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How would I use Jackson to flatten JSON with nested array?

I am using JackSon to parse the following JSON:
{
"AwardID": "1111111",
"AwardTitle": "Test Title",
"Effort":
"[
{
"PersonFirstName": "Jon",
"PersonLastName": "Snow"
}
]"
}
I would like to flatten this to be used in the following class:
public class Award {
private String awardId;
private String awardTitle;
private String personFirstName;
private String personLastName;
}
I have tried the following and have gotten the first two values, but I haven't been able to get the values from Effort trying to use JsonUnwrapped. I noted that it doesn't work with arrays, but I am trying the objectMapper.configure(DeserializationFeature.UNWRAP_SINGLE_VALUE_ARRAYS, true) configuration in the main method used to get the values.
public class Award {
#JsonProperty("AwardID")
private String awardId;
#JsonProperty("AwardTitle")
private String awardTitle;
#JsonUnwrapped
private Effort effort;
}
public class Effort {
private String personFirstName;
private String personLastName;
}
Note that I only expect one value in the Effort array from the API response at this time.
What is recommended to try next? Thank you!

The easiest way is having a List<Effort> if you have a JSON Array.
If there is always 1 item for Effort, the returning JSON should not have Effort as a JSON Array and instead should be a JSON Object.
But if you can only handle it codewise, you can have something like this (Note that there should always contain one item in Effort, otherwise it will throw Exception):
public class Award {
#JsonProperty("AwardID")
private String awardId;
#JsonProperty("AwardTitle")
private String awardTitle;
#JsonProperty("Effort")
private Effort effort;
}
public class Effort {
#JsonProperty("PersonFirstName")
private String personFirstName;
#JsonProperty("PersonLastName")
private String personLastName;
}
And your ObjectMapper needs to be enabled with DeserializationFeature.UNWRAP_SINGLE_VALUE_ARRAYS as well:
ObjectMapper mapper = new ObjectMapper();
mapper.enable(DeserializationFeature.UNWRAP_SINGLE_VALUE_ARRAYS);
Award award = mapper.readValue(rawJson, Award.class); // rawJson is your JSON String
And it should have the following output:
Award(awardId=1111111, awardTitle=Test Title, effort=Effort(personFirstName=Jon, personLastName=Snow))
Note that the annotation #JsonUnwrapped can only apply on JSON Object, not JSON Array:
Value is serialized as JSON Object (can not unwrap JSON arrays using this mechanism)

Parse a JSON structure with symbol instead of a string for an attribute

I am working on an HTTP Rest query.
Wikipedia API returns a JSON. The problem is the JSON structure returned by Wikipedia.
https://en.wikipedia.org/w/api.php?action=parse&section=0&prop=text&format=json&page=pizza
This is the JSON obtained via a rest request to the Wikipedia API. To view the full JSON, you can click on the above link.
{
"parse":
{
"title":"Pizza",
"pageid":24768,
"text":{"*":"<div class=\...>"}
}
}
I would parse this using a custom deserializer which I haven't got a chance to test. Trying to parse with simple Gson like the following return null;
Result res = new Gson(str,Result.class);
I have created the classes like the following:
public class Result
{
private Parse parse;
}
public class Parse
{
private String title;
private int pageid;
private Text text;
}
public class Text{
private String *;// what should I call this attribute.
}
My plan is to add a custom deserializer like the following:
public class TextBaseDeserializer implements JsonDeserializer<Text> {
#Override
public RespondentBase deserialize(JsonElement jsonElement, Type type, JsonDeserializationContext jsonDeserializationContext) throws JsonParseException {
return jsonDeserializationContext.deserialize(jsonElement.get("*"),Text.class);
}
}
I am using Gson to parse this, like the following:
Gson tmp = new GsonBuilder().registerTypeAdapter(Text.class, new TextBaseDeserializer());
// let's assume that str is the string obtained following Rest based request from Java.
Result res = tmp.parse(str,Result.class);
I have done all the above code to handle the symbolic JSON attribute.
My question is how to parse such a JSON. In the above example, the attribute is a *

