Android JSON gson Parsing

What is JSON:

JavaScript Object Notation is a lightweight data exchange format.

Differences from XML:

+ JSON is smaller than XML in size.

+ More convenient interaction between JSON and JavaScript

+ JSON is much faster than XML.

+ JSON is less descriptive than XML.

JSON structure:

(1) object: unordered "'name/value' pair" set. An object starts with "{" and ends. Each "name" is followed by a ":", and "," is used to separate the "name/value" pairs.
(2) array: an ordered set of values. An array ends with "[" and. Values are separated by commas. Values can be string, number, true, false, null, object, or array enclosed by double quotation marks ). These structures can be nested.

Gson method: array <---> JSON

int[] numbers = {1, 1, 2, 3, 5, 8, 13};String[] days = {"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"};Gson gson = new Gson();String numbersJson = gson.toJson(numbers);String daysJson = gson.toJson(days);System.out.println("numbersJson = " + numbersJson);//numbersJson = [1,1,2,3,5,8,13]System.out.println("daysJson = " + daysJson);//daysJson = ["Sun","Mon","Tue","Wed","Thu","Fri","Sat"]int[] fibonacci = gson.fromJson(numbersJson, int[].class);String[] weekDays = gson.fromJson(daysJson, String[].class);

Set <---> JSON

List<String> names = new ArrayList<String>();names.add("Alice");names.add("Bob");names.add("Carol");names.add("Mallory");Gson gson = new Gson();String jsonNames = gson.toJson(names);//jsonNames = ["Alice","Bob","Carol","Mallory"]Student a = new Student("Alice", "Apple St", new Date(2000, 10, 1));Student b = new Student("Bob", "Banana St", null);Student c = new Student("Carol", "Grape St", new Date(2000, 5, 21));Student d = new Student("Mallory", "Mango St", null);List<Student> students = new ArrayList<Student>();students.add(a);students.add(b);students.add(c);students.add(d);gson = new Gson();String jsonStudents = gson.toJson(students);//[{"name":"Alice","address":"Apple St","dateOfBirth":"Nov 1, 3900 12:00:00 AM"},{"name":"Bob","address":"Banana St"},{"name":"Carol","address":"Grape St","dateOfBirth":"Jun 21, 3900 12:00:00 AM"},{"name":"Mallory","address":"Mango St"}]Type type = new TypeToken<List<Student>>(){}.getType();List<Student> studentList = gson.fromJson(jsonStudents, type);Map<--->JsonMap<String, String> colours = new HashMap<String, String>();colours.put("BLACK", "#000000");colours.put("RED", "#FF0000");colours.put("GREEN", "#008000");colours.put("BLUE", "#0000FF");colours.put("YELLOW", "#FFFF00");colours.put("WHITE", "#FFFFFF");Gson gson = new Gson();String json = gson.toJson(colours);//{"WHITE":"#FFFFFF","BLUE":"#0000FF","YELLOW":"#FFFF00","GREEN":"#008000","BLACK":"#000000","RED":"#FF0000"}Type type = new TypeToken<Map<String, String>>(){}.getType();Map<String, String> map = gson.fromJson(json, type);for (String key : map.keySet()) {    System.out.println("map.get = " + map.get(key));}

Object <---> JSON

Student student = new Student("Duke", "Menlo Park", dob.getTime());Gson gson = new Gson();String json = gson.toJson(student);//{"name":"Duke","address":"Menlo Park","dateOfBirth":"Feb 1, 2000 12:00:00 AM"}Gson gson = new Gson();Student student = gson.fromJson(json, Student.class);

