public class DateStringFactoryBean implements FactoryBean<Object> {

    private boolean isDate;

    public void setDate(boolean date) {

        isDate = date;

    }

    @Override

    public Object getObject() {

        return isDate ? new Date() : "2018-03-04";

    }

    @Override

    public Class<?> getObjectType() {

        return isDate ? Date.class : String.class;

    }

    @Override

    public boolean isSingleton() {

        return false;

    }

}

public class AppConfig {

    @Bean(name = "dateFactoryBean")

    public DateStringFactoryBean createString(){

        DateStringFactoryBean bean = new DateStringFactoryBean();

        bean.setDate(true);

        return bean;

    }

    @Bean(name = "stringFactoryBean")

    public DateStringFactoryBean createDate(){

        DateStringFactoryBean bean = new DateStringFactoryBean();

        bean.setDate(false);

        return bean;

    }

}

public class Main {

    public static void main(String[] args) {

        AbstractApplicationContext context = new AnnotationConfigApplicationContext(AppConfig.class);

        System.out.println(context.getBean("dateFactoryBean", Date.class));

        System.out.println(context.getBean("stringFactoryBean", String.class));

        System.out.println(context.getBean("&dateFactoryBean"));  //使用&+beanName获得DateStringFactoryBean实例

        System.out.println(context.getBean("&stringFactoryBean"));

    }

}

public interface FactoryBean<T>

Interface to be implemented by objects used within a BeanFactory which are themselves factories for individual objects.

If a bean implements this interface, it is used as a factory for an object to expose, not directly as a bean instance that will be exposed itself.

NB: A bean that implements this interface cannot be used as a normal bean. A FactoryBean is defined in a bean style,

but the object exposed for bean references (getObject()) is always the object that it creates.

FactoryBeans can support singletons and prototypes, and can either create objects lazily on demand or eagerly on startup.

The SmartFactoryBean interface allows for exposing more fine-grained behavioral metadata.

This interface is heavily used within the framework itself, for example for the AOP ProxyFactoryBean .

It can be used for custom components as well; however, this is only common for infrastructure code.

FactoryBean is a programmatic contract. Implementations are not supposed to rely on annotation-driven injection

or other reflective facilities.   getObjectType() getObject() invocations may arrive early in the bootstrap process, even

ahead of any post-processor setup. If you need access other beans, implement BeanFactoryAware and obtain them programmatically.

Finally, FactoryBean objects participate in the containing BeanFactory's synchronization of bean creation. There is usually no

need for internal synchronization other than for purposes of lazy initialization within the FactoryBean itself (or the like).