org.apache.commons.lang.exception
Class ExceptionUtils

java.lang.Object
  extended byorg.apache.commons.lang.exception.ExceptionUtils

public class ExceptionUtils
extends java.lang.Object

Provides utilities for manipulating and examining Throwable objects.

Since:
1.0
Version:
$Id: ExceptionUtils.java 594278 2007-11-12 19:58:30Z bayard $
Author:
Daniel L. Rall, Dmitri Plotnikov, Stephen Colebourne, Gary Gregory, Pete Gieser

Constructor Summary
ExceptionUtils()
           Public constructor allows an instance of ExceptionUtils to be created, although that is not normally necessary.
 
Method Summary
static void addCauseMethodName(java.lang.String methodName)
          Adds to the list of method names used in the search for Throwable objects.
static java.lang.Throwable getCause(java.lang.Throwable throwable)
          Introspects the Throwable to obtain the cause.
static java.lang.Throwable getCause(java.lang.Throwable throwable, java.lang.String[] methodNames)
          Introspects the Throwable to obtain the cause.
static java.lang.String getFullStackTrace(java.lang.Throwable throwable)
          A way to get the entire nested stack-trace of an throwable.
static java.lang.String getMessage(java.lang.Throwable th)
          Gets a short message summarising the exception.
static java.lang.Throwable getRootCause(java.lang.Throwable throwable)
          Introspects the Throwable to obtain the root cause.
static java.lang.String getRootCauseMessage(java.lang.Throwable th)
          Gets a short message summarising the root cause exception.
static java.lang.String[] getRootCauseStackTrace(java.lang.Throwable throwable)
          Creates a compact stack trace for the root cause of the supplied Throwable.
static java.lang.String[] getStackFrames(java.lang.Throwable throwable)
          Captures the stack trace associated with the specified Throwable object, decomposing it into a list of stack frames.
static java.lang.String getStackTrace(java.lang.Throwable throwable)
          Gets the stack trace from a Throwable as a String.
static int getThrowableCount(java.lang.Throwable throwable)
          Counts the number of Throwable objects in the exception chain.
static java.util.List getThrowableList(java.lang.Throwable throwable)
          Returns the list of Throwable objects in the exception chain.
static java.lang.Throwable[] getThrowables(java.lang.Throwable throwable)
          Returns the list of Throwable objects in the exception chain.
static int indexOfThrowable(java.lang.Throwable throwable, java.lang.Class clazz)
          Returns the (zero based) index of the first Throwable that matches the specified class (exactly) in the exception chain.
static int indexOfThrowable(java.lang.Throwable throwable, java.lang.Class clazz, int fromIndex)
          Returns the (zero based) index of the first Throwable that matches the specified type in the exception chain from a specified index.
static int indexOfType(java.lang.Throwable throwable, java.lang.Class type)
          Returns the (zero based) index of the first Throwable that matches the specified class or subclass in the exception chain.
static int indexOfType(java.lang.Throwable throwable, java.lang.Class type, int fromIndex)
          Returns the (zero based) index of the first Throwable that matches the specified type in the exception chain from a specified index.
static boolean isCauseMethodName(java.lang.String methodName)
          Tests if the list of method names used in the search for Throwable objects include the given name.
static boolean isNestedThrowable(java.lang.Throwable throwable)
          Checks whether this Throwable class can store a cause.
static boolean isThrowableNested()
          Checks if the Throwable class has a getCause method.
static void printRootCauseStackTrace(java.lang.Throwable throwable)
          Prints a compact stack trace for the root cause of a throwable to System.err.
static void printRootCauseStackTrace(java.lang.Throwable throwable, java.io.PrintStream stream)
          Prints a compact stack trace for the root cause of a throwable.
static void printRootCauseStackTrace(java.lang.Throwable throwable, java.io.PrintWriter writer)
          Prints a compact stack trace for the root cause of a throwable.
static void removeCauseMethodName(java.lang.String methodName)
          Removes from the list of method names used in the search for Throwable objects.
static void removeCommonFrames(java.util.List causeFrames, java.util.List wrapperFrames)
          Removes common frames from the cause trace given the two stack traces.
static boolean setCause(java.lang.Throwable target, java.lang.Throwable cause)
          Sets the cause of a Throwable using introspection, allowing source code compatibility between pre-1.4 and post-1.4 Java releases.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

ExceptionUtils

public ExceptionUtils()

Public constructor allows an instance of ExceptionUtils to be created, although that is not normally necessary.

