Class ExceptionUtils
- java.lang.Object
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- org.apache.commons.lang.exception.ExceptionUtils
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public class ExceptionUtils extends java.lang.Object
Provides utilities for manipulating and examining
Throwable
objects.- Since:
- 1.0
- Version:
- $Id: ExceptionUtils.java 905837 2010-02-02 23:32:11Z niallp $
-
-
Field Summary
Fields Modifier and Type Field Description private static java.lang.String[]
CAUSE_METHOD_NAMES
The names of methods commonly used to access a wrapped exception.private static java.lang.Object
CAUSE_METHOD_NAMES_LOCK
private static java.lang.reflect.Method
THROWABLE_CAUSE_METHOD
The Method object for Java 1.4 getCause.private static java.lang.reflect.Method
THROWABLE_INITCAUSE_METHOD
The Method object for Java 1.4 initCause.(package private) static java.lang.String
WRAPPED_MARKER
Used when printing stack frames to denote the start of a wrapped exception.
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Constructor Summary
Constructors Constructor Description ExceptionUtils()
Public constructor allows an instance ofExceptionUtils
to be created, although that is not normally necessary.
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Method Summary
All Methods Static Methods Concrete Methods Modifier and Type Method Description static void
addCauseMethodName(java.lang.String methodName)
Adds to the list of method names used in the search forThrowable
objects.static java.lang.Throwable
getCause(java.lang.Throwable throwable)
Introspects theThrowable
to obtain the cause.static java.lang.Throwable
getCause(java.lang.Throwable throwable, java.lang.String[] methodNames)
Introspects theThrowable
to obtain the cause.private static java.util.ArrayList
getCauseMethodNameList()
ReturnsCAUSE_METHOD_NAMES
as a List.private static java.lang.Throwable
getCauseUsingFieldName(java.lang.Throwable throwable, java.lang.String fieldName)
Finds aThrowable
by field name.private static java.lang.Throwable
getCauseUsingMethodName(java.lang.Throwable throwable, java.lang.String methodName)
Finds aThrowable
by method name.private static java.lang.Throwable
getCauseUsingWellKnownTypes(java.lang.Throwable throwable)
Finds aThrowable
for known types.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 theThrowable
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 suppliedThrowable
.(package private) static java.util.List
getStackFrameList(java.lang.Throwable t)
Produces aList
of stack frames - the message is not included.(package private) static java.lang.String[]
getStackFrames(java.lang.String stackTrace)
Returns an array where each element is a line from the argument.static java.lang.String[]
getStackFrames(java.lang.Throwable throwable)
Captures the stack trace associated with the specifiedThrowable
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 ofThrowable
objects in the exception chain.static java.util.List
getThrowableList(java.lang.Throwable throwable)
Returns the list ofThrowable
objects in the exception chain.static java.lang.Throwable[]
getThrowables(java.lang.Throwable throwable)
Returns the list ofThrowable
objects in the exception chain.private static int
indexOf(java.lang.Throwable throwable, java.lang.Class type, int fromIndex, boolean subclass)
Worker method for theindexOfType
methods.static int
indexOfThrowable(java.lang.Throwable throwable, java.lang.Class clazz)
Returns the (zero based) index of the firstThrowable
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 firstThrowable
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 firstThrowable
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 firstThrowable
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 forThrowable
objects include the given name.static boolean
isNestedThrowable(java.lang.Throwable throwable)
Checks whether thisThrowable
class can store a cause.static boolean
isThrowableNested()
Checks if the Throwable class has agetCause
method.static void
printRootCauseStackTrace(java.lang.Throwable throwable)
Prints a compact stack trace for the root cause of a throwable toSystem.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 forThrowable
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 aThrowable
using introspection, allowing source code compatibility between pre-1.4 and post-1.4 Java releases.private static java.lang.String[]
toArray(java.util.List list)
Returns the given list as aString[]
.
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Field Detail
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WRAPPED_MARKER
static final java.lang.String WRAPPED_MARKER
Used when printing stack frames to denote the start of a wrapped exception.
Package private for accessibility by test suite.
- See Also:
- Constant Field Values
-
CAUSE_METHOD_NAMES_LOCK
private static final java.lang.Object CAUSE_METHOD_NAMES_LOCK
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CAUSE_METHOD_NAMES
private static java.lang.String[] CAUSE_METHOD_NAMES
The names of methods commonly used to access a wrapped exception.
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THROWABLE_CAUSE_METHOD
private static final java.lang.reflect.Method THROWABLE_CAUSE_METHOD
The Method object for Java 1.4 getCause.
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THROWABLE_INITCAUSE_METHOD
private static final java.lang.reflect.Method THROWABLE_INITCAUSE_METHOD
The Method object for Java 1.4 initCause.
