Port GroovyDynamicElementReader to Java

Prior to this commit, GroovyDynamicElementReader was implemented in
Groovy, which required that developers have Groovy language support
installed and configured in their IDEs.

This commit ports GroovyDynamicElementReader from Groovy to Java,
making the compilation much simpler and allowing developers to open the
project in Eclipse or VSCode (or other IDEs without Groovy support)
without compiler errors.

This commit also converts related tests from Groovy to Java.

Closes gh-27945

spring-context/src/test/java/org/springframework/context/groovy/GroovyApplicationContextDynamicBeanPropertyTests.java

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2002-2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.context.groovy;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.beans.factory.NoSuchBeanDefinitionException;
+import org.springframework.context.support.GenericGroovyApplicationContext;
+
+import static groovy.test.GroovyAssert.assertEquals;
+import static groovy.test.GroovyAssert.assertNotNull;
+import static groovy.test.GroovyAssert.assertThrows;
+
+/**
+ * @author Jeff Brown
+ * @author Sam Brannen
+ */
+class GroovyApplicationContextDynamicBeanPropertyTests {
+
+	@Test
+	void testAccessDynamicBeanProperties() {
+		var ctx = new GenericGroovyApplicationContext();
+		ctx.getReader().loadBeanDefinitions("org/springframework/context/groovy/applicationContext.groovy");
+		ctx.refresh();
+
+		var framework = ctx.getProperty("framework");
+		assertNotNull("could not find framework bean", framework);
+		assertEquals("Grails", framework);
+		ctx.close();
+	}
+
+	@Test
+	void testAccessingNonExistentBeanViaDynamicProperty() {
+		var ctx = new GenericGroovyApplicationContext();
+		ctx.getReader().loadBeanDefinitions("org/springframework/context/groovy/applicationContext.groovy");
+		ctx.refresh();
+
+		var err = assertThrows(NoSuchBeanDefinitionException.class, () -> ctx.getProperty("someNonExistentBean"));
+
+		assertEquals("No bean named 'someNonExistentBean' available", err.getMessage());
+		ctx.close();
+	}
+
+}