BrokenOutputStream.java

/*
 * 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.util.function.Function;
import java.util.function.Supplier;

import org.apache.commons.io.function.Erase;

/**
 * Always throws an exception from all {@link OutputStream} methods where {@link IOException} is declared.
 * <p>
 * This class is mostly useful for testing error handling.
 * </p>
 *
 * @since 2.0
 */
public class BrokenOutputStream extends OutputStream {

    /**
     * The singleton instance using a default IOException.
     *
     * @since 2.12.0
     */
    public static final BrokenOutputStream INSTANCE = new BrokenOutputStream();

    /**
     * Supplies the exception that is thrown by all methods of this class.
     */
    private final Function<String, Throwable> exceptionFunction;

    /**
     * Constructs a new stream that always throws an {@link IOException}.
     */
    public BrokenOutputStream() {
        this(m -> new IOException("Broken output stream: " + m));
    }

    /**
     * Constructs a new stream that always throws the given exception.
     *
     * @param exception the exception to be thrown.
     * @deprecated Use {@link #BrokenOutputStream(Throwable)}.
     */
    @Deprecated
    public BrokenOutputStream(final IOException exception) {
        this(m -> exception);
    }

    /**
     * Constructs a new stream that always throws the supplied exception.
     * <p>
     * This class uses the invoked method name as the function input.
     * </p>
     *
     * @param exceptionFunction a supplier for the IOException or RuntimeException to be thrown.
     * @since 2.19.0
     */
    public BrokenOutputStream(final Function<String, Throwable> exceptionFunction) {
        this.exceptionFunction = exceptionFunction;
    }

    /**
     * Constructs a new stream that always throws the supplied exception.
     *
     * @param exceptionSupplier a supplier for the IOException or RuntimeException to be thrown.
     * @since 2.12.0
     * @deprecated Use {@link #BrokenOutputStream(Function)}.
     */
    @Deprecated
    public BrokenOutputStream(final Supplier<Throwable> exceptionSupplier) {
        this.exceptionFunction = m -> exceptionSupplier.get();
    }

    /**
     * Constructs a new stream that always throws the given exception.
     *
     * @param exception the exception to be thrown.
     * @since 2.16.0
     */
    public BrokenOutputStream(final Throwable exception) {
        this(m -> exception);
    }

    /**
     * Throws the configured exception.
     *
     * @throws IOException always throws the exception configured in a constructor.
     */
    @Override
    public void close() throws IOException {
        throw rethrow("close()");
    }

    /**
     * Throws the configured exception.
     *
     * @throws IOException always throws the exception configured in a constructor.
     */
    @Override
    public void flush() throws IOException {
        throw rethrow("flush()");
    }

    /**
     * Throws the configured exception from its supplier.
     *
     * @param method The exception function argument.
     * @return Throws the configured exception from its supplier.
     */
    private RuntimeException rethrow(final String method) {
        return Erase.rethrow(exceptionFunction.apply(method));
    }

    /**
     * Throws the configured exception.
     *
     * @param b ignored.
     * @throws IOException always throws the exception configured in a constructor.
     */
    @Override
    public void write(final int b) throws IOException {
        throw rethrow("write(int)");
    }

}