JSON Learning Notes

Time: 2017-1-1-22:25

--What is JSON

JSON (JavaScript Object Notation) is a lightweight data interchange format.
JSON is a string representation of a JavaScript object, such as a JSON-formatted string that can be sent to the client in a servlet, and JavaScript can execute the string to get a JavaScript object.

XML can also be used as a data interchange format.

--json Object Syntax

JSON syntax:
1) data in key-value pairs
2) data separated by commas
3) Save the object with curly braces
4) square brackets to save the array

JSON value:
1) number (integer or floating point)
2) string (in double quotes)
3) Logical value (TRUE or FALSE)
4) Array (in square brackets)
5) object (in curly braces)
6) NULL

Apply JSON:
var person = {' name ': ' Zhangsan ', ' age ': ' A ', ' sex ': ' Male '};
Alert (Person.name + "," + Person.age + "," + person.sex);

Note: Key also needs to be in double quotes.

Comparison of--json and XML

1. Readability: XML wins
2, decoding difficulty: JSON itself is the JS object (Pro-son), so much simpler
3, Popularity: XML has been popular for many years, but in the field of Ajax, JSON is more popular

--Convert a Java object to a JSON object

Apache provides a json-lib gadget that makes it easy to use the Java language to create JSON strings, or to convert JavaBean into strings.

1. Json-lib Core JAR Package
* Json-lib.jar

2, Json-lib dependent jar Package
* Commons-lang.jar
* Commons-beanutils.jar
* Commons-logging.jar
* Commons-collections.jar
* Ezmorph.jar

3, the core class in Json-lib
* Jsonobject
> itself is a map
> ToString () method to get a JSON string
> Jsonobject map = jsonobject.fromobject (person);
Convert Objects to Jsonobject objects

* Jsonarray
> itself is a list
> ToString () method to get a JSON string
> Jsonarray list = jsonarray.fromobject (list)
Convert list to Jsonarray object

=============================================================================

Code:

Import Java.util.arraylist;import java.util.List; Import Net.sf.json.jsonarray;import Net.sf.json.JSONObject; Import Org.junit.Test;        /** * Demo Json-lib Gadget * * @author WYC * */public class Demo {/* * as Map with */@Test public void fun1 () {        Jsonobject map = new Jsonobject ();        Map.put ("name", "Zhangsan");         Map.put ("Age", 20);    System.out.println (Map.tostring ()); }

Output:
{"Name": "Zhangsan", "Age": 20}
--------------------------------------------------------------------------------------------------------------- -------------/* * When a person object is already in place, you can convert person to Jsonobject object to use */@Test public void fun2 () {Perso         n p = new person ("Zhangsan", 21);        /* * Convert object to jsonobject type */jsonobject map = Jsonobject.fromobject (p);    SYSTEM.OUT.PRINTLN (map); }

Output:
{"Name": "Zhangsan", "Age": 21}
--------------------------------------------------------------------------------------------------------------- -------------/* * Jsonarray */@Test public void Fun3 () {person P1 = new Person ("Zhangsan", 22)        ;         person P2 = new Person ("Lisi", 23);        Jsonarray list = new Jsonarray ();        List.add (p1);        List.add (p2);    SYSTEM.OUT.PRINTLN (list); }

Output:
[{' name ': ' Zhangsan ', ' age ': 22},{' name ': ' Lisi ', ' age ': 23}]
--------------------------------------------------------------------------------------------------------------- -------------/* * There is a list that needs to convert the list to Jsonarray */@Test public void Fun4 () {person P1 = new P        Erson ("Zhangsan", 22);         person P2 = new Person ("Lisi", 23);        list<person> list = new arraylist<person> ();        List.add (p1);        List.add (p2);    System.out.println (Jsonarray.fromobject (list)); }}

Output:
[{' name ': ' Zhangsan ', ' age ': 22},{' name ': ' Lisi ', ' age ': 23}]

JSON Learning notes