Add bean instance generator infrastructure

This commit provides the necessary infrastructure to let components
contribute statements that are used to fully instantiate a bean
instance.

To ease code generation, a dedicated infrastructure to register bean
definition is provided in the o.s.beans.factory.generator package.
BeanDefinitionRegistrar offers a builder style API that provides a way
to hide how injected elements are resolved at runtime and let
contributors provide code that may throw a checked exception.

BeanInstanceContributor is the interface that components can implement
to contribute to a bean instance setup. DefaultBeanInstanceGenerator
generates, for a particular bean definition, the necessary statements
to instantiate a bean.

Closes gh-28047

spring-beans/src/testFixtures/java/org/springframework/beans/testfixture/beans/factory/generator/InnerComponentConfiguration.java

@@ -0,0 +1,36 @@
+/*
+ * 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.beans.testfixture.beans.factory.generator;
+
+import org.springframework.core.env.Environment;
+
+public class InnerComponentConfiguration {
+
+	public class NoDependencyComponent {
+
+		public NoDependencyComponent() {
+
+		}
+	}
+
+	public class EnvironmentAwareComponent {
+
+		public EnvironmentAwareComponent(Environment environment) {
+
+		}
+	}
+}

spring-beans/src/testFixtures/java/org/springframework/beans/testfixture/beans/factory/generator/SimpleConfiguration.java

@@ -0,0 +1,32 @@
+/*
+ * 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.beans.testfixture.beans.factory.generator;
+
+public class SimpleConfiguration {
+
+	public SimpleConfiguration() {
+	}
+
+	public String stringBean() {
+		return "Hello";
+	}
+
+	public Integer integerBean() {
+		return 42;
+	}
+
+}

spring-beans/src/testFixtures/java/org/springframework/beans/testfixture/beans/factory/generator/factory/NumberHolder.java

@@ -0,0 +1,36 @@
+/*
+ * 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.beans.testfixture.beans.factory.generator.factory;
+
+import java.io.Serializable;
+
+/**
+ * A sample object with a generic type.
+ *
+ * @param <T> the number type
+ * @author Stephane Nicoll
+ */
+@SuppressWarnings("serial")
+public class NumberHolder<T extends Number> implements Serializable {
+
+	private final T number;
+
+	public NumberHolder(T number) {
+		this.number = number;
+	}
+
+}

spring-beans/src/testFixtures/java/org/springframework/beans/testfixture/beans/factory/generator/factory/NumberHolderFactoryBean.java

@@ -0,0 +1,45 @@
+/*
+ * 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.beans.testfixture.beans.factory.generator.factory;
+
+import org.springframework.beans.factory.FactoryBean;
+
+/**
+ * A sample factory bean with a generic type.
+ *
+ * @param <T> the type of the number generated by this factory bean
+ * @author Stephane Nicoll
+ */
+public class NumberHolderFactoryBean<T extends Number> implements FactoryBean<NumberHolder<T>> {
+
+	private T number;
+
+	public void setNumber(T number) {
+		this.number = number;
+	}
+
+	@Override
+	public NumberHolder<T> getObject() {
+		return new NumberHolder<>(this.number);
+	}
+
+	@Override
+	public Class<?> getObjectType() {
+		return NumberHolder.class;
+	}
+
+}

spring-beans/src/testFixtures/java/org/springframework/beans/testfixture/beans/factory/generator/factory/SampleFactory.java

@@ -0,0 +1,41 @@
+/*
+ * 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.beans.testfixture.beans.factory.generator.factory;
+
+public abstract class SampleFactory {
+
+	public static String create(String testBean) {
+		return testBean;
+	}
+
+	public static String create(char character) {
+		return String.valueOf(character);
+	}
+
+	public static String create(Number number, String test) {
+		return number + test;
+	}
+
+	public static String create(Class<?> type) {
+		return type.getName();
+	}
+
+	public static Integer integerBean() {
+		return 42;
+	}
+
+}

spring-beans/src/testFixtures/java/org/springframework/beans/testfixture/beans/factory/generator/injection/InjectionComponent.java

@@ -0,0 +1,37 @@
+/*
+ * 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.beans.testfixture.beans.factory.generator.injection;
+
+import org.springframework.beans.factory.annotation.Autowired;
+
+@SuppressWarnings("unused")
+public class InjectionComponent {
+
+	private final String bean;
+
+	private Integer counter;
+
+	public InjectionComponent(String bean) {
+		this.bean = bean;
+	}
+
+	@Autowired(required = false)
+	public void setCounter(Integer counter) {
+		this.counter = counter;
+	}
+
+}

spring-beans/src/testFixtures/java/org/springframework/beans/testfixture/beans/factory/generator/property/ConfigurableBean.java

@@ -0,0 +1,33 @@
+/*
+ * 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.beans.testfixture.beans.factory.generator.property;
+
+public class ConfigurableBean {
+
+	private String name;
+
+	private Integer counter;
+
+	public void setName(String name) {
+		this.name = name;
+	}
+
+	public void setCounter(Integer counter) {
+		this.counter = counter;
+	}
+
+}

spring-beans/src/testFixtures/java/org/springframework/beans/testfixture/beans/factory/generator/visibility/ProtectedConstructorComponent.java

@@ -0,0 +1,24 @@
+/*
+ * 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.beans.testfixture.beans.factory.generator.visibility;
+
+public class ProtectedConstructorComponent {
+
+	ProtectedConstructorComponent() {
+
+	}
+}

spring-beans/src/testFixtures/java/org/springframework/beans/testfixture/beans/factory/generator/visibility/ProtectedFactoryMethod.java

@@ -0,0 +1,25 @@
+/*
+ * 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.beans.testfixture.beans.factory.generator.visibility;
+
+public class ProtectedFactoryMethod {
+
+	String testBean(Integer number) {
+		return "test-" + number;
+	}
+
+}