As mentioned in a comment, you should annotated field with #SerializedName("*").
You can name the field whatever you want. We'll just name it star below, but maybe all is better, since * might be a wildchar? Doesn't really matter, just choose whatever name you like.
class Text
{
#SerializedName("*")
private String star;
}
Test
String str = "{\"parse\":{\"title\":\"Pizza\",\"pageid\":24768,\"text\":{\"*\":\"<div class=\\\"mw-parser-output\\\">...</div>\"}}}";
Gson tmp = new GsonBuilder().create();
Result res = tmp.fromJson(str, Result.class);
System.out.println(res.getParse().getText().getStar());
Output
<div class="mw-parser-output">...</div>

Parse JSON without object name in Java

I am trying to parse this JSON which is coming as the response to a REST API call. Can you please help me parsing it as key value pairs?
The object names are not present. There is nesting as well. There seems to be no new line between records.
The aim is to extract this data and load it into a database.
[
{
"cc_emails":["feedback#xyz.com"],
"fwd_emails":[],
"reply_cc_emails":["feedback#xyz.com"],
"fr_escalated":false,
"spam":false,
"email_config_id":6000038087,
"group_id":6000110481,
"priority":1,
"requester_id":6010410791,
"responder_id":6002817857,
"source":1,
"company_id":null,
"status":2,
"subject":"fare",
"to_emails":["feedback#xyz.com"],
"product_id":null,
"id":45043,
"type":null,
"due_by":"2016-03-12T08:58:02Z",
"fr_due_by":"2016-03-08T08:58:02Z",
"is_escalated":false,
"description":"Dear xyze Team,\r\n\r\nWhy r u increased fair again and againasas0mail.gmail.com</a>.<br>\n",
"custom_fields":
{
"category":null,
"issue":null,
"route_id":null,
"phone_number":null,
"department":null,
"booking_id":null
},
"created_at":"2016-03-07T08:58:02Z",
"updated_at":"2016-03-07T08:58:03Z",
// ...... repeat
}
]

The best way to do this would be to use http://www.jsonschema2pojo.org/
Enter your json there
Change source type to JSON
set the correct class name and package.
The resulting pojo can be directly mapped from the json
If you are using resttemplate to hit the api then you can use getForObject to automatically set the pojo from the output.
https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/web/client/RestTemplate.html#getForObject-java.lang.String-java.lang.Class-java.lang.Object...-

Using gson you can do this quite simply.
Do a class to match the fields in the json something like:
public class Example {
private List<String> cc_emails;
private List<String> fwd_emails;
private List<String> reply_cc_emails;
private Boolean fr_escalated;
private Boolean spam;
private Integer email_config_id;
...
private CustomFields custom_fields;
private String created_at;
private String updated_at;
}
Then you need to do another to map the custom fields
public class CustomFields {
private String category;
...
}
And using json you can parse it like this:
Type type = new TypeToken<Collection<Example>>(){}.getType();
new Gson().fromJson(json,type);
You have to exaplain to Gson it's a list, if it was a single object it would be this:
new Gson().fromJson(json,Example.class);
This is the aproach I usually take, also in the dates java.sql.Timestamp class might also parse it, you would need to try it though.

You can use Gson (https://github.com/google/gson) or Jackson (https://github.com/FasterXML/jackson) and deserialize it to a Map.

Parsing JSON String as simple as possible with GSON

Using GSON, how can i return a single key from a Multidimensional Json String?
Here is the Multidimensional Json String:
{"statusCode":0,"statusDescription":"OK","data":{"user":{"id":xxx,"company_id":xxx,"account_type":"5","enable_locations":true,"intuit_user_id":null,"nick_name":"xxx","is_owner":"1","enabled":"1"},"session_token":"xxx"}}
I want to return the "session_token" key value.
I'm trying this:
class app {
static class Response {
String session_token;
}
public void getSessionToken() {
String x = {"statusCode":0,"statusDescription":"OK","data":{"user":{"id":xxx,"company_id":xxx,"account_type":"5","enable_locations":true,"intuit_user_id":null,"nick_name":"xxx","is_owner":"1","enabled":"1"},"session_token":"xxx"}}
Response r = new Gson().fromJson(x, Response.class);
System.out.println(r.session_token);
}
}
But with this, my r.session_token returns null.

