org.codehaus.plexus.util.ExceptionUtils Maven / Gradle / Ivy
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* any, must include the following acknowlegement:
* "This product includes software developed by the
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* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Apache Software Foundation. For more
* information on the Apache Software Foundation, please see
* ExceptionUtils provides utilities for manipulating
* Throwable objects.
*
* @author Daniel Rall
* @author Dmitri Plotnikov
* @author Stephen Colebourne
* @since 1.0
* @version $Id: ExceptionUtils.java 5958 2007-02-28 10:29:55Z olamy $
*/
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 = (String[]) 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 ( int i = 0; i < methodNames.length; i++ )
{
cause = getCauseUsingMethodName( throwable, methodNames[i] );
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 = ExceptionUtils.getCause( throwable );
}
return (Throwable[]) 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 ( int i = 0; i < trace.length; i++ )
{
stream.println( trace[i] );
}
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 ( int i = 0; i < trace.length; i++ )
{
writer.println( trace[i] );
}
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 ( int j = 0; j < trace.size(); j++ )
{
frames.add( trace.get( j ) );
}
}
return (String[]) frames.toArray( new String[0] );
}
/**
* 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 = (String) causeFrames.get( causeFrameIndex );
String wrapperFrame = (String) 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 ( int i = 0; i < ts.length; i++ )
{
ts[i].printStackTrace( pw );
if ( isNestedThrowable( ts[i] ) )
{
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;
}
int sz = CAUSE_METHOD_NAMES.length;
for ( int i = 0; i < sz; i++ )
{
try
{
Method method = throwable.getClass().getMethod( CAUSE_METHOD_NAMES[i], 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 (String[]) list.toArray( new String[]{
} );
}
/**
* 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;
}
}