Method Detail

addCauseMethodName

public static void addCauseMethodName(java.lang.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
Since:
2.0

removeCauseMethodName

public static void removeCauseMethodName(java.lang.String methodName)

Removes from the list of method names used in the search for Throwable objects.

Parameters:
methodName - the methodName to remove from the list, null and empty strings are ignored
Since:
2.1

setCause

public static boolean setCause(java.lang.Throwable target,
                               java.lang.Throwable cause)

Sets the cause of a Throwable using introspection, allowing source code compatibility between pre-1.4 and post-1.4 Java releases.

The typical use of this method is inside a constructor as in the following example:

 import org.apache.commons.lang.exception.ExceptionUtils;
  
 public class MyException extends Exception {
  
    public MyException(String msg) {
       super(msg);
    }

    public MyException(String msg, Throwable cause) {
       super(msg);
       ExceptionUtils.setCause(this, cause);
    }
 }
 

Parameters:
target - the target Throwable
cause - the Throwable to set in the target
Returns:
a true if the target has been modified
Since:
2.2

isCauseMethodName

public static boolean isCauseMethodName(java.lang.String methodName)

Tests if the list of method names used in the search for Throwable objects include the given name.

Parameters:
methodName - the methodName to search in the list.
Returns:
if the list of method names used in the search for Throwable objects include the given name.
Since:
2.1

getCause

public static java.lang.Throwable getCause(java.lang.Throwable throwable)

Introspects the 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 NestableException. The method names can be added to using addCauseMethodName(String).

The default list searched for are:

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 throwable to introspect for a cause, may be null
Returns:
the cause of the Throwable, null if none found or null throwable input
Since:
1.0

getCause

public static java.lang.Throwable getCause(java.lang.Throwable throwable,
                                           java.lang.String[] methodNames)

Introspects the Throwable to obtain the cause.

  1. Try known exception types.
  2. Try the supplied array of method names.
  3. Try the field 'detail'.

A null set of method names means use the default set. A null in the set of method names will be ignored.

Parameters:
throwable - the throwable to introspect for a cause, may be null
methodNames - the method names, null treated as default set
Returns:
the cause of the Throwable, null if none found or null throwable input
Since:
1.0

getRootCause

public static java.lang.Throwable getRootCause(java.lang.Throwable throwable)

Introspects the Throwable to obtain the root cause.

This method walks through the exception chain to the last element, "root" of the tree, using getCause(Throwable), and returns that exception.

From version 2.2, this method handles recursive cause structures that might otherwise cause infinite loops. If the throwable parameter has a cause of itself, then null will be returned. If the throwable parameter cause chain loops, the last element in the chain before the loop is returned.

Parameters:
throwable - the throwable to get the root cause for, may be null
Returns:
the root cause of the Throwable, null if none found or null throwable input

isThrowableNested

public static boolean isThrowableNested()

Checks if the Throwable class has a getCause method.

This is true for JDK 1.4 and above.

Returns:
true if Throwable is nestable
Since:
2.0

isNestedThrowable

public static boolean isNestedThrowable(java.lang.Throwable throwable)

Checks whether this Throwable class can store a cause.

This method does not check whether it actually does store a cause.

Parameters:
throwable - the Throwable to examine, may be null
Returns:
boolean true if nested otherwise false
Since:
2.0

getThrowableCount

public static int getThrowableCount(java.lang.Throwable throwable)

Counts the number of Throwable objects in the exception chain.

A throwable without cause will return 1. A throwable with one cause will return 2 and so on. A null throwable will return 0.

From version 2.2, this method handles recursive cause structures that might otherwise cause infinite loops. The cause chain is processed until the end is reached, or until the next item in the chain is already in the result set.

