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Using Jackson, how can you get a list of objects from an interesting json?

I have this json, I need to get a list of currency objects using Jackson (the objects itself has a currency name field - "USD", "type" and "show") as a result. How can I do it in a simple and clear way?
Any help would be welcome
{
...
"result": "OK",
"currency": {
"currencies": {
"LB": {
"type": "A",
"setting": {
"show": true,
},
"access" : true
},
"USD": {
"type": "B",
"setting": {
"show": true,
},
"access" : true
},
"RUB": {
"type": "A",
"setting": {
"show": true,
},
"access" : true
},
....
// and more..
},
...
}
}

"currencies": {
"LB": {
"type": "A",
"setting": {
"show": true,
},
"access" : true
},
"USD": {
"type": "B",
"setting": {
"show": true,
},
"access" : true
},
"RUB": {
"type": "A",
"setting": {
"show": true,
},
"access" : true
},
....
// and more..
},
...
This looks like an Map, not a List. Does that help you? So you would need to create Currency class and have jackson parse this structure to Map<String, Currency>. Note that currency will not contain the identifier (like "USD"), only they key in the map will.

You can read your Json as a Map<String, Object>. Once you have the map you iterate through your map and build your List.
If you want to de-serialize (read) from Json to List of your custom objects you need to have your Json restructured to be Json List and not Json Object. Then you can read your Json into a List directly. In any case, there is an Open source Library that has a feature based on Jackson library really simplifies reading/writing objects from/to Json. If you have a json string all you have to do is:
Map<String, Object> map = JsonUtils.readObjectFromJsonString(jsonString, Map.class);
It throws IOException though, so you will need to handle it. Here is the Javadoc. The library is called MgntUtils and could be found as Maven artifact and on the Github (including javadoc and source code)

I was able to add object saving to the list, but in a rather inconvenient way, it seems to me...
ArrayList<Dto> currencyObjectList = new ArrayList<Dto>();
CurrencyStaticDto obj = null;
JsonNode currencies = mapper.readTree(response.getBody()).get("currencies");
Iterator<Map.Entry<String, JsonNode>> fields = currencies.fields();
while(fields.hasNext()) {
Map.Entry<String, JsonNode> field = fields.next();
String fieldName = field.getKey();
JsonNode fieldValue = field.getValue();
obj = mapper.readValue(fieldValue.toString(),CurrencyStaticDto.class);
obj.setCurrency(fieldName);
currencyObjectList.add(obj);
}

Get json object in Array based on key and value in Java

I have a Json body like the example below. I need to extract the value from a key that has another key with a specific value in an array. I am passing in a JsonNode with everything in the detail component of the message, I can easily extract from each level, however, I'm struggling with the array.
In this case, I need to extract the value of "value" (Police/Fire/Accident Report) from the object in the array which has a key/value pair of "name":"documentTitle". I understand this is a JSONArray, but I can't find a good example that shows me how to extract the values for an object in the array that contains a certain key/value pair, I don't think I can rely on getting the object in position [2] in the array as the same objects may not always be present in the additionalMetadata array.
Sample Json:
"sourceVersion": "1.0",
"eventId": "8d74b892-810a-47c3-882b-6e641fd509eb",
"clientRequestId": "b84f3a7b-03cc-4848-a1e8-3519106c6fcb",
"detail": {
"stack": "corona",
"visibilityIndicator": null,
"documentUid": "b84f3a7b-03cc-4848-a1e8-3519106c6fcb",
"additionalMetadata": [
{
"name": "lastModifiedDate",
"value": "2021-05-21T04:53:53Z"
},
{
"name": "documentName",
"value": "Police/Fire Report, 23850413, 2021-05-20 14:51:23"
},
{
"name": "documentTitle",
"value": "Police/Fire/Accident Report"
},
{
"name": "documentAuthor",
"value": "System Generated"
},
{
"name": "lastModifiedBy",
"value": "System Updated"
},
{
"name": "createdBy",
"value": "System Generated"
},
{
"name": "documentDescription",
"value": "Police/Fire Report received"
},
{
"name": "organizationCode",
"value": "Claims"
}
]
}
}```

Loop through the json array and extract the json object with name documentTitile. From that json object you can get the value

Well, either the JSON framework you're using supports this out of the box (check the documentation) or you could convert it manually to a map:
List<AdditionalMetadataEntry> additionalMetadata;
[...]
Map<String, String> additionalMetadataMap = additionalMetadata.stream().collect(Collectors.toMap(AdditionalMetadataEntry::getName, AdditionalMetadataEntry::getValue));

I was able to figure it out. I created a new node off the existing notificationBody JsonNode, then parsed through the metadata key/value pairs:
String docTitle = "";
JsonNode additionalMetadata = notificationBody.get("detail").get("additionalMetadata");
for (JsonNode node: additionalMetadata) {
String name = node.get("name").asText();
String value = node.get("value").asText();
if(name.equals("documentTitle")){
docTitle = value;
}
}

JSON to JSON Transform of input sample using any existing java library/tools

Input:
{
"Student": {
"name" :"abc",
"id" : 588,
"class : "12"
}
}
Reqired Output:
{
"Student": {
"key" :"name",
"value":"abc",
"key" :"id",
"value":"588",
"key" :"class",
"value":"12"
}
}

Your output json invalid. Json object can not duplicate key .
You can use the library org.json and do something like this:
JSONObject jsonObject = new JSONObject(inputJson);
JSONObject outputJson = new JSONObject();
JSONArray array = new JSONArray();
for (Object key : jsonObject.keySet()) {
JSONObject item = new JSONObject();
String keyStr = (String)key;
Object keyvalue = jsonObj.get(keyStr);
item.put(keyStr, keyvalue);
array.put(item);
}
outputJson.put("Student", array);
System.out.println(json.toString());
Output :
{
"Student": [
{
"key": "name",
"value": "abc"
},
{
"key": "id",
"value": "588"
},
{
"key": "class",
"value": "12"
}
]
}

