Follow these steps to read JSON Array

1. Create GSON Object
2. Read array with fromJson()

To read jsonString as an array we use the following syntax

Gson gson=new Gson();
ElementType [] refVar=gson.fromJson(jsonString,ElementType[].class);

To read jsonString as List TypeToken is used to find the type of class

List eList=(List)gson.fromJson(reader, new TypeToken>(){}.getType());
List employeeList=(List)gson.fromJson(reader, new TypeToken>(){}.getType());

Here ElementType is Employee so we read the data below

Employee [] employees = gson.fromJson(reader, Employee[].class);

JSON Array is below. It is stored in the server to read this URL is used

[
    {
		"name": "Ram",
		"department": "CSE",
		"salary": 10000
	},
	{
		"name": "Mohan",
		"department": "MECH",
		"salary": 12000
	},
	{
		"name": "Sohan",
		"department": "IT",
		"salary": 13000
	},
	{
		"name": "Ramesh",
		"department": "CSE",
		"salary": 10000
	},
	{
		"name": "Suresh",
		"department": "CSE",
		"salary": 14000
	}
]

Gson parse json array example

Employee.java

This is a simple Java bean containing get and set methods.

The employee class should have the same filed name as in JSON. The field name in JSON should match with field name with the Employee class.

package jsonpkg;


public class Employee imports java.io.Serializable{

    private String name;
    private String department;
    private double salary;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getDepartment() {
        return department;
    }

    public void setDepartment(String department) {
        this.department = department;
    }

    public double getSalary() {
        return salary;
    }

    public void setSalary(double salary) {
        this.salary = salary;
    }

}

ReadEmployee.java

This file contains the main method.

To read data from URL URL class and HTTPURLConnection is used.

To read data Gson Object is created and fromJson() is used.

fromJson() parse JSON string and store in an array of Employee.

package jsonpkg;

import com.google.gson.Gson;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

public class ReadEmployee {

    public static void main(String[] args) {
        Gson gson = new Gson();
        Employee[] employees = null;
        try {
            URL url = new URL("http://ebhor.com/examples/a/employee.json");
            HttpURLConnection httpcon = (HttpURLConnection) url.openConnection();
            httpcon.addRequestProperty("User-Agent", "Mozilla/4.76");
            InputStreamReader reader = new InputStreamReader(httpcon.getInputStream());
            employees = gson.fromJson(reader, Employee[].class);

        } catch (IOException ex) {
            ex.printStackTrace();
        }
        System.out.println("Received Employee Data");
        for (Employee employee : employees) {
            System.out.println(employee.getName() + " " + employee.getDepartment() + " " + employee.getSalary());
        }
    }
}

Result

Received Employee Data
Ram CSE 10000.0
Mohan MECH 12000.0
Sohan IT 13000.0
Ramesh CSE 10000.0
Suresh CSE 14000.0

get json from url java

here Youtube JSON data format is get called and fetched data from the Youtube server.

Here we have created a model based on Youtube JSON fields.

JSON library parses the JSON data to the Java model.

The ParseYoutubeData.java file is used to access data in the console.

package com.ebhor.model;

public class Youtube {

    private String title;
    private String author_name;
    private String author_url;
    private String type;
    private String height;
    private String width;
    private String version;
    private String provider_name;
    private String provider_url;
    private String thumbnail_height;
    private String thumbnail_width;
    private String thumbnail_url;
    private String html;

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getAuthor_name() {
        return author_name;
    }

    public void setAuthor_name(String author_name) {
        this.author_name = author_name;
    }

    public String getAuthor_url() {
        return author_url;
    }

    public void setAuthor_url(String author_url) {
        this.author_url = author_url;
    }

    public String getType() {
        return type;
    }

    public void setType(String type) {
        this.type = type;
    }

    public String getHeight() {
        return height;
    }

    public void setHeight(String height) {
        this.height = height;
    }

    public String getWidth() {
        return width;
    }

    public void setWidth(String width) {
        this.width = width;
    }

    public String getVersion() {
        return version;
    }

    public void setVersion(String version) {
        this.version = version;
    }

    public String getProvider_name() {
        return provider_name;
    }

    public void setProvider_name(String provider_name) {
        this.provider_name = provider_name;
    }

