fork download
copy 
  1. import java.lang.reflect.Array;
  2. import java.util.*;
  3.  
  4. class JsonStructureValidator {
  5.  
  6.     public static boolean isValidJson(Object input) {
  7.         Set<Object> seen = Collections.newSetFromMap(new IdentityHashMap<>());
  8.         return isValidJsonImpl(input, seen);
  9.     }
  10.  
  11.     private static boolean isValidJsonImpl(Object input, Set<Object> seen) {
  12.         if (input == null) return true;
  13.  
  14.         if (isPrimitiveAllowed(input)) return true;
  15.  
  16.         if (input instanceof Map) {
  17.             if (!seen.add(input)) return false;
  18.  
  19.             Map<?, ?> map = (Map<?, ?>) input;
  20.             for (Map.Entry<?, ?> e : map.entrySet()) {
  21.                 Object key = e.getKey();
  22.                 Object value = e.getValue();
  23.  
  24.                 if (!(key instanceof String)) {
  25.                     seen.remove(input);
  26.                     return false;
  27.                 }
  28.  
  29.                 if (!isValidJsonImpl(value, seen)) {
  30.                     seen.remove(input);
  31.                     return false;
  32.                 }
  33.             }
  34.             seen.remove(input);
  35.             return true;
  36.         }
  37.  
  38.         if (input instanceof List) {
  39.             if (!seen.add(input)) return false;
  40.  
  41.             List<?> list = (List<?>) input;
  42.             for (Object item : list) {
  43.                 if (!isValidJsonImpl(item, seen)) {
  44.                     seen.remove(input);
  45.                     return false;
  46.                 }
  47.             }
  48.             seen.remove(input);
  49.             return true;
  50.         }
  51.  
  52.         if (input.getClass().isArray()) {
  53.             if (!seen.add(input)) return false;
  54.  
  55.             int len = Array.getLength(input);
  56.             for (int i = 0; i < len; i++) {
  57.                 Object elem = Array.get(input, i);
  58.                 if (!isValidJsonImpl(elem, seen)) {
  59.                     seen.remove(input);
  60.                     return false;
  61.                 }
  62.             }
  63.             seen.remove(input);
  64.             return true;
  65.         }
  66.  
  67.         return false;
  68.     }
  69.  
  70.     private static boolean isPrimitiveAllowed(Object input) {
  71.         return input instanceof String
  72.                 || input instanceof Number
  73.                 || input instanceof Boolean;
  74.     }
  75.  
  76.     public static void main(String[] args) {
  77.         Map<String, Object> valid = Map.of("user", Map.of("name", "A", "age", 30));
  78.         System.out.println(isValidJson(valid)); // true
  79.  
  80.         Map<String, Object> m2 = new HashMap<>();
  81.         m2.put("tags", List.of("x", "y"));
  82.         m2.put("scores", new int[] {1, 2, 3});
  83.         System.out.println(isValidJson(m2)); // true
  84.  
  85.         Map<Object, Object> wrongKey = new HashMap<>();
  86.         wrongKey.put(123, "numberAsKey");
  87.         System.out.println(isValidJson(wrongKey)); // false
  88.  
  89.         Map<String, Object> withSet = new HashMap<>();
  90.         withSet.put("s", Set.of("a", "b"));
  91.         System.out.println(isValidJson(withSet)); // false
  92.  
  93.     }
  94. }
  95.  
Success #stdin #stdout 0.08s 54616KB
comments (?)
stdin
copy 
Standard input is empty
stdout
copy 
true
true
false
false
https://ideone.com/tbLCAG
language:
Java (HotSpot 12)
created:
4 hours ago
visibility:
public

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!