Spring Bean 实例化方式

1. InstanceSupplier方式
源码

        //createBeanInstance 方法下
        Supplier<?> instanceSupplier = mbd.getInstanceSupplier();
		if (instanceSupplier != null) {
			return obtainFromSupplier(instanceSupplier, beanName);
		}

protected BeanWrapper obtainFromSupplier(Supplier<?> instanceSupplier, String beanName) {
		Object instance;

		String outerBean = this.currentlyCreatedBean.get();
		this.currentlyCreatedBean.set(beanName);
		try {
			instance = instanceSupplier.get();
		}
		finally {
			if (outerBean != null) {
				this.currentlyCreatedBean.set(outerBean);
			}
			else {
				this.currentlyCreatedBean.remove();
			}
		}

		if (instance == null) {
			instance = new NullBean();
		}
		BeanWrapper bw = new BeanWrapperImpl(instance);
		initBeanWrapper(bw);
		return bw;
	}

所以只需要为mbd属性instanceSupplier添加值既可。实现方式如下

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	   xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
		http://www.springframework.org/schema/context  http://www.springframework.org/schema/context/spring-context.xsd">

	<bean id="supplierUser" class="com.self.bean.initialization.creation.method.supplier.SupplierUser"/>
	<bean class="com.self.bean.initialization.creation.method.supplier.SupplierBeanFactoryPostProcessor"/>
</beans>

public class SupplierUser {
	private String name;

	public SupplierUser() {
	}

	public SupplierUser(String name) {
		this.name = name;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	@Override
	public String toString() {
		return "SupplierUser{" +
				"name='" + name + '\'' +
				'}';
	}
}

public class CreateSupplier {
	public static SupplierUser createSupplierUser() {
		return new SupplierUser("zhangsan");
	}
}

public class SupplierBeanFactoryPostProcessor implements BeanFactoryPostProcessor {
	@Override
	public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
		BeanDefinition supplierUser = beanFactory.getBeanDefinition("supplierUser");
		GenericBeanDefinition genericBeanDefinition = (GenericBeanDefinition) supplierUser;
		genericBeanDefinition.setInstanceSupplier(CreateSupplier::createSupplierUser);
		genericBeanDefinition.setBeanClass(SupplierUser.class);
	}
}

public class SupplierCreateTest {
	public static void main(String[] args) {
		ClassPathXmlApplicationContext classPathXmlApplicationContext = new ClassPathXmlApplicationContext("creation.method.supplier.xml");
		SupplierUser supplierUser = (SupplierUser) classPathXmlApplicationContext.getBean("supplierUser");
		System.out.println(supplierUser.getName());
	}
}