    001    /*
    002     * Licensed to the Apache Software Foundation (ASF) under one or more
    003     * contributor license agreements.  See the NOTICE file distributed with
    004     * this work for additional information regarding copyright ownership.
    005     * The ASF licenses this file to You under the Apache License, Version 2.0
    006     * (the "License"); you may not use this file except in compliance with
    007     * the License.  You may obtain a copy of the License at
    008     *
    009     *      http://www.apache.org/licenses/LICENSE-2.0
    010     *
    011     * Unless required by applicable law or agreed to in writing, software
    012     * distributed under the License is distributed on an "AS IS" BASIS,
    013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014     * See the License for the specific language governing permissions and
    015     * limitations under the License.
    016     */
    017    package org.apache.commons.lang.exception;
    018
    019    import java.io.PrintStream;
    020    import java.io.PrintWriter;
    021    import java.io.Serializable;
    022    import java.io.StringWriter;
    023    import java.util.ArrayList;
    024    import java.util.Arrays;
    025    import java.util.Collections;
    026    import java.util.Iterator;
    027    import java.util.List;
    028
    029    /**
    030     * <p>A shared implementation of the nestable exception functionality.</p>
    031     * <p>
    032     * The code is shared between
    033     * {@link org.apache.commons.lang.exception.NestableError NestableError},
    034     * {@link org.apache.commons.lang.exception.NestableException NestableException} and
    035     * {@link org.apache.commons.lang.exception.NestableRuntimeException NestableRuntimeException}.
    036     * </p>
    037     *
    038     * @author Apache Software Foundation
    039     * @author <a href="mailto:Rafal.Krzewski@e-point.pl">Rafal Krzewski</a>
    040     * @author Daniel L. Rall
    041     * @author <a href="mailto:knielsen@apache.org">Kasper Nielsen</a>
    042     * @author <a href="mailto:steven@caswell.name">Steven Caswell</a>
    043     * @author Sean C. Sullivan
    044     * @since 1.0
    045     * @version $Id: NestableDelegate.java 905636 2010-02-02 14:03:32Z niallp $
    046     */
    047    public class NestableDelegate implements Serializable {
    048
    049        /**
    050         * Required for serialization support.
    051         *
    052         * @see java.io.Serializable
    053         */
    054        private static final long serialVersionUID = 1L;
    055
    056        /**
    057         * Constructor error message.
    058         */
    059        private transient static final String MUST_BE_THROWABLE =
    060            "The Nestable implementation passed to the NestableDelegate(Nestable) "
    061                + "constructor must extend java.lang.Throwable";
    062
    063        /**
    064         * Holds the reference to the exception or error that we're
    065         * wrapping (which must be a {@link
    066         * org.apache.commons.lang.exception.Nestable} implementation).
    067         */
    068        private Throwable nestable = null;
    069
    070        /**
    071         * Whether to print the stack trace top-down.
    072         * This public flag may be set by calling code, typically in initialisation.
    073         * This exists for backwards compatability, setting it to false will return
    074         * the library to v1.0 behaviour (but will affect all users of the library
    075         * in the classloader).
    076         * @since 2.0
    077         */
    078        public static boolean topDown = true;
    079
    080        /**
    081         * Whether to trim the repeated stack trace.
    082         * This public flag may be set by calling code, typically in initialisation.
    083         * This exists for backwards compatability, setting it to false will return
    084         * the library to v1.0 behaviour (but will affect all users of the library
    085         * in the classloader).
    086         * @since 2.0
    087         */
    088        public static boolean trimStackFrames = true;
    089
    090        /**
    091         * Whether to match subclasses via indexOf.
    092         * This public flag may be set by calling code, typically in initialisation.
    093         * This exists for backwards compatability, setting it to false will return
    094         * the library to v2.0 behaviour (but will affect all users of the library
    095         * in the classloader).
    096         * @since 2.1
    097         */
    098        public static boolean matchSubclasses = true;
    099
    100        /**
    101         * Constructs a new <code>NestableDelegate</code> instance to manage the
    102         * specified <code>Nestable</code>.
