Reimplement annotation literals without private APIs (#6)

pom.xml

@@ -55,6 +55,11 @@
       <groupId>com.google.inject</groupId>
       <artifactId>guice</artifactId>
     </dependency>
+    <dependency>
+      <groupId>org.apache.commons</groupId>
+      <artifactId>commons-lang3</artifactId>
+      <version>3.12.0</version>
+    </dependency>
     <dependency>
       <groupId>org.jenkins-ci</groupId>
       <artifactId>annotation-indexer</artifactId>

src/main/java/com/cloudbees/sdk/extensibility/AnnotationLiteral.java

@@ -17,7 +17,10 @@
 package com.cloudbees.sdk.extensibility;
 
 import java.lang.annotation.Annotation;
+import java.lang.reflect.Proxy;
 import java.util.Collections;
+import java.util.Map;
+import org.apache.commons.lang3.AnnotationUtils;
 
 /**
  * Factory for annotation objects.
@@ -41,4 +44,26 @@ public static <T extends Annotation> T of(Class<T> type, Object value) {
     public static <T extends Annotation> T of(Class<T> type, String key, Object value) {
         return of(type, Collections.singletonMap(key, value));
     }
+
+    public static <T extends Annotation> T of(Class<T> type, final Map<String, Object> values) {
+        return type.cast(Proxy.newProxyInstance(type.getClassLoader(), new Class<?>[] {type}, (proxy, method, args) -> {
+            Annotation annotation = (Annotation) proxy;
+            String methodName = method.getName();
+            switch (methodName) {
+                case "equals":
+                    return AnnotationUtils.equals(annotation, (Annotation) args[0]);
+                case "toString":
+                    return AnnotationUtils.toString(annotation);
+                case "hashCode":
+                    return AnnotationUtils.hashCode(annotation);
+                case "annotationType":
+                    return type;
+                default:
+                    if (!values.containsKey(methodName)) {
+                        throw new NoSuchMethodException("Missing value for annotation key: " + methodName);
+                    }
+                    return values.get(methodName);
+            }
+        }));
+    }
 }

src/test/java/com/cloudbees/sdk/extensibility/AnnotationLiteralTest.java

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2023, CloudBees Inc.
+ *
+ * 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
+ *
+ *     http://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 com.cloudbees.sdk.extensibility;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotEquals;
+
+import javax.inject.Named;
+import org.junit.Test;
+
+/**
+ * @author Basil Crow
+ */
+public class AnnotationLiteralTest {
+    @Test
+    public void smokes() {
+        Named a = AnnotationLiteral.of(Named.class, "cat");
+        assertEquals("@javax.inject.Named(value=cat)", a.toString());
+        assertEquals(Named.class, a.annotationType());
+
+        Named cat = Cat.class.getAnnotation(Named.class);
+        assertEquals(a, cat);
+        assertEquals(a.hashCode(), cat.hashCode());
+
+        Named dog = Dog.class.getAnnotation(Named.class);
+        assertNotEquals(a, dog);
+        assertNotEquals(a.hashCode(), dog.hashCode());
+    }
+}