在Java中展平3个嵌套的JSON字符串

  • Z时代
  • 2024-01-10
  • 分类：问答

要求是为将输入JSON对象输入到扁平化JSON对象创建通用的扁平化实用程序。

样本JSON如下所示

{
  "Source": "source-1",
  "Rows": [
    {
      "Keys": {
        "device-id": "BC04-EBH-N3K-01",
        "interface-name": "TenGigE0/0/0/39",
        "node-name": "0/0/CPU0"
      },
      "Timestamp": 1567621527656,
      "inner": {
        "donm": {
          "id": "0062",
          "mol": {
            "rem": 30,
            "len": 11,
            "org": {
              "ldp": [
                {
                  "t": 486,
                  "o": 322
                },
                {
                  "t": 487,
                  "o": 32,
                  "twss": 1,
                  "tlv": "00:01"
                }
              ]
            },
            "chlen": 14,
            "poe": 5,
            "combs": 10,
            "chaype": 4,
            "rek": 0,
            "rem-um": 67
          },
          "detail": {
            "enas": "B,R",
            "systes": "B,R",
            "timng": 91,
            "syn": "C",
            "met-type": 0,
            "neses": {
              "lldEDIT": [
                {
                  "ium": 830,
                  "m": 1,
                  "ass": {
                    "ape": "ipv4",
                    "ipvs": "94"
                  }
                }
              ]
            },
            "pess": "0008",
            "por]d": 0,
            "pon": "BCtive",
            "sysme": "BC1"
          },
          "reme": "Bu1",
          "hean": 0,
          "porl": "Et1"
        }
      }
    }
  ],
  "Tey": {
    "epath": "Cgetail",
    "sustr": "MX",
    "coime": 1567621527653,
    "msp": 1567621527653,
    "come": 1567621527660,
    "nor": "BC5",
    "cid": 14789654
  }
}

我一直试图将其展平到3个级别，并提出了以下实用程序。但是，当我不得不处理数组和String，long，Timestamp等类型的值时，事情变得越来越复杂。而且，我无法理解如何维护嵌套键的唯一性。

public static Map<String,Object> flattenJson(JsonNode input){
        Map<String,Object> finalMap = new HashMap<>();
        ObjectMapper datamapper = new ObjectMapper();
        Map<String,Object> topLevelJsonMap = datamapper.convertValue(input,Map.class);
        Set<String> topLevelKeys = topLevelJsonMap.keySet();
        for(String topLevelKey : topLevelKeys){
            System.out.println("Key :::: "+topLevelKey);
            Object topLevelData = topLevelJsonMap.get(topLevelKey);
            System.out.println("value :::: "+topLevelData.toString());
            if(topLevelData instanceof ArrayNode){
                ArrayNode arrayOfData = (ArrayNode) topLevelData;
                for(JsonNode dataNode : arrayOfData){
                    flattenJson(input);
                }
            } else if(topLevelData instanceof JsonNode){
                Map<String,Object> innerLevelJsonMap = datamapper.convertValue(topLevelData,Map.class);
                Set<String> innerLevelKeys = innerLevelJsonMap.keySet();
                for(String innerLevelKey : innerLevelKeys){
                    System.out.println("inner key :::: "+innerLevelKey);
                    flattenJson((JsonNode) innerLevelJsonMap.get(innerLevelKey));
                }
            }else {
               finalMap.put(topLevelKey,topLevelData);
            }
        }
        return finalMap;
    }

任何帮助是极大的赞赏。

回答：

为了避免与键名冲突，可以使用JSON指针规范创建它们。Jackson库也支持它，因此您以后可以使用它们遍历该JsonNode节点。

简单的实现可能如下所示：

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.node.ArrayNode;
import com.fasterxml.jackson.databind.node.ObjectNode;
import java.io.File;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Objects;
import java.util.concurrent.atomic.AtomicInteger;
public class JsonApp {
  public static void main(String[] args) throws Exception {
    File jsonFile = new File("./test.json");
    ObjectMapper mapper = new ObjectMapper();
    JsonNode root = mapper.readTree(jsonFile);
    Map<String, JsonNode> map = new JsonFlattener(root).flatten();
    System.out.println("Use key-value pairs:");
    map.forEach(
        (k, v) -> {
          System.out.println(k + " => " + v);
        });
    System.out.println();
    System.out.println("Use pointers:");
    map.forEach(
        (k, v) -> {
          System.out.println(k + " => " + root.at(k));
        });
  }
}
class JsonFlattener {
  private final Map<String, JsonNode> json = new LinkedHashMap<>(64);
  private final JsonNode root;
  JsonFlattener(JsonNode node) {
    this.root = Objects.requireNonNull(node);
  }
  public Map<String, JsonNode> flatten() {
    process(root, "");
    return json;
  }
  private void process(JsonNode node, String prefix) {
    if (node.isObject()) {
      ObjectNode object = (ObjectNode) node;
      object
          .fields()
          .forEachRemaining(
              entry -> {
                  process(entry.getValue(), prefix + "/" + entry.getKey());
              });
    } else if (node.isArray()) {
      ArrayNode array = (ArrayNode) node;
      AtomicInteger counter = new AtomicInteger();
      array
          .elements()
          .forEachRemaining(
              item -> {
                process(item, prefix + "/" + counter.getAndIncrement());
              });
    } else {
      json.put(prefix, node);
    }
  }
}

