fix(java): preserve precision for untyped JSON numbers

java/fory-json/src/main/java/org/apache/fory/json/codec/ScalarCodecs.java

@@ -223,7 +223,7 @@ public Object readLatin1(Latin1JsonReader reader) {
         reader.readNull();
         return null;
       }
-      return reader.readNumber();
+      return reader.readNaturalNumber();
     }
 
     @Override
@@ -241,7 +241,7 @@ public Object readUtf16(Utf16JsonReader reader) {
         reader.readNull();
         return null;
       }
-      return reader.readNumber();
+      return reader.readNaturalNumber();
     }
 
     @Override
@@ -259,7 +259,7 @@ public Object readUtf8(Utf8JsonReader reader) {
         reader.readNull();
         return null;
       }
-      return reader.readNumber();
+      return reader.readNaturalNumber();
     }
   }
 

java/fory-json/src/main/java/org/apache/fory/json/reader/JsonReader.java

@@ -719,6 +719,19 @@
     return materializeNumber(readNumberAsString());
   }
 
+  /** Reads a natural JSON number without reducing decimal values to binary floating point. */
+  @Internal
+  public Number readNaturalNumber() {
+    skipWhitespace();
+    int start = position;
+    String number = readNumberAsString();
+    if (hasDecimalSeparator(number)) {
+      position = start;
+      return materializeNaturalDecimal(readBigDecimal());
+    }
+    return materializeNumber(number);
+  }
+
   private String readNumberToken() {
     int start = position;
     scanNumberToken();
@@ -1905,6 +1918,26 @@
     }
   }
 
+  private static boolean hasDecimalSeparator(String number) {
+    int length = number.length();
+    for (int i = 0; i < length; i++) {
+      char ch = number.charAt(i);
+      if (ch == '.' || ch == 'e' || ch == 'E') {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  protected static Number materializeNaturalDecimal(BigDecimal value) {
+    double asDouble = value.doubleValue();
+    // Keep the compact representation when it preserves the decimal value exactly.
+    if (Double.isFinite(asDouble) && BigDecimal.valueOf(asDouble).compareTo(value) == 0) {
+      return Double.valueOf(asDouble);
+    }
+    return value;
+  }
+
   private byte[] bigNumberBytes(String number) {
     if (StringSerializer.isBytesBackedString() && StringSerializer.getStringCoder(number) == 0) {
       return StringSerializer.getStringBytes(number);
@@ -2013,7 +2046,7 @@
   private static BigInteger bigInteger(int[] magnitude, int signum) {
     try {
       return (BigInteger) BIG_INTEGER_CONSTRUCTOR.invokeExact(magnitude, signum);
     } catch (ThreadDeath e) {
       throw e;
     } catch (VirtualMachineError e) {
       throw e;

java/fory-json/src/main/java/org/apache/fory/json/reader/Utf8JsonReader.java

@@ -1006,6 +1006,13 @@
     return readIntegerToken(false);
   }
 
+  @Override
+  @Internal
+  public Number readNaturalNumber() {
+    skipWhitespaceFast();
+    return readIntegerToken(false, true);
+  }
+
   @Override
   long scanNumberToken() {
     byte[] bytes = input;
@@ -1094,6 +1101,10 @@
   // BigInteger requires integer syntax; Number chooses compact Long storage and also accepts
   // decimal suffixes. Share the validated prefix so representation selection does not rescan it.
   private Number readIntegerToken(boolean integerOnly) {
+    return readIntegerToken(integerOnly, false);
+  }
+
+  private Number readIntegerToken(boolean integerOnly, boolean exactDecimal) {
     byte[] bytes = input;
     int limit = inputLimit;
     int start = position;
@@ -1112,7 +1123,7 @@
       if (!integerOnly && position < limit) {
         int next = bytes[position];
         if (next == '.' || next == 'e' || next == 'E') {
-          return readDecimalNumber(start);
+          return readDecimalNumber(start, exactDecimal);
         }
       }
       rejectFractionOrExponentFast();
@@ -1160,13 +1171,13 @@
       offset++;
     }
     if (offset < limit && bytes[offset] >= '0' && bytes[offset] <= '9') {
-      return readIntegerTail(integerOnly, start, offset, value);
+      return readIntegerTail(integerOnly, exactDecimal, start, offset, value);
     }
     position = offset;
     if (!integerOnly && offset < limit) {
       int next = bytes[offset];
       if (next == '.' || next == 'e' || next == 'E') {
-        return readDecimalNumber(start);
+        return readDecimalNumber(start, exactDecimal);
       }
     }
     rejectFractionOrExponentFast();
@@ -1177,22 +1188,26 @@
     return integerOnly ? BigInteger.valueOf(signed) : Long.valueOf(signed);
   }
 
