JSON解析详解

简单来说,json就是键值对的形式

{"key":"value","key":"value","key":"value"}

json解析一般可以通过gson  (这是谷歌的)或着 fastJson (这是阿里巴巴的)

Gson(先New再用对象的方法):

Gson gson = new Gson()

String json = gson.toJson(JavaBean,List,Map);

public class GsonTest {
	/**
	 * 将Java对象（JavaBean、List、Map）转换成JSON格式的字符串
	 */
	@Test
	public void testJavaToJson() {
		// 得到gson对象
		Gson gson = new Gson();
		/**
		 {
		 	"userId":1,
		 	"uname":"张三",
		 	"upwd":"123456"
		 }
		 */
		// 创建JavaBean对象
		User user = new User(1,"张三","123456");
		// 将对象转换成字符串
		String json = gson.toJson(user);

将json格式的字符串转换成指定的Java对象:

new Gson().fromJson(String(json的格式的),利用反射)

public void testJsonToJava() {
		// 准备JSON格式的字符串
		String json1 = "{\"userId\":1,\"uname\":\"张三\",\"upwd\":\"123456\"}";
		String json2 = "[\"aa\",\"bb\",\"cc\"]";
		String json3 = "[{\"userId\":1,\"uname\":\"张三\",\"upwd\":\"123456\"},{\"userId\":2,\"uname\":\"lisi\",\"upwd\":\"123321\"},{\"userId\":3,\"uname\":\"wangwu\",\"upwd\":\"111222\"}]";
				
		// 将字符串转换成Java对象
		User user = new Gson().fromJson(json1, User.class);
		System.out.println(user.getUname());

		List list = new Gson().fromJson(json2, new TypeToken>(){}.getType());
		System.out.println(list.get(0));

		List userList = new Gson().fromJson(json3, new TypeToken>(){}.getType());
		System.out.println(userList.get(0).getUserId());
	}

fastJson(直接用类,因为是静态的):

导入插件

public void testJavaToJson() {	
		// 创建JavaBean对象
		User user = new User(1,"张三","123456");
		System.out.println(JSON.toJSONString(user));

		// 创建List
		List list = new ArrayList<>();
		list.add("aa");
		list.add("bb");
		list.add("cc");
		System.out.println(JSON.toJSONString(list));

		// 创建List
		List userList = new ArrayList<>();
		User user2 = new User(2,"lisi","123321");
		User user3 = new User(3,"wangwu","111222");
		userList.add(user);
		userList.add(user2);
		userList.add(user3);
		System.out.println(JSON.toJSONString(userList));

		// 创建Map
		Map map = new HashMap<>();
		map.put("name", "admin");
		map.put("user", user);
		map.put("userList", userList);
		System.out.println(JSON.toJSONString(map));
		
	}

fastJson,Json转对象:

public void testJsonToJava() {
		// 准备JSON格式的字符串
		String json1 = "{\"userId\":1,\"uname\":\"张三\",\"upwd\":\"123456\"}";
		String json2 = "[\"aa\",\"bb\",\"cc\"]";
		String json3 = "[{\"userId\":1,\"uname\":\"张三\",\"upwd\":\"123456\"},{\"userId\":2,\"uname\":\"lisi\",\"upwd\":\"123321\"},{\"userId\":3,\"uname\":\"wangwu\",\"upwd\":\"111222\"}]";
	
		User user = JSON.parseObject(json1,User.class);
		
		List list = JSON.parseArray(json2,String.class);
		
		List userList = JSON.parseArray(json3,User.class);
		
		System.out.println(user.getUname());
		System.out.println(list.get(0));
		System.out.println(userList.get(0).getUname());
		
	}

}