ExceptionUnwrapper.java

package com.sleepycat.util;
import de.ovgu.cide.jakutil.*;
/** 
 * Unwraps nested exceptions by calling the {@link ExceptionWrapper#getCause()} method for exceptions that implement the{@link ExceptionWrapper} interface.  Does not currently support the Java 1.4
 * <code>Throwable.getCause()</code> method.
 * @author Mark Hayes
 */
public class ExceptionUnwrapper {
  /** 
 * Unwraps an Exception and returns the underlying Exception, or throws an
 * Error if the underlying Throwable is an Error.
 * @param e is the Exception to unwrap.
 * @return the underlying Exception.
 * @throws Error if the underlying Throwable is an Error.
 * @throws IllegalArgumentException if the underlying Throwable is not an
 * Exception or an Error.
 */
  public static Exception unwrap(  Exception e){
    Throwable t=unwrapAny(e);
    if (t instanceof Exception) {
      return (Exception)t;
    }
 else     if (t instanceof Error) {
      throw (Error)t;
    }
 else {
      throw new IllegalArgumentException("Not Exception or Error: " + t);
    }
  }
  /** 
 * Unwraps an Exception and returns the underlying Throwable.
 * @param e is the Exception to unwrap.
 * @return the underlying Throwable.
 */
  public static Throwable unwrapAny(  Throwable e){
    while (true) {
      if (e instanceof ExceptionWrapper) {
        Throwable e2=((ExceptionWrapper)e).getCause();
        if (e2 == null) {
          return e;
        }
 else {
          e=e2;
        }
      }
 else {
        return e;
      }
    }
  }
}