Parameters:
throwable - the throwable to inspect, may be null
Returns:
the count of throwables, zero if null input

getThrowables

public static java.lang.Throwable[] getThrowables(java.lang.Throwable throwable)

Returns the list of Throwable objects in the exception chain.

A throwable without cause will return an array containing one element - the input throwable. A throwable with one cause will return an array containing two elements. - the input throwable and the cause throwable. A null throwable will return an array of size zero.

From version 2.2, this method handles recursive cause structures that might otherwise cause infinite loops. The cause chain is processed until the end is reached, or until the next item in the chain is already in the result set.

Parameters:
throwable - the throwable to inspect, may be null
Returns:
the array of throwables, never null
See Also:
getThrowableList(Throwable)

getThrowableList

public static java.util.List getThrowableList(java.lang.Throwable throwable)

Returns the list of Throwable objects in the exception chain.

A throwable without cause will return a list containing one element - the input throwable. A throwable with one cause will return a list containing two elements. - the input throwable and the cause throwable. A null throwable will return a list of size zero.

This method handles recursive cause structures that might otherwise cause infinite loops. The cause chain is processed until the end is reached, or until the next item in the chain is already in the result set.

Parameters:
throwable - the throwable to inspect, may be null
Returns:
the list of throwables, never null
Since:
Commons Lang 2.2

indexOfThrowable

public static int indexOfThrowable(java.lang.Throwable throwable,
                                   java.lang.Class clazz)

Returns the (zero based) index of the first Throwable that matches the specified class (exactly) in the exception chain. Subclasses of the specified class do not match - see indexOfType(Throwable, Class) for the opposite.

A null throwable returns -1. A null type returns -1. No match in the chain returns -1.

Parameters:
throwable - the throwable to inspect, may be null
clazz - the class to search for, subclasses do not match, null returns -1
Returns:
the index into the throwable chain, -1 if no match or null input

indexOfThrowable

public static int indexOfThrowable(java.lang.Throwable throwable,
                                   java.lang.Class clazz,
                                   int fromIndex)

Returns the (zero based) index of the first Throwable that matches the specified type in the exception chain from a specified index. Subclasses of the specified class do not match - see indexOfType(Throwable, Class, int) for the opposite.

A null throwable returns -1. A null type returns -1. No match in the chain returns -1. A negative start index is treated as zero. A start index greater than the number of throwables returns -1.

Parameters:
throwable - the throwable to inspect, may be null
clazz - the class to search for, subclasses do not match, null returns -1
fromIndex - the (zero based) index of the starting position, negative treated as zero, larger than chain size returns -1
Returns:
the index into the throwable chain, -1 if no match or null input

indexOfType

public static int indexOfType(java.lang.Throwable throwable,
                              java.lang.Class type)

Returns the (zero based) index of the first Throwable that matches the specified class or subclass in the exception chain. Subclasses of the specified class do match - see indexOfThrowable(Throwable, Class) for the opposite.

A null throwable returns -1. A null type returns -1. No match in the chain returns -1.

Parameters:
throwable - the throwable to inspect, may be null
type - the type to search for, subclasses match, null returns -1
Returns:
the index into the throwable chain, -1 if no match or null input
Since:
2.1

indexOfType

public static int indexOfType(java.lang.Throwable throwable,
                              java.lang.Class type,
                              int fromIndex)

Returns the (zero based) index of the first Throwable that matches the specified type in the exception chain from a specified index. Subclasses of the specified class do match - see indexOfThrowable(Throwable, Class) for the opposite.

A null throwable returns -1. A null type returns -1. No match in the chain returns -1. A negative start index is treated as zero. A start index greater than the number of throwables returns -1.

Parameters:
throwable - the throwable to inspect, may be null
type - the type to search for, subclasses match, null returns -1
fromIndex - the (zero based) index of the starting position, negative treated as zero, larger than chain size returns -1
Returns:
the index into the throwable chain, -1 if no match or null input
Since:
2.1

printRootCauseStackTrace

public static void printRootCauseStackTrace(java.lang.Throwable throwable)

Prints a compact stack trace for the root cause of a throwable to System.err.

