105 lines
3.4 KiB
Java
105 lines
3.4 KiB
Java
/*
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* The MIT License
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* Copyright © 2014-2019 Ilkka Seppälä
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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package com.iluwatar.mute;
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import java.io.ByteArrayOutputStream;
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import java.io.IOException;
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import java.util.Optional;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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/**
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* Mute pattern is utilized when we need to suppress an exception due to an API flaw or in situation
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* when all we can do to handle the exception is to log it. This pattern should not be used
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* everywhere. It is very important to logically handle the exceptions in a system, but some
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* situations like the ones described above require this pattern, so that we don't need to repeat
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* <pre>
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* <code>
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* try {
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* // code that may throwing exception we need to ignore or may never be thrown
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* } catch (Exception ex) {
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* // ignore by logging or throw error if unexpected exception occurs
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* }
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* </code>
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* </pre> every time we need to ignore an exception.
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*/
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public class App {
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private static final Logger LOGGER = LoggerFactory.getLogger(App.class);
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/**
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* Program entry point.
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*
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* @param args command line args.
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*/
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public static void main(String[] args) {
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useOfLoggedMute();
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useOfMute();
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}
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/*
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* Typically used when the API declares some exception but cannot do so. Usually a
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* signature mistake.In this example out is not supposed to throw exception as it is a
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* ByteArrayOutputStream. So we utilize mute, which will throw AssertionError if unexpected
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* exception occurs.
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*/
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private static void useOfMute() {
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var out = new ByteArrayOutputStream();
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Mute.mute(() -> out.write("Hello".getBytes()));
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}
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private static void useOfLoggedMute() {
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Optional<Resource> resource = Optional.empty();
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try {
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resource = Optional.of(acquireResource());
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utilizeResource(resource.get());
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} finally {
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resource.ifPresent(App::closeResource);
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}
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}
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/*
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* All we can do while failed close of a resource is to log it.
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*/
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private static void closeResource(Resource resource) {
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Mute.loggedMute(resource::close);
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}
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private static void utilizeResource(Resource resource) {
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LOGGER.info("Utilizing acquired resource: {}", resource);
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}
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private static Resource acquireResource() {
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return new Resource() {
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@Override
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public void close() throws IOException {
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throw new IOException("Error in closing resource: " + this);
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}
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};
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}
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}
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