You would need to use Gson's JsonParser class directly and extract the data from the parse tree:
String myJsonString = "{\"name\":\"john\",\"lastname\":\"smith\"}";
JsonParser parser = new JsonParser();
JsonElement element = parser.parse(myJsonString);
JsonObject jsonObject = element.getAsJsonObject();
String lastName = jsonObject.get("lastname").getAsString();
System.out.println(lastName);
That said, it's debatable whether this would save you any real time over:
(edited from comments below):
class App {
static class Response {
String lastname;
}
public static void main(String[] args) {
String myJsonString = "{\"name\":\"john\",\"lastname\":\"smith\"}";
Response r = new Gson().fromJson(myJsonString, Response.class);
System.out.println(r.lastname);
}
}
Gson will silently ignore the fact that there's more data in the JSON than you're interested in, and later on you might be interested in it, in which case it's trivial to add fields to your Response class.
Edit due to question changing:
You have a JSON object. It contains a field data whose value is an object. Inside that object you have a field session_token that you're interested in.
Either you have to navigate to that field through the parse tree, or you have to create Java classes that all will map to. The Java classes would resemble (at the bare minimum):
class Response {
Data data;
}
class Data {
String session_token;
}

How to convert HTTP Request Body into JSON Object in Java

I am trying find a Java lib/api that will allow me to turn the contents of a HTTP Request POST body into a JSON object.
Ideally I would like to use a Apache Sling library (as they are exposed in my container naturally).
The closest I've found it: org.apache.sling.commons.json.http which converts the header to JSON.
HTTP Post bodies are in the format; key1=value1&key2=value2&..&keyn=valueN so I assume there is something out there, but I havent been able to find it.
I may just have to use a custom JSONTokener (org.apache.sling.commons.json.JSONTokener) to do this if something doesn't already exist. Thoughts?
Thanks

Assuming you're using an HttpServlet and a JSON library like json-simple you could do something like this:
public JSONObject requestParamsToJSON(ServletRequest req) {
JSONObject jsonObj = new JSONObject();
Map<String,String[]> params = req.getParameterMap();
for (Map.Entry<String,String[]> entry : params.entrySet()) {
String v[] = entry.getValue();
Object o = (v.length == 1) ? v[0] : v;
jsonObj.put(entry.getKey(), o);
}
return jsonObj;
}
With example usage:
public void doPost(HttpServletRequest req, HttpServletResponse res) {
JSONObject jsonObj = requestParamsToJSON(req);
// Now "jsonObj" is populated with the request parameters.
// e.g. {"key1":"value1", "key2":["value2a", "value2b"], ...}
}

Jackson is also a good option - its used extensively in Spring. Here is the tutorial: http://wiki.fasterxml.com/JacksonInFiveMinutes

I recommend trying Apache Commons Beanutils.
ServeltRequest request;
Map map = request.getParameterMap();
MyObject object = new MyObject();
BeanUtils.populate(object, map);
String json = object.toJSON() //using any JSON library

Sorry on making this an own answer but obviously my reputation doesn't allow me to simply add a comment to the answer How to convert HTTP Request Body into JSON Object in Java of maerics.
I would also iterate over the request params but instead of using an arbitrary json library use the JSONObject that is provided by sling. http://sling.apache.org/apidocs/sling6/org/apache/sling/commons/json/JSONObject.html

import org.json.JSONObject;
JSONObject json = new JSONObject(request.getParameterMap())

Use Gson. With this you can create class with private variables which represent the data you want : for example.
meta:{
name:"Example"
firstname:"Example2"
}
data:[
{
title:"ecaetra"
description:"qwerty"
}
...
]
Json Object could be retrieve like this :
public class RetrieveData {
private Meta meta;
private List<Data> data;
public Meta getMeta(){
return meta;
}
public List<Data> getData(){
return data;
}
}
public class Meta {
private String name;
private String firstname;
public String getName(){
return name;
}
public String getFirstName(){
return firstname;
}
}
public class Data {
private String title;
private String description;
public String getTitle(){
return title;
}
public String getDescription(){
return description;
}
}
And your instruction are simple. Content is the content of your Page, you can retrieve it with Asynctask.
Object o = new Gson().fromJson(Content, RetrieveData.class);
data = (RetrieveData)o;
// Get Meta
data.getName(); // Example
data.getFirstName(); // Example2
// Get Data
data.get(0).getTitle(); // position 0 : ecaetra
data.get(0).getDescription(); // position 0 : qwerty