使用AopContext.currentProxy()获取当前类的代理类

你的名字 2023-01-22 11:50 10阅读 0赞

当我们在service方法里面进行方法的自调用时，会发生事务失效的情况，这个时候可以通过AopContext.currentProxy()来获取当前类的代理类。

AopContext.currentProxy()是通过ThreadLocal来实现的。

/**
     * Class containing static methods used to obtain information about the current AOP invocation.
     *
     * <p>The {@code currentProxy()} method is usable if the AOP framework is configured to
     * expose the current proxy (not the default). It returns the AOP proxy in use. Target objects
     * or advice can use this to make advised calls, in the same way as {@code getEJBObject()}
     * can be used in EJBs. They can also use it to find advice configuration.
     *
     * <p>Spring's AOP framework does not expose proxies by default, as there is a performance cost
     * in doing so.
     *
     * <p>The functionality in this class might be used by a target object that needed access
     * to resources on the invocation. However, this approach should not be used when there is
     * a reasonable alternative, as it makes application code dependent on usage under AOP and
     * the Spring AOP framework in particular.
     *
     * @author Rod Johnson
     * @author Juergen Hoeller
     * @since 13.03.2003
     */
    public abstract class AopContext {
    
    	/**
    	 * ThreadLocal holder for AOP proxy associated with this thread.
    	 * Will contain {@code null} unless the "exposeProxy" property on
    	 * the controlling proxy configuration has been set to "true".
    	 * @see ProxyConfig#setExposeProxy
    	 */
    	private static final ThreadLocal<Object> currentProxy = new NamedThreadLocal<>("Current AOP proxy");
    
    
    	/**
    	 * Try to return the current AOP proxy. This method is usable only if the
    	 * calling method has been invoked via AOP, and the AOP framework has been set
    	 * to expose proxies. Otherwise, this method will throw an IllegalStateException.
    	 * @return Object the current AOP proxy (never returns {@code null})
    	 * @throws IllegalStateException if the proxy cannot be found, because the
    	 * method was invoked outside an AOP invocation context, or because the
    	 * AOP framework has not been configured to expose the proxy
    	 */
    	public static Object currentProxy() throws IllegalStateException {
    		Object proxy = currentProxy.get();
    		if (proxy == null) {
    			throw new IllegalStateException(
    					"Cannot find current proxy: Set 'exposeProxy' property on Advised to 'true' to make it available.");
    		}
    		return proxy;
    	}
    
    	/**
    	 * Make the given proxy available via the {@code currentProxy()} method.
    	 * <p>Note that the caller should be careful to keep the old value as appropriate.
    	 * @param proxy the proxy to expose (or {@code null} to reset it)
    	 * @return the old proxy, which may be {@code null} if none was bound
    	 * @see #currentProxy()
    	 */
    	@Nullable
    	static Object setCurrentProxy(@Nullable Object proxy) {
    		Object old = currentProxy.get();
    		if (proxy != null) {
    			currentProxy.set(proxy);
    		}
    		else {
    			currentProxy.remove();
    		}
    		return old;
    	}
    
    }