-  private Number readIntegerTail(boolean integerOnly, int start, int offset, long prefix) {
+  private Number readIntegerTail(
+      boolean integerOnly, boolean exactDecimal, int start, int offset, long prefix) {
     int end = scanNumberDigits(input, offset, inputLimit);
     position = end;
     if (!integerOnly && end < inputLimit) {
       int next = input[end];
       if (next == '.' || next == 'e' || next == 'E') {
-        return readDecimalNumber(start);
+        return readDecimalNumber(start, exactDecimal);
       }
     }
     rejectFractionOrExponentFast();
     return parseBigInteger(input, start, end, prefix, offset);
   }
 
-  private Double readDecimalNumber(int start) {
-    // Preserve Number's Double representation and JDK conversion for points and exponents.
+  private Number readDecimalNumber(int start, boolean exact) {
     position = start;
+    if (exact) {
+      return materializeNaturalDecimal(readBigDecimal());
+    }
+    // Preserve Number's Double representation and JDK conversion for points and exponents.
     return Double.valueOf(Double.parseDouble(readNumberAsString()));
   }
 
@@ -2788,7 +2803,7 @@
     }
     try {
       return (Instant) INSTANT_FACTORY.invokeExact(seconds, nano);
     } catch (ThreadDeath e) {
       throw e;
     } catch (VirtualMachineError e) {
       throw e;
@@ -3197,7 +3212,7 @@
     }
     try {
       return (ZonedDateTime) ZONED_DATE_TIME_CONSTRUCTOR.invokeExact(dateTime, offset, zone);
     } catch (ThreadDeath | VirtualMachineError e) {
       throw e;
     } catch (Throwable e) {
       throw new ForyJsonException("Cannot construct JSON zoned date-time", e);
@@ -3269,7 +3284,7 @@
     }
     try {
       return (YearMonth) YEAR_MONTH_CONSTRUCTOR.invokeExact(year, month);
     } catch (ThreadDeath e) {
       throw e;
     } catch (VirtualMachineError e) {
       throw e;
@@ -3321,7 +3336,7 @@
     }
     try {
       return (MonthDay) MONTH_DAY_CONSTRUCTOR.invokeExact(month, day);
     } catch (ThreadDeath e) {
       throw e;
     } catch (VirtualMachineError e) {
       throw e;
@@ -3630,7 +3645,7 @@
     }
     try {
       return (LocalDate) LOCAL_DATE_FACTORY.invokeExact(year, month, day);
     } catch (ThreadDeath e) {
       throw e;
     } catch (VirtualMachineError e) {
       throw e;
@@ -3704,7 +3719,7 @@
     }
     try {
       return (LocalTime) LOCAL_TIME_FACTORY.invokeExact(hour, minute, second, nano);
     } catch (ThreadDeath e) {
       throw e;
     } catch (VirtualMachineError e) {
       throw e;

java/fory-json/src/test/java/org/apache/fory/json/JsonContainerTest.java

@@ -581,6 +581,24 @@ public void readJsonContainers() {
     assertTrue(((JsonObject) natural).get("items") instanceof JsonArray);
   }
 
+  @Test
+  public void preserveNaturalDecimalPrecision() {
+    ForyJson json = newJson();
+    String literal = "1.234567890123456789012345678901234567890";
+
+    Object value = json.fromJson(literal, Object.class);
+
+    assertEquals(value, new BigDecimal(literal));
+    assertEquals(value.getClass(), BigDecimal.class);
+    assertEquals(
+        json.fromJson(literal.getBytes(StandardCharsets.UTF_8), Object.class),
+        new BigDecimal(literal));
+    assertEquals(json.fromJson("1e400", Object.class), new BigDecimal("1e400"));
+    assertEquals(
+        json.fromJson("123456789012345678901234567890", Object.class),
+        new BigInteger("123456789012345678901234567890"));
+  }
+
   @Test
   public void parsedContainersStartSmall() {
     ForyJson json = newJson();