遍历 JSON 并将列表数组添加到对象/数组中

Question

我有这两个JSON 数组：

{ 
  "Person": {
    "Info": [
      "name": "Becky",
      "age": 14
    ]
   },
  "Fruits": [
    {
      "name": "avocado",
      "organic": true
    },
    {
      "name": "mango",
      "organic": true
    }
  ],
  "Vegetables": [
    {
      "name": "brocoli",
      "organic": true
    },
    {
      "name": "lettuce",
      "organic": true
    }
  ]
}

我想要做的是使用Jackson 和Gson 库让一切看起来都很漂亮。

类似的东西。这适用于Gson。所以我想要的输出是：

{ 
  "Person": {
    "Info": [
      "name":"Becky",
      "age": 14
    ]
  },
  "FruitsList": {
    "Fruits": [
      {
        "name": "avocado",
        "organic": true
      },
      {
        "name": "mango",
        "organic": true
      }
    ]
  },
  "VegetablesList": {
    "Vegetables": [
      {
        "name": "brocoli",
        "organic": true
      },
      {
        "name": "lettuce",
        "organic": true
      }
    ]
  }
}

我已将我的课程设置为：

class Person{
   private List<Info> InfoList;
   //Set and get were set
}

class Info{
   private String name;
   private int age;
   //Set and get were set
}

class Fruits{
   private String name;
   private boolean organic;
   //Set and get were set
   public String toString(){
            return "Fruits:{" +
            "name:'" + name+ '\'' +
            ", organic:" + organic+'\''+
            '}';
   }
 }

 class Vegetables{
   private String name;
   private boolean;
   //Set and get were set
   public String toString(){
            return "Fruits:[" +
            "name:'" + name+ '\'' +
            ", organic:" + organic+'\''+
            ']';
   }
 }

class rootFinal{
    private List<Fruits> fruitList;
    private List<Vegetables> vegetablesList;
    private List<Person> personList;
    //Set and get were set
}

class mainJson{
   final InputStream fileData = ..("testPVF.json");

   ObjectMapper map = new Ob..();
   rootFinal root = map.readValue(fileData,rootFinal.class);
   // I can access each class with 
   System.out.printl(root.getHeaderList.get(0));
}

这输出...

[Fruit{name:'avocado', organic:true}, Fruit{name:'mango', organic:true}]

但这不是我想要的。

我正在尝试对 JSON 文件进行迭代，或者是否有更好的方法来检查数组是否存在。向其中添加其他对象/数组。

如果我找到Veg 或Fruit，我想以某种方式添加VegList 和FruitList，如图所示。它应该忽略"Person": {}，因为它位于{} 符号中。

有没有办法用Gson 做到这一点？

Answer 1

如果我理解正确，您想使用 JSON Object 节点包装每个 JSON Array 节点。为此，您不需要使用POJO 模型，您可以将JSON 有效负载读取为ObjectNode 并使用它的API 来更新它。

杰克逊

Jackson 库的简单示例：

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

import java.io.File;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;

public class JsonObjectApp {

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

        ObjectMapper mapper = new ObjectMapper();
        mapper.enable(SerializationFeature.INDENT_OUTPUT);

        ObjectNode root = (ObjectNode) mapper.readTree(jsonFile);

        Map<String, JsonNode> valuesToAdd = new LinkedHashMap<>();

        // create fields iterator
        Iterator<Map.Entry<String, JsonNode>> fieldsIterator = root.fields();
        while (fieldsIterator.hasNext()) {
            Map.Entry<String, JsonNode> entry = fieldsIterator.next();

            // if entry represents array
            if (entry.getValue().isArray()) {
                // create wrapper object
                ObjectNode arrayWrapper = mapper.getNodeFactory().objectNode();
                arrayWrapper.set(entry.getKey(), root.get(entry.getKey()));

                valuesToAdd.put(entry.getKey(), arrayWrapper);

                // remove it from object.
                fieldsIterator.remove();
            }
        }

        valuesToAdd.forEach((k, v) -> root.set(k + "List", v));

        System.out.println(mapper.writeValueAsString(root));
    }
}

上面的代码打印为您的JSON：

{
  "Person" : {
    "Info" : [ {
      "name" : "Becky",
      "age" : 14
    } ]
  },
  "FruitsList" : {
    "Fruits" : [ {
      "name" : "avocado",
      "organic" : true
    }, {
      "name" : "mango",
      "organic" : true
    } ]
  },
  "VegetablesList" : {
    "Vegetables" : [ {
      "name" : "brocoli",
      "organic" : true
    }, {
      "name" : "lettuce",
      "organic" : true
    } ]
  }
}

格森

我们可以使用Gson 库实现非常相似的解决方案：

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;

import java.io.File;
import java.io.FileReader;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;

public class GsonApp {

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

        Gson gson = new GsonBuilder()
                .setPrettyPrinting()
                .create();

        try (FileReader reader = new FileReader(jsonFile)) {
            JsonObject root = gson.fromJson(reader, JsonObject.class);

            Map<String, JsonElement> valuesToAdd = new LinkedHashMap<>();

            // create fields iterator
            Iterator<Map.Entry<String, JsonElement>> fieldsIterator = root.entrySet().iterator();
            while (fieldsIterator.hasNext()) {
                Map.Entry<String, JsonElement> entry = fieldsIterator.next();
                // if entry represents array
                if (entry.getValue().isJsonArray()) {
                    // create wrapper object
                    JsonObject arrayWrapper = new JsonObject();
                    arrayWrapper.add(entry.getKey(), root.get(entry.getKey()));

                    valuesToAdd.put(entry.getKey(), arrayWrapper);

                    // remove it from object.
                    fieldsIterator.remove();
                }
            }

            valuesToAdd.forEach((k, v) -> root.add(k + "List", v));

            System.out.println(gson.toJson(root));
        }
    }
}

输出是一样的。

Answer 2

查看Get Pretty Printer

同时检查specific APIs for Pretty Printing

示例代码：

//This example is using Input as JSONNode
//One can serialize POJOs to JSONNode using ObjectMapper.
ObjectMapper mapper = new ObjectMapper();
mapper.writerWithDefaultPrettyPrinter().writeValueAsString(
					inputNode)