Added a utility for examining Throwable objects, as proposed by Costin
<costinm@covalent.net> and Henri Yandell <bayard@apache.org>. Comes complete with a full suite of tests for initial functionality. git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/proper/lang/trunk@136961 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Daniel Rall
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package org.apache.commons.lang.exception;
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/* ====================================================================
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* The Apache Software License, Version 1.1
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*
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* Copyright (c) 2002 The Apache Software Foundation. All rights
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* reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* 3. The end-user documentation included with the redistribution, if
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* any, must include the following acknowlegement:
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* "This product includes software developed by the
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* Apache Software Foundation (http://www.apache.org/)."
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* Alternately, this acknowlegement may appear in the software itself,
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* if and wherever such third-party acknowlegements normally appear.
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*
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* 4. The names "The Jakarta Project", "Commons", and "Apache Software
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* Foundation" must not be used to endorse or promote products derived
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* from this software without prior written permission. For written
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* permission, please contact apache@apache.org.
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*
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* 5. Products derived from this software may not be called "Apache"
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* nor may "Apache" appear in their names without prior written
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* permission of the Apache Software Foundation.
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*
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* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
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* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
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* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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* ====================================================================
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*
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* This software consists of voluntary contributions made by many
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* individuals on behalf of the Apache Software Foundation. For more
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* information on the Apache Software Foundation, please see
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* <http://www.apache.org/>.
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*/
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import java.lang.reflect.InvocationTargetException;
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import java.lang.reflect.Method;
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/**
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* Utility routines for manipulating <code>Throwable</code> objects.
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*
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* @author <a href="mailto:dlr@finemaltcoding.com">Daniel Rall</a>
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* @since 1.0
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*/
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public class ExceptionUtils
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{
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/**
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* The name of the <code>getCause()</code> method.
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*/
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protected static final String CAUSE_METHOD_NAME = "getCause";
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/**
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* The parameters of the <code>getCause()</code> method.
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*/
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protected static final Object[] CAUSE_METHOD_PARAMS = {};
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/**
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* Constructs a new <code>ExceptionUtils</code>. Protected to
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* discourage instantiation.
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*/
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protected ExceptionUtils()
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{
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}
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/**
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* Introspects the specified <code>Throwable</code> for a
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* <code>getCause()</code> method (standard as of JDK 1.4, and
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* part of the {@link
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* org.apache.commons.lang.exception.NestableException} API),
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* extracting and returning the cause of the exception.
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* Otherwise, returns <code>null</code>.
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* <p>
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* TODO: Examine for a "detail" public member attribute from
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* java.rmi.RemoteException.
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*
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* @param t The exception to introspect for a cause.
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* @return The cause of the <code>Throwable</code>.
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*/
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public static Throwable getCause(Throwable t)
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{
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Throwable cause = null;
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if (t instanceof NestableException)
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{
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cause = ((NestableException) t).getCause();
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}
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else if (t instanceof NestableRuntimeException)
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{
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cause = ((NestableRuntimeException) t).getCause();
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}
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else
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{
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Method getCause = null;
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Class c = t.getClass();
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try
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{
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getCause = c.getMethod(CAUSE_METHOD_NAME, null);
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}
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catch (NoSuchMethodException ignored)
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{
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}
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catch (SecurityException ignored)
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{
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}
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if (getCause != null && getCause.getReturnType() == Throwable.class)
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{
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try
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{
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cause = (Throwable) getCause.invoke(t, CAUSE_METHOD_PARAMS);
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}
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catch (IllegalAccessException ignored)
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{
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}
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catch (IllegalArgumentException ignored)
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{
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}
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catch (InvocationTargetException ignored)
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{
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}
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}
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}
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return cause;
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}
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/**
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* Walks through the exception chain to the last element -- the
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* "root" of the tree -- using {@link #getCause(Throwable)}, and
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* returns that exception.
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*
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* @return The root cause of the <code>Throwable</code>.
