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 */ 017 018package org.apache.commons.io.output; 019 020import java.io.FilterWriter; 021import java.io.IOException; 022import java.io.Writer; 023import java.util.Arrays; 024import java.util.Collection; 025import java.util.Collections; 026import java.util.Objects; 027import java.util.stream.Stream; 028 029import org.apache.commons.io.IOExceptionList; 030import org.apache.commons.io.IOIndexedException; 031import org.apache.commons.io.function.IOConsumer; 032 033/** 034 * Abstract class for writing filtered character streams to a {@link Collection} of writers. This is in contrast to 035 * {@link FilterWriter} which is backed by a single {@link Writer}. 036 * <p> 037 * This abstract class provides default methods that pass all requests to the contained writers. Subclasses should 038 * likely override some of these methods. 039 * </p> 040 * <p> 041 * The class {@link Writer} defines method signatures with {@code throws} {@link IOException}, which in this class are 042 * actually {@link IOExceptionList} containing a list of {@link IOIndexedException}. 043 * </p> 044 * 045 * @since 2.7 046 */ 047public class FilterCollectionWriter extends Writer { 048 049 /** 050 * Empty and immutable collection of writers. 051 */ 052 protected final Collection<Writer> EMPTY_WRITERS = Collections.emptyList(); 053 054 /** 055 * The underlying writers. 056 */ 057 protected final Collection<Writer> writers; 058 059 /** 060 * Constructs a new filtered collection writer. 061 * 062 * @param writers Writers to provide the underlying targets. 063 */ 064 protected FilterCollectionWriter(final Collection<Writer> writers) { 065 this.writers = writers == null ? EMPTY_WRITERS : writers; 066 } 067 068 /** 069 * Constructs a new filtered collection writer. 070 * 071 * @param writers Writers to provide the underlying targets. 072 */ 073 protected FilterCollectionWriter(final Writer... writers) { 074 this.writers = writers == null ? EMPTY_WRITERS : Arrays.asList(writers); 075 } 076 077 @Override 078 public Writer append(final char c) throws IOException { 079 return forAllWriters(w -> w.append(c)); 080 } 081 082 @Override 083 public Writer append(final CharSequence csq) throws IOException { 084 return forAllWriters(w -> w.append(csq)); 085 } 086 087 @Override 088 public Writer append(final CharSequence csq, final int start, final int end) throws IOException { 089 return forAllWriters(w -> w.append(csq, start, end)); 090 } 091 092 @SuppressWarnings("resource") // no allocation 093 @Override 094 public void close() throws IOException { 095 forAllWriters(Writer::close); 096 } 097 098 /** 099 * Flushes the stream. 100 * 101 * @throws IOException If an I/O error occurs 102 */ 103 @SuppressWarnings("resource") // no allocation 104 @Override 105 public void flush() throws IOException { 106 forAllWriters(Writer::flush); 107 } 108 109 private FilterCollectionWriter forAllWriters(final IOConsumer<Writer> action) throws IOExceptionList { 110 IOConsumer.forAll(action, writers()); 111 return this; 112 } 113 114 @SuppressWarnings("resource") // no allocation 115 @Override 116 public void write(final char[] cbuf) throws IOException { 117 forAllWriters(w -> w.write(cbuf)); 118 } 119 120 /** 121 * Writes a portion of an array of characters. 122 * 123 * @param cbuf Buffer of characters to be written 124 * @param off Offset from which to start reading characters 125 * @param len Number of characters to be written 126 * @throws IOException If an I/O error occurs 127 */ 128 @SuppressWarnings("resource") // no allocation 129 @Override 130 public void write(final char[] cbuf, final int off, final int len) throws IOException { 131 forAllWriters(w -> w.write(cbuf, off, len)); 132 } 133 134 /** 135 * Writes a single character. 136 * 137 * @throws IOException If an I/O error occurs 138 */ 139 @SuppressWarnings("resource") // no allocation 140 @Override 141 public void write(final int c) throws IOException { 142 forAllWriters(w -> w.write(c)); 143 } 144 145 @SuppressWarnings("resource") // no allocation 146 @Override 147 public void write(final String str) throws IOException { 148 forAllWriters(w -> w.write(str)); 149 } 150 151 /** 152 * Writes a portion of a string. 153 * 154 * @param str String to be written 155 * @param off Offset from which to start reading characters 156 * @param len Number of characters to be written 157 * @throws IOException If an I/O error occurs 158 */ 159 @SuppressWarnings("resource") // no allocation 160 @Override 161 public void write(final String str, final int off, final int len) throws IOException { 162 forAllWriters(w -> w.write(str, off, len)); 163 } 164 165 private Stream<Writer> writers() { 166 return writers.stream().filter(Objects::nonNull); 167 } 168 169}