com.free.exception.NestableDelegate.java Source code

Java tutorial

Introduction

Here is the source code for com.free.exception.NestableDelegate.java

Source

package com.free.exception;

/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2002-2003 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowledgement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgement may appear in the software itself,
 *    if and wherever such third-party acknowledgements normally appear.
 *
 * 4. The names "The Jakarta Project", "Commons", and "Apache Software
 *    Foundation" must not be used to endorse or promote products derived
 *    from this software without prior written permission. For written
 *    permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache"
 *    nor may "Apache" appear in their names without prior written
 *    permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * 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
 * <http://www.apache.org/>.
 */
import java.io.PrintStream;
import java.io.PrintWriter;
import java.io.Serializable;
import java.io.StringWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;

/**
 * <p>
 * A shared implementation of the nestable exception functionality.
 * </p>
 * <p/>
 * The code is shared between
 * {@link org.apache.commons.lang.exception.NestableError NestableError},
 * {@link org.apache.commons.lang.exception.NestableException NestableException}
 * and {@link org.apache.commons.lang.exception.NestableRuntimeException
 * NestableRuntimeException}.
 * </p>
 * 
 * @author <a href="mailto:Rafal.Krzewski@e-point.pl">Rafal Krzewski</a>
 * @author <a href="mailto:dlr@collab.net">Daniel Rall</a>
 * @author <a href="mailto:knielsen@apache.org">Kasper Nielsen</a>
 * @author <a href="mailto:steven@caswell.name">Steven Caswell</a>
 * @author Sean C. Sullivan
 * @author Stephen Colebourne
 * @version $Id: NestableDelegate.java,v 1.2 2004/11/21 00:11:27 pgmjsd Exp $
 * @since 1.0
 */
class NestableDelegate implements Serializable {

    private static final long serialVersionUID = 6383440074174865493L;

    /**
     * Constructor error message.
     */
    private static final String MUST_BE_THROWABLE = "The Nestable implementation passed to the NestableDelegate(Nestable) "
            + "constructor must extend java.lang.Throwable";

    /**
     * Holds the reference to the exception or error that we're wrapping (which
     * must be a {@link org.apache.commons.lang.exception.Nestable}
     * implementation).
     */
    private Throwable nestable = null;

    /**
     * Whether to print the stack trace top-down. This public flag may be set by
     * calling code, typically in initialisation.
     * 
     * @since 2.0
     */
    private static boolean topDown = true;

    /**
     * Whether to trim the repeated stack trace. This public flag may be set by
     * calling code, typically in initialisation.
     * 
     * @since 2.0
     */
    private static boolean trimStackFrames = true;

    /**
     * Constructs a new <code>NestableDelegate</code> instance to manage the
     * specified <code>Nestable</code>.
     * 
     * @param nestable
     *          the Nestable implementation (<i>must</i> extend
     *          {@link java.lang.Throwable})
     * @since 2.0
     */
    public NestableDelegate(Nestable nestable) {
        if (nestable instanceof Throwable) {
            this.nestable = (Throwable) nestable;
        } else {
            throw new IllegalArgumentException(MUST_BE_THROWABLE);
        }
    }

    /**
     * Returns the error message of the <code>Throwable</code> in the chain of
     * <code>Throwable</code>s at the specified index, numbererd from 0.
     * 
     * @param index
     *          the index of the <code>Throwable</code> in the chain of
     *          <code>Throwable</code>s
     * @return the error message, or null if the <code>Throwable</code> at the
     *         specified index in the chain does not contain a message
     * @throws IndexOutOfBoundsException
     *           if the <code>index</code> argument is negative or not less than
     *           the count of <code>Throwable</code>s in the chain
     * @since 2.0
     */
    public String getMessage(int index) {
        Throwable t = this.getThrowable(index);
        if (Nestable.class.isInstance(t)) {
            return ((Nestable) t).getMessage(0);
        } else {
            return t.getMessage();
        }
    }

