将 JSON 数组数组转换为对象映射 (Java)

【问题标题】：Convert JSON array of arrays to map of objects (Java)将 JSON 数组数组转换为对象映射 (Java)
【发布时间】：2020-09-12 13:44:38
【问题描述】：

我有使用 Java、Apache POI 和 Jackson 从 Excel 文件提取到 JSON 结构的数据。生成的 JSON 数据结构如下所示：

{
  "fileName" : "C:\\Users\\jgagnon\\sample_data\\PDM_BOM.xlsx",
  "sheets" : [ {
    "name" : "PDM_BOM",
    "data" : [ [ "BRANCH", "PARENT ITEM NUMBER", "2ND ITEM NUMBER", "QUANTITY REQUIRED", "UNIT OF MEASURE", "ISSUE TYPE CODE", "LINE TYPE", "STOCK TYPE", "TYPE BOM", "LINE NUMBER", "OPERATING SEQUENCE", "EFFECTIVE FROM DATE", "EFFECTIVE THRU DATE", "DRAWING NUMBER", "UNIT COST", "SCRAP PERCENT" ],
        [ "B20", "208E8840040", "5P884LPFSR2", 0.32031, "LB", "I", "S", "M", "M", 1.0, 10.0, "09/11/13", "12/31/40", null, 0.0, 0.0 ],
        [ "B20", "208E8840168", "5P884LPFSR2", 1.36, "LB", "I", "S", "M", "M", 1.0, 10.0, "02/26/08", "12/31/40", null, 0.0, 0.0 ],
        [ "B20", "208E8840172", "5P884LPFSR2", 1.3924, "LB", "I", "S", "M", "M", 1.0, 10.0, "02/26/08", "12/31/40", null, 0.0, 0.0 ],
        [ "B20", "208E8840180", "5P884LPFSR2", 1.4565, "LB", "I", "S", "P", "M", 1.0, 10.0, "03/04/09", "12/31/40", null, 0.0, 0.0 ],
        [ "B20", "21PPH150166", "8P315TPMRG", 1.39629, "LB", "I", "S", "M", "M", 1.0, 10.0, "03/05/18", "12/31/40", null, 0.0, 0.0 ] ],
    "maxCols" : 16,
    "maxRows" : 14996
  } ]
}

在data 元素中，本质上是一个数组数组，表示工作表中的所有行。第一行数组是后面数据行的列标题。

我希望能够重组data，使其采用对象映射的形式，其中每个键（对于本示例）是@987654325 中的值@ 柱子。与键关联的映射值将是一个 JSON 对象，由当前数据行的列标题和列值的键/值对组成。

所以，使用上面的例子，我最终会得到这样的结果： （我的 JSON 语法/结构可能不正确）

{
  "data": {
    "208E8840040": {
      "BRANCH": "B20",
      "PARENT ITEM NUMBER": "208E8840040",
      "2ND ITEM NUMBER": "5P884LPFSR2",
      "QUANTITY REQUIRED": 0.32031,
      "UNIT OF MEASURE": "LB",
      "ISSUE TYPE CODE": "I",
      "LINE TYPE": "S",
      "STOCK TYPE": "M",
      "TYPE BOM": "M", 
      "LINE NUMBER": 1.0, 
      "OPERATING SEQUENCE": 10.0, 
      "EFFECTIVE FROM DATE": "09/11/13", 
      "EFFECTIVE THRU DATE": "12/31/40", 
      "DRAWING NUMBER": null, 
      "UNIT COST": 0.0, 
      "SCRAP PERCENT": 0.0
    },
    "208E8840168": {
      "BRANCH": "B20",
      "PARENT ITEM NUMBER": "208E8840168",
      "2ND ITEM NUMBER": "5P884LPFSR2",
      "QUANTITY REQUIRED": 1.36,
      ...
    },
    ...
  }
}

我正在寻找一种将前者转换为后者的方法。

更新：

我刚刚意识到我遗漏了一个重要的细节。

此表（表）中的数据基本上由PARENT ITEM NUMBER 列键入。但是，尽管该列是主标识符，但它在表中并不总是唯一的。

在很多情况下，PARENT ITEM NUMBER 具有相同值的多行。这些行中的每一行都包含有关构成“父项”的元素的信息（将它们视为子项）。这些子项由2ND ITEM NUMBER 列标识。

