001 /* $Id: PluginAssertionFailure.java 729089 2008-12-23 20:22:26Z rahul $ 002 * 003 * Licensed to the Apache Software Foundation (ASF) under one or more 004 * contributor license agreements. See the NOTICE file distributed with 005 * this work for additional information regarding copyright ownership. 006 * The ASF licenses this file to You under the Apache License, Version 2.0 007 * (the "License"); you may not use this file except in compliance with 008 * the License. You may obtain a copy of the License at 009 * 010 * http://www.apache.org/licenses/LICENSE-2.0 011 * 012 * Unless required by applicable law or agreed to in writing, software 013 * distributed under the License is distributed on an "AS IS" BASIS, 014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 015 * See the License for the specific language governing permissions and 016 * limitations under the License. 017 */ 018 019 package org.apache.commons.digester.plugins; 020 021 /** 022 * Thrown when a bug is detected in the plugins code. 023 * <p> 024 * This class is intended to be used in assertion statements, similar to 025 * the way that java 1.4's native assertion mechanism is used. However there 026 * is a difference: when a java 1.4 assertion fails, an AssertionError 027 * is thrown, which is a subclass of Error; here, the PluginAssertionFailure 028 * class extends RuntimeException rather than Error. 029 * <p> 030 * This difference in design is because throwing Error objects is not 031 * good in a container-based architecture. 032 * <p> 033 * Example: 034 * <pre> 035 * if (impossibleCondition) { 036 * throw new PluginAssertionFailure( 037 * "internal error: impossible condition is true"); 038 * } 039 * </pre> 040 * <p> 041 * Note that PluginAssertionFailure should <i>not</i> be thrown when user 042 * input is bad, or when code external to the Digester module passes invalid 043 * parameters to a plugins method. It should be used only in checks for 044 * problems which indicate internal bugs within the plugins module. 045 * 046 * @since 1.6 047 */ 048 public class PluginAssertionFailure extends RuntimeException { 049 050 private static final long serialVersionUID = 1L; 051 private Throwable cause = null; 052 053 /** 054 * @param cause underlying exception that caused this to be thrown 055 */ 056 public PluginAssertionFailure(Throwable cause) { 057 this(cause.getMessage()); 058 this.cause = cause; 059 } 060 061 /** 062 * @param msg describes the reason this exception is being thrown. 063 */ 064 public PluginAssertionFailure(String msg) { 065 super(msg); 066 } 067 068 /** 069 * @param msg describes the reason this exception is being thrown. 070 * @param cause underlying exception that caused this to be thrown 071 */ 072 public PluginAssertionFailure(String msg, Throwable cause) { 073 this(msg); 074 this.cause = cause; 075 } 076 077 /** 078 * Return the cause of this exception (if any) as specified in the 079 * exception constructor. 080 * 081 * @since 1.8 082 */ 083 public Throwable getCause() { 084 return cause; 085 } 086 }