ex的cause是错的，应该是造成降级的异常信息

The BlockException does not carry a cause exception, so you cannot get the cause via getCause method. The self cause object is the default behaviour for JVM exceptions. See java.lang.Throwable#getCause:

/** * Returns the cause of this throwable or {@code null} if the * cause is nonexistent or unknown. (The cause is the throwable that * caused this throwable to get thrown.) * *

This implementation returns the cause that was supplied via one of * the constructors requiring a {@code Throwable}, or that was set after * creation with the {@link #initCause(Throwable)} method. While it is * typically unnecessary to override this method, a subclass can override * it to return a cause set by some other means. This is appropriate for * a "legacy chained throwable" that predates the addition of chained * exceptions to {@code Throwable}. Note that it is not * necessary to override any of the {@code PrintStackTrace} methods, * all of which invoke the {@code getCause} method to determine the * cause of a throwable. * * @return the cause of this throwable or {@code null} if the * cause is nonexistent or unknown. * @since 1.4 */ public synchronized Throwable getCause() { return (cause==this ? null : cause); }

原回答者GitHub用户sczyh30