此外，许多子项在表中都有自己的行，其中PARENT ITEM NUMBER 是由2ND ITEM NUMBER 为父项标识的子项编号。正如您可能已经猜到的那样，这些子项可以有自己的子项，依此类推。

基本上，这是相关数据的多个层次结构的表格表示。一些子项将出现（被重复使用）多个父项。

我不知道这会使我想做的事情变得复杂。

更新：

感谢https://stackoverflow.com/users/51591/micha%c5%82-ziober 的最初想法。我稍微调整了它以生成子项目列表的地图。修改后的代码如下：

  public String convertToJson(File jsonFile) throws IOException {
    ArrayNode arrayNode = readDataArray(jsonFile);

    List<Map<String, JsonNode>> rowMaps = convertArrayToMaps(arrayNode);

    Map<Object, List<Map<String, JsonNode>>> dataMap = rowMaps.stream()
        .collect(Collectors.groupingBy(map -> map.get("PARENT ITEM NUMBER").textValue()));
    return jsonMapper.writeValueAsString(Collections.singletonMap("data", dataMap));
  }

这是一个输出示例：

{
  "data" : {
    "MTDMN97PJ1A9" : [ {    <- 1 child
      "BRANCH" : "B70",
      "PARENT ITEM NUMBER" : "MTDMN97PJ1A9",
      "2ND ITEM NUMBER" : "MTDMN970144XO",
      "QUANTITY REQUIRED" : 12.0,
      "UNIT OF MEASURE" : "SY",
      "ISSUE TYPE CODE" : "I",
      "LINE TYPE" : "S",
      "STOCK TYPE" : "M",
      "TYPE BOM" : "M",
      "LINE NUMBER" : 1.0,
      "OPERATING SEQUENCE" : 10.0,
      "EFFECTIVE FROM DATE" : "01/18/19",
      "EFFECTIVE THRU DATE" : "12/31/40",
      "DRAWING NUMBER" : null,
      "UNIT COST" : 0.0,
      "SCRAP PERCENT" : 0.0
    } ],
    "ZCP723A1152" : [ {     <- 4 children
      "BRANCH" : "B70",
      "PARENT ITEM NUMBER" : "ZCP723A1152",
      "2ND ITEM NUMBER" : "5P587UMFSD2",
      "QUANTITY REQUIRED" : 2.32222,
      "UNIT OF MEASURE" : "LB",
      "ISSUE TYPE CODE" : "I",
      "LINE TYPE" : "S",
      "STOCK TYPE" : "M",
      "TYPE BOM" : "M",
      "LINE NUMBER" : 3.0,
      "OPERATING SEQUENCE" : 10.0,
      "EFFECTIVE FROM DATE" : "05/15/17",
      "EFFECTIVE THRU DATE" : "12/31/40",
      "DRAWING NUMBER" : null,
      "UNIT COST" : 0.0,
      "SCRAP PERCENT" : 0.0
    }, {
      "BRANCH" : "B70",
      "PARENT ITEM NUMBER" : "ZCP723A1152",
      "2ND ITEM NUMBER" : "8P550ZPPOOLE",
      "QUANTITY REQUIRED" : 2.32222,
      "UNIT OF MEASURE" : "LB",
      "ISSUE TYPE CODE" : "I",
      "LINE TYPE" : "S",
      "STOCK TYPE" : "M",
      "TYPE BOM" : "M",
      "LINE NUMBER" : 1.0,
      "OPERATING SEQUENCE" : 10.0,
      "EFFECTIVE FROM DATE" : "05/15/17",
      "EFFECTIVE THRU DATE" : "12/31/40",
      "DRAWING NUMBER" : null,
      "UNIT COST" : 0.0,
      "SCRAP PERCENT" : 0.0
    }, {
      "BRANCH" : "B70",
      "PARENT ITEM NUMBER" : "ZCP723A1152",
      "2ND ITEM NUMBER" : "8P906WPPA3077",
      "QUANTITY REQUIRED" : 4.64444,
      "UNIT OF MEASURE" : "LB",
      "ISSUE TYPE CODE" : "I",
      "LINE TYPE" : "S",
      "STOCK TYPE" : "M",
      "TYPE BOM" : "M",
      "LINE NUMBER" : 2.0,
      "OPERATING SEQUENCE" : 10.0,
      "EFFECTIVE FROM DATE" : "05/15/17",
      "EFFECTIVE THRU DATE" : "12/31/40",
      "DRAWING NUMBER" : null,
      "UNIT COST" : 0.0,
      "SCRAP PERCENT" : 0.0
    }, {
      "BRANCH" : "B70",
      "PARENT ITEM NUMBER" : "ZCP723A1152",
      "2ND ITEM NUMBER" : "8U910LKSHBL",
      "QUANTITY REQUIRED" : 2.32222,
      "UNIT OF MEASURE" : "LB",
      "ISSUE TYPE CODE" : "I",
      "LINE TYPE" : "S",
      "STOCK TYPE" : "M",
      "TYPE BOM" : "M",
      "LINE NUMBER" : 4.01,
      "OPERATING SEQUENCE" : 10.0,
      "EFFECTIVE FROM DATE" : "12/13/17",
      "EFFECTIVE THRU DATE" : "12/31/40",
      "DRAWING NUMBER" : null,
      "UNIT COST" : 0.0,
      "SCRAP PERCENT" : 0.0
    } ],
    ... many more entries
}

