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A collection of various utility classes to ease working with strings, files, command lines, XML and more.

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package org.codehaus.plexus.util;

/* ====================================================================
 * The Apache Software License, Version 1.1
 *
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 * reserved.
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 * Redistribution and use in source and binary forms, with or without
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 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
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 *    notice, this list of conditions and the following disclaimer in
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 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowledgement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.codehaus.org/)."
 *    Alternately, this acknowledgement may appear in the software itself,
 *    if and wherever such third-party acknowledgements normally appear.
 *
 * 4. The names "The Jakarta Project", "Commons", and "Apache Software
 *    Foundation" must not be used to endorse or promote products derived
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 * This software consists of voluntary contributions made by many
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 * .
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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.Arrays;
import java.util.LinkedList;
import java.util.List;
import java.util.StringTokenizer;

/**
 * 

* ExceptionUtils provides utilities for manipulating Throwable objects. *

* * @author Daniel Rall * @author Dmitri Plotnikov * @author Stephen Colebourne * @since 1.0 * @version $Id$ */ public class ExceptionUtils { /** * Used when printing stack frames to denote the start of a wrapped exception. Package private for accessibility by * test suite. */ static final String WRAPPED_MARKER = " [wrapped] "; /** * The names of methods commonly used to access a wrapped exception. */ protected static String[] CAUSE_METHOD_NAMES = { "getCause", "getNextException", "getTargetException", "getException", "getSourceException", "getRootCause", "getCausedByException", "getNested" }; /** * Constructs a new ExceptionUtils. Protected to discourage instantiation. */ protected ExceptionUtils() { } /** *

* Adds to the list of method names used in the search for Throwable objects. *

* * @param methodName the methodName to add to the list, null and empty strings are ignored */ public static void addCauseMethodName( String methodName ) { if ( methodName != null && methodName.length() > 0 ) { List list = new ArrayList( Arrays.asList( CAUSE_METHOD_NAMES ) ); list.add( methodName ); CAUSE_METHOD_NAMES = list.toArray( new String[list.size()] ); } } /** *

* Introspects the specified Throwable to obtain the cause. *

*

* The method searches for methods with specific names that return a Throwable object. This will pick * up most wrapping exceptions, including those from JDK 1.4, and The method names can be added to using * {@link #addCauseMethodName(String)}. The default list searched for are: *

*
    *
  • getCause() *
  • getNextException() *
  • getTargetException() *
  • getException() *
  • getSourceException() *
  • getRootCause() *
  • getCausedByException() *
  • getNested() *
*

* In the absence of any such method, the object is inspected for a detail field assignable to a * Throwable. *

*

* If none of the above is found, returns null. *

* * @param throwable The exception to introspect for a cause. * @return The cause of the Throwable. * @throws NullPointerException if the throwable is null */ public static Throwable getCause( Throwable throwable ) { return getCause( throwable, CAUSE_METHOD_NAMES ); } /** *

* Introspects the specified Throwable to obtain the cause using a supplied array of method names. *

* * @param throwable The exception to introspect for a cause. * @return The cause of the Throwable. * @throws NullPointerException if the method names array is null or contains null * @throws NullPointerException if the throwable is null */ public static Throwable getCause( Throwable throwable, String[] methodNames ) { Throwable cause = getCauseUsingWellKnownTypes( throwable ); if ( cause == null ) { for ( String methodName : methodNames ) { cause = getCauseUsingMethodName( throwable, methodName ); if ( cause != null ) { break; } } if ( cause == null ) { cause = getCauseUsingFieldName( throwable, "detail" ); } } return cause; } /** *

* Walks through the exception chain to the last element -- the "root" of the tree -- using * {@link #getCause(Throwable)}, and returns that exception. *

* * @param throwable the throwable to get the root cause for * @return The root cause of the Throwable. */ public static Throwable getRootCause( Throwable throwable ) { Throwable cause = getCause( throwable ); if ( cause != null ) { throwable = cause; while ( ( throwable = getCause( throwable ) ) != null ) { cause = throwable; } } return cause; } /** *

* Uses instanceof checks to examine the exception, looking for well known types which could contain * chained or wrapped exceptions. *

* * @param throwable the exception to examine * @return The wrapped exception, or null if not found. */ private static Throwable getCauseUsingWellKnownTypes( Throwable throwable ) { if ( throwable instanceof SQLException ) { return ( (SQLException) throwable ).getNextException(); } else if ( throwable instanceof InvocationTargetException ) { return ( (InvocationTargetException) throwable ).getTargetException(); } else { return null; } } /** *

