JSON parsing tool-org.json use tutorial

First, Introduction  

Org.json is a commonly used JSON parsing tool in Java, mainly providing jsonobject and Jsonarray classes, which are now explained by the use of each class .  

Second, prepare  

1. before using Org.json, we should start with the URL https://github.com/douglascrockford/ Json-java Download Org.json source code, and add the source to eclipse, you can call .  

2. View the relevant API documentation, visit:https://github.com/douglascrockford/ Json-java.  

Third, the explanation :  

1.JSONObject:  

• is an unordered collection of key / value pairs .  

• Its representation is a string wrapped in curly braces, separated by a colon between the key and the value, separated by a comma between the key value and the key value . Span class= "Normaltextrun SCX229584015".  

• Intrinsic form is a use get () and opt () methods access values by key, and use put Span class= "Normaltextrun SCX229584015" > () methods use keys to add or replace objects with values  

• values can be any of these types: Boolean,jsonarray,jsonobject,number and string, or Josonobject.null objects.  

The code demonstrates the following :  

public static void Jsonobjecttest () {jsonobject-jsonobj = new Jsonobject ("{' Name ': ' Xiazdong ', ' age ': +}");     String name = jsonobj.getstring ("name"); int age = Jsonobj.getint ("Age");     

Note: Jsonobject has many optxxx methods, such as Optboolean, optstring, optint...  

What they mean is that if the Jsonobject has this property, it returns this property, otherwise it returns a default value .  

2.JSONArray:  

• is an ordered sequence value .  

• It behaves as a string wrapped in square brackets, separated by commas between values and values .  

• Intrinsic form is a use get () and opt () methods access values by index, and use put Span class= "Normaltextrun SCX229584015" > () method to add or modify the value of the object . Span class= "Normaltextrun SCX229584015".  

• The values can be any of these types: Boolean,jsonarray,jsonobject,number, and string, or Jsonobject.null object.  

The code demonstrates the following :  

public static void Jsonarraytest () {Jsonarray Jsonarray = new Jsonarray ("[{' Name ': ' Xiazdong ', ' age ': 20},{' name ': ' Xzdong ', ' Age ': 15}] "); for (int i = 0; i < jsonarray.length (); i++) {Jsonobject jsonobj = Jsonarray.getjsonobject (i);         String name = jsonobj.getstring ("name");         int age = Jsonobj.getint ("Age");         System.out.println ("name =" + Name + ", age =" + age ");     

the nested jsonobject and Jsonarray codes are shown below :  

public static void Jsonobjectandarraytest () {String jsonstring = ' {' name ': ' Xiazdong ', ' age ': ' The ' book ': [' Book1 ', ' Book2 ' ]}"; Jsonobject jsonobj = new Jsonobject (jsonstring);      String name = jsonobj.getstring ("name"); System.out.println ("name" + ":" + name);      int age = Jsonobj.getint ("Age");     System.out.println ("Age" + ":" + age);  Jsonarray Jsonarray = Jsonobj.getjsonarray ("book"); for (int i = 0; i < jsonarray.length (); i++) {         String book = jsonarray.getstring (i); System.out.println ("book" + i + ":" + book);     }   

3.JSONStringer:  

• is a tool for quickly constructing JSON text  

• Subclass of Jsonwriter  

• bject () : {; enobject (): End an object, add  

•  array (): Start an array, that is, add [;  endarray (): End an array, add  

• Key (): indicates adding a key;value(): means adding a value  

The code demonstrates the following :  

public static void Jsonstringertest () {Jsonstringer stringer = new Jsonstringer ();      

load JSON format to write a demo ( Printwriter+jsonstringer can write to JSON file ):  

public static void JsonStringerTest2 () throws FileNotFoundException {Jsonstringer Jsonstringer = new Jsonstringer ();     Jsonobject obj6 = new Jsonobject (); Obj6.put ("title", "Book1"). Put ("Price", "$11");     Jsonobject obj3 = new Jsonobject (); Obj3.put ("book", Obj6);  Obj3.put ("Author", New Jsonobject (). Put ("name", "Author-1"));     Jsonobject obj5 = new Jsonobject (); Obj5.put ("title", "Book2"). Put ("Price", "$22");     Jsonobject obj4 = new Jsonobject ();  Obj4.put ("book", Obj5);  Obj4.put ("Author", New Jsonobject (). Put ("name", "Author-2"));     Jsonarray obj2 = new Jsonarray ();  Obj2.put (OBJ3). put (OBJ4);     Jsonobject obj1 = new Jsonobject ();     Obj1.put ("title", "book");      Obj1.put ("Signing", OBJ2);     Jsonstringer.object (). Key ("session"). Value (obj1). EndObject ();  System.out.println (Jsonstringer.tostring ()); PrintWriter out = new PrintWriter (New FileOutputStream ("1.txt"));     Out.println (Jsonstringer.tostring ()); Out.close ();  } 

4.jsontokener

• It is used with Jsonobject and Jsonarray constructors to parse the JSON source string  

The code is shown below (Jsonobject+jsontokener can get JSON-formatted text objects ):  

public static void Jsontokenertest () throws FileNotFoundException {     Jsonobject jsonobj = new Jsonobject (New Jsontoken ER (new FileReader (New File ("1.txt")));     

Note: In Java, a JSON-formatted string is best represented by single quotation marks  

JSON parsing tool-org.json use tutorial