org.apache.commons.lang.exception

Class NestableDelegate

public class NestableDelegate extends Object implements Serializable

A shared implementation of the nestable exception functionality.

The code is shared between NestableError, NestableException and NestableRuntimeException.

Since: 1.0

Version: $Id: NestableDelegate.java 512889 2007-02-28 18:18:20Z dlr $

Author: Rafal Krzewski Daniel L. Rall Kasper Nielsen Steven Caswell Sean C. Sullivan Stephen Colebourne

Field Summary
static boolean	matchSubclasses Whether to match subclasses via indexOf.
static boolean	topDown Whether to print the stack trace top-down.
static boolean	trimStackFrames Whether to trim the repeated stack trace.

Constructor Summary
	NestableDelegate(Nestable nestable) Constructs a new `NestableDelegate` instance to manage the specified `Nestable`.

Method Summary
String	getMessage(int index) Returns the error message of the `Throwable` in the chain of `Throwable`s at the specified index, numbered from 0.
String	getMessage(String baseMsg) Returns the full message contained by the `Nestable` and any nested `Throwable`s.
String[]	getMessages() Returns the error message of this and any nested `Throwable`s in an array of Strings, one element for each message.
protected String[]	getStackFrames(Throwable t) Captures the stack trace associated with the specified `Throwable` object, decomposing it into a list of stack frames.
Throwable	getThrowable(int index) Returns the `Throwable` in the chain of `Throwable`s at the specified index, numbered from 0.
int	getThrowableCount() Returns the number of `Throwable`s contained in the `Nestable` contained by this delegate.
Throwable[]	getThrowables() Returns this delegate's `Nestable` and any nested `Throwable`s in an array of `Throwable`s, one element for each `Throwable`.
int	indexOfThrowable(Class type, int fromIndex) Returns the index, numbered from 0, of the first `Throwable` that matches the specified type, or a subclass, in the chain of `Throwable`s with an index greater than or equal to the specified index.
void	printStackTrace() Prints the stack trace of this exception the the standar error stream.
void	printStackTrace(PrintStream out) Prints the stack trace of this exception to the specified stream.
void	printStackTrace(PrintWriter out) Prints the stack trace of this exception to the specified writer.
protected void	trimStackFrames(List stacks) Trims the stack frames.

Whether to match subclasses via indexOf. This public flag may be set by calling code, typically in initialisation. This exists for backwards compatability, setting it to false will return the library to v2.0 behaviour (but will affect all users of the library in the classloader).

Since: 2.1

topDown

public static boolean topDown

Whether to print the stack trace top-down. This public flag may be set by calling code, typically in initialisation. This exists for backwards compatability, setting it to false will return the library to v1.0 behaviour (but will affect all users of the library in the classloader).

Since: 2.0

trimStackFrames

public static boolean trimStackFrames

Whether to trim the repeated stack trace. This public flag may be set by calling code, typically in initialisation. This exists for backwards compatability, setting it to false will return the library to v1.0 behaviour (but will affect all users of the library in the classloader).

Since: 2.0

Constructor Detail

NestableDelegate

public NestableDelegate(Nestable nestable)

Constructs a new NestableDelegate instance to manage the specified Nestable.

Parameters: nestable the Nestable implementation (must extend java.lang.Throwable)

Since: 2.0

Method Detail

getMessage

public String getMessage(int index)

Returns the error message of the Throwable in the chain of Throwables at the specified index, numbered from 0.

Parameters: index the index of the Throwable in the chain of Throwables

Returns: the error message, or null if the Throwable at the specified index in the chain does not contain a message

Throws: IndexOutOfBoundsException if the index argument is negative or not less than the count of Throwables in the chain

Since: 2.0

getMessage

public String getMessage(String baseMsg)

Returns the full message contained by the Nestable and any nested Throwables.

Parameters: baseMsg the base message to use when creating the full message. Should be generally be called via nestableHelper.getMessage(super.getMessage()), where super is an instance of java.lang.Throwable.

Returns: The concatenated message for this and all nested Throwables

Since: 2.0

getMessages

public String[] getMessages()

Returns the error message of this and any nested Throwables in an array of Strings, one element for each message. Any Throwable not containing a message is represented in the array by a null. This has the effect of cause the length of the returned array to be equal to the result of the getThrowableCount operation.

Returns: the error messages

Since: 2.0

getStackFrames

protected 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.

Since: 2.0

getThrowable

public Throwable getThrowable(int index)

Returns the Throwable in the chain of Throwables at the specified index, numbered from 0.

Parameters: index the index, numbered from 0, of the Throwable in the chain of Throwables

Returns: the Throwable

Throws: IndexOutOfBoundsException if the index argument is negative or not less than the count of Throwables in the chain

Since: 2.0

getThrowableCount

public int getThrowableCount()

Returns the number of Throwables contained in the Nestable contained by this delegate.

Returns: the throwable count

Since: 2.0

getThrowables

public Throwable[] getThrowables()

Returns this delegate's Nestable and any nested Throwables in an array of Throwables, one element for each Throwable.

Returns: the Throwables

Since: 2.0

indexOfThrowable

public int indexOfThrowable(Class type, int fromIndex)

Returns the index, numbered from 0, of the first Throwable that matches the specified type, or a subclass, in the chain of Throwables with an index greater than or equal to the specified index. The method returns -1 if the specified type is not found in the chain.

NOTE: From v2.1, we have clarified the Nestable interface such that this method matches subclasses. If you want to NOT match subclasses, please use ExceptionUtils (which is avaiable in all versions of lang). An alternative is to use the public static flag matchSubclasses on NestableDelegate, however this is not recommended.

Parameters: type the type to find, subclasses match, null returns -1 fromIndex the index, numbered from 0, of the starting position in the chain to be searched

Returns: index of 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

Since: 2.0

printStackTrace

public void printStackTrace()

Prints the stack trace of this exception the the standar error stream.

printStackTrace

public void printStackTrace(PrintStream out)

Prints the stack trace of this exception to the specified stream.

Parameters: out PrintStream to use for output.

printStackTrace

public void printStackTrace(PrintWriter out)

Prints the stack trace of this exception to the specified writer. If the Throwable class has a getCause method (i.e. running on jre1.4 or higher), this method just uses Throwable's printStackTrace() method. Otherwise, generates the stack-trace, by taking into account the 'topDown' and 'trimStackFrames' parameters. The topDown and trimStackFrames are set to 'true' by default (produces jre1.4-like stack trace).

Parameters: out PrintWriter to use for output.

trimStackFrames

protected void trimStackFrames(List stacks)

Trims the stack frames. The first set is left untouched. The rest of the frames are truncated from the bottom by comparing with one just on top.

Parameters: stacks The list containing String[] elements

Since: 2.0