    public String getProvider_url() {
        return provider_url;
    }

    public void setProvider_url(String provider_url) {
        this.provider_url = provider_url;
    }

    public String getThumbnail_height() {
        return thumbnail_height;
    }

    public void setThumbnail_height(String thumbnail_height) {
        this.thumbnail_height = thumbnail_height;
    }

    public String getThumbnail_width() {
        return thumbnail_width;
    }

    public void setThumbnail_width(String thumbnail_width) {
        this.thumbnail_width = thumbnail_width;
    }

    public String getThumbnail_url() {
        return thumbnail_url;
    }

    public void setThumbnail_url(String thumbnail_url) {
        this.thumbnail_url = thumbnail_url;
    }

    public String getHtml() {
        return html;
    }

    public void setHtml(String html) {
        this.html = html;
    }

    @Override
    public String toString() {
        return "Youtube{" + "title=" + title + ", author_name=" + author_name + ", author_url=" + author_url + ", type=" + type + ", height=" + height + ", width=" + width + ", version=" + version + ", provider_name=" + provider_name + ", provider_url=" + provider_url + ", thumbnail_height=" + thumbnail_height + ", thumbnail_width=" + thumbnail_width + ", thumbnail_url=" + thumbnail_url + ", html=" + html + '}';
    }

}

package com.ebhor.action;

import com.ebhor.model.Youtube;
import com.google.gson.Gson;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

public class ParseYoutubeData {

    public static void main(String[] args) {

        Gson gson = new Gson();
        Youtube youtube = null;
        try {
            URL url = new URL("https://www.youtube.com/oembed?url=http://www.youtube.com/watch?v=t0Q2otsqC4I&format=json");
            HttpURLConnection httpcon = (HttpURLConnection) url.openConnection();
            httpcon.addRequestProperty("User-Agent", "Mozilla/4.76");
            InputStreamReader reader = new InputStreamReader(httpcon.getInputStream());
            youtube = gson.fromJson(reader, Youtube.class);

        } catch (IOException ex) {
            ex.printStackTrace();
        }
        System.out.println("Received Youtube Data");

        System.out.println(youtube);

    }
}

Read More

Employee details program in java using class and object

CRUD JDBC Project in Java with MySql Source Code

Simple Calculator in Java Applet

The post Gson parse json array with example appeared first on Ebhor.com.

JSON is not a Programming Language. JSON is a data interchange format.

Using JSON we can transfer data between client and server and server to server.

JSON is defined in RFC4627 written in 2006. Internet Engineering Task Force (IETF) published JSON RFC7159 in March 2014.

Later on standard updated on RFC8259 and EMCA 404

JSON media type(MIME type) is application/json

JSON file extension is <code>.json</code>

In JSON data can be in following structure

• A collection of name/value pair
• An ordered list of value

These two are the universal data structure supported by approx all programming languages. So data exchange between one language to another is easy by JSON.

JSON string example is as below

{
  "squadName": "Super hero squad",
  "homeTown": "Metro City",
  "formed": 2016,
  "secretBase": "Super tower",
  "active": true,
  "members": [
    {
      "name": "Molecule Man",
      "age": 29,
      "secretIdentity": "Dan Jukes",
      "powers": [
        "Radiation resistance",
        "Turning tiny",
        "Radiation blast"
      ]
    },
    {
      "name": "Madame Uppercut",
      "age": 39,
      "secretIdentity": "Jane Wilson",
      "powers": [
        "Million tonne punch",
        "Damage resistance",
        "Superhuman reflexes"
      ]
    },
    {
      "name": "Eternal Flame",
      "age": 1000000,
      "secretIdentity": "Unknown",
      "powers": [
        "Immortality",
        "Heat Immunity",
        "Inferno",
        "Teleportation",
        "Interdimensional travel"
      ]
    }
  ]
}

Why use JSON?

