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How to create one generic jsondatareader class for different JSON

I have created customer json file as below:
[
{
"firstName": “test”,
"lastName": “temp”,
"age": 35,
"emailAddress": “test#Gmail.com",
"address": {
"streetAddress": “test testing“,
"city": “city”,
"postCode": “12343546”,
"state": “state”,
"country": “cy”,
"county": “abc”
},
"phoneNumber": {
"home": "012345678",
"mob": "0987654321"
}
},
{
"firstName": “tug”,
"lastName": “kjk”,
"age": 35,
"emailAddress": “jhgj#Gmail.com",
"address": {
"streetAddress": “jh hjgjhg ,
"city": “kjhjh”,
"postCode": "122345",
"state": “jhgl”,
"country": “jaj”,
"county": “jhgkg”
},
"phoneNumber": {
"home": "012345678",
"mob": "0987654321"
}
}
]
For the Customer JSON data file, I have created below JSON datareader class:
public class JsonDataReader {
private final String customerFilePath = new ConfigFileReader().getTestDataResourcePath() + "Customer.json";
private List<Customer> customerList;
public JsonDataReader(){
customerList = getCustomerData();
}
private List<Customer> getCustomerData() {
Gson gson = new Gson();
BufferedReader bufferReader = null;
try {
bufferReader = new BufferedReader(new FileReader(customerFilePath));
Customer[] customers = gson.fromJson(bufferReader, Customer[].class);
return Arrays.asList(customers);
}catch(FileNotFoundException e) {
throw new RuntimeException("Json file not found at path : " + customerFilePath);
}finally {
try { if(bufferReader != null) bufferReader.close();}
catch (IOException ignore) {}
}
}
public final Customer getCustomerByName(String customerName){
for(Customer customer : customerList) {
if(customer.firstName.equalsIgnoreCase(customerName)) return customer;
}
return null;
}
}
Created POJO class as below:
public class Customer {
public String firstName;
public String lastName;
public int age;
public String emailAddress;
public Address address;
public PhoneNumber phoneNumber;
public class Address {
public String streetAddress;
public String city;
public String postCode;
public String state;
public String country;
public String county;
}
public class PhoneNumber {
public String home;
public String mob;
}
}
This is working fine so far as there is only one JSON data file, however I will create more JSON data files, so may be I have to create multiple POJOs for each one, but is there any way I can write common generic jsondatareader class for all those JSON files?

A class (or an Object) is a well defined entity. By well defined I mean that its structure is known at compile time, and cannot be changed after that point.
Having to create multiple classes to represent multiple JSON documents is perfectly fine. So if you're worried about the amount of files you'll create, it's a non-problem.
But, if the JSON document structure will keep changing along with every request, there is no point in defining a series of classes. To handle totally dynamic JSON you should stick with what Gson offers you. That is JsonElement and its subclasses.
JsonElement
> JsonArray
> JsonObject
> JsonPrimitive
> JsonNull
That's all what is needed to describe a JSON object.

If that is the case then why not convert JSON into a Map instead of a POJO! If you go POJO route then you will utilizing Jackson or GSon heavily in your code base adding bunch of utility methods to iterate over every resulting JSonArray or JSonelements.

How to map A JSON single item from a list<int, String) to String with Jackson?

In some incoming JSON there is a list
"age" : 27,
"country", USA,
"fields": [
{
"id": 261762251,
"value": "Fred"
},
{
"id": 261516162,
"value": "Dave"
},
]
I know the key int for what I am looking for [261762251].
I would like to map that to a plain String field firstname in the User object with the rest of the bottom level fields from the JSON. I have tried extending com.fasterxml.jackson.databind.util.StdConverter and adding the annotation #JsonSerialize(converter=MyConverterClass.class) to the variable in the User class with no luck.
My architecture is like this:
public class User {
private String age;
private String country;
private String firstname; // this is the field in the list that needs converting
// getters and setters
}
public class ApiClient{
public User getUsers(){
Response response;
//some code to call a service
return response.readEntity(User.class)
}
}
What is the best approach to achieve this?

