {
            ObjectNode filteredNode = objectMapper.createObjectNode();
            Iterator<Map.Entry<String, JsonNode>> iterator = node.fields();
            while (iterator.hasNext()) {
                Map.Entry<String, JsonNode> entry = iterator.next();
                String key = entry.getKey();
                JsonNode value = entry.getValue();
                if (fields.contains(key)) {
                    filteredNode.set(key, value);
                } else {
                    JsonNode filteredValue = filterFields(value, fields);
                    if (!filteredValue.isNull() && !filteredValue.isEmpty()) {
                        filteredNode.set(key, filteredValue);
                    }
                }
            }
            return filteredNode;
        } else if (node.isArray()) {
            // if node is an array, filter each element recursively
            List<JsonNode> filteredList = new ArrayList<>();
            for (JsonNode element : node) {
                JsonNode filteredElement = filterFields(element, fields);
                if (!filteredElement.isNull() && !filteredElement.isEmpty()) {
                    filteredList.add(filteredElement);
                }
            }
            return objectMapper.valueToTree(filteredList);
        } else {
            // if node is neither object nor array, return the original node
            return node;
        }
    }
}

在这个示例中，我们首先定义了一个 JSON 字符串，然后使用 Jackson 的 ObjectMapper 将其转换为 JsonNode 对象。然后，我们定义了一个包含我们要保留的字段的集合，并调用 filterFields 方法来过滤不需要的字段。filterFields 方法递归地处理嵌套的对象和数组，以确保所有字段都被正确地过滤。

最后，我们使用 ObjectMapper 将过滤后的 JsonNode 对象转换回 JSON 字符串并将其打印出来。