    103         *
    104         * @param nestable the Nestable implementation (<i>must</i> extend
    105         * {@link java.lang.Throwable})
    106         * @since 2.0
    107         */
    108        public NestableDelegate(Nestable nestable) {
    109            if (nestable instanceof Throwable) {
    110                this.nestable = (Throwable) nestable;
    111            } else {
    112                throw new IllegalArgumentException(MUST_BE_THROWABLE);
    113            }
    114        }
    115
    116        /**
    117         * Returns the error message of the <code>Throwable</code> in the chain of <code>Throwable</code>s at the
    118         * specified index, numbered from 0.
    119         *
    120         * @param index
    121         *            the index of the <code>Throwable</code> in the chain of <code>Throwable</code>s
    122         * @return the error message, or null if the <code>Throwable</code> at the specified index in the chain does not
    123         *         contain a message
    124         * @throws IndexOutOfBoundsException
    125         *             if the <code>index</code> argument is negative or not less than the count of <code>Throwable</code>s
    126         *             in the chain
    127         * @since 2.0
    128         */
    129        public String getMessage(int index) {
    130            Throwable t = this.getThrowable(index);
    131            if (Nestable.class.isInstance(t)) {
    132                return ((Nestable) t).getMessage(0);
    133            }
    134            return t.getMessage();
    135        }
    136
    137        /**
    138         * Returns the full message contained by the <code>Nestable</code> and any nested <code>Throwable</code>s.
    139         *
    140         * @param baseMsg
    141         *            the base message to use when creating the full message. Should be generally be called via
    142         *            <code>nestableHelper.getMessage(super.getMessage())</code>, where <code>super</code> is an
    143         *            instance of {@link java.lang.Throwable}.
    144         * @return The concatenated message for this and all nested <code>Throwable</code>s
    145         * @since 2.0
    146         */
    147        public String getMessage(String baseMsg) {
    148            Throwable nestedCause = ExceptionUtils.getCause(this.nestable);
    149            String causeMsg = nestedCause == null ? null : nestedCause.getMessage();
    150            if (nestedCause == null || causeMsg == null) {
    151                return baseMsg; // may be null, which is a valid result
    152            }
    153            if (baseMsg == null) {
    154                return causeMsg;
    155            }
    156            return baseMsg + ": " + causeMsg;
    157        }
    158
    159        /**
    160         * Returns the error message of this and any nested <code>Throwable</code>s in an array of Strings, one element
    161         * for each message. Any <code>Throwable</code> not containing a message is represented in the array by a null.
    162         * This has the effect of cause the length of the returned array to be equal to the result of the
    163         * {@link #getThrowableCount()} operation.
    164         *
    165         * @return the error messages
    166         * @since 2.0
    167         */
    168        public String[] getMessages() {
    169            Throwable[] throwables = this.getThrowables();
    170            String[] msgs = new String[throwables.length];
    171            for (int i = 0; i < throwables.length; i++) {
    172                msgs[i] =
    173                    (Nestable.class.isInstance(throwables[i])
    174                        ? ((Nestable) throwables[i]).getMessage(0)
    175                        : throwables[i].getMessage());
    176            }
    177            return msgs;
    178        }
    179
    180        /**
    181         * Returns the <code>Throwable</code> in the chain of
    182         * <code>Throwable</code>s at the specified index, numbered from 0.
    183         *
    184         * @param index the index, numbered from 0, of the <code>Throwable</code> in
    185         * the chain of <code>Throwable</code>s
    186         * @return the <code>Throwable</code>
    187         * @throws IndexOutOfBoundsException if the <code>index</code> argument is
    188         * negative or not less than the count of <code>Throwable</code>s in the
    189         * chain
    190         * @since 2.0
    191         */
    192        public Throwable getThrowable(int index) {
    193            if (index == 0) {
    194                return this.nestable;
    195            }
    196            Throwable[] throwables = this.getThrowables();
    197            return throwables[index];
    198        }
    199
    200        /**
    201         * Returns the number of <code>Throwable</code>s contained in the
    202         * <code>Nestable</code> contained by this delegate.
