JSON - JavaScript Object Notation

什麼是 JSON

JSON 是一種與開發語言無關的、輕量級的資料格式。

優點

易於人的閱讀和編寫，易於程式解析與生產。

JSON 的樣例

{
    "name" : "JSON快速入門"，
    "author" : "xq"，
    "content" : ["JSON 基礎入門","常用的 JSON 處理"],
    "time" : {
        "value" : "30" 
        "unit" : "min"
    }
}

JSON 資料表示

• 資料結構
  • Object
    • 使用花括號{}包含的鍵值對結構，Key 必須是 string 型別
      ，value 為任何基本型別或資料結構。
  • Array
    • 使用中括號[]來起始，並用逗號，來分隔元素。
• 基本型別
  • string
  • number
  • true
  • false
  • null

JSON 的生成

Maven pom.xml檔案設計

<project xmlns="http://maven.apache.org/POM/4.0.0"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>com.xq</groupId>
	<artifactId>json</artifactId>
	<version>0.0.1-SNAPSHOT</version>

	<dependencies>
		<dependency>
			<groupId>com.google.code.gson</groupId>
			<artifactId>gson</artifactId>
			<version>2.4</version>
		</dependency>
		
		<dependency>
			<groupId>org.json</groupId>
			<artifactId>json</artifactId>
			<version>20090211</version>
		</dependency>
	
		<dependency>
			<groupId>commons-io</groupId>
			<artifactId>commons-io</artifactId>
			<version>2.4</version>
		</dependency>
		
	</dependencies>

</project>

 

package json;

import java.util.HashMap;
import java.util.Map;

import org.json.JSONException;
import org.json.JSONObject;

import bean.Student;

public class JsonObjectSample {

	public static void main(String[] args) {
		jSONObjectSample();
		//creatJsonByMap();
		//creatJsonByBean();
	}

	/**
	 * { "name" : "熊奇", "age" : 25.2, "birthday" : "1998-09-17" }
	 */
 

	
	//生成
	private static void jSONObjectSample() {
		JSONObject wxe = new JSONObject();
		Object nullObj = null;
		try {
			wxe.put("name", "wangxiaoer");
			wxe.put("age", 25.2);
			wxe.put("birthday", "1990-11-11");
			wxe.put("school", "beida");
			wxe.put("major", new String[] { "理髮", "挖掘機" });
			wxe.put("has_girlfrieng", false);
			wxe.put("car", nullObj);
			wxe.put("house", nullObj);
			wxe.put("comment", "這是一個註釋");
			// print
			System.out.println(wxe.toString());

		} catch (JSONException e) {
			e.printStackTrace();
		}

	}

	private static void creatJsonByMap() {

		Map<String, Object> wxe = new HashMap<String, Object>();
		Object nullObj = null;
		wxe.put("name", "wangxiaoer");
		wxe.put("age", 25.2);
		wxe.put("birthday", "1990-11-11");
		wxe.put("school", "beida");
		wxe.put("major", new String[] { "理髮", "挖掘機" });
		wxe.put("has_girlfrieng", false);
		wxe.put("car", nullObj);
		wxe.put("house", nullObj);
		wxe.put("comment", "這是一個註釋");
		
		System.out.println(new JSONObject(wxe).toString());
	}
	
	/**
	 * 推薦使用
	 */
	
	private static void creatJsonByBean() {
		Student student = new Student();
		student.setName("王小二");
		student.setAge(25.2);
		student.setBirthday("1999-11-11");
		student.setSchool("lanxiang");
		student.setHas_girlfriend(false);
		student.setCar(null);
		student.setHouse(null);
		student.setComment("這是一個註釋");
		System.out.println(new JSONObject(student));
	}

}

通過檔案讀取 JSON

package json;

import java.io.File;
import java.io.IOException;

import org.apache.commons.io.FileUtils;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

/**
 * 通過檔案讀取 JSON
 * @author lenovo
 *
 */

public class ReadJsonSample {
	
	public static void main(String[] args) throws IOException, JSONException {
		
		File file = new File(ReadJsonSample.class.getResource("/wxe.json").getFile());
		String content = FileUtils.readFileToString(file);
		
		JSONObject jsonObject = new JSONObject(content);
		
		if(!jsonObject.isNull("name")) {
			System.out.println("姓名是：" + jsonObject.getString("name"));
		}
		if(!jsonObject.isNull("nickname")) {
			System.out.println("姓名是：" + jsonObject.getString("nickname"));
		}
		
		System.out.println("年齡是：" + jsonObject.getDouble("age"));
		System.out.println(jsonObject.getBoolean("has_girlfriend"));
		
		//獲取陣列物件
		JSONArray majorArray = jsonObject.getJSONArray("major");
		for (int i = 0; i < majorArray.length(); i++) {
			String m = (String) majorArray.get(i);
			System.out.println("專業-" + (i + 1) + m);
		}
	}
}

GSON

GsonCreateSample 類設計

package gson;

import java.lang.reflect.Field;

import com.google.gson.FieldNamingStrategy;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

import bean.Student;

public class GsonCreatSample {

	public static void main(String[] args) {
		Student student = new Student();
		student.setName("王小二");
		student.setAge(25.2);
		student.setBirthday("1999-11-11");
		student.setSchool("lanxiang");
		student.setMajor(new String[] {"藍翔","挖掘機"});
		student.setHas_girlfriend(false);
		student.setCar(null);
		student.setHouse(null);
		student.setComment("這是一個註釋");
		student.setIgnore("不要看見我");

		//
		GsonBuilder gsonBuilder = new GsonBuilder();
		gsonBuilder.setPrettyPrinting();
		gsonBuilder.setFieldNamingStrategy(new FieldNamingStrategy() {
			
			public String translateName(Field f) {
				if(f.getName().equals("name")) {
					return "NAME";
				}
				return f.getName();
			}
		});
		Gson gson = gsonBuilder.create();
		System.out.println(gson.toJson(student));
	}
}

GsonReadSample 類設計

package gson;

import java.io.File;
import java.io.IOException;

import org.apache.commons.io.FileUtils;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

import bean.Student;
import bean.StudentWithBirthday;
import json.ReadJsonSample;

public class GsonReadSample {
	
	public static void main(String[] args) throws IOException {
		
		File file = new File(ReadJsonSample.class.getResource("/wxe.json").getFile());
		String content = FileUtils.readFileToString(file);
		
		//定製 Date 類
		Gson gson = new GsonBuilder().setDateFormat("yyyy-MM-dd").create();
		StudentWithBirthday student = gson.fromJson(content, StudentWithBirthday.class);
		System.out.println(student.getBirthday().toLocaleString());
		
		//
		System.out.println(student.getMajor());
		System.out.println(student.getMajor().getClass());
	}
	
}