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 output of this method is consistent across JDK versions. Note that this is the opposite order to the JDK1.4 display.

The method is equivalent to printStackTrace for throwables that don't have nested causes.

Parameters:
throwable - the throwable to output
Since:
2.0

printRootCauseStackTrace

public static void printRootCauseStackTrace(java.lang.Throwable throwable,
                                            java.io.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 output of this method is consistent across JDK versions. Note that this is the opposite order to the JDK1.4 display.

The method is equivalent to printStackTrace for throwables that don't have nested causes.

Parameters:
throwable - the throwable to output, may be null
stream - the stream to output to, may not be null
Throws:
java.lang.IllegalArgumentException - if the stream is null
Since:
2.0

printRootCauseStackTrace

public static void printRootCauseStackTrace(java.lang.Throwable throwable,
                                            java.io.PrintWriter writer)

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 output of this method is consistent across JDK versions. Note that this is the opposite order to the JDK1.4 display.

The method is equivalent to printStackTrace for throwables that don't have nested causes.

Parameters:
throwable - the throwable to output, may be null
writer - the writer to output to, may not be null
Throws:
java.lang.IllegalArgumentException - if the writer is null
Since:
2.0

getRootCauseStackTrace

public static java.lang.String[] getRootCauseStackTrace(java.lang.Throwable throwable)

Creates a compact stack trace for the root cause of the supplied Throwable.

The output of this method is consistent across JDK versions. It consists of the root exception followed by each of its wrapping exceptions separated by '[wrapped]'. Note that this is the opposite order to the JDK1.4 display.

Parameters:
throwable - the throwable to examine, may be null
Returns:
an array of stack trace frames, never null
Since:
2.0

removeCommonFrames

public static void removeCommonFrames(java.util.List causeFrames,
                                      java.util.List wrapperFrames)

Removes common frames from the cause trace given the two stack traces.

Parameters:
causeFrames - stack trace of a cause throwable
wrapperFrames - stack trace of a wrapper throwable
Throws:
java.lang.IllegalArgumentException - if either argument is null
Since:
2.0

getFullStackTrace

public static java.lang.String getFullStackTrace(java.lang.Throwable throwable)

A way to get the entire nested stack-trace of an throwable.

The result of this method is highly dependent on the JDK version and whether the exceptions override printStackTrace or not.

Parameters:
throwable - the Throwable to be examined
Returns:
the nested stack trace, with the root cause first
Since:
2.0

getStackTrace

public static java.lang.String getStackTrace(java.lang.Throwable throwable)

Gets the stack trace from a Throwable as a String.

The result of this method vary by JDK version as this method uses Throwable.printStackTrace(java.io.PrintWriter). On JDK1.3 and earlier, the cause exception will not be shown unless the specified throwable alters printStackTrace.

Parameters:
throwable - the Throwable to be examined
Returns:
the stack trace as generated by the exception's printStackTrace(PrintWriter) method

getStackFrames

public static java.lang.String[] getStackFrames(java.lang.Throwable throwable)

Captures the stack trace associated with the specified Throwable object, decomposing it into a list of stack frames.

The result of this method vary by JDK version as this method uses Throwable.printStackTrace(java.io.PrintWriter). On JDK1.3 and earlier, the cause exception will not be shown unless the specified throwable alters printStackTrace.

Parameters:
throwable - the Throwable to examine, may be null
Returns:
an array of strings describing each stack frame, never null

getMessage

public static java.lang.String getMessage(java.lang.Throwable th)
Gets a short message summarising the exception.

The message returned is of the form {ClassNameWithoutPackage}: {ThrowableMessage}

Parameters:
th - the throwable to get a message for, null returns empty string
Returns:
the message, non-null
Since:
Commons Lang 2.2

getRootCauseMessage

public static java.lang.String getRootCauseMessage(java.lang.Throwable th)
Gets a short message summarising the root cause exception.

The message returned is of the form {ClassNameWithoutPackage}: {ThrowableMessage}

Parameters:
th - the throwable to get a message for, null returns empty string
Returns:
the message, non-null
Since:
Commons Lang 2.2


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