Java Operation JSON

First, JSON syntax

Json:javascript Object Notation (JavaScript object Notation), JSON is the syntax for storing and exchanging textual information. XML-like, but smaller, faster, and easier to parse than XML.
The writing format for JSON data is: name/value pairs.
Name/value pairs include the field name (in double quotation marks), followed by a colon, and then the value:

"firstName""John"

The JSON array is written in square brackets:
An array can contain multiple objects:

{    "employees[        { "firstName":"John" , "lastName":"Doe" },        { "firstName":"Anna" , "lastName":"Smith" },        { "firstName":"Peter" , "lastName":"Jones" }     ]}

Ii. introduction of Gson

Gson is a Java class library provided by Google for mapping between Java objects and JSON data. You can turn a JSON string into a Java object, or vice versa. Download jar Package: http://download.csdn.net/detail/yang_xing_/8363795. Create a new Java project in Eclipse and introduce Gson-2.2.4.jar. Create a Employee.json file under the project root directory:

{    "Department":"Design",    "Employees":[{"firstName":"Bill" , "lastName":"Gates "}, {" firstName":" George " ,"lastName":" Bush " }, {"firs Tname":Thomas" , "lastName":"Carter" }]}

Second, read JSON

First create a JSON parser, then create a Jsonobject object, and then call the Get method to access the property values:

Package Ucas. JSON. Test;Import Java. IO. File;Import Java. IO. FileNotFoundException;Import Java. IO. FileReader;Importcom. Google. Gson. Jsonioexception;Importcom. Google. Gson. Jsonobject;Importcom. Google. Gson. Jsonparser;Importcom. Google. Gson. Jsonsyntaxexception;public class Jsontest {public static void main (string[] args) {try {jsonparser jparser = new JsonP Arser ();Jsonobject jobject = (jsonobject) jparser. Parse(New FileReader ("Employee.json"));System. out. println(Jobject. Get("department"). getasstring());System. out. println(Jobject. Get("Employees"));} catch (Jsonioexception e) {E. Printstacktrace();} catch (Jsonsyntaxexception e) {E. Printstacktrace();} catch (FileNotFoundException e) {E. Printstacktrace();}    }}

Output Result:

design[{"firstName":"Bill","lastName":"Gates"},{"firstName":"George","lastName":"Bush"},{"firstName":"Thomas","lastName":"Carter"}]

You can see that the "Employees" attribute is an array, converted to Jsonarray, and then recycled:

Package Ucas. JSON. Test;Import Java. IO. File;Import Java. IO. FileNotFoundException;Import Java. IO. FileReader;Importcom. Google. Gson. Jsonarray;Importcom. Google. Gson. Jsonioexception;Importcom. Google. Gson. Jsonobject;Importcom. Google. Gson. Jsonparser;Importcom. Google. Gson. Jsonsyntaxexception;public class Jsontest {public static void main (string[] args) {try {jsonparser jparser = new JsonP Arser ();Jsonobject jobject = (jsonobject) jparser. Parse(New FileReader ("Employee.json"));System. out. println(Jobject. Get("department"). getasstring());Jsonarray jarray= (Jsonarray) jobject. Get("Employees");for (int i =0; i < jarray.size (); i++) {System. out. println("-----------");Jsonobject jobject2= (jsonobject) Jarray. Get(i);System. out. println("ID:"+jobject2. Get("id"). getasstring());System. out. println("FirstName:"+jobject2. Get("FirstName"). getasstring());System. out. println("LastName:"+jobject2. Get("LastName"). getasstring());}} catch (Jsonioexception e) {E. Printstacktrace();} catch (Jsonsyntaxexception e) {E. Printstacktrace();} catch (FileNotFoundException e) {E. Printstacktrace();}    }}

Output Result:

design-----------id:1firstName:BilllastName:Gates-----------id:1firstName:GeorgelastName:Bush-----------id:3firstName:ThomaslastName:Carter

Third, create JSON

To create a JSON object, add an attribute using the AddProperty method, add an object using the Add method, for example:

Import Java. IO. BufferedReader;Import Java. IO. BufferedWriter;Import Java. IO. File;Import Java. IO. FileOutputStream;Import Java. IO. IOException;Import Java. IO. InputStream;Import Java. IO. OutputStreamWriter;Importcom. Google. Gson. Jsonarray;Importcom. Google. Gson. Jsonobject;public class JsonDemo2 {public static void main (string[] args) {//Create JSON data jsonobject Jsonobject = new Jsonobject ();Jsonobject. AddProperty("Cat","It");Jsonarray Jarray = new Jsonarray ();Jsonobject lan1 = new Jsonobject ();Lan1. AddProperty("id",1);Lan1. AddProperty("Name","Java");Lan1. AddProperty("IDE","Eclipse");Jarray. Add(LAN1);Jsonobject lan2 = new Jsonobject ();Lan2. AddProperty("id",2);Lan2. AddProperty("Name","C + +");Lan2. AddProperty("IDE","VC6.0");Jarray. Add(lan2);Jsonobject lan3 = new Jsonobject ();Lan3. AddProperty("id",3);Lan3. AddProperty("Name","C #");Lan3. AddProperty("IDE","Visual Studio");Jarray. Add(LAN3);Jsonobject lan4 = new Jsonobject ();Lan4. AddProperty("id",4);Lan4. AddProperty("Name","Swift");Lan4. AddProperty("IDE","Xcode");Jarray. Add(LAN4);Jsonobject. Add("Languages", Jarray);Jsonobject. AddProperty("Pop", true);System. out. println(Jsonobject);File Jsonfile = new file ("Test.json");try {Jsonfile. CreateNewFile();FileOutputStream fos = new FileOutputStream (jsonfile);OutputStreamWriter osq = new OutputStreamWriter (FOS);BufferedWriter BFW = new BufferedWriter (OSQ);BfW. Write(Jsonobject. toString());BfW. Close();Osq. Close();Fos. Close();} catch (IOException e) {//TODO auto-generated catch block E. Printstacktrace();}    }}

This will generate a Test.json file in the project root directory:

{"Cat":"It","Languages":[{"ID":1,"name":"haha","IDE":"eclipse\n"},{"ID":2,"name":"C + +","IDE":"VC6.0"},{"ID":3,"name":"C #","IDE":"Visual Studio"},{"ID":4,"name":"Swift","IDE":"Xcode"}],"Pop":true}

Summarize:

1. JSON introduction and syntax can refer to the JSON website http://www.json.org/and web tutorial JSON tutorial
2. There are many libraries for manipulating JSON, so you can choose to learn.

Java Operation JSON