Nested Parsing

Package test0328; import Java. util. arrays; public class person {/** {"phone": ["112233", "445566"], // array "name": "android ", // string "Age": 5, // value "Address": {"country": "China", "Province": "Shanghai "}, // object "married": false // Boolean value}, **/private string [] Phone;/*** @ return the address */Public Address getaddress () {return address;}/*** @ Param address * the address to set */Public void setaddress (Address) {This. address = address;} private string name; private int age; private Address = NULL; private Boolean married;/*** @ return the phone */Public String [] getphone () {return phone;}/*** @ Param phone * the phone to set */Public void setphone (string [] Phone) {This. phone = phone;}/** (non-javadoc) ** @ see Java. lang. object # tostring () */@ overridepublic string tostring () {return "person [Phone =" + arrays. tostring (phone) + ", name =" + name + ", age =" + age + ", address =" + address + ", married = "+ Married +"] ";}/*** @ return the name */Public String getname () {return name ;} /*** @ Param name * the name to set */Public void setname (string name) {This. name = Name;}/*** @ return the age */Public int getage () {return age ;} /*** @ Param age * the age to set */Public void setage (INT age) {This. age = age;}/*** @ return the married */Public Boolean ismarried () {return married ;} /*** @ Param married * The Married To Set */Public void setmarried (Boolean married) {This. married = married ;}}

Package test0328; public class address {// "Address": {"country": "China", "Province": "Shanghai"}, // object private string country; private string province;/*** @ return the country */Public String getcountry () {return country ;} /*** @ Param country * the country to set */Public void setcountry (string country) {This. country = country;}/*** @ return the province */Public String getprovince () {return province ;} /*** @ Param province * the province to set */Public void setprovince (string province) {This. province = province;}/** (non-javadoc) ** @ see Java. lang. object # tostring () */@ overridepublic string tostring () {return "Address [Country =" + country + ", Province =" + province + "]" ;}}

Package test0328; import Java. io. stringreader; import COM. google. gson. gson; import COM. google. gson. stream. jsonreader; public class JSON {/* [{"phone": ["112233", "445566"], // array "name": "android ", // string "Age": 5, // value "Address": {"country": "PRC", "Province": "Shanghai "}, // object "married": false // Boolean}, {"phone": ["778899", "224466"], // array "name": "Linux ", // string "Age": 15, // value "Address": {"country": "USA", "Province": "NY "}, // object "married": True // Boolean}] */Private Static final string JSON = "[{\" phone \ ": [\" 112233 \", \ "445566 \"], \ "Name \": \ "android \", \ "Age \": 5, \ "address \" :{\ "country \": \ "China \", \ "province \": \ "Shanghai \" },\ "Married \": false },{ \ "phone \": [\ "778899 \", \ "224466 \"], \ "Name \": \ "Linux \", \ "Age \": 15, \ "address \": {\ "country \": \ "USA \", \ "province \": \ "NY \"}, \ "Married \": true}] "; private Static gson = new gson (); public static void main (string [] ARGs) throws exception {jsonreader reader = new jsonreader (New stringreader (JSON); reader. beginarray (); // start array while (reader. hasnext () {// loop reader. beginobject (); // start object person = new person (); While (reader. hasnext () {// loop string tagname = reader. nextname (); If ("phone ". equals (tagname) {reader. beginarray (); string [] phones = new string [2]; phones [0] = reader. nextstring (); phones [1] = reader. nextstring (); person. setphone (Phones); reader. endarray ();} else if ("name ". equals (tagname) {person. setname (reader. nextstring ();} else if ("age ". equals (tagname) {person. setage (reader. nextint ();} else if ("Address ". equals (tagname) {reader. beginobject (); Address = new address (); While (reader. hasnext () {int I = 0; string tagname2 = reader. nextname (); If ("country ". equals (tagname2) {address. setcountry (reader. nextstring ();} else {address. setprovince (reader. nextstring ();} person. setaddress (Address); reader. endobject ();} else if ("married ". equals (tagname) {person. setmarried (reader. nextboolean ();} reader. endobject (); system. out. println (person);} reader. endarray ();} public static int [] intsfromjson (string JSON) {return gson. fromjson (JSON, int []. class);} public static string [] stringsfromjson (string JSON) {return gson. fromjson (JSON, string []. class );}}