Java In A Nutshell, 5th Edition

Thrown by a method of a Proxy object if the invoke( ) method of the proxy's InvocationHandler throws a checked exception not declared by the original method. This class serves as an unchecked exception wrapper around the checked exception. Use getUndeclaredThrowable( ) to obtain the checked exception thrown by invoke( ) . In Java 1.4 and later, all exceptions can be "chained" in this way, and getUndeclaredThrowable( ) is superseded by the more general getCause( ) method.

public class UndeclaredThrowableException extends RuntimeException { // Public Constructors public UndeclaredThrowableException (Throwable undeclaredThrowable ); public UndeclaredThrowableException (Throwable undeclaredThrowable , String s ); // Public Instance Methods public Throwable getUndeclaredThrowable ( ); // Public Methods Overriding Throwable 1.4 public Throwable getCause ( ); }