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How to sort and create hash string using LinkedHashMap?

I am developing an application within that I have to create the SHA256 hash for the incoming data. To make that I have to follow the specific sorting order for each property. Hence, I have created a class TemplateNodeMap which extends LinkedHashMap, within that I have specified the order that I need to follow.
Now, I would like to read each property in the incoming JSON data, add a specific field, and create the Hash string. I am a bit confused about adding the data and creating the string. I am worried if I am following the optimal procedure or not as I need to follow the process for a large amount of data.
Can someone please let me know if this is the right approach?
Following is the incoming JSON (Since JSON can have any order I need to obtain properties according to my required Hash String order):
{
"age": 30,
"name": "Batman",
"address": {
"city": "Gotham",
"street": {
"name": "Gotham 123"
}
}
}
Following is my TemplateNodeMap class:
package io.hash;
import java.util.LinkedHashMap;
public class TemplateNodeMap extends LinkedHashMap {
public TemplateNodeMap() {
put("name", null);
put("age", null);
put("address", new LinkedHashMap<>() {{
put("street", new LinkedHashMap<>() {{
put("name", null);
}});
put("city", null);
}});
}
}
Following is my ApplicationMain class which is reading and loading the data to TemplateNodeMap:
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.node.ObjectNode;
import java.io.IOException;
import java.io.InputStream;
public class ApplicationMain {
public static void main(String[] args) throws IOException {
final ObjectMapper objectMapper = new ObjectMapper();
final InputStream jsonStream = ApplicationMain.class.getResourceAsStream("/InputJSON.json");
final ObjectNode inputTemplate = objectMapper.readValue(jsonStream, ObjectNode.class);
System.out.println(objectMapper.writerWithDefaultPrettyPrinter().writeValueAsString(inputTemplate));
final TemplateNodeMap templateNodeMap = new TemplateNodeMap();
templateNodeMap.put("name", inputTemplate.get("name"));
templateNodeMap.put("age", inputTemplate.get("age"));
//Unable to understand how to insert the complex object values into LinkedHashMap and follow the order
}
}
I am not understanding how to add the complex object to LinkedHashMap and create a string out of it.
Not all fields are mandatory so I would like to omit the null values during the creation of Hash String.
Can someone please suggest to me how to achieve this and if this is the right approach to creating a Hash String based on the required order?

There are two jackson annotations that can help you to serialize the jackson properties in a custom order excluding the non null values:
JsonPropertyOrder annotation that can be used to define ordering (possibly partial) to use when serializing object properties.
JsonInclude annotation used to indicate when value of the annotated property, or all properties of the annotated class, is to be serialized.
You can then deserialize your json to the pojo java classes and then serialize them obtaining a new json with the expected order of the properties and without null properties:
#Data
#JsonPropertyOrder(value = {"name", "age", "address"})
#JsonInclude(JsonInclude.Include.NON_NULL)
public class Person {
private int age;
private String name;
private Address address;
}
#Data
#JsonPropertyOrder(value = {"street", "city"})
#JsonInclude(JsonInclude.Include.NON_NULL)
public class Address {
private String city;
private Street street;
}
#Data
#JsonInclude(JsonInclude.Include.NON_NULL)
public class Street {
private String name;
}
//you can delete for example the name property from your json
Person person = mapper.readValue(json, Person.class);
String output = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(person);
//ok, the name property will not appear in the output because it's null
System.out.println(output);