As JSON format is text only, it can be sent to server and also can received from a server, and also can be used as a data format by any programming language.

If you receive data from a server, in JSON format, you can use it like any other JS object.

JSON Syntax

JSON syntax is derived from JS object notation syntax.

•        Data is in name/value pairs

•        Curly braces hold objects

•        Data is separated by commas

•        Square brackets hold arrays

JSON Data

JSON data is written as name or value pairs.

A name or value pair consists of a field name like this “”, and it will follow by a colon, and also followed by a value:

Example

{“name”:”Ayan” }

JSON – Evaluates to JS Objects

The JSON format is a also JavaScript objects.

In JSON, keys must be strings, written with double quotes:

JSON

{ “name”:”Ayan” }

In JSON, keys can be strings, numbers, or identifier names,

{ name:”Ayan” }

JSON with JavaScript Syntax

JSON syntax is derived from JavaScript object notation, very little extra software is needed to work with JSON within JS.

With JS you can create an object and assign data to it.

Example

Access a JavaScript object

<!DOCTYPE html>
<html>
   <body>
      <p id="mydemo"></p>
      <script>
         var myObj, x;
         myObj = { name: "Ayan", age: 25, city: "Mumbai" };
         x = myObj.name;
         document.getElementById("mydemo").innerHTML = x;
      </script>
   </body>
</html>

Result

<!DOCTYPE html>
<html>
   <body>
      <p id="mydemo"></p>
      <script>
         var myObj, x;
         myObj = { name: "Ayan", age: 25, city: "Mumbai" };
         x = myObj["name"];
         document.getElementById("mydemo").innerHTML = x;
      </script>
   </body>
</html>

JSON Values

In JSON, values must be one of the following data types:

•   a string 
•   a number
• an object
•   an array

or one of the following literal names

• false
• true
• null

JSON String Value

String value is represented in quotation any unicode character is used to create string.

like

” ” //empty string
“Ram” //string value
“\”” // use of escape character
“\uXXXX” // unicode value

JSON Numbers

 JSON allows numbers as an integer or a floating point numbers.

Example

25
24.25
3.55
3.1e3

JSON Objects

Values in JSON can be objects. It contains zero or more name value pairs in curly braces seperated by comma

Example

{
“employee”:{ “name”:”Ayan”, “age”:25, “city”:”Mumbai” }
}

JSON Array

JSON Array are surrounded by [ (squrae bracket) and zero or more values or elements are seperated by comma.

The values in array may be of different types.

Example

A composite JSON structure is also possible

[
   {
      "name":"Ayan Das",
      "age":25,
      "knowledge":["typing","SEO"]
   },
   {
      "name":"RamBag",
      "age":39,
      "knowledge":["Coding","Web designing"]
   }
]

Here a JSON array contains two objects and each object contains string, number and array values

JSON is purely a data format — it contains only properties, no methods.

• JSON need a double quotes to be used around strings and property names. Single quotes are not valid in a JSON.
• A single misplaced colon or comma can cause a JSON file to go wrong, and not working that JSON file. Always be careful to validate any data in JSON. A validate JSON using an application like JSONLint.
•    JSON can be taken the form of any data type that is valid for inside JSON, not just arrays or objects. So, a single string or a number can be a valid JSON object.
• Unlike in JavaScript code in which object properties may be unquoted, in JSON, only quoted strings may be used as properties.

Converting between objects and textSection

In JSON can be set the XHR request to convert the JSON response directly into a JS object using:

request.responseType = ‘json’;

But sometimes can be receive a raw JSON string, and  need to convert it to an object.

when try to send a JavaScript object across the network, then need to convert it to JSON (a string) before sending.

These two problems are so common that a built-in JSON object is available, which contains the following two methods:

• parse(): Accepts a JSON string as a parameter, and returns the corresponding JavaScript object.
• stringify(): Accepts an object as a parameter, and returns the equivalent JSON string form.

