JSON与Java对象、List、Map的互相转换

一、导入依赖项

本文采用Jackson完成JSON的转换，因此要导入jackson相关的依赖项，创建Maven项目自动导入包。jackson依赖可从下列网址获得：http://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-databind/2.9.6

	com.fasterxml.jackson.core
	jackson-databind
	2.7.3

二、创建对象

创建TaskPath对象，接下来所有Json转换的对象都与该对象有关。

public class TaskPath {

	private Integer X;                     //X坐标
	private Integer Y;                     //Y坐标
	private Integer Theta;                 //转角
	public Integer getX() {
		return X;
	}
	public void setX(Integer x) {
		X = x;
	}
	public Integer getY() {
		return Y;
	}
	public void setY(Integer y) {
		Y = y;
	}
	public Integer getTheta() {
		return Theta;
	}
	public void setTheta(Integer theta) {
		Theta = theta;
	}

}

三、创建测试程序，main函数

以下是Json和Java对象、List、Map的互相转换实现

public class JsonTest {
	 
	public static void main(String[] args) throws Exception {

		
			ObjectMapper mapper = new ObjectMapper();
		
			//Json转对象
			String json="{\"x\":154,\"y\":24,\"theta\":14}";

			TaskPath user = mapper.readValue(json, TaskPath.class);
			System.out.println(user.getX()+"  "+user.getY()+"  "+user.getTheta());

			//对象转Json
			TaskPath taskPath1 = new TaskPath();
			taskPath1.setX(123);
			taskPath1.setY(345);
			taskPath1.setTheta(15);
			
			TaskPath taskPath2 = new TaskPath();
			taskPath2.setX(12);
			taskPath2.setY(34);
			taskPath2.setTheta(15);

	                String string = mapper.writeValueAsString(taskPath1);

	                System.out.println(string);
	        
	                //list转Json
	                List list = new ArrayList<>();
	                list.add(taskPath1);
	                list.add(taskPath2);
			String ljson = mapper.writeValueAsString(list);
			
			System.out.println(ljson); 
			
			//Json转list
			JavaType jt = mapper.getTypeFactory().constructParametricType(ArrayList.class, TaskPath.class);
	                List urlist = mapper.readValue(ljson, jt);
	        
	                for(int i = 0;i < urlist.size();i++)
	                {
	        	        System.out.println(urlist.get(i).getX()+"  "+ urlist.get(i).getY()+"  "+urlist.get(i).getTheta());
	                }
	        
	                //Map转Json
			HashMap map = new HashMap();
			map.put("001", taskPath1);
			map.put("002", taskPath2);
			String mmjson = mapper.writeValueAsString(map);
			System.out.println(mmjson);
			
			//json转map
			JavaType jvt = mapper.getTypeFactory().constructParametricType(HashMap.class,String.class,TaskPath.class);
	                Map Map = mapper.readValue(mmjson, jvt);
	        
	                Set set = Map.keySet();
	                Iterator it = set.iterator();
	                while(it.hasNext())
	                {
	        	        String str = it.next();
	        	        TaskPath path = Map.get(str);
	        	        System.out.println(str + ":"+path.getX()+"  " + path.getY()+"  " + path.getTheta());
	                }

	            }
}

实现结果如下：

154  24  14
{"x":123,"y":345,"theta":15}
[{"x":123,"y":345,"theta":15},{"x":12,"y":34,"theta":15}]
123  345  15
12  34  15
{"001":{"x":123,"y":345,"theta":15},"002":{"x":12,"y":34,"theta":15}}
001:123  345  15
002:12  34  15