Commons IO example source code file (TaggedOutputStream.java)

This example Commons IO source code file (TaggedOutputStream.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Commons IO tags/keywords

io, ioexception, ioexception, override, proxyoutputstream, serializable, serializable, taggedioexception, taggedioexception, taggedoutputstream, taggedoutputstream, util

The Commons IO TaggedOutputStream.java source code

/*
 * 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.io.output;

import java.io.IOException;
import java.io.OutputStream;
import java.io.Serializable;
import java.util.UUID;

import org.apache.commons.io.TaggedIOException;

/**
 * An output stream decorator that tags potential exceptions so that the
 * stream that caused the exception can easily be identified. This is
 * done by using the {@link TaggedIOException} class to wrap all thrown
 * {@link IOException}s. See below for an example of using this class.
 * <pre>
 * TaggedOutputStream stream = new TaggedOutputStream(...);
 * try {
 *     // Processing that may throw an IOException either from this stream
 *     // or from some other IO activity like temporary files, etc.
 *     writeToStream(stream);
 * } catch (IOException e) {
 *     if (stream.isCauseOf(e)) {
 *         // The exception was caused by this stream.
 *         // Use e.getCause() to get the original exception.
 *     } else {
 *         // The exception was caused by something else.
 *     }
 * }
 * </pre>
 * <p>
 * Alternatively, the {@link #throwIfCauseOf(Exception)} method can be
 * used to let higher levels of code handle the exception caused by this
 * stream while other processing errors are being taken care of at this
 * lower level.
 * <pre>
 * TaggedOutputStream stream = new TaggedOutputStream(...);
 * try {
 *     writeToStream(stream);
 * } catch (IOException e) {
 *     stream.throwIfCauseOf(e);
 *     // ... or process the exception that was caused by something else
 * }
 * </pre>
 *
 * @see TaggedIOException
 * @since Commons IO 2.0
 */
public class TaggedOutputStream extends ProxyOutputStream {

    /**
     * The unique tag associated with exceptions from stream.
     */
    private final Serializable tag = UUID.randomUUID();

    /**
     * Creates a tagging decorator for the given output stream.
     *
     * @param proxy output stream to be decorated
     */
    public TaggedOutputStream(OutputStream proxy) {
        super(proxy);
    }

    /**
     * Tests if the given exception was caused by this stream.
     *
     * @param exception an exception
     * @return <code>true if the exception was thrown by this stream,
     *         <code>false otherwise
     */
    public boolean isCauseOf(Exception exception) {
        return TaggedIOException.isTaggedWith(exception, tag);
    }

    /**
     * Re-throws the original exception thrown by this stream. This method
     * first checks whether the given exception is a {@link TaggedIOException}
     * wrapper created by this decorator, and then unwraps and throws the
     * original wrapped exception. Returns normally if the exception was
     * not thrown by this stream.
     *
     * @param exception an exception
     * @throws IOException original exception, if any, thrown by this stream
     */
    public void throwIfCauseOf(Exception exception) throws IOException {
        TaggedIOException.throwCauseIfTaggedWith(exception, tag);
    }

    /**
     * Tags any IOExceptions thrown, wrapping and re-throwing.
     *
     * @param e The IOException thrown
     * @throws IOException if an I/O error occurs
     */
    @Override
    protected void handleIOException(IOException e) throws IOException {
        throw new TaggedIOException(e, tag);
    }

}