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* @see #getCause(Throwable)
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*/
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public static Throwable getRootCause(Throwable t)
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{
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Throwable cause = getCause(t);
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if (cause != null)
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{
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t = cause;
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while ((t = getCause(t)) != null)
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{
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cause = t;
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}
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}
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return cause;
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}
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}
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@ -88,6 +88,7 @@ public class ExceptionTestSuite extends TestCase
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suite.addTest(NestableDelegateTestCase.suite());
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suite.addTest(NestableDelegateTestCase.suite());
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suite.addTest(NestableExceptionTestCase.suite());
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suite.addTest(NestableExceptionTestCase.suite());
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suite.addTest(NestableRuntimeExceptionTestCase.suite());
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suite.addTest(NestableRuntimeExceptionTestCase.suite());
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suite.addTest(ExceptionUtilsTestCase.suite());
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return suite;
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return suite;
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}
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}
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}
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}
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@ -0,0 +1,128 @@
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package org.apache.commons.lang.exception;
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/* ====================================================================
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* The Apache Software License, Version 1.1
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*
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* Copyright (c) 2002 The Apache Software Foundation. All rights
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* reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* 3. The end-user documentation included with the redistribution, if
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* any, must include the following acknowlegement:
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* "This product includes software developed by the
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* Apache Software Foundation (http://www.apache.org/)."
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* Alternately, this acknowlegement may appear in the software itself,
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* if and wherever such third-party acknowlegements normally appear.
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*
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* 4. The names "The Jakarta Project", "Commons", and "Apache Software
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* Foundation" must not be used to endorse or promote products derived
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* from this software without prior written permission. For written
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* permission, please contact apache@apache.org.
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*
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* 5. Products derived from this software may not be called "Apache"
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* nor may "Apache" appear in their names without prior written
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* permission of the Apache Software Foundation.
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*
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* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
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* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
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* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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* ====================================================================
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*
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* This software consists of voluntary contributions made by many
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* individuals on behalf of the Apache Software Foundation. For more
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* information on the Apache Software Foundation, please see
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* <http://www.apache.org/>.
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*/
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import junit.framework.Test;
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import junit.framework.TestCase;
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import junit.framework.TestSuite;
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/**
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* Tests {@link org.apache.commons.lang.exception.ExceptionUtils}.
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*
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* @author <a href="mailto:dlr@finemaltcoding.com">Daniel Rall</a>
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* @since 1.0
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*/
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public class ExceptionUtilsTestCase extends junit.framework.TestCase
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{
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private NestableException nested;
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private Throwable withCause;
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private Throwable withoutCause;
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public ExceptionUtilsTestCase(String name)
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{
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super(name);
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}
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public static Test suite()
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{
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return new TestSuite(ExceptionUtilsTestCase.class);
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}
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public void setUp()
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{
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withoutCause = new ExceptionWithoutCause();
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nested = new NestableException(withoutCause);
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withCause = new ExceptionWithCause(nested);
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}
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public void testGetCause()
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{
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assertNull(ExceptionUtils.getCause(withoutCause));
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assertTrue(ExceptionUtils.getCause(nested) == withoutCause);
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assertTrue(ExceptionUtils.getCause(withCause) == nested);
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}
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public void testGetRootCause()
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{
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assertNull(ExceptionUtils.getRootCause(withoutCause));
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assertTrue(ExceptionUtils.getRootCause(withCause) == withoutCause);
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assertTrue(ExceptionUtils.getRootCause(withCause) == withoutCause);
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}
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private static class ExceptionWithCause extends Exception
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{
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private Throwable cause;
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public ExceptionWithCause(Throwable cause)
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{
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this.cause = cause;
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}
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public Throwable getCause()
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{
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return cause;
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}
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}
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private static class ExceptionWithoutCause extends Exception
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{
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/**
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* Bogus signature.
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*/
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public void getCause()
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{
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}
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}
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}
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