【问题讨论】：

    标签： java arrays json jackson


    【解决方案1】：

    您可以将整个 JSON 有效负载读取为 JsonNode 并检索作为数组的 data 属性。如果我们可以假设始终第一个元素是名称数组并且所有其他元素的大小相同，则可以手动创建Map 并将其序列化回JSON。一个棘手的部分是如何为结果JSON 生成唯一键值。示例代码如下所示：

    import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;
import com.fasterxml.jackson.databind.node.ArrayNode;

import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.function.Function;
import java.util.stream.Collectors;

public class Excel2JonsApp {
    public static void main(String[] args) throws IOException {
        File jsonFile = new File("./resource/test.json").getAbsoluteFile();

        Excel2JsonMapper mapper = new Excel2JsonMapper();
        String json = mapper.convertToJson(jsonFile);
        System.out.println(json);
    }
}

class Excel2JsonMapper {
    private final ObjectMapper jsonMapper;

    Excel2JsonMapper() {
        this.jsonMapper = createJsonMapper();
    }

    private ObjectMapper createJsonMapper() {
        ObjectMapper mapper = new ObjectMapper();
        mapper.enable(SerializationFeature.INDENT_OUTPUT);

        return mapper;
    }

    String convertToJson(File jsonFile) throws IOException {
        ArrayNode arrayNode = readDataArray(jsonFile);
        Map<Object, Map<String, JsonNode>> dataMap = convertArrayToMaps(arrayNode)
                .stream()
                .collect(Collectors.toMap(
                        map -> map.get("PARENT ITEM NUMBER").textValue(), //key generator function
                        Function.identity()));

        return jsonMapper.writeValueAsString(Collections.singletonMap("data", dataMap));
    }

    private List<Map<String, JsonNode>> convertArrayToMaps(ArrayNode arrayNode) {
        ArrayNode names = (ArrayNode) arrayNode.get(0);

        Iterator<JsonNode> iterator = arrayNode.iterator();
        iterator.next();// skip names

        List<Map<String, JsonNode>> list = new ArrayList<>();
        while (iterator.hasNext()) {
            ArrayNode values = (ArrayNode) iterator.next();
            Map<String, JsonNode> map = new LinkedHashMap<>();
            for (int i = 0; i < names.size(); i++) {
                map.put(names.get(i).textValue(), values.get(i));
            }
            list.add(map);
        }
        return list;
    }

    private ArrayNode readDataArray(File jsonFile) throws IOException {
        JsonNode root = jsonMapper.readTree(jsonFile);
        return (ArrayNode) root.at("/sheets/0/data");
    }
}

