Json

JSON stands for JavaScript Object Notation. It is a lightweight text-based interchange format which is language indepent.

It looks like next :

{
   "book": [
      {
         "id":1,
         "language": null,
         "edition": true,
         "author": {"name":"abc"}
      },
      {
         "id":7,
         "language": "C++", 
         "edition": false,
         "author": {"name":"def"}
      }
   ]
}

JSON is key-value pair, key has to be string, while value has following types:

type	remark
Number	double precision floating point
String
Boolean	true or false
Array	it begins with [ and ends with ]
Object	it begins with { and ends with }
null

In JavaScript, we can create json object like

var books = {
              "Pascal" : [ 
                { "Name"  : "Pascal Made Simple", "price" : 700 },
                { "Name"  : "Guide to Pascal", "price" : 400 }
              ],  
              "Scala"  : [
                { "Name"  : "Scala for the Impatient", "price" : 1000 }, 
                { "Name"  : "Scala in Depth", "price" : 1300 }
              ]    
            } 
         
for(i = 0;i<books.Pascal.length;i++){
      books.Pascal[i].Name+"</td></tr>");
           
}

And there are JSON.parse()/JSON.stringify() to convert json from/to js object.

If we want to merge two json, then we can use jQuery extend like jQuery.extend(true, json, newJson), this will merge newJson into json.

In java, there are some 3rd library to do convertion, e.g. Gson, Jackson.

For Gson, its code as follows

Gson gson = new Gson();
JsonObject json = gson.fromJson(gson.toJson(c), JsonObject.class);
System.out.println(json.get("name").getAsString());

Written on July 20, 2017