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Java Simplified. Extensions and Useful Constructs for the Java Platform. Codeprimate Elements (a.k.a. cp-elements) is a Java library and micro-framework used to simplify the development of software applications written in Java. Elements packages several APIs into one library in order to address various application concerns and aspects of software design and development collectively and conveniently. Elements is a highly simple, yet robust and proven library built on solid OO principles, software design patterns and best practices to effectively solve common and reoccurring problems in software development.

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 /*
 * Copyright 2016 Author or Authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.cp.elements.lang;

import java.io.PrintWriter;
import java.io.StringWriter;
import java.lang.reflect.InvocationTargetException;

/**
 * The ThrowableUtils class provides methods for working with Throwable objects (Errors and Exceptions).
 * 
 * @author John J. Blum
 * @see java.lang.Error
 * @see java.lang.Throwable
 * @since 1.0.0
 */
public abstract class ThrowableUtils {

  /**
   * Null-safe method returning the cause of the given {@link Throwable} object.  If the {@link Throwable} object
   * reference is {@literal null} then this method returns {@literal null}.
   *
   * @param throwable {@link Throwable} object who's cause is returned.
   * @return the cause of the given {@link Throwable} object.
   * @see java.lang.Throwable#getCause()
   */
  @NullSafe
  public static Throwable getCause(Throwable throwable) {
    return (throwable != null ? throwable.getCause() : null);
  }

  /**
   * Returns the underlying cause of the given {@link Throwable} object if the {@link Throwable} object
   * is an instance of {@link InvocationTargetException}.  An {@link InvocationTargetException} is typically thrown
   * when a method on some object is invoked reflectively.
   * 
   * @param throwable {@link Throwable} object to evaluate as a {@link InvocationTargetException}.
   * @return a {@link Throwable} object indicating the underlying cause of {@code throwable} if {@code throwable} is an instance
   * of {@link InvocationTargetException} otherwise return {@code throwable}.
   * @see java.lang.reflect.InvocationTargetException
   * @see java.lang.Throwable#getCause()
   */
  @NullSafe
  public static Throwable getCauseOfInvocationTargetException(Throwable throwable) {
    return (throwable instanceof InvocationTargetException ? throwable.getCause() : throwable);
  }

  /**
   * Null-safe method returning the message of the given {@link Throwable} object.  If the {@link Throwable} object
   * reference is {@literal null} then this method returns {@literal null}.
   * 
   * @param throwable {@link Throwable} object who's message is returned.
   * @return the message of the given {@link Throwable} object.
   * @see java.lang.Throwable#getMessage()
   */
  @NullSafe
  public static String getMessage(Throwable throwable) {
    return (throwable != null ? throwable.getMessage() : null);
  }

  /**
   * Determines the original, root cause of the given {@link Throwable} object.
   * 
   * @param throwable {@link Throwable} object who's root cause will be determined.
   * @return a {@link Throwable} object indicating the root cause of the given {@link Throwable} object,
   * or {@literal null} if the {@link Throwable} object reference is {@literal null}.
   * @see java.lang.Throwable#getCause()
   */
  @NullSafe
  @SuppressWarnings("all")
  public static Throwable getRootCause(Throwable throwable) {
    while (getCause(throwable) != null) {
      throwable = throwable.getCause();
    }

    return throwable;
  }

  /**
   * Returns the Stack Trace of the given {@link Throwable} object as a {@link String}.  Returns {@literal null}
   * if the given {@link Throwable} object reference is {@literal null}.
   * 
   * @param throwable {@link Throwable} object who's Stack Trace is returned.
   * @return the Stack Trace of the given {@link Throwable} object as a {@link String}.
   * @see java.lang.Throwable#printStackTrace(java.io.PrintWriter)
   */
  public static String getStackTrace(Throwable throwable) {
    String stackTraceValue = null;

    if (throwable != null) {
      StringWriter writer = new StringWriter();
      throwable.printStackTrace(new PrintWriter(writer));
      stackTraceValue = writer.toString();
    }

    return stackTraceValue;
  }
}