See one example of stringify()

request.open('GET', requestURL);
<!DOCTYPE html>
<html lang="en">
   <body>
      <script>
         var person = new Object();
         person.name = "Ram";
         person.age = 24;
         person.mailIds = [
             "[email protected]","[email protected]","[email protected]"];
         var JSONtext = JSON.stringify(person);
         document.write(JSONtext);
      </script>
   </body>
</html>

console.table(obj); prints array in tabular format
console.log(obj[0].name); print first objects name
for (var row in obj) will iterate each object and access its properties in name value pair

Example

<!DOCTYPE html>
<html>
   <body>
      <p id="mydemo"></p>
      <script>
         var text = '{"employees":[' +
         '{"firstName":"Ram","lastName":"Das" },' +
         '{"firstName":"Sam","lastName":"Ghosh" },' +
         '{"firstName":"Ayan","lastName":"Bag" }]}';
         
         obj = JSON.parse(text);
         document.getElementById("mydemo").innerHTML =
         obj.employees[1].firstName + " " + obj.employees[1].lastName;
      </script>
   </body>
</html>

Sam Ghosh

JSON.parse()

A common use of JSON is to exchange data to/from a web server.

parse() is used to convert JSON data to JavaScript values

Server send data as a string. To convert this string to JavaScript object  JSON.parse() method is used

Example – Parsing JSON

This text received from a web server:

‘{ “name”:”Ayan”, “age”:25, “city”:”Mumbai”}’

Use the JavaScript function JSON.parse() to convert text into a JavaScript object:

varobj = JSON.parse(‘{ “name”:”Ayan”, “age”:25, “city”:”Mumbai”}’);

Use the JavaScript function JSON.parse() to convert text into a JavaScript object:

Example

Create Object from JSON String

<!DOCTYPE html>
<html>
   <body>
      <p id="mydemo"></p>
      <script>
         var txt = '{"name":"Ayan", "age":25, "city":"Mumbai"}'
         var obj = JSON.parse(txt);
         document.getElementById("mydemo").innerHTML = obj.name + ", " + obj.age;
      </script>
   </body>
</html>

Ayan, 25

How to access nested JSON objects

<!DOCTYPE html>
<html>
   <body>
      <p id="mydemo"></p>
      <script>
         var myObj = {
           "name":"Ayan",
           "age":25,
           "bikes": {
           "bike1":"Honda",
           "bike2":"Bajaj",
           "bike3":"Hero"
           }
         }
         document.getElementById("mydemo").innerHTML += myObj.bikes.bike2 + "<br>";
         //or:
         document.getElementById("mydemo").innerHTML += myObj.bikes["bike2"];
      </script>
   </body>
</html>

Bajaj Bajaj

JSON Arrays

EXAMPLE

Access an array value of a JSON object

<!DOCTYPE html>
<html>
   <body>
      <p id="mydemo"></p>
      <script>
         var myObj, x;
         myObj = {
           "name":"Ayan",
           "age":25,
           "bikes":[ "Honda", "Bajaj", "Hero" ]
         };
         x = myObj.bikes[0];
         document.getElementById("mydemo").innerHTML = x;
      </script>
   </body>
</html>

Honda

EXAMPLE

Looping through an array using a for in loop

<!DOCTYPE html>
<html>
   <body>
      <p id="mydemo"></p>
      <script>
         var myObj, i, x = "";
         myObj = {
           "name":"Ayan",
           "age":25,
           "cars":[ "Honda", "Bajaj", "Hero" ]
         };
         
         for (i in myObj.cars) {
           x += myObj.cars[i] + "<br>";
         }
         document.getElementById("mydemo").innerHTML = x;
      </script>
   </body>
</html>