* Find a throwable by method name. *

* * @param throwable the exception to examine * @param methodName the name of the method to find and invoke * @return The wrapped exception, or null 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, new Object[0] ); } catch ( IllegalAccessException ignored ) { } catch ( IllegalArgumentException ignored ) { } catch ( InvocationTargetException ignored ) { } } return null; } /** *

* Find a throwable by field name. *

* * @param throwable the exception to examine * @param fieldName the name of the attribute to examine * @return The wrapped exception, or null 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; } /** *

* Returns the number of Throwable objects in the exception chain. *

* * @param throwable the exception to inspect * @return The throwable count. */ public static int getThrowableCount( Throwable throwable ) { // Count the number of throwables int count = 0; while ( throwable != null ) { count++; throwable = ExceptionUtils.getCause( throwable ); } return count; } /** *

* Returns the list of Throwable objects in the exception chain. *

* * @param throwable the exception to inspect * @return The list of Throwable objects. */ public static Throwable[] getThrowables( Throwable throwable ) { List list = new ArrayList(); while ( throwable != null ) { list.add( throwable ); throwable = getCause( throwable ); } return list.toArray( new Throwable[list.size()] ); } /** *

* Delegates to {@link #indexOfThrowable(Throwable, Class, int)}, starting the search at the beginning of the * exception chain. *

* * @see #indexOfThrowable(Throwable, Class, int) */ public static int indexOfThrowable( Throwable throwable, Class type ) { return indexOfThrowable( throwable, type, 0 ); } /** *

* Returns the (zero based) index, of the first Throwable that matches the specified type in the * exception chain of Throwable objects with an index greater than or equal to the specified index, or * -1 if the type is not found. *

* * @param throwable the exception to inspect * @param type Class to look for * @param fromIndex the (zero based) index of the starting position in the chain to be searched * @return the first occurrence of the type in the chain, or -1 if the type is not found * @throws IndexOutOfBoundsException If the fromIndex argument is negative or not less than the count * of Throwables in the chain. */ public static int indexOfThrowable( Throwable throwable, Class type, int fromIndex ) { if ( fromIndex < 0 ) { throw new IndexOutOfBoundsException( "Throwable index out of range: " + fromIndex ); } Throwable[] throwables = ExceptionUtils.getThrowables( throwable ); if ( fromIndex >= throwables.length ) { throw new IndexOutOfBoundsException( "Throwable index out of range: " + fromIndex ); } for ( int i = fromIndex; i < throwables.length; i++ ) { if ( throwables[i].getClass().equals( type ) ) { return i; } } return -1; } /** * Prints a compact stack trace for the root cause of a throwable. The compact stack trace starts with the root * cause and prints stack frames up to the place where it was caught and wrapped. Then it prints the wrapped * exception and continues with stack frames until the wrapper exception is caught and wrapped again, etc. *

