org.unidal.helper.Exceptions Maven / Gradle / Ivy
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* "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 $Id$
*/
public class Exceptions {
/**
* 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 Exceptions() {
}
/**
*
* 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 = 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 (String methodName : methodNames) {
cause = getCauseUsingMethodName(throwable, methodName);
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);
} 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 = 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 = getCause(throwable);
}
return 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 = 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 (String aTrace : trace) {
stream.println(aTrace);
}
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 (String aTrace : trace) {
writer.println(aTrace);
}
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 (String aTrace : trace) {
frames.add(aTrace);
}
}
return frames.toArray(new String[frames.size()]);
}
/**
* 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 = causeFrames.get(causeFrameIndex);
String wrapperFrame = 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(1024);
PrintWriter pw = new PrintWriter(sw, true);
t.printStackTrace(pw);
return sw.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(1024);
PrintWriter pw = new PrintWriter(sw, true);
Throwable[] ts = getThrowables(t);
for (Throwable t1 : ts) {
t1.printStackTrace(pw);
if (isNestedThrowable(t1)) {
break;
}
}
return sw.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;
}
for (String CAUSE_METHOD_NAME : CAUSE_METHOD_NAMES) {
try {
Method method = throwable.getClass().getMethod(CAUSE_METHOD_NAME);
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 list.toArray(new String[list.size()]);
}
/**
* 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;
}
}