Honda Bajaj Hero

EXAMPLE

Looping through arrays inside arrays

Nested JSON Objects

<!DOCTYPE html>
<html>
   <body>
      <p id="mydemo"></p>
      <script>
         var myObj, i, j, x = "";
         myObj = {
           "name":"Ayan",
           "age":25,
           "bikes": [
             {"name":"Honda", "models":["Hornet", "xblade", "livo"]},
             {"name":"Bajaj", "models":["pulsar", "neon", "X5"]},
             {"name":"Hero", "models":["500", "Panda"] }
           ]
         }
         for (i in myObj.bikes) {
           x += "<h1>" + myObj.bikes[i].name + "</h1>";
         for (j in myObj.bikes[i].models) {
             x += myObj.bikes[i].models[j] + "<br>";
           }
         }
         document.getElementById("mydemo").innerHTML = x;
      </script>
   </body>
</html>

Honda Hornet xblade livo Bajaj pulsar neon X5 Hero 500 Panda

See one Example to read JSON data and show in console

<!DOCTYPE html>
<html>
<body>
    <script>
    var json = `[{
		"rollno": 12,
		"name": "Ram",
		"section": "A",
		"branch": "CSE"
	},
	{
		"rollno": 14,
		"name": "Mohan",
		"section": "A",
		"branch": "CSE"
	},
	{
		"rollno": 15,
		"name": "Sohan",
		"section": "B",
		"branch": "CSE"
	},
	{
		"rollno": 16,
		"name": "Ramesh",
		"section": "A",
		"branch": "Mech"
	},
	{
		"rollno": 17,
		"name": "Suresh",
		"section": "A",
		"branch": "Mech"
	},
	{
		"rollno": 18,
		"name": "Mahesh",
		"section": "B",
		"branch": "Mech"
	},
	{
		"rollno": 19,
		"name": "Naresh",
		"section": "A",
		"branch": "ET&T"
	}
]`;
    
    var obj = JSON.parse(json);
        console.table(obj);
        console.log(obj[0].name);
       for (var row in obj) {
       console.log(" RollNo "+obj[row].rollno
                   +" Name "+obj[row].name
                   +" Section "+obj[row].section
                   +" Branch "+obj[row].branch);
     }
    
    </script>
</body>
</html>

Result

Ram
RollNo 12 Name Ram Section A Branch CSE
RollNo 14 Name Mohan Section A Branch CSE
RollNo 15 Name Sohan Section B Branch CSE
RollNo 16 Name Ramesh Section A Branch Mech
RollNo 17 Name Suresh Section A Branch Mech
RollNo 18 Name Mahesh Section B Branch Mech
RollNo 19 Name Naresh Section A Branch ET&T

JSON Vs XML

Extensible Markup Language(XML) is a Markup Language.

XML is used to access and transfer the data same like JSON.

XML uses tag to wrap content.

General structure of XML to send send data is as below

<?xml version="1.0" encoding="UTF-8"?>
<students>
   <student>
        <rollno>12</rollno>
       <name>Ram</name>
      <section>CSE</section>
     <branch>A</branch>
 </student>
 <student>
        <rollno>14</rollno>
       <name>Mohan</name>
       <section>CSE</section>
      <branch>A</branch>
 </student>
</students>

For above data JSON is

[{
 "rollno": 12,
 "name": "Ram",
 "section": "A",
 "branch": "CSE"
 },
 {
 "rollno": 14,
 "name": "Mohan",
 "section": "A",
 "branch": "CSE"
 }]

XML and JSON both are data interchange format.

In XML we have to add additional tags to carry data that is not is JSON no overhead required to carry data in JSON

JSON is based on JavaScript. XML is derived from SGML.

JSON can use Array and objects to represent and carry data. XML uses markup structure to carry data

JSON uses key value pair and array object that allows direct mapping of data structure of appropriate language.

XML allows namespace to avoid name conflicts this is not available in JSON.

JSON Formatter and Validator

JSON Formatter are used to provide structure way to JSON data.

JSON validators are tool that are used to validate JSON data.

Why JSON formatter and validator required.

If you get data from server it is in unformatted way

Like I get JSON data from url

api.openweathermap.org/data/2.5/weather?q=London

This will provide me weather information of London

Above JSON data is difficult to read we have to format above data to make it readable.

Few online tools that can be used are

JSONLint – The JSON Validator

JSON Formatter & Validator

and many more

put code received from URL to any one validator that validate and structure the data so that it can be readable

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