Java fastjson中JSONObject 常用的方法及转换

1.JSONObject 的常用方法

//数据准备
	List<Student> list=new ArrayList<Student>();
	list.add(new Student(1,1000d,"旅游",new Date()));
	list.add(new Student(2,1500d,"玩电脑游戏",new Date()));
	list.add(new Student(3,3000d,"看电影",new Date()));
	Student student=new Student(1,1000d,"旅游",new Date());
	JSONObject jsonObject=new JSONObject();
	jsonObject.put("8", "签名");
	jsonObject.put("d", 10.0);
	jsonObject.put("date", new Date());
	jsonObject.put("stu", new Student(8,8000d,"购物",new Date()));
	jsonObject.put("arr", list);
	//相当于
	Map<String,Object> map=new HashMap<String, Object>();
	//常用方法
	//1.判断该JSONObject对象是否为空
	jsonObject.isEmpty();
	//2.获取键值对的数量
	jsonObject.size();
	//3.根据键获取value;
	jsonObject.get("1");
	jsonObject.getString("8");
	jsonObject.getDouble("d");
	Date date = jsonObject.getDate("date");
	System.out.println(date);
	//4.是否包含指定的key
	jsonObject.containsKey("1");
	//5.是否包含指定的value
	jsonObject.containsValue("签名");	
	//6.根据key获取对应的JSONObject对象
	System.out.println(jsonObject);
	JSONObject stuJson=jsonObject.getJSONObject("stu");
	           stuJson.put("bz", "好学生");
	           stuJson.put("hobby", "学习");
	           jsonObject.put("stu", stuJson);
	System.out.println(stuJson);
	System.out.println(jsonObject);
	//7.根据key获取对应的JSONObject数组
	JSONArray arrJson=jsonObject.getJSONArray("arr");
     相当于List<Object> list=new ArrayList<Object>();
	//8.将数组转换为list
	List<Student> javaList = jsonObject.getJSONArray("arr").toJavaList(Student.class);
	System.out.println(arrJson);
	//9.将JSONObject转为json字符串
	String jsonString = jsonObject.toJSONString();
	System.out.println(jsonString);
	//10.public class JSONObject extends JSON implements Map<String, Object>, Cloneable, Serializable, InvocationHandler{}
	//具有map的特点
	Set<Entry<String, Object>> entrySet = jsonObject.entrySet();
	Iterator<Entry<String, Object>> iterator = entrySet.iterator();
	while(iterator.hasNext()){
		Entry<String, Object> next = iterator.next();
		System.out.println(next.getKey()+":"+next.getValue());
	}
	Set<String> keySet = jsonObject.keySet();
	Collection<Object> values = jsonObject.values();
	//11.根据key移除键值对
	jsonObject.remove("arr");
	//12.清楚所有的元素
	jsonObject.clear();

2.相关转换

  JSONObject----》JSON字符串

  
	JSONObject jsonObject=new JSONObject();
    jsonObject.put("date", new Date());
     //JSONObject--->json 字符串
	String jsonString = jsonObject.toJSONString();

	//JSONObject--->json 字符串	
	String string = jsonObject.toString();

JavaBean----》JSONObject

//javaBen--->JSONObject
//1.将javaBen转换为JSON字符串
String jsonString2 = JSONObject.toJSONString(student);
//2.JSON字符串---》JSONObject
JSONObject parseObject = JSONObject.parseObject(jsonString2);

JSONObject------》JavaBean

 //JSONObject---->JavaBen
	    Student javaObject = JSONObject.toJavaObject(parseObject, Student.class);