    203         *
    204         * @return the throwable count
    205         * @since 2.0
    206         */
    207        public int getThrowableCount() {
    208            return ExceptionUtils.getThrowableCount(this.nestable);
    209        }
    210
    211        /**
    212         * Returns this delegate's <code>Nestable</code> and any nested
    213         * <code>Throwable</code>s in an array of <code>Throwable</code>s, one
    214         * element for each <code>Throwable</code>.
    215         *
    216         * @return the <code>Throwable</code>s
    217         * @since 2.0
    218         */
    219        public Throwable[] getThrowables() {
    220            return ExceptionUtils.getThrowables(this.nestable);
    221        }
    222
    223        /**
    224         * Returns the index, numbered from 0, of the first <code>Throwable</code>
    225         * that matches the specified type, or a subclass, in the chain of <code>Throwable</code>s
    226         * with an index greater than or equal to the specified index.
    227         * The method returns -1 if the specified type is not found in the chain.
    228         * <p>
    229         * NOTE: From v2.1, we have clarified the <code>Nestable</code> interface
    230         * such that this method matches subclasses.
    231         * If you want to NOT match subclasses, please use
    232         * {@link ExceptionUtils#indexOfThrowable(Throwable, Class, int)}
    233         * (which is avaiable in all versions of lang).
    234         * An alternative is to use the public static flag {@link #matchSubclasses}
    235         * on <code>NestableDelegate</code>, however this is not recommended.
    236         *
    237         * @param type  the type to find, subclasses match, null returns -1
    238         * @param fromIndex the index, numbered from 0, of the starting position in
    239         * the chain to be searched
    240         * @return index of the first occurrence of the type in the chain, or -1 if
    241         * the type is not found
    242         * @throws IndexOutOfBoundsException if the <code>fromIndex</code> argument
    243         * is negative or not less than the count of <code>Throwable</code>s in the
    244         * chain
    245         * @since 2.0
    246         */
    247        public int indexOfThrowable(Class type, int fromIndex) {
    248            if (type == null) {
    249                return -1;
    250            }
    251            if (fromIndex < 0) {
    252                throw new IndexOutOfBoundsException("The start index was out of bounds: " + fromIndex);
    253            }
    254            Throwable[] throwables = ExceptionUtils.getThrowables(this.nestable);
    255            if (fromIndex >= throwables.length) {
    256                throw new IndexOutOfBoundsException("The start index was out of bounds: "
    257                    + fromIndex + " >= " + throwables.length);
    258            }
    259            if (matchSubclasses) {
    260                for (int i = fromIndex; i < throwables.length; i++) {
    261                    if (type.isAssignableFrom(throwables[i].getClass())) {
    262                        return i;
    263                    }
    264                }
    265            } else {
    266                for (int i = fromIndex; i < throwables.length; i++) {
    267                    if (type.equals(throwables[i].getClass())) {
    268                        return i;
    269                    }
    270                }
    271            }
    272            return -1;
    273        }
    274
    275        /**
    276         * Prints the stack trace of this exception the the standar error
    277         * stream.
    278         */
    279        public void printStackTrace() {
    280            printStackTrace(System.err);
    281        }
    282
    283        /**
    284         * Prints the stack trace of this exception to the specified
    285         * stream.
    286         *
    287         * @param out <code>PrintStream</code> to use for output.
    288         * @see #printStackTrace(PrintWriter)
    289         */
    290        public void printStackTrace(PrintStream out) {
    291            synchronized (out) {
    292                PrintWriter pw = new PrintWriter(out, false);
    293                printStackTrace(pw);
    294                // Flush the PrintWriter before it's GC'ed.
