org.codehaus.plexus.util

Class ExceptionUtils


public class ExceptionUtils
extends java.lang.Object

ExceptionUtils provides utilities for manipulating Throwable objects.
Version:
$Id: ExceptionUtils.java 1106 2004-10-07 19:29:57Z jdcasey $
Authors:
Daniel Rall
Dmitri Plotnikov
Stephen Colebourne
Since:
1.0

Field Summary

protected static String[]
CAUSE_METHOD_NAMES
The names of methods commonly used to access a wrapped exception.
(package private) static String
WRAPPED_MARKER
Used when printing stack frames to denote the start of a wrapped exception.

Constructor Summary

ExceptionUtils()
Constructs a new ExceptionUtils.

Method Summary

static void
addCauseMethodName(String methodName)
Adds to the list of method names used in the search for Throwable objects.
static Throwable
getCause(Throwable throwable)
Introspects the specified Throwable to obtain the cause.
static Throwable
getCause(Throwable throwable, String[] methodNames)
Introspects the specified Throwable to obtain the cause using a supplied array of method names.
private static Throwable
getCauseUsingFieldName(Throwable throwable, String fieldName)
Find a throwable by field name.
private static Throwable
getCauseUsingMethodName(Throwable throwable, String methodName)
Find a throwable by method name.
private static Throwable
getCauseUsingWellKnownTypes(Throwable throwable)
Uses instanceof checks to examine the exception, looking for well known types which could contain chained or wrapped exceptions.
static String
getFullStackTrace(Throwable t)
A way to get the entire nested stack-trace of an throwable.
static Throwable
getRootCause(Throwable throwable)
Walks through the exception chain to the last element -- the "root" of the tree -- using getCause(Throwable), and returns that exception.
static String[]
getRootCauseStackTrace(Throwable t)
Creates a compact stack trace for the root cause of the supplied throwable.
(package private) static List
getStackFrameList(Throwable t)
Produces a List of stack frames - the message is not included.
(package private) static String[]
getStackFrames(String stackTrace)
Functionality shared between the getStackFrames(Throwable) methods of this and the classes.
static String[]
getStackFrames(Throwable t)
Captures the stack trace associated with the specified Throwable object, decomposing it into a list of stack frames.
static String
getStackTrace(Throwable t)
A convenient way of extracting the stack trace from an exception.
static int
getThrowableCount(Throwable throwable)
Returns the number of Throwable objects in the exception chain.
static Throwable[]
getThrowables(Throwable throwable)
Returns the list of Throwable objects in the exception chain.
static int
indexOfThrowable(Throwable throwable, Class type)
Delegates to indexOfThrowable(Throwable,Class,int), starting the search at the beginning of the exception chain.
static int
indexOfThrowable(Throwable throwable, Class type, int fromIndex)
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.
static boolean
isNestedThrowable(Throwable throwable)
Whether an Throwable is considered nested or not.
static void
printRootCauseStackTrace(Throwable t)
Equivalent to printRootCauseStackTrace(t, System.err)
static void
printRootCauseStackTrace(Throwable t, PrintStream stream)
Prints a compact stack trace for the root cause of a throwable.
static void
printRootCauseStackTrace(Throwable t, PrintWriter writer)
Same as printRootCauseStackTrace(t, stream), except it takes a PrintWriter as an argument.
private static void
removeCommonFrames(List causeFrames, List wrapperFrames)
Given two stack traces, removes common frames from the cause trace.

Field Details

CAUSE_METHOD_NAMES

protected static String[] CAUSE_METHOD_NAMES
The names of methods commonly used to access a wrapped exception.

WRAPPED_MARKER

(package private) static final String WRAPPED_MARKER
Used when printing stack frames to denote the start of a wrapped exception. Package private for accessibility by test suite.

Constructor Details

ExceptionUtils

protected ExceptionUtils()
Constructs a new ExceptionUtils. Protected to discourage instantiation.

Method Details

addCauseMethodName

public static void addCauseMethodName(String methodName)
Adds to the list of method names used in the search for Throwable objects.
Parameters:
methodName - the methodName to add to the list, null and empty strings are ignored

getCause

public static Throwable getCause(Throwable throwable)
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 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.