    /**
     * Returns the full message contained by the <code>Nestable</code> and any
     * nested <code>Throwable</code>s.
     * 
     * @param baseMsg
     *          the base message to use when creating the full message. Should be
     *          generally be called via
     *          <code>nestableHelper.getMessage( super.getMessage() )</code>,
     *          where <code>super</code> is an instance of
     *          {@link java.lang.Throwable}.
     * @return The concatenated message for this and all nested
     *         <code>Throwable</code>s
     * @since 2.0
     */
    public String getMessage(String baseMsg) {
        StringBuilder msg = new StringBuilder();
        if (baseMsg != null) {
            msg.append(baseMsg);
        }

        Throwable nestedCause = ExceptionHelper.getCause(this.nestable);
        if (nestedCause != null) {
            String causeMsg = nestedCause.getMessage();
            if (causeMsg != null) {
                if (baseMsg != null) {
                    msg.append(": ");
                }
                msg.append(causeMsg);
            }

        }
        return (msg.length() > 0 ? msg.toString() : null);
    }

    /**
     * Returns the error message of this and any nested <code>Throwable</code>s in
     * an array of Strings, one element for each message. Any
     * <code>Throwable</code> not containing a message is represented in the array
     * by a null. This has the effect of cause the length of the returned array to
     * be equal to the result of the {@link #getThrowableCount()} operation.
     * 
     * @return the error messages
     * @since 2.0
     */
    public String[] getMessages() {
        Throwable[] throwables = this.getThrowables();
        String[] msgs = new String[throwables.length];
        for (int i = 0; i < throwables.length; i++) {
            msgs[i] = Nestable.class.isInstance(throwables[i]) ? ((Nestable) throwables[i]).getMessage(0)
                    : throwables[i].getMessage();
        }
        return msgs;
    }

    /**
     * Returns the <code>Throwable</code> in the chain of <code>Throwable</code> s
     * at the specified index, numbererd from 0.
     * 
     * @param index
     *          the index, numbered from 0, of the <code>Throwable</code> in the
     *          chain of <code>Throwable</code>s
     * @return the <code>Throwable</code>
     * @throws IndexOutOfBoundsException
     *           if the <code>index</code> argument is negative or not less than
     *           the count of <code>Throwable</code>s in the chain
     * @since 2.0
     */
    public Throwable getThrowable(int index) {
        if (index == 0) {
            return this.nestable;
        }
        Throwable[] throwables = this.getThrowables();
        return throwables[index];
    }

    /**
     * Returns the number of <code>Throwable</code>s contained in the
     * <code>Nestable</code> contained by this delegate.
     * 
     * @return the throwable count
     * @since 2.0
     */
    public int getThrowableCount() {
        return ExceptionHelper.getThrowableCount(this.nestable);
    }

    /**
     * Returns this delegate's <code>Nestable</code> and any nested
     * <code>Throwable</code>s in an array of <code>Throwable</code>s, one element
     * for each <code>Throwable</code>.
     * 
     * @return the <code>Throwable</code>s
     * @since 2.0
     */
    public Throwable[] getThrowables() {
        return ExceptionHelper.getThrowables(this.nestable);
    }

    /**
     * Returns the index, numbered from 0, of the first <code>Throwable</code>
     * that matches the specified type in the chain of <code>Throwable</code>s
     * held in this delegate's <code>Nestable</code> with an index greater than or
     * equal to the specified index, or -1 if the type is not found.
     * 
     * @param type
     *          <code>Class</code> to be found
     * @param fromIndex
     *          the index, numbered from 0, of the starting position in the chain
     *          to be searched
     * @return index of the first occurrence of the type in the chain, or -1 if
     *         the type is not found
     * @throws IndexOutOfBoundsException
     *           if the <code>fromIndex</code> argument is negative or not less
     *           than the count of <code>Throwable</code>s in the chain
     * @since 2.0
     */
    public int indexOfThrowable(Class<?> type, int fromIndex) {
        if (fromIndex < 0) {
            throw new IndexOutOfBoundsException("The start index was out of bounds: " + fromIndex);
        }
        Throwable[] throwables = ExceptionHelper.getThrowables(this.nestable);
        if (fromIndex >= throwables.length) {
            throw new IndexOutOfBoundsException(
                    "The start index was out of bounds: " + fromIndex + " >= " + throwables.length);
        }
        for (int i = fromIndex; i < throwables.length; i++) {
            if (throwables[i].getClass().equals(type)) {
                return i;
            }
        }
        return -1;
    }