Requirements:
"I am developing an application within that I have to create the SHA256 hash for the incoming data."
"To make that I have to follow the specific sorting order for each property."
Proposal:
Create data classes for your incoming data, order their attributes as you like
Transform data class into a 'standard' JSON representation using prettyprint
Calculate hash over 'standard' JSON representation
For completeness a manual parsing of the linked hashmap is included
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.node.ObjectNode;
import java.io.*;
import java.nio.*;
import java.nio.charset.StandardCharsets;
import java.security.*;
import java.util.*;
class Person {
int age; String name; Address address; // Attribute order effects output order!
public Person(){}
public Person(int age, String name, Address address) {
this.age = age; this.address = address; this.name = name;
}
public void setAge(int age){this.age = age;}
public int getAge(){return age;}
public void setName(String name){this.name = name;}
public String getName(){return name;}
public void setAddress(Address address){this.address = address;}
public Address getAddress(){return address;}
}
class Address {
String city;
Street street;
public Address(){}
public Address(String city, Street street){this.city = city; this.street = street;}
public void setCity(String city){this.city = city;}
public String getCity(){return city;}
public void setStreet(Street street){this.street = street;}
public Street getStreet(){return street;}
}
class Street {
String name;
public Street(){}
public Street(String name) {this.name = name;}
public String getName(){return name;}
public void setName(String name) {this.name = name;}
}
public class ApplicationMain {
static String inputJson = "{\"age\": 30,\"name\": \"Batman\",\"address\": {\"city\": \"Gotham\",\"street\": {\"name\": \"Gotham 123\"}}}";
public static void main(String[] args) throws IOException, NoSuchAlgorithmException {
final ObjectMapper objectMapper = new ObjectMapper();
try {
// use Paths.get("InputJSON.json").toFile() as alternative to the string
Map<?, ?> map = objectMapper.readValue(inputJson, Map.class);
System.out.println("The linked hashmap to process for sorting:");
System.out.println(map);
System.out.println("Individual elements:");
System.out.println("name: " + map.get("name"));
System.out.println("age: " + map.get("age"));
System.out.println("address:");
Map<?, ?> addressMap = (Map<?, ?>)map.get("address");
System.out.println(" city: " + addressMap.get("city"));
System.out.println(" street:");
System.out.println(" name: " + ((Map<?, ?>)addressMap.get("street")).get("name"));
} catch (Exception ex) {
ex.printStackTrace();
}
Person person = objectMapper.readValue(inputJson, Person.class);
System.out.println("Original JSON:\n" + inputJson);
String prettyJson = objectMapper.writerWithDefaultPrettyPrinter().writeValueAsString(person);
System.out.println("Standardized JSON:\n" + prettyJson);
byte[] hash = MessageDigest.getInstance("SHA-256").digest(prettyJson.getBytes(StandardCharsets.UTF_8));
for ( byte b : hash) {
System.out.printf("%02x", b);
}
System.out.println();
}
}
$ java -cp .:jackson-databind-2.13.3.jar:jackson-core-2.13.3.jar:jackson-annotations-2.13.3.jar ApplicationMain
The linked hashmap to process for sorting:
{age=30, name=Batman, address={city=Gotham, street={name=Gotham 123}}}
Individual elements:
name: Batman
age: 30
address:
city: Gotham
street:
name: Gotham 123
Original JSON:
{"age": 30,"name": "Batman","address": {"city": "Gotham","street": {"name": "Gotham 123"}}}
Standardized JSON:
{
"age" : 30,
"name" : "Batman",
"address" : {
"city" : "Gotham",
"street" : {
"name" : "Gotham 123"
}
}
}
5f962abf0cdc5150eb2614c629592d889d59b82499b13dd1b8d12e421bb0440a
$
You can check the hash value at https://dencode.com/hash
(The link already contains the JSON data. If you paste text there, verify that the correct line ending type is selected.)

JSON to POJO: How to generate abstract java class names from unique JSON fields?