You can try something like below:
class Tester
{
public static void main(String[] args) throws Exception {
String s1 = "{\"fields\": [ { \"id\": 261762251, \"value\": \"Fred\" }, { \"id\": 261516162, \"value\": \"Dave\" }]}";
ObjectMapper om = new ObjectMapper();
Myclass mine = om.readValue(s1, Myclass.class);
System.out.println(mine);
}
}
public class User {
private String age;
private String country;
private String firstname; // this is the field in the list that needs converting
#JsonProperty("fields")
private void unpackNested(List<Map<String,Object>> fields) {
for(Map<String,Object> el: fields) {
if((Integer)el.get("id") == 261762251) {
firstname = el.toString();
}
}
}
// getters and setters
}

How do I consume an array of JSON objects with Spring Boot?

With reference to this guide:
https://spring.io/guides/gs/consuming-rest/
The guide shows how to consume a RESTful web service.
The response from the REST API query results in the following JSON:
{
type: "success",
value: {
id: 10,
quote: "Really loving Spring Boot, makes stand alone Spring apps easy."
}
}
It creates a domain class called Quote.java to contain the data in the response:
package hello;
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
#JsonIgnoreProperties(ignoreUnknown = true)
public class Quote {
private String type;
private Value value;
public Quote() {
}
public String getType() {
return type;
}
public void setType(String type) {
this.type = type;
}
public Value getValue() {
return value;
}
public void setValue(Value value) {
this.value = value;
}
#Override
public String toString() {
return "Quote{" +
"type='" + type + '\'' +
", value=" + value +
'}';
}
}
My questions is how do I represent the following json:
{
"size": 1,
"limit": 25,
"isLastPage": true,
"values": [
{
"user": {
"name": "jcitizen",
"emailAddress": "jane#example.com",
"id": 101,
"displayName": "Jane Citizen",
"active": true,
"slug": "jcitizen",
"type": "NORMAL"
},
"permission": "ADMIN"
}
],
"start": 0
}
The outer objects like size and limit are straightforward but I can't figure out how to represent the values object, which looks like an array of json objects.

This should work.
class Output {
private String size,
private int limit;
private boolean isLastPage,
private List<Value> values;
private int start ;
}
class Value
{
User user,
private String permission;
}
class User {
private String name,
private String emailAddress,
private int id,
private String displayName,
private boolean active,
private String slug,
private String type
}

Gson calls returns empty objects over multiple classes

I'm trying to serialize to serialize the json string I have included below.
{
"mood": {
"is_featured": true,
"description": null,
"title": "2014 ",
"ordering": null,
"is_recently_modified": true,
"is_test": false,
"tracks": [
{
"album": {
"release_date": "2014-11-06",
"id": 359778,
"name": "Amansız Gücenik"
},
"name": "Hırpalandı Mayıs",
"artist": {
"id": 491169,
"name": "Ceylan Ertem"
},
"duration": 227,
"isrc": "TRA161400207",
"id": 3903997
},
{
"album": {
"release_date": "2013-08-05",
"id": 329129,
"name": "For Fuld Musik - 25 Danske Sommer Pop & Rock Hits Vol. 2"
},
"name": "Am I Wrong",
"artist": {
"id": 755957,
"name": "Nico & Vinz"
},
"duration": 387,
"isrc": "NO2G31301011",
"id": 3655085
}
],
"image_url": "some_url",
"is_recently_created": true,
"id": 128
}
}
I'm using this gson call to serialize it
Mood mood = new Gson().fromJson(result, Mood.class);
My class structers are like this.
public class Mood {
private boolean is_featured;
private boolean is_recently_modified;
private boolean is_recently_created;
private boolean is_test;
private String description;
private String title;
private String image_url;
private int id;
private int ordering;
private Track[] tracks;
public static class MoodContainer {
public Mood[] moods;
}
}
public class Track {
//variables
private Album album;
private Artist artist;
private Provider provider;
private String secure_url;
private String name;
private String region;
private String isrc;
private int duration;
private int track_order;
private int id;
}
And it goes on like this for any additional class variable. When I try to use the above call I end up with objects that have all null values. One thing to notice is some fields are not supplied in json string because different api calls supply different parts of these json strings. What I am doing wrong?

