JSON解析方式

JSON

解析方式

Gson

Gson 是一个 Google 提供的一个 Java 库，可用于将 Java 对象转换为 JSON 表示。它也可以被用来
将 JSON 字符串转换成一个等效的 Java 对象。

json解析成java对象

/**
 * Gson
 * 对象转json
 * json转对象
 * 
 * gson.toJson
 * gson.fromJson
 * 
 * map和list  json转换为对象的时候     类型  new TypeToken<类型>(){}.getType()
 * 
 * 下载jar包网址  https://mvnrepository.com
 */
@WebServlet("/js01")
public class JsonServlet01 extends HttpServlet {
	private static final long serialVersionUID = 1L;

	protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		System.out.println("=================对象转json=================");
		// 创建对象
		User user = new User("余爽","宜春",true);
		// 创建Gson对象
		Gson gson = new Gson();
		// 将user转换为json字符串
		String json = gson.toJson(user);
		System.out.println(json); // {"name":"余爽","address":"宜春","sex":true}
		
		
		System.out.println("=================json转对象=================");
		// 创建json字符串
		String json1 = "{\"name\":\"余爽\",\"address\":\"宜春\",\"sex\":true}";
		// 创建Gson对象
		Gson gson1 = new Gson();
		// 将json字符串转换为user对象
		User user1 = gson1.fromJson(json1, User.class);
		System.out.println(user1);
	}

}

Json 解析 成 List

@WebServlet("/js02")
public class JsonServlet02 extends HttpServlet {
	private static final long serialVersionUID = 1L;

	protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		System.out.println("=================List转json=================");
		// 创建List<User>集合
		List<User> userList = new ArrayList<>();
		// 创建user 添加到 userList中
		userList.add(new User("余爽","宜春",true));
		userList.add(new User("刘杭","萍乡",true));
		userList.add(new User("万鲲","长沙",true));
		// 创建gson对象
		Gson gson = new Gson();
		// List转json
		String json = gson.toJson(userList);  // [{},{},{}]
		System.out.println(json); // [{"name":"余爽","address":"宜春","sex":true},{"name":"刘杭","address":"萍乡","sex":true},{"name":"万鲲","address":"长沙","sex":true}]
		
		
		System.out.println("=================json转List=================");
		// 创建json字符串
		String json1 = "[{\"name\":\"余爽\",\"address\":\"宜春\",\"sex\":true},{\"name\":\"刘杭\",\"address\":\"萍乡\",\"sex\":true},{\"name\":\"万鲲\",\"address\":\"长沙\",\"sex\":true}]";
		// 创建gson对象
		Gson gson1 = new Gson();
		// json转List
		List<User> userList1 = gson1.fromJson(json1, new TypeToken<List<User>>(){}.getType());
		for (User user : userList1) {
			System.out.println(user);
		}
	}

}

json解析成map

/**
 * Gson
 * Map转json
 * json转Map
 */
@WebServlet("/js03")
public class JsonServlet03 extends HttpServlet {
	private static final long serialVersionUID = 1L;

	protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		System.out.println("=================Map转json=================");
		// 创建Map集合
		Map<String, Object> map = new HashMap<>();
		map.put("id", "008");
		map.put("user", new User("余爽","宜春",true));
		
		// 创建Gson对象
		Gson gson = new Gson();
		// Map转json
		String json = gson.toJson(map); // { : , : {}}
		System.out.println(json);// {"id":"008","user":{"name":"余爽","address":"宜春","sex":true}}
		
		
		System.out.println("=================json转Map=================");
		// 来一个json字符串
		String json1 = "{\"id\":\"008\",\"user\":{\"name\":\"罗碧娴\",\"address\":\"抚州\",\"sex\":false}}";
		// 创建Gson对象
		Gson gson1 = new Gson();
		// json转map
		Map<String,Object> map1 = gson1.fromJson(json1, new TypeToken<Map<String,Object>>(){}.getType());
		for (String key : map1.keySet()) {
			System.out.println(key + "：" + map1.get(key));
		}
	}

}