exceptionutils.java

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/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * Copyright (c) 2008, Red Hat Middleware LLC or third-party contributors as
 * indicated by the @author tags or express copyright attribution
 * statements applied by the authors.  All third-party contributions are
 * distributed under license by Red Hat Middleware LLC.
 *
 * This copyrighted material is made available to anyone wishing to use, modify,
 * copy, or redistribute it subject to the terms and conditions of the GNU
 * Lesser General Public License, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License
 * for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this distribution; if not, write to:
 * Free Software Foundation, Inc.
 * 51 Franklin Street, Fifth Floor
 * Boston, MA  02110-1301  USA
 *
 */
package org.hibernate.exception;

import org.hibernate.util.ArrayHelper;

import java.io.PrintStream;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import java.util.StringTokenizer;

/**
 * <p>Provides utilities for manipulating and examining
 * <code>Throwable</code> objects.</p>
 *
 * @author <a href="mailto:[e-mail]">Daniel Rall</a>
 * @author Dmitri Plotnikov
 * @author Stephen Colebourne
 * @author <a href="mailto:[e-mail]">Gary Gregory</a>
 * @author Pete Gieser
 * @version $Id: ExceptionUtils.java 4782 2004-11-21 00:11:27Z pgmjsd $
 * @since 1.0
 */
public final class ExceptionUtils {

	private static final String LINE_SEPARATOR = System.getProperty( "line.separator" );

	/**
	 * <p>Used when printing stack frames to denote the start of a
	 * wrapped exception.</p>
	 * <p/>
	 * <p>Package private for accessibility by test suite.</p>
	 */
	static final String WRAPPED_MARKER = " [wrapped] ";

	/**
	 * <p>The names of methods commonly used to access a wrapped exception.</p>
	 */
	private static final String[] CAUSE_METHOD_NAMES = {
		"getCause",
		"getNextException",
		"getTargetException",
		"getException",
		"getSourceException",
		"getRootCause",
		"getCausedByException",
		"getNested"
	};

	/**
	 * <p>The Method object for JDK1.4 getCause.</p>
	 */
	private static final Method THROWABLE_CAUSE_METHOD;

	static {
		Method getCauseMethod;
		try {
			getCauseMethod = Throwable.class.getMethod( "getCause", null );
		}
		catch ( Exception e ) {
			getCauseMethod = null;
		}
		THROWABLE_CAUSE_METHOD = getCauseMethod;
	}

	private ExceptionUtils() {
	}

	//-----------------------------------------------------------------------
	/**
	 * <p>Adds to the list of method names used in the search for <code>Throwable</code>
	 * objects.</p>
	 *
	 * @param methodName  the methodName to add to the list, <code>null</code>
	 *  and empty strings are ignored
	 * @since 2.0
	 */
	/*public static void addCauseMethodName(String methodName) {
		if ( StringHelper.isNotEmpty(methodName) ) {
			List list = new ArrayList( Arrays.asList(CAUSE_METHOD_NAMES );
			list.add(methodName);
			CAUSE_METHOD_NAMES = (String[]) list.toArray(new String[list.size()]);
		}
	}*/

	/**
	 * <p>Introspects the <code>Throwable</code> to obtain the cause.</p>
	 * <p/>
	 * <p>The method searches for methods with specific names that return a
	 * <code>Throwable</code> object. This will pick up most wrapping exceptions,
	 * including those from JDK 1.4, and
	 * {@link org.apache.commons.lang.exception.NestableException NestableException}.
	 * The method names can be added to using {@link #addCauseMethodName(String)}.</p>
	 * <p/>
	 * <p>The default list searched for are:</p>
	 * <ul>
	 * <li><code>getCause()</code></li>
	 * <li><code>getNextException()</code></li>
	 * <li><code>getTargetException()</code></li>
	 * <li><code>getException()</code></li>
	 * <li><code>getSourceException()</code></li>
	 * <li><code>getRootCause()</code></li>
	 * <li><code>getCausedByException()</code></li>
	 * <li><code>getNested()</code></li>
	 * </ul>
	 * <p/>
	 * <p>In the absence of any such method, the object is inspected for a
	 * <code>detail</code> field assignable to a <code>Throwable</code>.</p>
	 * <p/>
	 * <p>If none of the above is found, returns <code>null</code>.</p>
	 *
	 * @param throwable the throwable to introspect for a cause, may be null
	 * @return the cause of the <code>Throwable</code>,
	 *         <code>null</code> if none found or null throwable input
	 */
	public static Throwable getCause(Throwable throwable) {
		return getCause( throwable, CAUSE_METHOD_NAMES );
	}

	/**
	 * <p>Introspects the <code>Throwable</code> to obtain the cause.</p>
	 * <p/>
	 * <ol>
	 * <li>Try known exception types.</li>
	 * <li>Try the supplied array of method names.</li>
	 * <li>Try the field 'detail'.</li>
	 * </ol>
	 * <p/>
	 * <p>A <code>null</code> set of method names means use the default set.
	 * A <code>null</code> in the set of method names will be ignored.</p>
	 *
	 * @param throwable   the throwable to introspect for a cause, may be null
	 * @param methodNames the method names, null treated as default set
	 * @return the cause of the <code>Throwable</code>,
	 *         <code>null</code> if none found or null throwable input
	 */
	public static Throwable getCause(Throwable throwable, String[] methodNames) {
		if ( throwable == null ) {
			return null;
		}
		Throwable cause = getCauseUsingWellKnownTypes( throwable );
		if ( cause == null ) {
			if ( methodNames == null ) {
				methodNames = CAUSE_METHOD_NAMES;
			}
			for ( int i = 0; i < methodNames.length; i++ ) {
				String methodName = methodNames[i];
				if ( methodName != null ) {
					cause = getCauseUsingMethodName( throwable, methodName );
					if ( cause != null ) {
						break;
					}
				}
			}

			if ( cause == null ) {
				cause = getCauseUsingFieldName( throwable, "detail" );
			}
		}
		return cause;
	}