Root JSON object you provided has property mood - so you either have two options for deserialization to work properly:
Wrap your Mood class inside another object like this:
public class MoodWrapper { private Mood mood; }
and change de-serialization code to
MoodWrapper moodWrapper = new Gson().fromJson(result, MoodWrapper.class);
Skip a root object when deserializing:
final Gson gson = new Gson();
JsonParser parser = new JsonParser();
JsonObject rootObj = parser.parse(json).getAsJsonObject();
Mood mood = gson.fromJson(rootObj.getAsJsonObject("mood"), Mood.class);

The top-level elements in the JSON string should be your object's properties, not the outer element "mood" which you have.

Parsing a complex Json Object using GSON in Java

I have a very long JSON to parse with Gson, but for brevity I have trimmed it to this example:
{
"volumes": [
{
"status": "available",
"managed": true,
"name": "va_85621143-1133-412f-83b4-57a01a552638_",
"support": {
"status": "supported"
},
"storage_pool": "pfm9253_pfm9254_new",
"id": "afb8e294-6188-4907-9f6f-963c7623cecb",
"size": 9
},
{
"status": "in-use",
"managed": false,
"name": "bt_newd20",
"support": {
"status": "not_supported",
"reasons": [
"This volume is not a candidate for management because it is already attached to a virtual machine. To manage this volume with PowerVC, select the virtual machine to which the volume is attached for management. The attached volume will be automatically included for management."
]
},
"storage_pool": "KVM",
"mapped_wwpns": [
"2101001B32BD4280",
"2100001B329D4280",
"2101001B32BD637E",
"2100001B329D637E"
],
"id": "c7838c79-17ca-3cbc-98e5-3567fde902d8",
"size": 0
},
{
"status": "available",
"managed": true,
"name": "vdisk138",
"support": {
"status": "supported"
},
"storage_pool": "Chassis2_IBMi",
"id": "b6d00783-9f8c-40b8-ad78-956b0299478c",
"size": 100
}
]
}
From SO and few other places, I have found that I need to define a top level container like one below but I do not know how to complete its definition
static class VolumeContainer {
//I don't know what do in here. This is the first problem
}
and then a class for each Volume
static class Volume {
private String status;
private boolean managed;
private String name;
//This is the second problem.The "support" variable should not be a string.
//It is in {}. Just for information, I won't use it.
//private String support;
private String storagePool;
private List<String> mapped_wwpns;
private String id;
private String size;
}
I am trying to parse it and this is what I coded so far:
JsonParser parser = new JsonParser();
JsonObject obj = parser.parse(response).getAsJsonObject();
Gson gson = new Gson();
The JSON string is stored in a variable named response
VolumeContainer vc = gson.fromJson(response,VolumeContainer.class);
My final requirement is a HashTable of id and associated name.

First problem: your VolumeContainer needs to be:
public class VolumeContainer {
public List<Volume> volumes;
}
it does not need to be static.
Second problem: your Volume class should be like this:
public class Volume {
private String status;
private Boolean managed;
private String name;
private Support support;
private String storage_pool;
private String id;
private int size;
private List<String> mapped_wwpns;
public String getId(){return id;}
public String getName(){return name;}
}
I defined a class named Support like this:
public class Support {
private String status;
private List<String> reasons;
}
Third problem: parsing, If response string contains your example data, simply parse like this:
Gson g = new Gson();
VolumeContainer vc = g.fromJson(response, VolumeContainer.class);
Fourth problem: get the map. Finally to get your HashMap, just do like this:
HashMap<String, String> hm = new HashMap<String,String>();
for(Volume v: vc.volumes){
hm.put(v.getId(), v.getName());
}