I want to generate Java Classes using a given JSON schema
Using the WikiMedia API, I receive the page info from a search
JSON schema:
(The small part that gives me problems)
"pages": {
"352214": {
"pageid": 352214,
"ns": 0,
"title": "Montellano",
"extract": "Montellano es un municipio español..."
}
}
As you can see the field 352214 is unique to this search which gives a problem using the POJO.
I'm using jsonschema2pojo with Jackson2 as Annotation Style
POJO
import java.util.HashMap;
import java.util.Map;
import com.fasterxml.jackson.annotation.JsonAnyGetter;
import com.fasterxml.jackson.annotation.JsonAnySetter;
import com.fasterxml.jackson.annotation.JsonIgnore;
import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.annotation.JsonPropertyOrder;
#JsonInclude(JsonInclude.Include.NON_NULL)
#JsonPropertyOrder({
"pageid",
"ns",
"title",
"extract"
})
public class _352214 {
#JsonProperty("pageid")
private Integer pageid;
#JsonProperty("ns")
private Integer ns;
#JsonProperty("title")
private String title;
#JsonProperty("extract")
private String extract;
#JsonIgnore
private Map<String, Object> additionalProperties = new HashMap<String, Object>();
#JsonProperty("pageid")
public Integer getPageid() {
return pageid;
}
#JsonProperty("pageid")
public void setPageid(Integer pageid) {
this.pageid = pageid;
}
#JsonProperty("ns")
public Integer getNs() {
return ns;
}
#JsonProperty("ns")
public void setNs(Integer ns) {
this.ns = ns;
}
#JsonProperty("title")
public String getTitle() {
return title;
}
#JsonProperty("title")
public void setTitle(String title) {
this.title = title;
}
#JsonProperty("extract")
public String getExtract() {
return extract;
}
#JsonProperty("extract")
public void setExtract(String extract) {
this.extract = extract;
}
#JsonAnyGetter
public Map<String, Object> getAdditionalProperties() {
return this.additionalProperties;
}
#JsonAnySetter
public void setAdditionalProperty(String name, Object value) {
this.additionalProperties.put(name, value);
}
}
_352214 class will suit only for the wiki search with the same field name, whenever I make another search and this field changes, it crashes. How do I solve this?

There is no standard way to parse situations like this(situations when you don't know field name). As an option you can manually parse your file using Jackson:
public void parseWikiResponse(String wikiResponse) {
JsonFactory jsonFactory = new JsonFactory();
ObjectMapper mapper = new ObjectMapper(jsonFactory);
JsonNode jsonNodes = mapper.readTree(wikiResponse);
Iterator<Map.Entry<String,JsonNode>> fieldsIterator = jsonNodes.fields();
while (fieldsIterator.hasNext()) {
Map.Entry<String,JsonNode> field = fieldsIterator.next();
/* Here you can find your field with unknown name using regExp eg */
field.getKey();
}
}
If you want only for parsing this approach should solve the problem.
There is a similar question on this topic:
Parsing JSON in Java without knowing JSON format
Hope something helped (:

How to store values using Jackson JSON to Java

I am having a really hard time understanding how to place a mapped valued into an array and how to iterate that array.
test.json
[
{
"Name": "Bob",
"Nationality": "",
"City": "Chicago",
"Phone" : "451232424234"
},
......continues with more objects
]
testTemplate.java
//imports
#JSONInclude(Json.Include.Non_NULL)
#JsonPropertyOrder({"Name,"Nationality","City","Phone"})
Public class testTemplate {
#JsonProperty("Name")
private String userName;
#JsonProperty("Nationality")
private String nation;
#JsonProperty("City")
private String city;
#JsonProperty("Phone")
private String phone;
#JsonProperty("Name")
public String getName (String userName) {
this.userName = userName;
}
#JsonProperty("Nationality")
public String nation (String nation) {
this.nation = nation;
}
#JsonProperty("City")
public String city (String city) {
this.city = city;
}
#JsonProperty("Phone")
public String phone (String phone) {
this.phone = phone;
}
public String toString() {
return ToStringBuilder.reflectionToString(this);
}
testParse.java
Public Class testParse {
List<testParse> test;
ObjectMapper mapper;
protected void setUp() throws IOException {
mapper = new ObjectMapper();
mapper.enable(SerializationFeature.INDENT_OUTPUT();
test = mapper.readValue(this.getClass().getResourcesAsStream("test.json"),
mapper.getTypeFactory().constructCollectionType(List.class, testParse.class));
I need to help first clarifying exactly what the code is doing, and how to put JSON properties (Name, Nationality,City,Phone) into Java.
My understanding is the testTemplate file create the strings in which the properties will be held, then the testParse file has the mapper feature (from Jackson) that reads through the json and puts all into "test" (as an array?)
My goal is in testParse, where if everything thing is in "test", then I read through that, and start to pull it out and place it into a folderList.
public static Map<String, String> userName throws IOException {
Map<String, String> folderList = new TreeMap<>();
//Don't know how, but iterate through "test"
LineIterator it = new LineIterator(//the method used to read the json file);
try {
while(it.hasNext()) {
String line = it.nextLine();
folderList.put(userName,nation) //can I also put city and phone at once as well or should I create another put: folderList.put(userName, city)
return folderList;
How does one do this? Is there a better way to put the properties of json into the folderList after using the jackson mapper?

