/*
* 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;
import java.io.IOException;
import java.io.Serializable;
/**
* An {@link IOException} decorator that adds a serializable tag to the
* wrapped exception. Both the tag and the original exception can be used
* to determine further processing when this exception is caught.
*
* @since Commons IO 2.0
*/
public class TaggedIOException extends IOExceptionWithCause {
/**
* Generated serial version UID.
*/
private static final long serialVersionUID = -6994123481142850163L;
/**
* Checks whether the given throwable is tagged with the given tag.
* <p>
* This check can only succeed if the throwable is a
* {@link TaggedIOException} and the tag is {@link Serializable}, but
* the argument types are intentionally more generic to make it easier
* to use this method without type casts.
* <p>
* A typical use for this method is in a <code>catch</code> block to
* determine how a caught exception should be handled:
* <pre>
* Serializable tag = ...;
* try {
* ...;
* } catch (Throwable t) {
* if (TaggedIOExcepton.isTaggedWith(t, tag)) {
* // special processing for tagged exception
* } else {
* // handling of other kinds of exceptions
* }
* }
* </pre>
*
* @param throwable The Throwable object to check
* @param tag tag object
* @return <code>true</code> if the throwable has the specified tag,
* otherwise <code>false</code>
*/
public static boolean isTaggedWith(Throwable throwable, Object tag) {
return tag != null
&& throwable instanceof TaggedIOException
&& tag.equals(((TaggedIOException) throwable).tag);
}
/**
* Throws the original {@link IOException} if the given throwable is
* a {@link TaggedIOException} decorator the given tag. Does nothing
* if the given throwable is of a different type or if it is tagged
* with some other tag.
* <p>
* This method is typically used in a <code>catch</code> block to
* selectively rethrow tagged exceptions.
* <pre>
* Serializable tag = ...;
* try {
* ...;
* } catch (Throwable t) {
* TaggedIOExcepton.throwCauseIfTagged(t, tag);
* // handle other kinds of exceptions
* }
* </pre>
*
* @param throwable an exception
* @param tag tag object
* @throws IOException original exception from the tagged decorator, if any
*/
public static void throwCauseIfTaggedWith(Throwable throwable, Object tag)
throws IOException {
if (isTaggedWith(throwable, tag)) {
throw ((TaggedIOException) throwable).getCause();
}
}
/**
* The tag of this exception.
*/
private final Serializable tag;
/**
* Creates a tagged wrapper for the given exception.
*
* @param original the exception to be tagged
* @param tag tag of this exception
*/
public TaggedIOException(IOException original, Serializable tag) {
super(original.getMessage(), original);
this.tag = tag;
}
/**
* Returns the serializable tag object.
*
* @return tag object
*/
public Serializable getTag() {
return tag;
}
/**
* Returns the wrapped exception. The only difference to the overridden
* {@link Throwable#getCause()} method is the narrower return type.
*
* @return wrapped exception
*/
@Override
public IOException getCause() {
return (IOException) super.getCause();
}
}
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