spring bean 缓存实现

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如何自定义缓存spring bean

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public class SpringBeanHolder implements ApplicationContextAware {

	private static ApplicationContext context;

	private static ConcurrentHashMap<String, Object> cachedBeans = new ConcurrentHashMap<>(7000);

	@Override
	public void setApplicationContext(ApplicationContext context) throws BeansException {
		SpringBeanHolder.context = context;
	}

	@Nonnull public static <T> T getBean(String beanName) throws NullPointerException{
		T bean = getBeanMaybeNull(beanName);
		if (bean == null) throw new NullPointerException("bean[" + beanName + "] is not exist in spring container");
		return bean;
	}

	@SuppressWarnings("unchecked")
	@Nullable public static <T> T getBeanMaybeNull(String beanName) {
		notEmpty(beanName, beanName + " bean name is required");

		checkState(context != null, "spring application context is not injected");

		T bean = (T) cachedBeans.get(beanName);

		if (bean == null) {
			bean = cache(beanName, (T) context.getBean(beanName));
		}
		return bean;
	}

	@SuppressWarnings("unchecked")
	private static <T> T cache(String beanName, T exist) {
		if (exist == null) return null;

		T bean = (T) cachedBeans.putIfAbsent(beanName, exist);
		if (bean == null) {
			bean = exist;
		}
		return bean;
	}

	@SuppressWarnings("unchecked")
	public static <T> T getBean(Class<?> beanType) {
		String clazzName = beanType.getName();
		T bean = getBeanMaybeNull(clazzName);
		if (bean == null) { // 对于非注入的类, 直接new...
			try {
				bean = (T) beanType.newInstance();
				cache(clazzName, bean);
			} catch (Exception e) {
				throw new RuntimeException("cannot get instance from class:" + clazzName, e);
			}
		}
		return bean;
	}

}