src/java/org/apache/commons/math/MathException.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.commons.math;

import java.io.PrintStream;
import java.io.PrintWriter;
import java.text.MessageFormat;
import java.util.Locale;
import java.util.MissingResourceException;
import java.util.ResourceBundle;


/**
* Base class for commons-math checked exceptions.
* <p>
* Supports nesting, emulating JDK 1.4 behavior if necessary.</p>
* <p>
* Adapted from {@link org.apache.commons.collections.FunctorException}.</p>
* 
* @version $Revision$ $Date$
*/
public class MathException extends Exception {
    
    /** Serializable version identifier */
    private static final long serialVersionUID = -8602234299177097102L;

    /**
     * Does JDK support nested exceptions?
     */
    private static final boolean JDK_SUPPORTS_NESTED;
    
    static {
        boolean flag = false;
        try {
            Throwable.class.getDeclaredMethod("getCause", new Class[0]);
            flag = true;
        } catch (NoSuchMethodException ex) {
            flag = false;
        }
        JDK_SUPPORTS_NESTED = flag;
    }

    /** Cache for resources bundle. */
    private static ResourceBundle cachedResources = null;
 
    /**
     * Pattern used to build the message.
     */
    private final String pattern;

    /**
     * Arguments used to build the message.
     */
    private final Object[] arguments;

    /**
     * Root cause of the exception
     */
    private final Throwable rootCause;
    
    /**
     * Translate a string to a given locale.
     * @param s string to translate
     * @param locale locale into which to translate the string
     * @return translated string or original string
     * for unsupported locales or unknown strings
     */
    private static String translate(String s, Locale locale) {
        try {
            if ((cachedResources == null) || (! cachedResources.getLocale().equals(locale))) {
                // caching the resource bundle
                cachedResources =
                    ResourceBundle.getBundle("org.apache.commons.math.MessagesResources", locale);
            }

            if (cachedResources.getLocale().getLanguage().equals(locale.getLanguage())) {
                // the value of the resource is the translated string
                return cachedResources.getString(s);
            }
            
        } catch (MissingResourceException mre) {
            // do nothing here
        }

        // the locale is not supported or the resource is unknown
        // don't translate and fall back to using the string as is
        return s;

    }

    /**
     * Builds a message string by from a pattern and its arguments.
     * @param pattern format specifier
     * @param arguments format arguments
     * @param locale Locale in which the message should be translated
     * @return a message string
     */
    private static String buildMessage(String pattern, Object[] arguments, Locale locale) {
        // do it the hard way, for Java 1.3. compatibility
        MessageFormat mf = new MessageFormat(translate(pattern, locale));
        mf.setLocale(locale);
        return mf.format(arguments);        
    }

    /**
     * Constructs a new <code>MathException</code> with no
     * detail message.
     */
    public MathException() {
        super();
        this.pattern   = null;
        this.arguments = new Object[0];
        this.rootCause = null;
    }
    
    /**
     * Constructs a new <code>MathException</code> with specified
     * detail message.
     *
     * @param msg  the error message.
     * @deprecated as of 1.2, replaced by {@link #MathException(String, Object[])}
     */
    public MathException(String msg) {
        super(msg);
        this.pattern   = msg;
        this.arguments = new Object[0];
        this.rootCause = null;
    }

    /**
     * Constructs a new <code>MathException</code> with specified
     * formatted detail message.
     * Message formatting is delegated to {@link java.text.MessageFormat}.
     * @param pattern format specifier
     * @param arguments format arguments
     */
    public MathException(String pattern, Object[] arguments) {
      super(buildMessage(pattern, arguments, Locale.US));
      this.pattern   = pattern;
      this.arguments = (Object[]) arguments.clone();
      this.rootCause = null;
    }

    /**
     * Constructs a new <code>MathException</code> with specified
     * nested <code>Throwable</code> root cause.
     *
     * @param rootCause  the exception or error that caused this exception
     *                   to be thrown.
     */
    public MathException(Throwable rootCause) {
        super((rootCause == null ? null : rootCause.getMessage()));
        this.pattern   = getMessage();
        this.arguments = new Object[0];
        this.rootCause = rootCause;
    }
    
    /**
     * Constructs a new <code>MathException</code> with specified
     * detail message and nested <code>Throwable</code> root cause.
     *
     * @param msg  the error message.
     * @param rootCause  the exception or error that caused this exception
     *                   to be thrown.
     * @deprecated as of 1.2, replaced by {@link #MathException(String, Object[], Throwable)}
     */
    public MathException(String msg, Throwable rootCause) {
        super(msg);
        this.pattern   = msg;
        this.arguments = new Object[0];
        this.rootCause = rootCause;
    }

    /**
     * Constructs a new <code>MathException</code> with specified
     * formatted detail message and nested <code>Throwable</code> root cause.
     * Message formatting is delegated to {@link java.text.MessageFormat}.
     * @param pattern format specifier
     * @param arguments format arguments
     * @param rootCause  the exception or error that caused this exception
     *                   to be thrown.
     */
    public MathException(String pattern, Object[] arguments, Throwable rootCause) {
      super(buildMessage(pattern, arguments, Locale.US));
      this.pattern   = pattern;
      this.arguments = (Object[]) arguments.clone();
      this.rootCause = rootCause;
    }

    /** Gets the pattern used to build the message of this throwable.
     *
     * @return the pattern used to build the message of this throwable
     */
    public String getPattern() {
        return pattern;
    }

    /** Gets the arguments used to build the message of this throwable.
     *
     * @return the arguments used to build the message of this throwable
     */
    public Object[] getArguments() {
        return (Object[]) arguments.clone();
    }

    /** Gets the message in a specified locale.
     *
     * @param locale Locale in which the message should be translated
     * 
     * @return localized message
     */
    public String getMessage(Locale locale) {
        return (pattern == null) ? null : buildMessage(pattern, arguments, locale);
    }

    /**
     * Gets the cause of this throwable.
     * 
     * @return  the cause of this throwable, or <code>null</code>
     */
    public Throwable getCause() {
        return rootCause;
    }
    
    /**
     * Prints the stack trace of this exception to the standard error stream.
     */
    public void printStackTrace() {
        printStackTrace(System.err);
    }
    
    /**
     * Prints the stack trace of this exception to the specified stream.
     *
     * @param out  the <code>PrintStream</code> to use for output
     */
    public void printStackTrace(PrintStream out) {
        synchronized (out) {
            PrintWriter pw = new PrintWriter(out, false);
            printStackTrace(pw);
            // Flush the PrintWriter before it's GC'ed.
            pw.flush();
        }
    }
    
    /**
     * Prints the stack trace of this exception to the specified writer.
     *
     * @param out  the <code>PrintWriter</code> to use for output
     */
    public void printStackTrace(PrintWriter out) {
        synchronized (out) {
            super.printStackTrace(out);
            if (rootCause != null && JDK_SUPPORTS_NESTED == false) {
                out.print("Caused by: ");
                rootCause.printStackTrace(out);
            }
        }
    }

}