看到不少朋友讨论 sPRing 配置时认为 spring 配置中只能静态的设置一些参数(典型情况如数据库配置, 定时器配置等)导致不方便, 其实 spring 已经提供了非常便利的方式来实现动态配置, 我们要做的只是实现一个自己的 FactoryBean , 来看一下 FactoryBean 接口的定义
代码
/** * Interface to be implemented by objects used within a BeanFactory * that are themselves factories. If a bean implements this interface, * it is used as a factory, not directly as a bean. * * <p><b>NB: A bean that implements this interface cannot be used * as a normal bean.</b> A FactoryBean is defined in a bean style, * but the object eXPosed for bean references is always the object * that it creates. * * <p>FactoryBeans can support singletons and prototypes, and can * either create objects lazily on demand or eagerly on startup. * * <p>This interface is heavily used within the framework, for * example for the AOP ProxyFactoryBean or JndiObjectFactoryBean. * It can be used for application components, but this is not common * outside of infrastrUCture code. * * @author Rod Johnson * @author Juergen Hoeller * @since 08.03.2003 * @see org.springframework.beans.factory.BeanFactory * @see org.springframework.aop.framework.ProxyFactoryBean * @see org.springframework.jndi.JndiObjectFactoryBean */ public interface FactoryBean {
/** * Return an instance (possibly shared or independent) of the object * managed by this factory. As with a BeanFactory, this allows * support for both the Singleton and Prototype design pattern. * <p>If this method returns <code>null</code>, the factory will consider * the FactoryBean as not fully initialized and throw a corresponding * FactoryBeanNotInitializedException. * @return an instance of the bean (should not be <code>null</code>; * a <code>null</code> value will be considered as an indication of * incomplete initialization) * @throws Exception in case of creation errors * @see FactoryBeanNotInitializedException */ Object getObject() throws Exception;
/** * Return the type of object that this FactoryBean creates, or <code>null</code> * if not known in advance. This allows to check for specific types * of beans without instantiating objects, for example on autowiring. * <p>For a singleton, this should try to avoid singleton creation * as far as possible; it should rather estimate the type in advance. * For prototypes, returning a meaningful type here is advisable too. * <p>This method can be called <i>before</i> this FactoryBean has * been fully initialized. It must not rely on state created during * initialization; of course, it can still use such state if available. * <p>