Actually, testTemplate don't generate anything, what Jackson have done here is just get data from "test.json" as String, then using Reflection read the format of testTemplate.java. Based on template it've just have + setting you add to ObjectMapper object, Jackson will convert test.json to array of object Java.
P/S: you don't need to add annotation in both attributes and get function of POJO class, just do it in get function or attributes only, it's enough for Jackson.

How can I loosen up the naming strategy when deserializing using Jackson?

I've been trying to upgrade the JSON modules to use the FasterXML (2.6.3) versions of Jackson instead of the old Codehaus modules. During the upgrade, I've noticed that the naming strategy differs when using FasterXML instead of Codehaus.
Codehaus was more flexible when it came to the naming strategy. The test below highlights the issue I'm facing with FasterXML. How can I configure the ObjectMapper so it follows the same strategy like Codehaus?
I cannot alter the JSONProperty annotations as there are hundreds of them. I would like the upgrade to be backwards compatible with respect to the naming strategy.
import java.io.IOException;
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.PropertyNamingStrategy;
/*import org.codehaus.jackson.annotate.JsonIgnoreProperties;
import org.codehaus.jackson.annotate.JsonProperty;
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.map.PropertyNamingStrategy;*/
import org.junit.Assert;
import org.junit.Test;
public class JSONTest extends Assert {
#JsonIgnoreProperties(ignoreUnknown = true)
public static class Product {
#JsonProperty(value = "variationId")
private String variantId;
#JsonProperty(value = "price_text")
private String priceText;
#JsonProperty(value = "listPrice")
public String listPrice;
#JsonProperty(value = "PRODUCT_NAME")
public String name;
#JsonProperty(value = "Product_Desc")
public String description;
}
private static final String VALID_PRODUCT_JSON =
"{ \"list_price\": 289," +
" \"price_text\": \"269.00\"," +
" \"variation_id\": \"EUR\"," +
" \"product_name\": \"Product\"," +
" \"product_desc\": \"Test\"" +
"}";
#Test
public void testDeserialization() throws IOException {
ObjectMapper mapper = new ObjectMapper();
mapper.setPropertyNamingStrategy(PropertyNamingStrategy.CAMEL_CASE_TO_LOWER_CASE_WITH_UNDERSCORES);
Product product = mapper.readValue(VALID_PRODUCT_JSON, Product.class);
System.out.println(mapper.writerWithDefaultPrettyPrinter().writeValueAsString(product));
assertNotNull(product.listPrice);
assertNotNull(product.variantId);
assertNotNull(product.priceText);
assertNotNull(product.name);
assertNotNull(product.description);
}
}

#JsonProperty overrides any PropertyNamingStrategy in fasterxml since version 2.4.0. However, yet-to-be-released version 2.7.0 will provide a feature to allow you to opt back in to the old behavior. There is also an unimplemented suggestion to toggle this at the per-annotation level, but that would not really help you.
It appears that Codehaus does apply the PropertyNamingStrategy on top of the #JsonProperty values when mapping, although I can't find any clear docs on that. This appears to have been the behavior in fasterxml before 2.4.0 as well. Here is another example of someone noticing the same difference in behavior.