    /**
     * Prints the stack trace of this exception the the standar error stream.
     */
    public void printStackTrace() {
        printStackTrace(System.err);
    }

    /**
     * Prints the stack trace of this exception to the specified stream.
     * 
     * @param out
     *          <code>PrintStream</code> to use for output.
     * @see #printStackTrace(PrintWriter)
     */
    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. If the
     * Throwable class has a <code>getCause</code> method (i.e. running on jre1.4
     * or higher), this method just uses Throwable's printStackTrace() method.
     * Otherwise, generates the stack-trace, by taking into account the 'topDown'
     * and 'trimStackFrames' parameters. The topDown and trimStackFrames are set
     * to 'true' by default (produces jre1.4-like stack trace).
     * 
     * @param out
     *          <code>PrintWriter</code> to use for output.
     */
    public void printStackTrace(PrintWriter out) {
        Throwable throwable = this.nestable;
        // if running on jre1.4 or higher, use default printStackTrace
        if (ExceptionHelper.isThrowableNested()) {
            if (throwable instanceof Nestable) {
                ((Nestable) throwable).printPartialStackTrace(out);
            } else {
                throwable.printStackTrace(out);
            }
            return;
        }

        // generating the nested stack trace
        List<String[]> stacks = new ArrayList<String[]>();
        while (throwable != null) {
            String[] st = getStackFrames(throwable);
            stacks.add(st);
            throwable = ExceptionHelper.getCause(throwable);
        }

        // If NOT topDown, reverse the stack
        String separatorLine = "Caused by: ";
        if (!topDown) {
            separatorLine = "Rethrown as: ";
            Collections.reverse(stacks);
        }

        // Remove the repeated lines in the stack
        if (trimStackFrames)
            trimStackFrames(stacks);

        synchronized (out) {
            for (Iterator<String[]> iter = stacks.iterator(); iter.hasNext();) {
                String[] st = (String[]) iter.next();
                for (int i = 0, len = st.length; i < len; i++) {
                    out.println(st[i]);
                }
                if (iter.hasNext())
                    out.print(separatorLine);
            }
        }
    }

    /**
     * Captures the stack trace associated with the specified
     * <code>Throwable</code> object, decomposing it into a list of stack frames.
     * 
     * @param t
     *          The <code>Throwable</code>.
     * @return An array of strings describing each stack frame.
     * @since 2.0
     */
    protected String[] getStackFrames(Throwable t) {
        StringWriter sw = new StringWriter();
        PrintWriter pw = new PrintWriter(sw, true);

        // Avoid infinite loop between decompose() and printStackTrace().
        if (t instanceof Nestable) {
            ((Nestable) t).printPartialStackTrace(pw);
        } else {
            t.printStackTrace(pw);
        }
        return ExceptionHelper.getStackFrames(sw.getBuffer().toString());
    }

    /**
     * Trims the stack frames. The first set is left untouched. The rest of the
     * frames are truncated from the bottom by comparing with one just on top.
     * 
     * @param stacks
     *          The list containing String[] elements
     * @since 2.0
     */
    protected void trimStackFrames(List<String[]> stacks) {
        for (int size = stacks.size(), i = size - 1; i > 0; i--) {
            String[] curr = (String[]) stacks.get(i);
            String[] next = (String[]) stacks.get(i - 1);

            List<String> currList = new ArrayList<String>(Arrays.asList(curr));
            List<String> nextList = new ArrayList<String>(Arrays.asList(next));
            ExceptionHelper.removeCommonFrames(currList, nextList);

            int trimmed = curr.length - currList.size();
            if (trimmed > 0) {
                currList.add("\t... " + trimmed + " more");
                stacks.set(i, currList.toArray(new String[currList.size()]));
            }
        }
    }
}