Spring中的 bean 标签中的 factory-bean , factory-method

1.首先说说 factory-method 是指定创造实例的工厂方法,用法:

factory-method 和 class 配合使用,这时 factory-method 必须是class所指定的类中的一个静态方法,也就是Spring会直接调用 class 所指定的类的静态工厂方法创建一个实例,然后注册到IOC 容器中

factory-method 和 factory-bean 配合使用,factory-bean必须是IOC容器中存在的一个bean实例 beanA,factory-method 配置 factory-bean 所指定的实例 beanA 的一个工厂方法,也就是Spring会先创建 factory-bean 所指定的这个实例 beanA,然后调用beanA的工厂方法,创建一个新的实例 beanB,然后注册到IOC 容器中

以上描述可以看出

1.factory-bean 这个属性和 接口 FactoryBean 没有关系

2.factory-method 必须要和 class 或者 factory-bean 中的一个配合使用,如果class 和 factory-bean都配置了,那么class就不起作用了

复制代码
factory-bean的官方说明:
Alternative to class attribute for factory-method usage.If this is specified, no class attribute should be used.This must be set to the name of a bean in the current or
ancestor factories that contains the relevant factory method.This allows the factory itself to be configured using Dependency Injection, and an instance (rather than static) method to be used.
翻译:使用factory-method时,class属性的替代方案,如果指定了这个(factory-bean),class属性就不用了。factory-bean必须设置一个在当前容器或者父容器中存在的bean,并且这个bean必须拥有factory-method所指定的工厂方法。这种配置方式容许这个工厂bean通过依赖注入进行配置,factory-method 配置的是一个实例方法,不是静态方法
XML 复制代码
<bean id="exampleFactory" class="com.example.ExampleFactory">
    <!-- Inject dependencies here -->
</bean>

<bean id="exampleBean" factory-bean="exampleFactory" factory-method="createInstance"/>
复制代码
factory-method的官方说明:
The name of a factory method to use to create this object. Use constructor-arg elements to specify arguments to the factory method,if it takes arguments. Autowiring does not apply to factory methods.

If the "class" attribute is present, the factory method will be a static method on the class specified by the "class" attribute on this bean definition. Often this will be the same class as that of the constructed object - for example, when the factory method is used as an alternative to a constructor. However, it may be on a different class. In that case, the created object will *not* be of the class specified in the "class" attribute. This is analogous to FactoryBean behavior.

If the "factory-bean" attribute is present, the "class" attribute is not used, and the factory method will be an instance method on the object returned from a getBean call with the specified bean name. The factory bean may be defined as a singleton or a prototype.

The factory method can have any number of arguments. Autowiring is not supported. Use indexed constructor-arg elements in conjunction with the factory-method attribute.

Setter Injection can be used in conjunction with a factory method.Method Injection cannot, as the factory method returns an instance,which will be used when the container creates the bean.
相关推荐
舒一笑3 分钟前
Saga分布式事务框架执行逻辑
后端·程序员·设计
Emma歌小白31 分钟前
完整后台模块模板
后端
得物技术34 分钟前
MySQL单表为何别超2000万行?揭秘B+树与16KB页的生死博弈|得物技术
数据库·后端·mysql
Emma歌小白35 分钟前
配套后端(Node.js + Express + SQLite)
后端
isysc11 小时前
面了一个校招生,竟然说我是老古董
java·后端·面试
uhakadotcom1 小时前
静态代码检测技术入门:Python 的 Tree-sitter 技术详解与示例教程
后端·面试·github
幂简集成explinks1 小时前
e签宝签署API更新实战:新增 signType 与 FDA 合规参数配置
后端·设计模式·开源
River4161 小时前
Javer 学 c++(十三):引用篇
c++·后端
RoyLin1 小时前
TypeScript设计模式:迭代器模式
javascript·后端·node.js