Skipping over groovy metadata class + groovy test.

jr-objects/pom.xml

@@ -40,6 +40,12 @@ has no other dependencies, and provides additional builder-style content generat
       <artifactId>jackson-core</artifactId>
       <version>${jackson.version.core}</version>
     </dependency>
+    <dependency>
+      <groupId>org.codehaus.groovy</groupId>
+      <artifactId>groovy</artifactId>
+      <version>3.0.18</version>
+      <scope>test</scope>
+    </dependency>
   </dependencies>
 
   <build>
@@ -64,9 +70,6 @@ has no other dependencies, and provides additional builder-style content generat
                 <goal>replace</goal>
             </goals>
             <phase>generate-sources</phase>
-<!--
-            <phase>process-sources</phase>
--->
           </execution>
         </executions>
           <configuration>

jr-objects/src/main/java/com/fasterxml/jackson/jr/ob/impl/BeanPropertyIntrospector.java

@@ -88,7 +88,7 @@ private POJODefinition _construct(Class<?> beanType, int features)
     private static void _introspect(Class<?> currType, Map<String, PropBuilder> props,
             int features)
     {
-        if (currType == null || currType == Object.class) {
+        if (currType == null || currType == Object.class || isGroovyMetaClass(currType)) {
             return;
         }
         // First, check base type
@@ -117,7 +117,7 @@ private static void _introspect(Class<?> currType, Map<String, PropBuilder> prop
             // 13-Jun-2015, tatu: Skip synthetic, bridge methods altogether, for now
             //    at least (add more complex handling only if absolutely necessary)
             if (Modifier.isStatic(flags)
-                    || m.isSynthetic() || m.isBridge()) {
+                    || m.isSynthetic() || m.isBridge() || isGroovyMetaClass(m.getReturnType())) {
                 continue;
             }
             Class<?> argTypes[] = m.getParameterTypes();
@@ -158,12 +158,7 @@ private static void _introspect(Class<?> currType, Map<String, PropBuilder> prop
     }
 
     private static PropBuilder _propFrom(Map<String,PropBuilder> props, String name) {
-        PropBuilder prop = props.get(name);
-        if (prop == null) {
-            prop = Prop.builder(name);
-            props.put(name, prop);
-        }
-        return prop;
+        return props.computeIfAbsent(name, Prop::builder);
     }
 
     private static String decap(String name) {
@@ -182,4 +177,13 @@ private static String decap(String name) {
         return name;
     }
 
+    /**
+     * Another helper method to deal with Groovy's problematic metadata accessors
+     *
+     * @implNote Groovy MetaClass have cyclic reference, and hence the class containing it should not be serialised without
+     * either removing that reference, or skipping over such references.
+     */
+    protected static boolean isGroovyMetaClass(Class<?> clazz) {
+        return clazz.getName().startsWith("groovy.lang");
+    }
 }

jr-objects/src/test/java/com/fasterxml/jackson/jr/GroovyTest.groovy

@@ -0,0 +1,58 @@
+package com.fasterxml.jackson.jr
+
+import com.fasterxml.jackson.jr.ob.JSON
+import com.fasterxml.jackson.jr.ob.TestBase
+
+class GroovyTest extends TestBase {
+
+    void testSimpleObject() throws Exception {
+        var data = JSON.std.asString(new MyClass())
+        var expected = """{"AAAAA_A_Field_Starting_With_Two_Capital_Letters":"XYZ","aDouble":0.0,"aPublicInitializedInteger":56,"aPublicInitializedIntegerObject":1516,"aPublicUninitializedInteger":0,"anInitializedIntegerObject":1112,"anInitializedPublicString":"stringData","anInitializedString":"ABC","anInteger":0,"anIntegerWithValue":12}"""
+        assertEquals(data, expected)
+    }
+
+    private class MyClass {
+        int anInteger
+        int anIntegerWithValue = 12
+
+        static int anStaticInteger = 34
+        static int anStaticIntegerWithValue = 34
+
+        public int aPublicUninitializedInteger
+        public int aPublicInitializedInteger = 56
+
+        private int aPrivateUninitializedInteger
+        private int aPrivateInitializedInteger = 78
+
+        public static int aPublicStaticUninitializedInteger
+        public static int aPublicStaticInitializedInteger = 910
+
+        Integer anIntegerObject
+        Integer anInitializedIntegerObject = 1112
+
+        static Integer aStaticIntegerObject
+        static Integer aStaticInitializedIntegerObject = 1314
+
+        public Integer aPublicUninitializedIntegerObject
+        public Integer aPublicInitializedIntegerObject = 1516
+
+        public static Integer aPublicStaticUninitializedIntegerObject
+        public static Integer aPublicStaticInitializedIntegerObject = 1718
+
+        String aString
+        String anInitializedString = "ABC"
+
+        static String aStaticString = "jacksonJR"
+
+        public String aPublicString
+        public String anInitializedPublicString = "stringData"
+
+        public String AAAAA_A_Field_Starting_With_Two_Capital_Letters = "XYZ"
+        //Other Items
+        public static String staticStr = "jacksonJR"        // Public Static Object
+        static int anStaticInt                              // Uninitialized Static Object
+        public double aDouble                               // uninitialized primitive
+        public Double aDoubleObject                         // testing boxing object
+        private int hiddenvalue = 123                       // private value
+    }
+}