René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Support for Java enums in Native Types","articleBody":"Imagine a class with an enum property:\n\n```java\npublic class Foo {\n\n    private Bar bar;\n\n    public Bar getBar() {\n        return bar;\n    }\n\n    public void setBar(Bar bar) {\n        this.bar = bar;\n    }\n\n}\n\npublic enum Bar {\n    FOO,\n    BAR\n}\n```\n\nRegistering such a class with Native Types results in an exception:\n```\nException in thread \"main\" java.lang.ExceptionInInitializerError\nCaused by: java.lang.IllegalArgumentException: Unsupported type for property 'typeParameters' in class java.lang.Class\n\tat dev.cel.extensions.CelNativeTypesExtensions$NativeTypeScanner.validateRegisteredClasses(CelNativeTypesExtensions.java:236)\n\tat dev.cel.extensions.CelNativeTypesExtensions$NativeTypeScanner.scan(CelNativeTypesExtensions.java:221)\n\tat dev.cel.extensions.CelNativeTypesExtensions$NativeTypeScanner.access$000(CelNativeTypesExtensions.java:154)\n\tat dev.cel.extensions.CelNativeTypesExtensions.nativeTypes(CelNativeTypesExtensions.java:131)\n\tat dev.cel.extensions.CelExtensions.nativeTypes(CelExtensions.java:362)\n\tat CELTest.\u003cclinit\u003e(CELTest.java:40)\nCaused by: java.lang.IllegalArgumentException: Unsupported interface type: java.lang.reflect.TypeVariable\n\tat dev.cel.extensions.CelNativeTypesExtensions$NativeTypeScanner.mapJavaTypeToCelType(CelNativeTypesExtensions.java:302)\n\tat dev.cel.extensions.CelNativeTypesExtensions$NativeTypeScanner.mapJavaTypeToCelType(CelNativeTypesExtensions.java:296)\n\tat dev.cel.extensions.CelNativeTypesExtensions$NativeTypeScanner.getPropertyType(CelNativeTypesExtensions.java:276)\n\tat dev.cel.extensions.CelNativeTypesExtensions$NativeTypeScanner.validateRegisteredClasses(CelNativeTypesExtensions.java:233)\n\t... 5 more\n```\n\nThis happens because CEL tries to introspect the implicit `declaringClass` property of the Java enum (which resolves to `java.lang.Class`, which has an interface-typed property `typeParameters`, which is not supported because of #1061). Perhaps we need to blacklist the standard `java.lang.Enum` methods the same way we [do](https://github.com/google/cel-java/blob/7452e0d71bf0c8ddaf806df36cae5423e794745d/extensions/src/main/java/dev/cel/extensions/CelNativeTypesExtensions.java#L606) for `java.lang.Object`.","author":{"url":"https://github.com/dteleguin","@type":"Person","name":"dteleguin"},"datePublished":"2026-06-03T22:10:25.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":2},"url":"https://github.com/1077/cel-java/issues/1077"}