    上面的代码打印：

    {
  "data" : {
    "208E8840168" : {
      "BRANCH" : "B20",
      "PARENT ITEM NUMBER" : "208E8840168",
      "2ND ITEM NUMBER" : "5P884LPFSR2",
      "QUANTITY REQUIRED" : 1.36,
      "UNIT OF MEASURE" : "LB",
      "ISSUE TYPE CODE" : "I",
      "LINE TYPE" : "S",
      "STOCK TYPE" : "M",
      "TYPE BOM" : "M",
      "LINE NUMBER" : 1.0,
      "OPERATING SEQUENCE" : 10.0,
      "EFFECTIVE FROM DATE" : "02/26/08",
      "EFFECTIVE THRU DATE" : "12/31/40",
      "DRAWING NUMBER" : null,
      "UNIT COST" : 0.0,
      "SCRAP PERCENT" : 0.0
    },
    "21PPH150166" : {
      "BRANCH" : "B20",
      "PARENT ITEM NUMBER" : "21PPH150166",
      "2ND ITEM NUMBER" : "8P315TPMRG",
      "QUANTITY REQUIRED" : 1.39629,
      "UNIT OF MEASURE" : "LB",
      "ISSUE TYPE CODE" : "I",
      "LINE TYPE" : "S",
      "STOCK TYPE" : "M",
      "TYPE BOM" : "M",
      "LINE NUMBER" : 1.0,
      "OPERATING SEQUENCE" : 10.0,
      "EFFECTIVE FROM DATE" : "03/05/18",
      "EFFECTIVE THRU DATE" : "12/31/40",
      "DRAWING NUMBER" : null,
      "UNIT COST" : 0.0,
      "SCRAP PERCENT" : 0.0
    },
    "208E8840180" : {
      "BRANCH" : "B20",
      "PARENT ITEM NUMBER" : "208E8840180",
      "2ND ITEM NUMBER" : "5P884LPFSR2",
      "QUANTITY REQUIRED" : 1.4565,
      "UNIT OF MEASURE" : "LB",
      "ISSUE TYPE CODE" : "I",
      "LINE TYPE" : "S",
      "STOCK TYPE" : "P",
      "TYPE BOM" : "M",
      "LINE NUMBER" : 1.0,
      "OPERATING SEQUENCE" : 10.0,
      "EFFECTIVE FROM DATE" : "03/04/09",
      "EFFECTIVE THRU DATE" : "12/31/40",
      "DRAWING NUMBER" : null,
      "UNIT COST" : 0.0,
      "SCRAP PERCENT" : 0.0
    },
    "208E8840172" : {
      "BRANCH" : "B20",
      "PARENT ITEM NUMBER" : "208E8840172",
      "2ND ITEM NUMBER" : "5P884LPFSR2",
      "QUANTITY REQUIRED" : 1.3924,
      "UNIT OF MEASURE" : "LB",
      "ISSUE TYPE CODE" : "I",
      "LINE TYPE" : "S",
      "STOCK TYPE" : "M",
      "TYPE BOM" : "M",
      "LINE NUMBER" : 1.0,
      "OPERATING SEQUENCE" : 10.0,
      "EFFECTIVE FROM DATE" : "02/26/08",
      "EFFECTIVE THRU DATE" : "12/31/40",
      "DRAWING NUMBER" : null,
      "UNIT COST" : 0.0,
      "SCRAP PERCENT" : 0.0
    },
    "208E8840040" : {
      "BRANCH" : "B20",
      "PARENT ITEM NUMBER" : "208E8840040",
      "2ND ITEM NUMBER" : "5P884LPFSR2",
      "QUANTITY REQUIRED" : 0.32031,
      "UNIT OF MEASURE" : "LB",
      "ISSUE TYPE CODE" : "I",
      "LINE TYPE" : "S",
      "STOCK TYPE" : "M",
      "TYPE BOM" : "M",
      "LINE NUMBER" : 1.0,
      "OPERATING SEQUENCE" : 10.0,
      "EFFECTIVE FROM DATE" : "09/11/13",
      "EFFECTIVE THRU DATE" : "12/31/40",
      "DRAWING NUMBER" : null,
      "UNIT COST" : 0.0,
      "SCRAP PERCENT" : 0.0
    }
  }
}

    【讨论】：

    • 这很有帮助。你向我展示了一些我不知道的巧妙技巧。不过有一个问题。因为PARENT ITEM NUMBER 并不总是唯一的（请参阅我在帖子中的解释），我遇到了一个问题，它试图将重复的键插入dataMap。我认为dataMap 值需要是“行”条目的列表，代表子项（由2ND ITEM NUMBER 标识）。
    • @JosephGagnon，我不明白您所说的子项和父项是什么意思。如果出现重复键，您需要使用列表并保存所有重复的对象。之后，您可以遍历列表并使用其他方法添加到Map 以生成密钥。您可以创建新问题，链接到此问题，并描述您想要实现的目标。还提供一个示例，以便更好地理解。
    • 我能够使用您的示例找到解决方案。在原始帖子中查看我的更新。
    • @JosephGagnon，我很高兴它有所帮助。现在我明白了，你可以说你想在给定键下有一个列表?
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