编程式配置Spring bean

今晚翻看了以前写的RPC框架。发现这个框架中编程式配置Spring bean的技巧还是比较通用的，其他的一些框架或基础服务可能也会用到。记得当时也是从Struts2的代码里找到的，在此先做下记录，以供以后参考。

public class RpcMethodHelper implements ApplicationContextAware {
	protected static final Logger logger = LoggerFactory.getLogger(RpcMethodHelper.class);

	protected ApplicationContext appContext;
	protected AutowireCapableBeanFactory autoWiringFactory;
	protected int autowireStrategy = AutowireCapableBeanFactory.AUTOWIRE_BY_NAME;

	/**
	 * 初始化Action如果已经在spring中注册过则从spring容器中得到Action实例， 如果spring容器中没有注册则先注册并返回实例
	 * 返回的Action实例已经注入了依赖的其他对象及请求参数
	 * 
	 * @param <T>
	 * @param clazz
	 * @return
	 */
	protected <T> T createAction(Class<T> clazz) {
		T action = null;
		String beanName = clazz.getName();
		try {
			logger.debug("Trying the application context... appContext = {},\n bean name = {}" ,appContext,beanName);
			action = clazz.cast(appContext.getBean(beanName));//先从spring容器中得到bean
		} catch (NoSuchBeanDefinitionException e) {
			//如果spring容器中没有注册则先注册并返回实例
			logger.debug("Did not find bean definition for bean named {}, creating a new one...",beanName);

			if (autoWiringFactory instanceof BeanDefinitionRegistry) {
				BeanDefinitionRegistry registry = (BeanDefinitionRegistry) autoWiringFactory;
				RootBeanDefinition def = new RootBeanDefinition(clazz,
						autowireStrategy);//设置autowire策略,根据具体应用来决定
				// def.setSingleton(false);
				def.setScope("prototype");//这里的scope类型可以根据需要设置
				logger.debug("Registering a new bean definition for class "
						+ beanName);

				registry.registerBeanDefinition(beanName, def);
				try {
					
					action = clazz.cast(appContext.getBean(beanName));
				} catch (NoSuchBeanDefinitionException e2) {
					logger.warn("Could not register new bean definition for bean {}"
									,beanName);
				}

			}
		}
		return action;
	}

	public void setApplicationContext(ApplicationContext context)
			throws BeansException {
		appContext = context;
		autoWiringFactory = findAutoWiringBeanFactory(this.appContext);
	}

	/**
	 * 
	 * @see com.opensymphony.xwork2.spring.SpringObjectFactory#findAutoWiringBeanFactory
	 * @param context
	 */
	protected AutowireCapableBeanFactory findAutoWiringBeanFactory(
			ApplicationContext context) {
		if (context instanceof AutowireCapableBeanFactory) {
			// Check the context
			return (AutowireCapableBeanFactory) context;
		} else if (context instanceof ConfigurableApplicationContext) {
			// Try and grab the beanFactory
			return ((ConfigurableApplicationContext) context).getBeanFactory();
		} else if (context.getParent() != null) {
			// And if all else fails, try again with the parent context
			return findAutoWiringBeanFactory(context.getParent());
		}
		return null;
	}

	/**
	 * Sets the autowiring strategy
	 * 
	 * @see com.opensymphony.xwork2.spring.SpringObjectFactory#setAutowireStrategy
	 * @param autowireStrategy
	 */
	public void setAutowireStrategy(int autowireStrategy) {
		switch (autowireStrategy) {
		case AutowireCapableBeanFactory.AUTOWIRE_AUTODETECT:
			logger.info("Setting autowire strategy to autodetect");
			this.autowireStrategy = autowireStrategy;
			break;
		case AutowireCapableBeanFactory.AUTOWIRE_BY_NAME:
			logger.info("Setting autowire strategy to name");
			this.autowireStrategy = autowireStrategy;
			break;
		case AutowireCapableBeanFactory.AUTOWIRE_BY_TYPE:
			logger.info("Setting autowire strategy to type");
			this.autowireStrategy = autowireStrategy;
			break;
		case AutowireCapableBeanFactory.AUTOWIRE_CONSTRUCTOR:
			logger.info("Setting autowire strategy to constructor");
			this.autowireStrategy = autowireStrategy;
			break;
		default:
			throw new IllegalStateException("Invalid autowire type set");
		}
	}
}

使用方式：
1.上面的RpcMethodHelper本身也应该配置到spring容器中

<bean id="rpcMethodHelper" class="com.niagara.rpc.RpcMethodHelper"></bean>

2.如果不想将上面的类配置为Spring bean，那只要在工具类中得到ApplicationContext的引用即可。