上面的代码打印：

Use key-value pairs:
/Source => "source-1"
/Rows/0/Keys/device-id => "BC04-EBH-N3K-01"
/Rows/0/Keys/interface-name => "TenGigE0/0/0/39"
/Rows/0/Keys/node-name => "0/0/CPU0"
/Rows/0/Timestamp => 1567621527656
/Rows/0/inner/donm/id => "0062"
/Rows/0/inner/donm/mol/rem => 30
/Rows/0/inner/donm/mol/len => 11
/Rows/0/inner/donm/mol/org/ldp/0/t => 486
/Rows/0/inner/donm/mol/org/ldp/0/o => 322
/Rows/0/inner/donm/mol/org/ldp/1/t => 487
/Rows/0/inner/donm/mol/org/ldp/1/o => 32
/Rows/0/inner/donm/mol/org/ldp/1/twss => 1
/Rows/0/inner/donm/mol/org/ldp/1/tlv => "00:01"
/Rows/0/inner/donm/mol/chlen => 14
/Rows/0/inner/donm/mol/poe => 5
/Rows/0/inner/donm/mol/combs => 10
/Rows/0/inner/donm/mol/chaype => 4
/Rows/0/inner/donm/mol/rek => 0
/Rows/0/inner/donm/mol/rem-um => 67
/Rows/0/inner/donm/detail/enas => "B,R"
/Rows/0/inner/donm/detail/systes => "B,R"
/Rows/0/inner/donm/detail/timng => 91
/Rows/0/inner/donm/detail/syn => "C"
/Rows/0/inner/donm/detail/met-type => 0
/Rows/0/inner/donm/detail/neses/lldEDIT/0/ium => 830
/Rows/0/inner/donm/detail/neses/lldEDIT/0/m => 1
/Rows/0/inner/donm/detail/neses/lldEDIT/0/ass/ape => "ipv4"
/Rows/0/inner/donm/detail/neses/lldEDIT/0/ass/ipvs => "94"
/Rows/0/inner/donm/detail/pess => "0008"
/Rows/0/inner/donm/detail/por]d => 0
/Rows/0/inner/donm/detail/pon => "BCtive"
/Rows/0/inner/donm/detail/sysme => "BC1"
/Rows/0/inner/donm/reme => "Bu1"
/Rows/0/inner/donm/hean => 0
/Rows/0/inner/donm/porl => "Et1"
/Tey/epath => "Cgetail"
/Tey/sustr => "MX"
/Tey/coime => 1567621527653
/Tey/msp => 1567621527653
/Tey/come => 1567621527660
/Tey/nor => "BC5"
/Tey/cid => 14789654
Use pointers:
/Source => "source-1"
/Rows/0/Keys/device-id => "BC04-EBH-N3K-01"
/Rows/0/Keys/interface-name => "TenGigE0/0/0/39"
/Rows/0/Keys/node-name => "0/0/CPU0"
/Rows/0/Timestamp => 1567621527656
/Rows/0/inner/donm/id => "0062"
/Rows/0/inner/donm/mol/rem => 30
/Rows/0/inner/donm/mol/len => 11
/Rows/0/inner/donm/mol/org/ldp/0/t => 486
/Rows/0/inner/donm/mol/org/ldp/0/o => 322
/Rows/0/inner/donm/mol/org/ldp/1/t => 487
/Rows/0/inner/donm/mol/org/ldp/1/o => 32
/Rows/0/inner/donm/mol/org/ldp/1/twss => 1
/Rows/0/inner/donm/mol/org/ldp/1/tlv => "00:01"
/Rows/0/inner/donm/mol/chlen => 14
/Rows/0/inner/donm/mol/poe => 5
/Rows/0/inner/donm/mol/combs => 10
/Rows/0/inner/donm/mol/chaype => 4
/Rows/0/inner/donm/mol/rek => 0
/Rows/0/inner/donm/mol/rem-um => 67
/Rows/0/inner/donm/detail/enas => "B,R"
/Rows/0/inner/donm/detail/systes => "B,R"
/Rows/0/inner/donm/detail/timng => 91
/Rows/0/inner/donm/detail/syn => "C"
/Rows/0/inner/donm/detail/met-type => 0
/Rows/0/inner/donm/detail/neses/lldEDIT/0/ium => 830
/Rows/0/inner/donm/detail/neses/lldEDIT/0/m => 1
/Rows/0/inner/donm/detail/neses/lldEDIT/0/ass/ape => "ipv4"
/Rows/0/inner/donm/detail/neses/lldEDIT/0/ass/ipvs => "94"
/Rows/0/inner/donm/detail/pess => "0008"
/Rows/0/inner/donm/detail/por]d => 0
/Rows/0/inner/donm/detail/pon => "BCtive"
/Rows/0/inner/donm/detail/sysme => "BC1"
/Rows/0/inner/donm/reme => "Bu1"
/Rows/0/inner/donm/hean => 0
/Rows/0/inner/donm/porl => "Et1"
/Tey/epath => "Cgetail"
/Tey/sustr => "MX"
/Tey/coime => 1567621527653
/Tey/msp => 1567621527653
/Tey/come => 1567621527660
/Tey/nor => "BC5"
/Tey/cid => 14789654

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