• JSON basics and Liferay API

    Posted on September 26, 2014 by Hamidul Islam in Liferay.

    json

     
    Aim of this Article:
    In this article I will explain the basics of JSON and how we can create JSON using Liferay API.

    Whats JSON:

    • JSON stands for JavaScript Object Notation
    • JSON is lightweight data interchange format
    • JSON is language independent

    JSON
    JSON (JavaScript Object Notation) is a lightweight data-interchange format. It is easy for humans to read and write. It is easy for machines to parse and generate. It is based on a subset of the JavaScript Programming Language, Standard ECMA-262 3rd Edition - December 1999.

    Example of JSON Object:

    
    {"name":"Hamidul Islam","country":"India","phone":"8095185442"}
    
    

    Note

    Note 1: A JSON Object is formed in between {  }

    Note 2: A JSON Object can contains many data. Each data is separated by comma(,). For example in the above example  "name":"Hamidul Islam" is the data.

    Note 3: Each data is consist of key and value pair. In "name":"Hamidul Islam" name is the key and Hamidul Islam is the value.


    Example of JSON Array:

    "persons":[
        {"firstName":"Hamidul", "lastName":"Islam"},
        {"firstName":"John", "lastName":"Abraham"},
        {"firstName":"Raja", "lastName": "Kunal"}
    ];
    

    Note

    Note 1: A [  ] represents JSON Array. In the above example the name of the array is persons

    Note 2: A JSON Array contains multiple Objects. Each object in the array is represented by {  }. In the above example there are 3 JSON Objects inside the array.

     


     

    JSON object creation by JavaScript:

    Anything can not be converted to JSON Object. A string of JSON format can be converted to JSON object by  using  JSON.parse

    <html>
    <body>
    <h2>JSON Object Creation by JavaScript</h2>
    <script>
    
    //Below is the JSON String
    var jsonString = '{"name":"Hamidul Islam","country":"India","phone":"8095185442"}'
    
    //Below is the JSON Object
    var jsonObject = JSON.parse(jsonString);
    
    //Access value from JSON Object
    alert("Value of name:"+jsonObject.name);
    alert("Value of country:"+jsonObject.country);
    </script>
    </body>
    </html>
    

    JSON Array Creation by JavaScript:

    <html>
    <body>
    <h2>JSON Array Creation by JavaScript</h2>
    <script>
    //Create the JSON Array
    var persons = [
        {"firstName":"Hamidul", "lastName":"Islam"},
        {"firstName":"John", "lastName":"Abraham"},
        {"firstName":"Raja", "lastName": "Kunal"}
    ];
    //Access the JSON Object inside the array
    alert("Value of firstName in the first object:"+persons[0].firstName);
    alert("Value of lastName in the first object:"+persons[0].lastName);
    </script>
    </body>
    </html>
    

    Note: While creating JSON Array don't use JSON.parse

    Liferay API to create JSON Object:

    Consider we need to create JSON object like {"name":"Hamidul Islam","country":"India"}. This can be done in 2 ways

    First Option:

    JSONObject jsonObject =  JSONFactoryUtil.createJSONObject();
    jsonObject.put("name", "Hamidul Islam");
    jsonObject.put("country", "India");
    

    Second Option:

    String jsonString = "{'name':'Hamidul Islam','country':'India'} ";
    JSONObject jsonObject = JSONFactoryUtil.createJSONObject(jsonString);
    

    Liferay API to create JSON Array:

    Suppose we want to create a JSON Array

     [{"name":"Hamidul Islam","country":"India"},{"name":"Jacob","country":"Canada"},{"name":"Smith","country":"US"}]

    Below is the code

    JSONArray jsonArray = JSONFactoryUtil.createJSONArray();
    JSONObject jsonObject1 = JSONFactoryUtil.createJSONObject("{'name':'Hamidul Islam','country':'India'}");
    JSONObject jsonObject2 = JSONFactoryUtil.createJSONObject("{'name':'Jacob','country':'Canada'}");
    JSONObject jsonObject3 = JSONFactoryUtil.createJSONObject("{'name':'Smith','country':'US'}");
    jsonArray.put(jsonObject1);
    jsonArray.put(jsonObject2);
    jsonArray.put(jsonObject3);
    

    Below are the imports

    com.liferay.portal.kernel.json.JSONArray
    com.liferay.portal.kernel.json.JSONFactory
    com.liferay.portal.kernel.json.JSONObject
    com.liferay.portal.kernel.json.JSONFactoryUtil
    

    http://www.w3schools.com/json/

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