在JSON上迭代，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
}
]
}

我想做的是使用Jackson和Gson库，使一切看起来都很漂亮。

像这样的东西。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));
}

此输出。。。

[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。向其添加额外的对象/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": {}，因为它在{}符号中。

有没有办法用Gson做到这一点？

Answer 1

如果我理解正确，您希望使用JSON Object节点包装每个JSON Array节点。要做到这一点，您不需要使用POJO模型，您可以将JSON有效载荷读取为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));
}
}

以上代码打印用于您的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
} ]
}
}

Gson

我们可以用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));
}
}
}

输出是相同的。

Answer 2

检查Get Pretty Printer

还要检查Pretty Printing 的特定API

样本代码：

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