Created
March 13, 2026 11:05
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кастомний джейсон серіалізатор
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| import java.util.LinkedHashMap; | |
| import java.util.List; | |
| import java.util.Map; | |
| public class Program { | |
| public static void main(String[] args) { | |
| Map<String, Object> person = new LinkedHashMap<>(); | |
| person.put("name", "Олег"); | |
| person.put("age", 28); | |
| person.put("isStudent", false); | |
| person.put("grades", List.of(12, 12, 11, 12)); | |
| Map<String, Object> address = new LinkedHashMap<>(); | |
| address.put("city", "Одеса"); | |
| address.put("street", "вул. Дерибасівська"); | |
| address.put("zip", "65005"); | |
| person.put("address", address); | |
| // серіалізація в JSON-рядок | |
| String json = toJson(person); | |
| System.out.println(json); | |
| } | |
| // кастомний перетворювач об'єкта в JSON-рядок | |
| // підтримує: String, Number, Boolean, null, List, Map | |
| public static String toJson(Object obj) { | |
| if (obj == null) { | |
| return "null"; | |
| } | |
| if (obj instanceof String) { | |
| return "\"" + escapeJsonString((String) obj) + "\""; | |
| } | |
| if (obj instanceof Number || obj instanceof Boolean) { | |
| return obj.toString(); | |
| } | |
| if (obj instanceof List<?> list) { | |
| var sb = new StringBuilder("["); | |
| for (int i = 0; i < list.size(); i++) { | |
| if (i > 0) sb.append(","); | |
| sb.append(toJson(list.get(i))); | |
| } | |
| sb.append("]"); | |
| return sb.toString(); | |
| } | |
| if (obj instanceof Map) { | |
| @SuppressWarnings("unchecked") | |
| Map<String, Object> map = (Map<String, Object>) obj; | |
| StringBuilder sb = new StringBuilder("{"); | |
| boolean first = true; | |
| for (Map.Entry<String, Object> entry : map.entrySet()) { | |
| if (!first) sb.append(","); | |
| first = false; | |
| sb.append(toJson(entry.getKey())) | |
| .append(":") | |
| .append(toJson(entry.getValue())); | |
| } | |
| sb.append("}"); | |
| return sb.toString(); | |
| } | |
| // якщо тип не підтримується - можна кинути виняток або повернути toString | |
| throw new IllegalArgumentException("Тип не підтримується: " + obj.getClass().getName()); | |
| } | |
| private static String escapeJsonString(String s) { | |
| if (s == null) return ""; | |
| var sb = new StringBuilder(); | |
| for (char c : s.toCharArray()) { | |
| switch (c) { | |
| case '"': sb.append("\\\""); break; | |
| case '\\': sb.append("\\\\"); break; | |
| case '\b': sb.append("\\b"); break; | |
| case '\f': sb.append("\\f"); break; | |
| case '\n': sb.append("\\n"); break; | |
| case '\r': sb.append("\\r"); break; | |
| case '\t': sb.append("\\t"); break; | |
| default: | |
| if (c <= 0x1F) { | |
| sb.append(String.format("\\u%04x", (int) c)); | |
| } else { | |
| sb.append(c); | |
| } | |
| } | |
| } | |
| return sb.toString(); | |
| } | |
| } |
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