Although the solution provided by SkinnyJ is perfect for your problem, but if you can't wait till 2.7 is released, you can apply the below hack to get around the problem.
The idea is to transform the incoming JSON to match the attributes in your bean definition. Below code does that. Following points should be noted:
If you are dealing with nested structures, you will have to implement a recursive function to achieve this transformation.
There is a little overhead involved in doing the transformation.
Code:
public class JSONTest extends Assert {
#JsonIgnoreProperties(ignoreUnknown = true)
public static class Product {
#JsonProperty(value = "variationId")
private String variantId;
#JsonProperty(value = "price_text")
private String priceText;
#JsonProperty(value = "listPrice")
public String listPrice;
#JsonProperty(value = "PRODUCT_NAME")
public String name;
#JsonProperty(value = "Product_Desc")
public String description;
}
private static final String VALID_PRODUCT_JSON =
"{ \"list_price\": 289," +
" \"price_text\": \"269.00\"," +
" \"variation_id\": \"EUR\"," +
" \"product_name\": \"Product\"," +
" \"product_desc\": \"Test\"" +
"}";
#Test
public void testDeserialization() throws IOException {
ObjectMapper mapper = new ObjectMapper();
mapper.setPropertyNamingStrategy(PropertyNamingStrategy.CAMEL_CASE_TO_LOWER_CASE_WITH_UNDERSCORES);
//Capture the original JSON in org.json.JSONObject
JSONObject obj = new JSONObject(VALID_PRODUCT_JSON);
JSONArray keys = obj.names();
//New json object to be created using property names defined in bean
JSONObject matchingJson = new JSONObject();
//Map of lowercased key to original keys in incoming json. eg: Prod_id > prodid
Map<String, String> jsonMappings = new LinkedHashMap<String, String>();
for (int i = 0; i < keys.length(); i++) {
String key = lowerCaseWithoutUnderScore(keys.getString(i));
String value = keys.getString(i);
jsonMappings.put(key, value);
}
/*
* Iternate all jsonproperty beans and create new json
* such that keys in json map to that defined in bean
*/
Field[] fields = Product.class.getDeclaredFields();
for (Field field : fields) {
JsonProperty prop = field.getAnnotation(JsonProperty.class);
String propNameInBean = prop.value();
String keyToLook = lowerCaseWithoutUnderScore(propNameInBean);
String keyInJson = jsonMappings.get(keyToLook);
matchingJson.put(propNameInBean, obj.get(keyInJson));
}
String json = matchingJson.toString();
System.out.println(json);
//Pass the matching json to Object mapper
Product product = mapper.readValue(json, Product.class);
System.out.println(mapper.writerWithDefaultPrettyPrinter().writeValueAsString(product));
assertNotNull(product.listPrice);
assertNotNull(product.variantId);
assertNotNull(product.priceText);
assertNotNull(product.name);
assertNotNull(product.description);
}
private String lowerCaseWithoutUnderScore(String key){
return key.replaceAll("_", "").toLowerCase();
}
}

How to deserialize Json with Java from Url [duplicate]

I want to be able to access properties from a JSON string within my Java action method. The string is available by simply saying myJsonString = object.getJson(). Below is an example of what the string can look like:
{
'title': 'ComputingandInformationsystems',
'id': 1,
'children': 'true',
'groups': [{
'title': 'LeveloneCIS',
'id': 2,
'children': 'true',
'groups': [{
'title': 'IntroToComputingandInternet',
'id': 3,
'children': 'false',
'groups': []
}]
}]
}
In this string every JSON object contains an array of other JSON objects. The intention is to extract a list of IDs where any given object possessing a group property that contains other JSON objects. I looked at Google's Gson as a potential JSON plugin. Can anyone offer some form of guidance as to how I can generate Java from this JSON string?

