用FactoryBean让Spring配置动起来

 1/**//**
 2* Interface to be implemented by objects used within a BeanFactory
 3* that are themselves factories. If a bean implements this interface,
 4* it is used as a factory, not directly as a bean.
 5*
 6* ＜p＞＜b＞NB: A bean that implements this interface cannot be used
 7* as a normal bean.＜/b＞ A FactoryBean is defined in a bean style,
 8* but the object exposed for bean references is always the object
 9* that it creates.
10*
11* ＜p＞FactoryBeans can support singletons and prototypes, and can
12* either create objects lazily on demand or eagerly on startup.
13*
14* ＜p＞This interface is heavily used within the framework, for
15* example for the AOP ProxyFactoryBean or JndiObjectFactoryBean.
16* It can be used for application components, but this is not common
17* outside of infrastructure code.
18*
19* @author Rod Johnson
20* @author Juergen Hoeller
21* @since 08.03.2003
22* @see org.springframework.beans.factory.BeanFactory
23* @see org.springframework.aop.framework.ProxyFactoryBean
24* @see org.springframework.jndi.JndiObjectFactoryBean
25*/
26public interface FactoryBean ...{
27
28　/**//**
29　* Return an instance (possibly shared or independent) of the object
30　* managed by this factory. As with a BeanFactory, this allows
31　* support for both the Singleton and Prototype design pattern.
32　* ＜p＞If this method returns ＜code＞null＜/code＞, the factory will consider
33　* the FactoryBean as not fully initialized and throw a corresponding
34　* FactoryBeanNotInitializedException.
35　* @return an instance of the bean (should not be ＜code＞null＜/code＞;
36　* a ＜code＞null＜/code＞ value will be considered as an indication of
37　* incomplete initialization)
38　* @throws Exception in case of creation errors
39　* @see FactoryBeanNotInitializedException
40　*/
41　Object getObject() throws Exception;
42
43　/**//**
44　* Return the type of object that this FactoryBean creates, or ＜code＞null＜/code＞
45　* if not known in advance. This allows to check for specific types
46　* of beans without instantiating objects, for example on autowiring.
47　* ＜p＞For a singleton, this should try to avoid singleton creation
48　* as far as possible; it should rather estimate the type in advance.
49　* For prototypes, returning a meaningful type here is advisable too.
50　* ＜p＞This method can be called ＜i＞before＜/i＞ this FactoryBean has
51　* been fully initialized. It must not rely on state created during
52　* initialization; of course, it can still use such state if available.
53　* ＜p＞＜b＞NOTE:＜/b＞ Autowiring will simply ignore FactoryBeans that return
54　* ＜code＞null＜/code＞ here. Therefore it is highly recommended to implement
55　* this method properly, using the current state of the FactoryBean.
56　* @return the type of object that this FactoryBean creates,
57　* or ＜code＞null＜/code＞ if not known at the time of the call
58　* @see ListableBeanFactory#getBeansOfType
59　*/
60　Class getObjectType();
61
62　/**//**
63　* Is the bean managed by this factory a singleton or a prototype?
64　* That is, will ＜code＞getObject()＜/code＞ always return the same object
65　* (a reference that can be cached)?
66　* ＜p＞＜b＞NOTE:＜/b＞ If a FactoryBean indicates to hold a singleton object,
67　* the object returned from ＜code＞getObject()＜/code＞ might get cached
68　* by the owning BeanFactory. Hence, do not return ＜code＞true＜/code＞
69　* unless the FactoryBean always exposes the same reference.
70　* ＜p＞The singleton status of the FactoryBean itself will generally
71　* be provided by the owning BeanFactory; usually, it has to be
72　* defined as singleton there.
73　* @return if this bean is a singleton
74　* @see #getObject()
75　*/
76　boolean isSingleton();
77
78}
79

 1public class BasicDataSourceFactoryBean implements FactoryBean ...{
 2　public Object getObject() throws Exception ...{
 3　　BasicDataSource dataSource = new BasicDataSource();
 4　　// 读取外部配置, 设置到 dataSource 中 ... 
 5　　return dataSource;
 6　}
 7
 8　public Class getObjectType() ...{
 9　　return BasicDataSource.class;
10　}
11
12　public boolean isSingleton() ...{
13　　return true;
14　}
15}
16

1＜bean id="dataSource" class="BasicDataSourceFactoryBean "＞
2... 你的配置来源
3＜/bean＞
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