Add support for generating method names

Add `MethodNameGenerator` to support generation of method names.

See gh-28414

spring-core/src/main/java/org/springframework/aot/generate/MethodNameGenerator.java

@@ -0,0 +1,124 @@
+/*
+ * Copyright 2002-2022 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.aot.generate;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
+import org.springframework.util.ClassUtils;
+import org.springframework.util.StringUtils;
+
+/**
+ * Generates unique method names that can be used in ahead-of-time generated
+ * source code. This class is stateful so one instance should be used per
+ * generated type.
+ *
+ * @author Phillip Webb
+ * @since 6.0
+ */
+public class MethodNameGenerator {
+
+	private final Map<String, AtomicInteger> sequenceGenerator = new ConcurrentHashMap<>();
+
+
+	/**
+	 * Create a new {@link MethodNameGenerator} instance without any reserved
+	 * names.
+	 */
+	public MethodNameGenerator() {
+	}
+
+	/**
+	 * Create a new {@link MethodNameGenerator} instance with the specified
+	 * reserved names.
+	 * @param reservedNames the method names to reserve
+	 */
+	public MethodNameGenerator(String... reservedNames) {
+		this(List.of(reservedNames));
+	}
+
+	/**
+	 * Create a new {@link MethodNameGenerator} instance with the specified
+	 * reserved names.
+	 * @param reservedNames the method names to reserve
+	 */
+	public MethodNameGenerator(Iterable<String> reservedNames) {
+		Assert.notNull(reservedNames, "'reservedNames' must not be null");
+		for (String reservedName : reservedNames) {
+			addSequence(StringUtils.uncapitalize(reservedName));
+		}
+	}
+
+
+	/**
+	 * Generate a new method name from the given parts.
+	 * @param parts the parts used to build the name.
+	 * @return the generated method name
+	 */
+	public String generateMethodName(Object... parts) {
+		String generatedName = join(parts);
+		return addSequence(generatedName.isEmpty() ? "$$aot" : generatedName);
+	}
+
+	private String addSequence(String name) {
+		int sequence = this.sequenceGenerator
+				.computeIfAbsent(name, key -> new AtomicInteger()).getAndIncrement();
+		return (sequence > 0) ? name + sequence : name;
+	}
+
+	/**
+	 * Join the specified parts to create a valid camel case method name.
+	 * @param parts the parts to join
+	 * @return a method name from the joined parts.
+	 */
+	public static String join(Object... parts) {
+		Stream<String> capitalizedPartNames = Arrays.stream(parts)
+				.map(MethodNameGenerator::getPartName).map(StringUtils::capitalize);
+		return StringUtils
+				.uncapitalize(capitalizedPartNames.collect(Collectors.joining()));
+	}
+
+	private static String getPartName(@Nullable Object part) {
+		if (part == null) {
+			return "";
+		}
+		if (part instanceof Class<?> clazz) {
+			return clean(ClassUtils.getShortName(clazz));
+		}
+		return clean(part.toString());
+	}
+
+	private static String clean(String string) {
+		char[] chars = string.toCharArray();
+		StringBuilder name = new StringBuilder(chars.length);
+		boolean uppercase = false;
+		for (char ch : chars) {
+			char outputChar = (!uppercase) ? ch : Character.toUpperCase(ch);
+			name.append((!Character.isLetter(ch)) ? "" : outputChar);
+			uppercase = ch == '.';
+		}
+		return name.toString();
+	}
+
+}