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Method Detail
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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
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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
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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 targetThrowable
cause
- theThrowable
to set in the target- Returns:
- a
true
if the target has been modified - Since:
- 2.2
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toArray
private static java.lang.String[] toArray(java.util.List list)
Returns the given list as aString[]
.- Parameters:
list
- a list to transform.- Returns:
- the given list as a
String[]
.
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getCauseMethodNameList
private static java.util.ArrayList getCauseMethodNameList()
ReturnsCAUSE_METHOD_NAMES
as a List.- Returns:
CAUSE_METHOD_NAMES
as a List.
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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
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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, andNestableException
. The method names can be added to usingaddCauseMethodName(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 aThrowable
.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
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getCause
public static java.lang.Throwable getCause(java.lang.Throwable throwable, java.lang.String[] methodNames)
Introspects the
Throwable
to obtain the cause.- Try known exception types.
- Try the supplied array of method names.
- Try the field 'detail'.
A
null
set of method names means use the default set. Anull
in the set of method names will be ignored.- Parameters:
throwable
- the throwable to introspect for a cause, may be nullmethodNames
- 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
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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
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getCauseUsingWellKnownTypes
private static java.lang.Throwable getCauseUsingWellKnownTypes(java.lang.Throwable throwable)
Finds a
Throwable
for known types.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
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getCauseUsingMethodName
private static java.lang.Throwable getCauseUsingMethodName(java.lang.Throwable throwable, java.lang.String methodName)
Finds a
Throwable
by method name.- Parameters:
throwable
- the exception to examinemethodName
- the name of the method to find and invoke- Returns:
- the wrapped exception, or
null
if not found
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getCauseUsingFieldName
private static java.lang.Throwable getCauseUsingFieldName(java.lang.Throwable throwable, java.lang.String fieldName)
Finds a
Throwable
by field name.- Parameters:
throwable
- the exception to examinefieldName
- the name of the attribute to examine- Returns:
- the wrapped exception, or
null
if not found
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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
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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
- theThrowable
to examine, may be null- Returns:
- boolean
true
if nested otherwisefalse
- Since:
- 2.0
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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 return2
and so on. Anull
throwable will return0
.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
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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)
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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
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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 - seeindexOfType(Throwable, Class)
for the opposite.A
null
throwable returns-1
. Anull
type returns-1
. No match in the chain returns-1
.- Parameters:
throwable
- the throwable to inspect, may be nullclazz
- 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
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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 - seeindexOfType(Throwable, Class, int)
for the opposite.A
null
throwable returns-1
. Anull
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 nullclazz
- the class to search for, subclasses do not match, null returns -1fromIndex
- 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
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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 - seeindexOfThrowable(Throwable, Class)
for the opposite.A
null
throwable returns-1
. Anull
type returns-1
. No match in the chain returns-1
.- Parameters:
throwable
- the throwable to inspect, may be nulltype
- 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
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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 - seeindexOfThrowable(Throwable, Class)
for the opposite.A
null
throwable returns-1
. Anull
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 nulltype
- the type to search for, subclasses match, null returns -1fromIndex
- 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
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indexOf
private static int indexOf(java.lang.Throwable throwable, java.lang.Class type, int fromIndex, boolean subclass)
Worker method for the
indexOfType
methods.- Parameters:
throwable
- the throwable to inspect, may be nulltype
- the type to search for, subclasses match, null returns -1fromIndex
- the (zero based) index of the starting position, negative treated as zero, larger than chain size returns -1subclass
- iftrue
, compares withClass.isAssignableFrom(Class)
, otherwise compares using references- Returns:
- index of the
type
within throwables nested withing the specifiedthrowable
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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
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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 nullstream
- the stream to output to, may not be null- Throws:
java.lang.IllegalArgumentException
- if the stream isnull
- Since:
- 2.0
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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 nullwriter
- the writer to output to, may not be null- Throws:
java.lang.IllegalArgumentException
- if the writer isnull
- Since:
- 2.0
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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 throwablewrapperFrames
- stack trace of a wrapper throwable- Throws:
java.lang.IllegalArgumentException
- if either argument is null- Since:
- 2.0
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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
- theThrowable
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
- theThrowable
to be examined- Returns:
- the stack trace as generated by the exception's
printStackTrace(PrintWriter)
method
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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
- theThrowable
to examine, may be null- Returns:
- an array of strings describing each stack frame, never null
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getStackFrames
static java.lang.String[] getStackFrames(java.lang.String stackTrace)
Returns an array where each element is a line from the argument.
The end of line is determined by the value of
SystemUtils.LINE_SEPARATOR
.Functionality shared between the
getStackFrames(Throwable)
methods of this and theNestableDelegate
classes.- Parameters:
stackTrace
- a stack trace String- Returns:
- an array where each element is a line from the argument
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getStackFrameList
static java.util.List getStackFrameList(java.lang.Throwable t)
Produces a
List
of stack frames - the message is not included. Only the trace of the specified exception is returned, any caused by trace is stripped.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
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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
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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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