I looked at Google's Gson as a potential JSON plugin. Can anyone offer some form of guidance as to how I can generate Java from this JSON string?
Google Gson supports generics and nested beans. The [] in JSON represents an array and should map to a Java collection such as List or just a plain Java array. The {} in JSON represents an object and should map to a Java Map or just some JavaBean class.
You have a JSON object with several properties of which the groups property represents an array of nested objects of the very same type. This can be parsed with Gson the following way:
package com.stackoverflow.q1688099;
import java.util.List;
import com.google.gson.Gson;
public class Test {
public static void main(String... args) throws Exception {
String json =
"{"
+ "'title': 'Computing and Information systems',"
+ "'id' : 1,"
+ "'children' : 'true',"
+ "'groups' : [{"
+ "'title' : 'Level one CIS',"
+ "'id' : 2,"
+ "'children' : 'true',"
+ "'groups' : [{"
+ "'title' : 'Intro To Computing and Internet',"
+ "'id' : 3,"
+ "'children': 'false',"
+ "'groups':[]"
+ "}]"
+ "}]"
+ "}";
// Now do the magic.
Data data = new Gson().fromJson(json, Data.class);
// Show it.
System.out.println(data);
}
}
class Data {
private String title;
private Long id;
private Boolean children;
private List<Data> groups;
public String getTitle() { return title; }
public Long getId() { return id; }
public Boolean getChildren() { return children; }
public List<Data> getGroups() { return groups; }
public void setTitle(String title) { this.title = title; }
public void setId(Long id) { this.id = id; }
public void setChildren(Boolean children) { this.children = children; }
public void setGroups(List<Data> groups) { this.groups = groups; }
public String toString() {
return String.format("title:%s,id:%d,children:%s,groups:%s", title, id, children, groups);
}
}
Fairly simple, isn't it? Just have a suitable JavaBean and call Gson#fromJson().
See also:
Json.org - Introduction to JSON
Gson User Guide - Introduction to Gson

Bewaaaaare of Gson! It's very cool, very great, but the second you want to do anything other than simple objects, you could easily need to start building your own serializers (which isn't that hard).
Also, if you have an array of Objects, and you deserialize some json into that array of Objects, the true types are LOST! The full objects won't even be copied! Use XStream.. Which, if using the jsondriver and setting the proper settings, will encode ugly types into the actual json, so that you don't loose anything. A small price to pay (ugly json) for true serialization.
Note that Jackson fixes these issues, and is faster than GSON.

Oddly, the only decent JSON processor mentioned so far has been GSON.
Here are more good choices:
Jackson (Github) -- powerful data binding (JSON to/from POJOs), streaming (ultra fast), tree model (convenient for untyped access)
Flex-JSON -- highly configurable serialization
EDIT (Aug/2013):
One more to consider:
Genson -- functionality similar to Jackson, aimed to be easier to configure by developer

Or with Jackson:
String json = "...";
ObjectMapper m = new ObjectMapper();
Set<Product> products = m.readValue(json, new TypeReference<Set<Product>>() {});

Easy and working java code to convert JSONObject to Java Object
Employee.java
import java.util.HashMap;
import java.util.Map;
import javax.annotation.Generated;
import com.fasterxml.jackson.annotation.JsonAnyGetter;
import com.fasterxml.jackson.annotation.JsonAnySetter;
import com.fasterxml.jackson.annotation.JsonIgnore;
import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.annotation.JsonPropertyOrder;
#JsonInclude(JsonInclude.Include.NON_NULL)
#Generated("org.jsonschema2pojo")
#JsonPropertyOrder({
"id",
"firstName",
"lastName"
})
public class Employee {
#JsonProperty("id")
private Integer id;
#JsonProperty("firstName")
private String firstName;
#JsonProperty("lastName")
private String lastName;
#JsonIgnore
private Map<String, Object> additionalProperties = new HashMap<String, Object>();
/**
*
* #return
* The id
*/
#JsonProperty("id")
public Integer getId() {
return id;
}
/**
*
* #param id
* The id
*/
#JsonProperty("id")
public void setId(Integer id) {
this.id = id;
}
/**
*
* #return
* The firstName
*/
#JsonProperty("firstName")
public String getFirstName() {
return firstName;
}
/**
*
* #param firstName
* The firstName
*/
#JsonProperty("firstName")
public void setFirstName(String firstName) {
this.firstName = firstName;
}
/**
*
* #return
* The lastName
*/
#JsonProperty("lastName")
public String getLastName() {
return lastName;
}
/**
*
* #param lastName
* The lastName
*/
#JsonProperty("lastName")
public void setLastName(String lastName) {
this.lastName = lastName;
}
#JsonAnyGetter
public Map<String, Object> getAdditionalProperties() {
return this.additionalProperties;
}
#JsonAnySetter
public void setAdditionalProperty(String name, Object value) {
this.additionalProperties.put(name, value);
}
}
LoadFromJSON.java
import org.codehaus.jettison.json.JSONObject;
import com.fasterxml.jackson.databind.ObjectMapper;
public class LoadFromJSON {
public static void main(String args[]) throws Exception {
JSONObject json = new JSONObject();
json.put("id", 2);
json.put("firstName", "hello");
json.put("lastName", "world");
byte[] jsonData = json.toString().getBytes();
ObjectMapper mapper = new ObjectMapper();
Employee employee = mapper.readValue(jsonData, Employee.class);
System.out.print(employee.getLastName());
}
}

