Exception Util
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//package flex.messaging.util;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.NoSuchElementException;
import java.util.StringTokenizer;
/**
* @exclude
*/
public class ExceptionUtil {
/**
* List of no-arg methods that are known to return a wrapped throwable.
**/
public static String[] unwrapMethods = { "getRootCause",
"getTargetException", "getTargetError", "getException",
"getCausedByException", "getLinkedException" };
public static Throwable wrappedException(Throwable t) {
// Handle these statically since they are core to Java
return (t instanceof InvocationTargetException) ? ((InvocationTargetException) t)
.getTargetException() : getRootCauseWithReflection(t);
}
/**
* Get to the base exception (if any).
*/
public static Throwable baseException(Throwable t) {
Throwable wrapped = wrappedException(t);
return wrapped != null ? baseException(wrapped) : t;
}
/**
* Return the stack trace in a String.
*/
public static String toString(Throwable t) {
StringWriter strWrt = new StringWriter();
t.printStackTrace(new PrintWriter(strWrt));
return strWrt.toString();
}
/**
* Return the stack trace up to the first line that starts with prefix.
*
* <p>
* Example: ExceptionUtil.getStackTraceUpTo(exception, "jrunx.");
* </p>
*/
public static String getStackTraceUpTo(Throwable t, String prefix) {
StringTokenizer tokens = new StringTokenizer(toString(t), "\n\r");
StringBuffer trace = new StringBuffer();
boolean done = false;
String lookingFor = "at " + prefix;
while (!done && tokens.hasMoreElements()) {
String token = tokens.nextToken();
if (token.indexOf(lookingFor) == -1)
trace.append(token);
else
done = true;
trace.append("\n");
}
return trace.toString();
}
/**
* return the top n lines of this stack trace.
*
* <p>
* Example: ExceptionUtil.getStackTraceLines(exception, 10);
* </p>
*/
public static String getStackTraceLines(Throwable t, int numLines) {
StringTokenizer tokens = new StringTokenizer(toString(t), "\n\r");
StringBuffer trace = new StringBuffer();
for (int i = 0; i < numLines; i++) {
String token = tokens.nextToken();
trace.append(token);
trace.append("\n");
}
return trace.toString();
}
/**
* Return the "nth" method call from the stack trace of "t", where 0 is the
* top.
*/
public static String getCallAt(Throwable t, int nth) {
StringTokenizer tokens = new StringTokenizer(toString(t), "\n\r");
try {
// Skip the first line - the exception message
for (int i = 0; i <= nth; ++i)
tokens.nextToken();
// get the method name from the next token
String token = tokens.nextToken();
int index1 = token.indexOf(' ');
int index2 = token.indexOf('(');
StringBuffer call = new StringBuffer();
call.append(token.substring(index1 < 0 ? 0 : index1 + 1,
index2 < 0 ? call.length() : index2));
int index3 = token.indexOf(':', index2 < 0 ? 0 : index2);
if (index3 >= 0) {
int index4 = token.indexOf(')', index3);
call.append(token.substring(index3, index4 < 0 ? token.length()
: index4));
}
return call.toString();
} catch (NoSuchElementException e) {
}
return "unknown";
}
/**
* Utility method for converting an exception into a string. This method
* unwinds all wrapped exceptions
*
* @param t
* The throwable exception
* @return The printable exception
*/
public static String exceptionToString(Throwable t) {
StringWriter sw = new StringWriter();
PrintWriter out = new PrintWriter(sw);
// print out the exception stack.
printExceptionStack(t, out, 0);
return sw.toString();
}
/**
* Utility method for converting an exception and all chained root causes
* into a string. Unlike <code>exceptionToString(Throwable)</code> which
* prints the chain from most nested root cause down to the top-level
* exception, this method prints from the top-level exception down to the
* most nested root cause.
*
* @param t
* The throwable exception.
* @return The printable exception.
*/
public static String exceptionFollowedByRootCausesToString(Throwable t) {
StringBuffer output = new StringBuffer();
Throwable root = t;
while (root != null) {
output.append((root == t) ? ((root instanceof Exception) ? " Exception: "
: " Error: ")
: " Root cause: ");
output.append(ExceptionUtil.toString(root));
// Do not recurse if the root cause has already been printed; this
// will have happened if the root cause has
// been assigned to the current Throwable via initCause() or as a
// constructor argument.
Throwable cause = root.getCause();
root = ExceptionUtil.wrappedException(root);
if (cause == root)
break;
}
return output.toString();
}
/**
* Recursively prints out a stack of wrapped exceptions.
*/
protected static void printExceptionStack(Throwable th, PrintWriter out,
int depth) {
// only print the stack depth if the depth is greater than 0
boolean printStackDepth = depth > 0;
Throwable wrappedException = ExceptionUtil.wrappedException(th);
if (wrappedException != null) {
printStackDepth = true;
printExceptionStack(wrappedException, out, depth + 1);
}
if (printStackDepth) {
out.write("[" + depth + "]");
}
th.printStackTrace(out);
}
private static Throwable getRootCauseWithReflection(Throwable t) {
for (int i = 0; i < unwrapMethods.length; i++) {
Method m = null;
try {
m = t.getClass().getMethod(unwrapMethods[i], (Class[]) null);
return (Throwable) m.invoke(t, (Object[]) null);
} catch (Exception nsme) {
// ignore
}
}
return null;
}
}
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