    295                pw.flush();
    296            }
    297        }
    298
    299        /**
    300         * Prints the stack trace of this exception to the specified
    301         * writer. If the Throwable class has a <code>getCause</code>
    302         * method (i.e. running on jre1.4 or higher), this method just
    303         * uses Throwable's printStackTrace() method. Otherwise, generates
    304         * the stack-trace, by taking into account the 'topDown' and
    305         * 'trimStackFrames' parameters. The topDown and trimStackFrames
    306         * are set to 'true' by default (produces jre1.4-like stack trace).
    307         *
    308         * @param out <code>PrintWriter</code> to use for output.
    309         */
    310        public void printStackTrace(PrintWriter out) {
    311            Throwable throwable = this.nestable;
    312            // if running on jre1.4 or higher, use default printStackTrace
    313            if (ExceptionUtils.isThrowableNested()) {
    314                if (throwable instanceof Nestable) {
    315                    ((Nestable)throwable).printPartialStackTrace(out);
    316                } else {
    317                    throwable.printStackTrace(out);
    318                }
    319                return;
    320            }
    321
    322            // generating the nested stack trace
    323            List stacks = new ArrayList();
    324            while (throwable != null) {
    325                String[] st = getStackFrames(throwable);
    326                stacks.add(st);
    327                throwable = ExceptionUtils.getCause(throwable);
    328            }
    329
    330            // If NOT topDown, reverse the stack
    331            String separatorLine = "Caused by: ";
    332            if (!topDown) {
    333                separatorLine = "Rethrown as: ";
    334                Collections.reverse(stacks);
    335            }
    336
    337            // Remove the repeated lines in the stack
    338            if (trimStackFrames) {
    339              trimStackFrames(stacks);
    340            }
    341
    342            synchronized (out) {
    343                for (Iterator iter=stacks.iterator(); iter.hasNext();) {
    344                    String[] st = (String[]) iter.next();
    345                    for (int i=0, len=st.length; i < len; i++) {
    346                        out.println(st[i]);
    347                    }
    348                    if (iter.hasNext()) {
    349                        out.print(separatorLine);
    350                    }
    351                }
    352            }
    353        }
    354
    355        /**
    356         * Captures the stack trace associated with the specified
    357         * <code>Throwable</code> object, decomposing it into a list of
    358         * stack frames.
    359         *
    360         * @param t The <code>Throwable</code>.
    361         * @return  An array of strings describing each stack frame.
    362         * @since 2.0
    363         */
    364        protected String[] getStackFrames(Throwable t) {
    365            StringWriter sw = new StringWriter();
    366            PrintWriter pw = new PrintWriter(sw, true);
    367
    368            // Avoid infinite loop between decompose() and printStackTrace().
    369            if (t instanceof Nestable) {
    370                ((Nestable) t).printPartialStackTrace(pw);
    371            } else {
    372                t.printStackTrace(pw);
    373            }
    374            return ExceptionUtils.getStackFrames(sw.getBuffer().toString());
    375        }
    376
    377        /**
    378         * Trims the stack frames. The first set is left untouched. The rest
    379         * of the frames are truncated from the bottom by comparing with
    380         * one just on top.
    381         *
    382         * @param stacks The list containing String[] elements
    383         * @since 2.0
    384         */
    385        protected void trimStackFrames(List stacks) {
    386             for (int size=stacks.size(), i=size-1; i > 0; i--) {
    387                 String[] curr = (String[]) stacks.get(i);
    388                 String[] next = (String[]) stacks.get(i-1);
    389
    390                 List currList = new ArrayList(Arrays.asList(curr));
    391                 List nextList = new ArrayList(Arrays.asList(next));
    392                 ExceptionUtils.removeCommonFrames(currList, nextList);
    393
    394                 int trimmed = curr.length - currList.size();
    395                 if (trimmed > 0) {
    396                     currList.add("\t... "+trimmed+" more");
    397                     stacks.set(
    398                         i,
    399                         currList.toArray(new String[currList.size()])
    400                     );
    401                 }
    402             }
    403         }
    404    }