Add support for generating class names

Add `ClassNameGenerator` to support generation of class names.

See gh-28414

spring-core/src/test/java/org/springframework/aot/generate/ClassNameGeneratorTests.java

@@ -0,0 +1,119 @@
+/*
+ * 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.io.InputStream;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.javapoet.ClassName;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
+
+/**
+ * Tests for {@link ClassNameGenerator}.
+ *
+ * @author Phillip Webb
+ */
+class ClassNameGeneratorTests {
+
+	private final ClassNameGenerator generator = new ClassNameGenerator();
+
+	@Test
+	void generateClassNameWhenTargetClassIsNullThrowsException() {
+		assertThatIllegalArgumentException()
+				.isThrownBy(
+						() -> this.generator.generateClassName((Class<?>) null, "Test"))
+				.withMessage("'target' must not be null");
+	}
+
+	@Test
+	void generateClassNameWhenTargetStringIsEmptyThrowsException() {
+		assertThatIllegalArgumentException()
+				.isThrownBy(() -> this.generator.generateClassName("", "Test"))
+				.withMessage("'target' must not be empty");
+	}
+
+	@Test
+	void generatedClassNameWhenFeatureIsEmptyThrowsException() {
+		assertThatIllegalArgumentException()
+				.isThrownBy(() -> this.generator.generateClassName(InputStream.class, ""))
+				.withMessage("'featureName' must not be empty");
+	}
+
+	@Test
+	void generatedClassNameWhenFeatureIsNotAllLettersThrowsException() {
+		String expectedMessage = "'featureName' must contain only letters";
+		assertThatIllegalArgumentException().isThrownBy(
+				() -> this.generator.generateClassName(InputStream.class, "noway!"))
+				.withMessage(expectedMessage);
+		assertThatIllegalArgumentException().isThrownBy(
+				() -> this.generator.generateClassName(InputStream.class, "1WontWork"))
+				.withMessage(expectedMessage);
+		assertThatIllegalArgumentException()
+				.isThrownBy(
+						() -> this.generator.generateClassName(InputStream.class, "N0pe"))
+				.withMessage(expectedMessage);
+	}
+
+	@Test
+	void generateClassNameWithClassWhenLowercaseFeatureNameGeneratesName() {
+		ClassName generated = this.generator.generateClassName(InputStream.class,
+				"bytes");
+		assertThat(generated).hasToString("java.io.InputStream__Bytes");
+	}
+
+	@Test
+	void generateClassNameWithClassWhenInnerClassGeneratesName() {
+		ClassName generated = this.generator.generateClassName(TestBean.class,
+				"EventListener");
+		assertThat(generated).hasToString(
+				"org.springframework.aot.generate.ClassNameGeneratorTests_TestBean__EventListener");
+	}
+
+	@Test
+	void generateClassWithClassWhenMultipleCallsGeneratesSequencedName() {
+		ClassName generated1 = this.generator.generateClassName(InputStream.class,
+				"bytes");
+		ClassName generated2 = this.generator.generateClassName(InputStream.class,
+				"bytes");
+		ClassName generated3 = this.generator.generateClassName(InputStream.class,
+				"bytes");
+		assertThat(generated1).hasToString("java.io.InputStream__Bytes");
+		assertThat(generated2).hasToString("java.io.InputStream__Bytes1");
+		assertThat(generated3).hasToString("java.io.InputStream__Bytes2");
+	}
+
+	@Test
+	void generateClassNameWithStringGeneratesNameUsingOnlyLetters() {
+		ClassName generated = this.generator.generateClassName("my-bean--factoryStuff",
+				"beans");
+		assertThat(generated).hasToString("__.MyBeanFactoryStuff__Beans");
+	}
+
+	@Test
+	void generateClassNameWithStringWhenNoLettersGeneratesAotName() {
+		ClassName generated = this.generator.generateClassName("1234!@#", "beans");
+		assertThat(generated).hasToString("__.Aot__Beans");
+	}
+
+	static class TestBean {
+
+	}
+
+}