Fix additionalProperties default value in JTD validator

.github/workflows/ci.yml

@@ -39,7 +39,7 @@ jobs:
                       for k in totals: totals[k]+=int(r.get(k,'0'))
                   except Exception:
                       pass
-          exp_tests=460
+          exp_tests=464
           exp_skipped=0
           if totals['tests']!=exp_tests or totals['skipped']!=exp_skipped:
               print(f"Unexpected test totals: {totals} != expected tests={exp_tests}, skipped={exp_skipped}")

json-java21-jtd/README.md

@@ -69,6 +69,14 @@ Validates primitive types:
 
 Supported types: `boolean`, `string`, `timestamp`, `int8`, `uint8`, `int16`, `uint16`, `int32`, `uint32`, `float32`, `float64`
 
+#### Integer Type Validation
+Integer types (`int8`, `uint8`, `int16`, `uint16`, `int32`, `uint32`) validate based on **numeric value**, not textual representation:
+
+- **Valid integers**: `3`, `3.0`, `3.000`, `42.00` (mathematically integers)
+- **Invalid integers**: `3.1`, `3.14`, `3.0001` (have fractional components)
+
+This follows RFC 8927 §2.2.3.1: "An integer value is a number without a fractional component."
+
 ### 4. Enum Schema
 Validates against string values:
 ```json

json-java21-jtd/src/main/java/json/java21/jtd/Jtd.java

@@ -442,8 +442,8 @@ JtdSchema compilePropertiesSchema(JsonObject obj) {
       }
       additionalProperties = bool.value();
     } else if (properties.isEmpty() && optionalProperties.isEmpty()) {
-      // Empty schema with no properties defined allows additional properties by default
-      additionalProperties = true;
+      // Empty schema with no properties defined rejects additional properties by default
+      additionalProperties = false;
     }
 
     return new JtdSchema.PropertiesSchema(properties, optionalProperties, additionalProperties);

json-java21-jtd/src/main/java/json/java21/jtd/JtdSchema.java

@@ -244,6 +244,13 @@ Jtd.Result validateInteger(JsonValue instance, String type, boolean verboseError
           return Jtd.Result.failure(Jtd.Error.EXPECTED_INTEGER.message());
         }
 
+        // Handle BigDecimal - check if it has fractional component (not just scale > 0)
+        // RFC 8927 §2.2.3.1: "An integer value is a number without a fractional component"
+        // Values like 3.0 or 3.000 are valid integers despite positive scale, but 3.1 is not
+        if (value instanceof java.math.BigDecimal bd && bd.remainder(java.math.BigDecimal.ONE).signum() != 0) {
+          return Jtd.Result.failure(Jtd.Error.EXPECTED_INTEGER.message());
+        }
+
         // Convert to long for range checking
         long longValue = value.longValue();