将预构造的Bean添加到Spring应用程序上下文中

Question

我正在编写一个实现以下方法的类:

public void run(javax.sql.DataSource dataSource);

在此方法中,我希望使用类似于以下的配置文件构造Spring应用程序上下文:

<bean id="dataSource" abstract="true" />

<bean id="dao" class="my.Dao">
  <property name="dataSource" ref="dataSource" />
</bean>

是否可以强制Spring在配置文件中引用"dataSource"bean的任何地方使用传递给我的方法的DataSource对象？

Answer 1

我一直处于相同的情况.由于没有人提出我的解决方案(我认为我的解决方案更优雅),我会在这里为后代添加它:-)

该解决方案包括两个步骤:

1. 创建父ApplicationContext并在其中注册现有的bean.
2. 创建子ApplicationContext(在父上下文中传递)并从XML文件加载bean

步骤1:

//create parent BeanFactory
DefaultListableBeanFactory parentBeanFactory = new DefaultListableBeanFactory();
//register your pre-fabricated object in it
parentBeanFactory.registerSingleton("dataSource", dataSource);
//wrap BeanFactory inside ApplicationContext
GenericApplicationContext parentContext = 
        new GenericApplicationContext(parentBeanFactory);
parentContext.refresh(); //as suggested "itzgeoff", to overcome a warning about events

第2步:

//create your "child" ApplicationContext that contains the beans from "beans.xml"
//note that we are passing previously made parent ApplicationContext as parent
ApplicationContext context = new ClassPathXmlApplicationContext(
        new String[] {"beans.xml"}, parentContext);

Answer 2

我发现可以使用两个Spring接口来实现我需要的东西.该BeanNameAware接口允许Spring通过调用来告诉一个对象的应用程序上下文中它的名字setBeanName(字符串)方法.该FactoryBean的接口告诉Spring不使用对象本身,而是当对象返回的getObject()方法被调用.把它们放在一起你会得到:

public class PlaceholderBean implements BeanNameAware, FactoryBean {

    public static Map<String, Object> beansByName = new HashMap<String, Object>();

    private String beanName;

    @Override
    public void setBeanName(String beanName) {
        this.beanName = beanName;
    }

    @Override
    public Object getObject() {
        return beansByName.get(beanName);
    }

    @Override
    public Class<?> getObjectType() {
        return beansByName.get(beanName).getClass();
    }

    @Override
    public boolean isSingleton() {
        return true;
    }

}

bean定义现在简化为:

<bean id="dataSource" class="PlaceholderBean" />

占位符在创建应用程序上下文之前接收其值.

public void run(DataSource externalDataSource) {
    PlaceholderBean.beansByName.put("dataSource", externalDataSource);
    ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");
    assert externalDataSource == context.getBean("dataSource");
}

事情似乎成功了!