	/**
	 * <p>Introspects the <code>Throwable</code> to obtain the root cause.</p>
	 * <p/>
	 * <p>This method walks through the exception chain to the last element,
	 * "root" of the tree, using {@link #getCause(Throwable)}, and
	 * returns that exception.</p>
	 *
	 * @param throwable the throwable to get the root cause for, may be null
	 * @return the root cause of the <code>Throwable</code>,
	 *         <code>null</code> if none found or null throwable input
	 */
	public static Throwable getRootCause(Throwable throwable) {
		Throwable cause = getCause( throwable );
		if ( cause != null ) {
			throwable = cause;
			while ( ( throwable = getCause( throwable ) ) != null ) {
				cause = throwable;
			}
		}
		return cause;
	}

	/**
	 * <p>Finds a <code>Throwable</code> for known types.</p>
	 * <p/>
	 * <p>Uses <code>instanceof</code> checks to examine the exception,
	 * looking for well known types which could contain chained or
	 * wrapped exceptions.</p>
	 *
	 * @param throwable the exception to examine
	 * @return the wrapped exception, or <code>null</code> if not found
	 */
	private static Throwable getCauseUsingWellKnownTypes(Throwable throwable) {
		if ( throwable instanceof Nestable ) {
			return ( ( Nestable ) throwable ).getCause();
		}
		else if ( throwable instanceof SQLException ) {
			return ( ( SQLException ) throwable ).getNextException();
		}
		else if ( throwable instanceof InvocationTargetException ) {
			return ( ( InvocationTargetException ) throwable ).getTargetException();
		}
		else {
			return null;
		}
	}

	/**
	 * <p>Finds a <code>Throwable</code> by method name.</p>
	 *
	 * @param throwable  the exception to examine
	 * @param methodName the name of the method to find and invoke
	 * @return the wrapped exception, or <code>null</code> if not found
	 */
	private static Throwable getCauseUsingMethodName(Throwable throwable, String methodName) {
		Method method = null;
		try {
			method = throwable.getClass().getMethod( methodName, null );
		}
		catch ( NoSuchMethodException ignored ) {
		}
		catch ( SecurityException ignored ) {
		}

		if ( method != null && Throwable.class.isAssignableFrom( method.getReturnType() ) ) {
			try {
				return ( Throwable ) method.invoke( throwable, ArrayHelper.EMPTY_OBJECT_ARRAY );
			}
			catch ( IllegalAccessException ignored ) {
			}
			catch ( IllegalArgumentException ignored ) {
			}
			catch ( InvocationTargetException ignored ) {
			}
		}
		return null;
	}

	/**
	 * <p>Finds a <code>Throwable</code> by field name.</p>
	 *
	 * @param throwable the exception to examine
	 * @param fieldName the name of the attribute to examine
	 * @return the wrapped exception, or <code>null</code> if not found
	 */
	private static Throwable getCauseUsingFieldName(Throwable throwable, String fieldName) {
		Field field = null;
		try {
			field = throwable.getClass().getField( fieldName );
		}
		catch ( NoSuchFieldException ignored ) {
		}
		catch ( SecurityException ignored ) {
		}

		if ( field != null && Throwable.class.isAssignableFrom( field.getType() ) ) {
			try {
				return ( Throwable ) field.get( throwable );
			}
			catch ( IllegalAccessException ignored ) {
			}
			catch ( IllegalArgumentException ignored ) {
			}
		}
		return null;
	}

	//-----------------------------------------------------------------------
	/**
	 * <p>Checks if the Throwable class has a <code>getCause</code> method.</p>
	 * <p/>
	 * <p>This is true for JDK 1.4 and above.</p>
	 *
	 * @return true if Throwable is nestable
	 * @since 2.0
	 */
	public static boolean isThrowableNested() {
		return ( THROWABLE_CAUSE_METHOD != null );
	}

	/**
	 * <p>Checks whether this <code>Throwable</code> class can store a cause.</p>
	 * <p/>
	 * <p>This method does <b>not</b> check whether it actually does store a cause.<p>
	 *
	 * @param throwable the <code>Throwable</code> to examine, may be null
	 * @return boolean <code>true</code> if nested otherwise <code>false</code>
	 * @since 2.0
	 */
	public static boolean isNestedThrowable(Throwable throwable) {
		if ( throwable == null ) {
			return false;
		}

		if ( throwable instanceof Nestable ) {
			return true;
		}
		else if ( throwable instanceof SQLException ) {
			return true;
		}
		else if ( throwable instanceof InvocationTargetException ) {
			return true;
		}
		else if ( isThrowableNested() ) {
			return true;
		}

		Class cls = throwable.getClass();
		for ( int i = 0, isize = CAUSE_METHOD_NAMES.length; i < isize; i++ ) {
			try {
				Method method = cls.getMethod( CAUSE_METHOD_NAMES[i], null );
				if ( method != null && Throwable.class.isAssignableFrom( method.getReturnType() ) ) {
					return true;
				}
			}
			catch ( NoSuchMethodException ignored ) {
			}
			catch ( SecurityException ignored ) {
			}
		}

		try {