Parameters:
throwable - The exception to introspect for a cause.
Returns:
The cause of the Throwable.

getCause

public static Throwable getCause(Throwable throwable,
                                 String[] methodNames)
Introspects the specified Throwable to obtain the cause using a supplied array of method names.
Parameters:
throwable - The exception to introspect for a cause.
Returns:
The cause of the Throwable.

getCauseUsingFieldName

private static Throwable getCauseUsingFieldName(Throwable throwable,
                                                String fieldName)
Find a throwable by field name.
Parameters:
throwable - the exception to examine
fieldName - the name of the attribute to examine
Returns:
The wrapped exception, or null if not found.

getCauseUsingMethodName

private static Throwable getCauseUsingMethodName(Throwable throwable,
                                                 String methodName)
Find a throwable by method name.
Parameters:
throwable - the exception to examine
methodName - the name of the method to find and invoke
Returns:
The wrapped exception, or null if not found.

getCauseUsingWellKnownTypes

private static Throwable getCauseUsingWellKnownTypes(Throwable throwable)
Uses instanceof checks to examine the exception, looking for well known types which could contain chained or wrapped exceptions.
Parameters:
throwable - the exception to examine
Returns:
The wrapped exception, or null if not found.

getFullStackTrace

public static String getFullStackTrace(Throwable t)
A way to get the entire nested stack-trace of an throwable.
Parameters:
t - The Throwable.
Returns:
The nested stack trace, with the root cause first.

getRootCause

public static Throwable getRootCause(Throwable throwable)
Parameters:
throwable - the throwable to get the root cause for
Returns:
The root cause of the Throwable.

getRootCauseStackTrace

public static String[] getRootCauseStackTrace(Throwable t)
Creates a compact stack trace for the root cause of the supplied throwable. See printRootCauseStackTrace(Throwable t, PrintStream s)

getStackFrameList

(package private) static List getStackFrameList(Throwable t)
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".
Parameters:
t - is any throwable
Returns:
List of stack frames

getStackFrames

(package private) static String[] getStackFrames(String stackTrace)
Functionality shared between the getStackFrames(Throwable) methods of this and the classes.

getStackFrames

public static String[] getStackFrames(Throwable t)
Captures the stack trace associated with the specified Throwable object, decomposing it into a list of stack frames.
Parameters:
t - The Throwable.
Returns:
An array of strings describing each stack frame.

getStackTrace

public static String getStackTrace(Throwable t)
A convenient way of extracting the stack trace from an exception.
Parameters:
t - The Throwable.
Returns:
The stack trace as generated by the exception's printStackTrace(PrintWriter) method.

getThrowableCount

public static int getThrowableCount(Throwable throwable)
Returns the number of Throwable objects in the exception chain.
Parameters:
throwable - the exception to inspect
Returns:
The throwable count.

getThrowables

public static Throwable[] getThrowables(Throwable throwable)
Returns the list of Throwable objects in the exception chain.
Parameters:
throwable - the exception to inspect
Returns:
The list of Throwable objects.

indexOfThrowable

public static int indexOfThrowable(Throwable throwable,
                                   Class type)
Delegates to indexOfThrowable(Throwable,Class,int), starting the search at the beginning of the exception chain.

indexOfThrowable

public static int indexOfThrowable(Throwable throwable,
                                   Class type,
                                   int fromIndex)
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.
Parameters:
throwable - the exception to inspect
type - Class to look for
fromIndex - the (zero based) index of the starting position in the chain to be searched
Returns:
the first occurrence of the type in the chain, or -1 if the type is not found

isNestedThrowable

public static boolean isNestedThrowable(Throwable throwable)
Whether an Throwable is considered nested or not.
Parameters:
throwable - The Throwable.
Returns:
boolean true/false

printRootCauseStackTrace

public static void printRootCauseStackTrace(Throwable t)
Equivalent to printRootCauseStackTrace(t, System.err)

printRootCauseStackTrace

public static void printRootCauseStackTrace(Throwable t,
                                            PrintStream stream)
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.


printRootCauseStackTrace

public static void printRootCauseStackTrace(Throwable t,
                                            PrintWriter writer)
Same as printRootCauseStackTrace(t, stream), except it takes a PrintWriter as an argument.

removeCommonFrames

private static void removeCommonFrames(List causeFrames,
                                       List wrapperFrames)
Given two stack traces, removes common frames from the cause trace.
Parameters:
causeFrames - stack trace of a cause throwable
wrapperFrames - stack trace of a wrapper throwable