/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
*
* C E D A R
* S O L U T I O N S "Software done right."
* S O F T W A R E
*
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
*
* Copyright (c) 2013-2014 Kenneth J. Pronovici.
* All rights reserved.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the Apache License, Version 2.0.
* See LICENSE for more information about the licensing terms.
*
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
*
* Author : Kenneth J. Pronovici <pronovic@ieee.org>
* Language : Java 6
* Project : Common Java Functionality
*
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
package com.cedarsolutions.util;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintWriter;
import com.cedarsolutions.exception.context.ExceptionContext;
import com.cedarsolutions.exception.context.IHasExceptionContext;
import com.cedarsolutions.exception.context.RootCause;
/**
* Server-side exception utilities.
* @author Kenneth J. Pronovici <pronovic@ieee.org>
*/
public class ExceptionUtils {
/**
* Generate a stack trace for an exception.
* @param exception Exception to generate the stack trace for
* @return Stack trace as a string.
*/
public static String generateStackTrace(Throwable exception) {
String stackTrace = null;
if (exception != null) {
OutputStream stream = null;
PrintWriter writer = null;
try {
stream = new ByteArrayOutputStream();
writer = new PrintWriter(stream);
exception.printStackTrace(writer);
writer.flush();
stream.flush();
stackTrace = stream.toString();
} catch (IOException e) {
// hopefully shouldn't ever happen?
} finally {
try {
if (writer != null) {
writer.close();
}
} catch (Exception e) { }
try {
if (stream != null) {
stream.close();
}
} catch (Exception e) { }
}
}
if (stackTrace == null) {
return null;
} else {
stackTrace = stackTrace.replaceAll("\tat", " at"); // shrink leading indentation
return stackTrace;
}
}
/**
* Add exception context to an exception which supports it.
* @param exception Exception to modify
* @param level Number of stack levels above the exception instantiation level to take the line number from
* @return The same exception, for convenience.
*/
@SuppressWarnings("unchecked")
public static <T> T addExceptionContext(Throwable exception, int level) {
if (exception instanceof IHasExceptionContext) {
IHasExceptionContext hasContext = (IHasExceptionContext) exception;
ExceptionContext context = generateExceptionContext(exception, level);
hasContext.setContext(context);
}
return (T) exception;
}
/** Generate the exception context for an exception. */
public static ExceptionContext generateExceptionContext(Throwable exception, int level) {
if (exception == null) {
return null;
} else {
ExceptionContext context = new ExceptionContext();
context.setLocation(getLocation(exception, level));
context.setStackTrace(generateStackTrace(exception));
context.setRootCause(generateRootCause(exception.getCause()));
return context;
}
}
/**
* Create a root cause based on a Throwable exception.
* @param exception Exception to use as source
* @return ExceptionCause generated from the input cause.
*/
public static RootCause generateRootCause(Throwable exception) {
if (exception == null) {
return null;
} else {
String name = exception.getClass().getName();
String canonicalName = exception.getClass().getCanonicalName();
String simpleName = exception.getClass().getSimpleName();
String message = exception.getMessage();
String location = getLocation(exception);
RootCause cause = generateRootCause(exception.getCause());
return new RootCause(name, canonicalName, simpleName, message, location, cause);
}
}
/** Create a location string describing where the exception was instantiated. */
private static String getLocation(Throwable exception) {
return getLocation(exception, 0);
}
/**
* Create a location string describing where the exception was instantated.
* @param level Number of levels back to look, zero being the location, 1 being the caller, etc.
* @return A string like "com.cedarsolutions.whatever.MyClass.myMethod(MyClass.java:14)"
*/
private static String getLocation(Throwable exception, int level) {
try {
return getLocation(exception.getStackTrace()[level]);
} catch (IndexOutOfBoundsException e) {
return null;
}
}
/** Create a location string like "com.cedarsolutions.whatever.MyClass.myMethod(MyClass.java:14)". */
private static String getLocation(StackTraceElement element) {
String fileName = element.getFileName();
String lineNumber = String.valueOf(element.getLineNumber());
String className = element.getClassName();
String methodName = element.getMethodName();
return className + "." + methodName + "(" + fileName + ":" + lineNumber + ")";
}
}