* The method is equivalent to t.printStackTrace() for throwables that don't have nested causes. */ public static void printRootCauseStackTrace( Throwable t, PrintStream stream ) { String trace[] = getRootCauseStackTrace( t ); for ( String aTrace : trace ) { stream.println( aTrace ); } stream.flush(); } /** * Equivalent to printRootCauseStackTrace(t, System.err) */ public static void printRootCauseStackTrace( Throwable t ) { printRootCauseStackTrace( t, System.err ); } /** * Same as printRootCauseStackTrace(t, stream), except it takes a PrintWriter as an argument. */ public static void printRootCauseStackTrace( Throwable t, PrintWriter writer ) { String trace[] = getRootCauseStackTrace( t ); for ( String aTrace : trace ) { writer.println( aTrace ); } writer.flush(); } /** * Creates a compact stack trace for the root cause of the supplied throwable. See * printRootCauseStackTrace(Throwable t, PrintStream s) */ public static String[] getRootCauseStackTrace( Throwable t ) { Throwable[] throwables = getThrowables( t ); int count = throwables.length; ArrayList frames = new ArrayList(); List nextTrace = getStackFrameList( throwables[count - 1] ); for ( int i = count; --i >= 0; ) { List trace = nextTrace; if ( i != 0 ) { nextTrace = getStackFrameList( throwables[i - 1] ); removeCommonFrames( trace, nextTrace ); } if ( i == ( count - 1 ) ) { frames.add( throwables[i].toString() ); } else { frames.add( WRAPPED_MARKER + throwables[i].toString() ); } for ( String aTrace : trace ) { frames.add( aTrace ); } } return frames.toArray( new String[frames.size()] ); } /** * Given two stack traces, removes common frames from the cause trace. * * @param causeFrames stack trace of a cause throwable * @param wrapperFrames stack trace of a wrapper throwable */ private static void removeCommonFrames( List causeFrames, List wrapperFrames ) { int causeFrameIndex = causeFrames.size() - 1; int wrapperFrameIndex = wrapperFrames.size() - 1; while ( causeFrameIndex >= 0 && wrapperFrameIndex >= 0 ) { // Remove the frame from the cause trace if it is the same // as in the wrapper trace String causeFrame = causeFrames.get( causeFrameIndex ); String wrapperFrame = wrapperFrames.get( wrapperFrameIndex ); if ( causeFrame.equals( wrapperFrame ) ) { causeFrames.remove( causeFrameIndex ); } causeFrameIndex--; wrapperFrameIndex--; } } /** * A convenient way of extracting the stack trace from an exception. * * @param t The Throwable. * @return The stack trace as generated by the exception's printStackTrace(PrintWriter) method. */ public static String getStackTrace( Throwable t ) { StringWriter sw = new StringWriter(); PrintWriter pw = new PrintWriter( sw, true ); t.printStackTrace( pw ); return sw.getBuffer().toString(); } /** * A way to get the entire nested stack-trace of an throwable. * * @param t The Throwable. * @return The nested stack trace, with the root cause first. */ public static String getFullStackTrace( Throwable t ) { StringWriter sw = new StringWriter(); PrintWriter pw = new PrintWriter( sw, true ); Throwable[] ts = getThrowables( t ); for ( Throwable t1 : ts ) { t1.printStackTrace( pw ); if ( isNestedThrowable( t1 ) ) { break; } } return sw.getBuffer().toString(); } /** * Whether an Throwable is considered nested or not. * * @param throwable The Throwable. * @return boolean true/false */ public static boolean isNestedThrowable( Throwable throwable ) { if ( throwable == null ) { return false; } if ( throwable instanceof SQLException ) { return true; } else if ( throwable instanceof InvocationTargetException ) { return true; } for ( String CAUSE_METHOD_NAME : CAUSE_METHOD_NAMES ) { try { Method method = throwable.getClass().getMethod( CAUSE_METHOD_NAME, null ); if ( method != null ) { return true; } } catch ( NoSuchMethodException ignored ) { } catch ( SecurityException ignored ) { } } try { Field field = throwable.getClass().getField( "detail" ); if ( field != null ) { return true; } } catch ( NoSuchFieldException ignored ) { } catch ( SecurityException ignored ) { } return false; } /** * Captures the stack trace associated with the specified Throwable object, decomposing it into a list * of stack frames. * * @param t The Throwable. * @return An array of strings describing each stack frame. */ public static String[] getStackFrames( Throwable t ) { return getStackFrames( getStackTrace( t ) ); } /** * Functionality shared between the getStackFrames(Throwable) methods of this and the classes. */ static String[] getStackFrames( String stackTrace ) { String linebreak = System.getProperty( "line.separator" ); StringTokenizer frames = new StringTokenizer( stackTrace, linebreak ); List list = new LinkedList(); while ( frames.hasMoreTokens() ) { list.add( frames.nextToken() ); } return list.toArray( new String[list.size()] ); } /** * Produces a List of stack frames - the message is not included. This works in most cases - it will only fail if * the exception message contains a line that starts with: " at". * * @param t is any throwable * @return List of stack frames */ static List getStackFrameList( Throwable t ) { String stackTrace = getStackTrace( t ); String linebreak = System.getProperty( "line.separator" ); StringTokenizer frames = new StringTokenizer( stackTrace, linebreak ); List list = new LinkedList(); boolean traceStarted = false; while ( frames.hasMoreTokens() ) { String token = frames.nextToken(); // Determine if the line starts with at int at = token.indexOf( "at" ); if ( at != -1 && token.substring( 0, at ).trim().length() == 0 ) { traceStarted = true; list.add( token ); } else if ( traceStarted ) { break; } } return list; } }





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