If, by any change, you are in an application which already uses http://restfb.com/ then you can do:
import com.restfb.json.JsonObject;
...
JsonObject json = new JsonObject(jsonString);
json.get("title");
etc.

HashMap keyArrayList = new HashMap();
Iterator itr = yourJson.keys();
while (itr.hasNext())
{
String key = (String) itr.next();
keyArrayList.put(key, yourJson.get(key).toString());
}

Depending on the input JSON format(string/file) create a jSONString. Sample Message class object corresponding to JSON can be obtained as below:
Message msgFromJSON = new ObjectMapper().readValue(jSONString, Message.class);

If you use any kind of special maps with keys or values also of special maps, you will find it's not contemplated by the implementation of google.

What's wrong with the standard stuff?
JSONObject jsonObject = new JSONObject(someJsonString);
JSONArray jsonArray = jsonObject.getJSONArray("someJsonArray");
String value = jsonArray.optJSONObject(i).getString("someJsonValue");

Pass your JSON file in this way, it will return the object.
File file = new File("D:\\Coding\\tickets\\temp.json");
ObjectMapper om = new ObjectMapper();
Profile profile = om.readValue(file, new TypeReference<Profile>() {});

Give boon a try:
https://github.com/RichardHightower/boon
It is wicked fast:
https://github.com/RichardHightower/json-parsers-benchmark
Don't take my word for it... check out the gatling benchmark.
https://github.com/gatling/json-parsers-benchmark
(Up to 4x is some cases, and out of the 100s of test. It also has a index overlay mode that is even faster. It is young but already has some users.)
It can parse JSON to Maps and Lists faster than any other lib can parse to a JSON DOM and that is without Index Overlay mode. With Boon Index Overlay mode, it is even faster.
It also has a very fast JSON lax mode and a PLIST parser mode. :) (and has a super low memory, direct from bytes mode with UTF-8 encoding on the fly).
It also has the fastest JSON to JavaBean mode too.
It is new, but if speed and simple API is what you are looking for, I don't think there is a faster or more minimalist API.

The easiest way is that you can use this softconvertvalue method which is a custom method in which you can convert jsonData into your specific Dto class.
Dto response = softConvertValue(jsonData, Dto.class);
public static <T> T softConvertValue(Object fromValue, Class<T> toValueType)
{
ObjectMapper objMapper = new ObjectMapper();
return objMapper
.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false)
.convertValue(fromValue, toValueType);
}

<!-- GSON -->
<dependency>
<groupId>com.google.code.gson</groupId>
<artifactId>gson</artifactId>
<version>2.8.7</version>
</dependency>
#Test
void readListJsonFromFileTest() throws IOException {
Type type = new TypeToken<List<SimplePojo>>(){}.getType();
String fromJsonFile = readFromJsonFile("json/simplePojoJsonList.json");
List<SimplePojo> pojoList = gson.fromJson(fromJsonFile, type);
Assertions.assertNotNull(pojoList);
}
#Test
void readJsonFromFileTest() throws IOException {
Type type = new TypeToken<SimplePojo>(){}.getType();
String fromJsonFile = readFromJsonFile("json/simplePojoJson.json");
SimplePojo simplePojo = gson.fromJson(fromJsonFile, type);
Assertions.assertNotNull(simplePojo);
}
String readFromJsonFile(String pathToJson) throws IOException {
InputStream resource = new ClassPathResource(pathToJson).getInputStream();
String json = StreamUtils.copyToString(resource, StandardCharsets.UTF_8);
return json;
}