    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 */
    017package org.apache.commons.io.input;
    018
    019import java.io.IOException;
    020import java.io.InputStream;
    021import java.io.Serializable;
    022import java.util.UUID;
    023
    024import org.apache.commons.io.TaggedIOException;
    025
    026/**
    027 * An input stream decorator that tags potential exceptions so that the
    028 * stream that caused the exception can easily be identified. This is
    029 * done by using the {@link TaggedIOException} class to wrap all thrown
    030 * {@link IOException}s. See below for an example of using this class.
    031 * <pre>
    032 * TaggedInputStream stream = new TaggedInputStream(...);
    033 * try {
    034 *     // Processing that may throw an IOException either from this stream
    035 *     // or from some other IO activity like temporary files, etc.
    036 *     processStream(stream);
    037 * } catch (IOException e) {
    038 *     if (stream.isCauseOf(e)) {
    039 *         // The exception was caused by this stream.
    040 *         // Use e.getCause() to get the original exception.
    041 *     } else {
    042 *         // The exception was caused by something else.
    043 *     }
    044 * }
    045 * </pre>
    046 * <p>
    047 * Alternatively, the {@link #throwIfCauseOf(Throwable)} method can be
    048 * used to let higher levels of code handle the exception caused by this
    049 * stream while other processing errors are being taken care of at this
    050 * lower level.
    051 * </p>
    052 * <pre>
    053 * TaggedInputStream stream = new TaggedInputStream(...);
    054 * try {
    055 *     processStream(stream);
    056 * } catch (IOException e) {
    057 *     stream.throwIfCauseOf(e);
    058 *     // ... or process the exception that was caused by something else
    059 * }
    060 * </pre>
    061 * <h2>Deprecating Serialization</h2>
    062 * <p>
    063 * <em>Serialization is deprecated and will be removed in 3.0.</em>
    064 * </p>
    065 *
    066 * @see TaggedIOException
    067 * @since 2.0
    068 */
    069public class TaggedInputStream extends ProxyInputStream {
    070
    071    /**
    072     * The unique tag associated with exceptions from stream.
    073     */
    074    private final Serializable tag = UUID.randomUUID();
    075
    076    /**
    077     * Constructs a tagging decorator for the given input stream.
    078     *
    079     * @param proxy input stream to be decorated
    080     */
    081    public TaggedInputStream(final InputStream proxy) {
    082        super(proxy);
    083    }
    084
    085    /**
    086     * Tags any IOExceptions thrown, wrapping and re-throwing.
    087     *
    088     * @param e The IOException thrown
    089     * @throws IOException if an I/O error occurs.
    090     */
    091    @Override
    092    protected void handleIOException(final IOException e) throws IOException {
    093        throw new TaggedIOException(e, tag);
    094    }
    095
    096    /**
    097     * Tests if the given exception was caused by this stream.
    098     *
    099     * @param exception an exception
    100     * @return {@code true} if the exception was thrown by this stream,
    101     *         {@code false} otherwise
    102     */
    103    public boolean isCauseOf(final Throwable exception) {
    104        return TaggedIOException.isTaggedWith(exception, tag);
    105    }
    106
    107    /**
    108     * Re-throws the original exception thrown by this stream. This method
    109     * first checks whether the given exception is a {@link TaggedIOException}
    110     * wrapper created by this decorator, and then unwraps and throws the
    111     * original wrapped exception. Returns normally if the exception was
    112     * not thrown by this stream.
    113     *
    114     * @param throwable an exception
    115     * @throws IOException original exception, if any, thrown by this stream
    116     */
    117    public void throwIfCauseOf(final Throwable throwable) throws IOException {
    118        TaggedIOException.throwCauseIfTaggedWith(throwable, tag);
    119    }
    120
    121}