Similar to the other answer, the desired output JSON format is not valid.
The closest valid output would be
{
"Student" : [ {
"key" : "name",
"value" : "abc"
}, {
"key" : "id",
"value" : 588
}, {
"key" : "class",
"value" : "12"
} ]
}
This can be generated via Jolt with the following spec
[
{
"operation": "shift",
"spec": {
"Student": {
"name": {
"$": "Student[0].key",
"#": "Student[0].value"
},
"id": {
"$": "Student[1].key",
"#": "Student[1].value"
},
"class": {
"$": "Student[2].key",
"#": "Student[2].value"
}
}
}
}
]

This is easy to solve with JSLT if we assume the output is made valid JSON by making an array of key/value objects like the other respondents do.
The array function converts an object into an array of key/value objects exactly like you ask for, so the transform becomes:
{"Student" : array(.Student)}

read json file and parse inner json array in java

{
"vers": 0.01,
"config": {
"rate": "perhr",
"valueColumns": [
"vCPU",
"ECU",
"memoryGiB",
"storageGB",
"linux"
],
"currencies": [
"USD"
],
"regions": [
{
"region": "us-east",
"instanceTypes": [
{
"type": "generalCurrentGen",
"sizes": [
{
"size": "t2.micro",
"vCPU": "1",
"ECU": "variable",
"memoryGiB": "1",
"storageGB": "ebsonly",
"valueColumns": [
{
"name": "linux",
"prices": {
"USD": "0.013"
}
}
]
},
{
"size": "t2.small",
"vCPU": "1",
"ECU": "variable",
"memoryGiB": "2",
"storageGB": "ebsonly",
"valueColumns": [
{
"name": "linux",
"prices": {
"USD": "0.026"
}
}
]
}
]
}
]
}
]
}
}
Hi, i wanted to read this json file. I tried various ways from google but getting a null at valuesColumns. I have to read sizes array and have to put in list.

I think it will help your cause if you format your json. As it is it's quite hard to read. Googling for a JSON beautifier quickly found me this one.
When working with JSON your browser console provides a nice environment for inspecting and playing with the data. I pasted it into the browser console and did (hit enter after each line):
var x = { ... paste JSON here ... }
x
x.config
x.config.valueColumns
This tells me that x is a JSON object, config is a JSON object and valueColumns is a JSON array
Now to java. Grab yourself a json library, and accessing valueColumns will be something like:
JSONObject x = new JSONObject("{ ... JSON string ... }");
JSONObject config = x.getJSONObject("config");
JSONArray valueColumns = config.getJSONArray("valueColumns");
You can then iterate over valueColumns and pull out what you need.
Note that the above only gets you to the first valueColumns array under config. By following the same principle you can go deeper into the structure and get out the valueColumns for the objects in the sizes array if that's what you're really after.

For parsing json to java there are simple step.
Below code snippet may help you.
// parse json to java
Object obj = parser.parse(s);
JSONObject json = (JSONObject) obj;
JSONObject o = (JSONObject) json.get("config");
//get json array.
JSONArray array = (JSONArray) o.get("valueColumns");
System.out.println(array.toJSONString());
//access element by index
System.out.println(array.get(0));

Get sub-array from JSON

I parsing some data from a json file. Here is my JSON File.
[
{
"topic": "Example1",
"contact": [
{
"ref": [
1
],
"corresponding": true,
"name": "XYZ"
},
{
"ref": [
1
],
"name": "ZXY"
},
{
"ref": [
1
],
"name": "ABC"
},
{
"ref": [
1,
2
],
"name":"BCA"
}
] ,
"type": "Presentation"
},
{
"topic": "Example2",
"contact": [
{
"ref": [
1
],
"corresponding": true,
"name": "XYZ"
},
{
"ref": [
1
],
"name": "ZXY"
},
{
"ref": [
1
],
"name": "ABC"
},
{
"ref": [
1,
2
],
"name":"BCA"
}
] ,
"type": "Poster"
}
]
I can fetch and store data one by one. Like this one
JSONArray getContactsArray = new JSONArray(jsonObject.getString("contact"));
for(int a =0 ; a < getContactsArray.length(); a++)
{
JSONObject getJSonObj = (JSONObject)getContactsArray.get(a);
String Name = getJSonObj.getString("name");
}
1)Now, my question is there any way to get all name values for each array with single query.
2) Can I get all those values in an Array ?
Please correct me, if I am doing anything wrong. Thank you.

Iteration cannot be avoided here as org.json and other Json parsers as well provide random access to objects but not to their properties collectively (as a collection). So, you can't query something like "all name properties of all contact objects" unless you probably get a Json parser like Gson to unmarshall it that way.
But, that's too much to just avoid a for loop when you can definitely shorten the parse by making use of the appropriate API methods to avoid unnecessary object casts.
JSONArray contacts = jsonObject.getJSONArray("contact");
String[] contactNames = new String[contacts.length()];
for(int i = 0 ; i < contactNames.length; i++) {
contactNames[i] = contacts.getJSONObject(i).getString("name");
}

Better to use a json parser such as GSon or Jackson to marshall your json to a java object. Then you can write utitlity method in your java class to retrieve all the names in that object.

Try this:
Create JSONObject of your file and try to get array of all names and iterate it to get all values.
public static String[] getNames(JSONObject jo) {
int length = jo.length();
if (length == 0) {
return null;
}
Iterator i = jo.keys();
String[] names = new String[length];
int j = 0;
while (i.hasNext()) {
names[j] = (String) i.next();
j += 1;
}
return names;
}