1 /* 2 * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved. 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 8 * - Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 11 * - Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * - Neither the name of Oracle nor the names of its 16 * contributors may be used to endorse or promote products derived 17 * from this software without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS 20 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, 21 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR 23 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 24 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 25 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 26 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 27 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 28 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 29 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 30 */ 31 32 /* 33 * This source code is provided to illustrate the usage of a given feature 34 * or technique and has been deliberately simplified. Additional steps 35 * required for a production-quality application, such as security checks, 36 * input validation, and proper error handling, might not be present in 37 * this sample code. 38 */ 39 40 import java.io.BufferedOutputStream; 41 import java.io.IOException; 42 import java.io.OutputStream; 43 import java.io.PrintStream; 44 import java.nio.file.Files; 45 import java.nio.file.Path; 46 import java.nio.file.Paths; 47 48 /** 49 * This sample demonstrates the ability to create custom resource that 50 * implements the {@code AutoCloseable} interface. This resource can be used in 51 * the try-with-resources construct. 52 */ 53 public class CustomAutoCloseableSample { 54 55 /** 56 * The main method for the CustomAutoCloseableSample program. 57 * 58 * @param args is not used. 59 */ 60 public static void main(String[] args) { 61 /* 62 * TeeStream will be closed automatically after the try block. 63 */ 64 try (TeeStream teeStream = new TeeStream(System.out, Paths.get("out.txt")); 65 PrintStream out = new PrintStream(teeStream)) { 66 out.print("Hello, world"); 67 } catch (Exception e) { 68 e.printStackTrace(); 69 System.exit(1); 70 } 71 } 72 73 /** 74 * Passes the output through to the specified output stream while copying it into a file. 75 * The TeeStream functionality is similar to the Unix tee utility. 76 * TeeStream implements AutoCloseable interface. See OutputStream for details. 77 */ 78 public static class TeeStream extends OutputStream { 79 80 private final OutputStream fileStream; 81 private final OutputStream outputStream; 82 83 /** 84 * Creates a TeeStream. 85 * 86 * @param outputStream an output stream. 87 * @param outputFile an path to file. 88 * @throws IOException If an I/O error occurs. 89 */ 90 public TeeStream(OutputStream outputStream, Path outputFile) throws IOException { 91 this.fileStream = new BufferedOutputStream(Files.newOutputStream(outputFile)); 92 this.outputStream = outputStream; 93 } 94 95 /** 96 * Writes the specified byte to the specified output stream 97 * and copies it to the file. 98 * 99 * @param b the byte to be written. 100 * @throws IOException If an I/O error occurs. 101 */ 102 @Override 103 public void write(int b) throws IOException { 104 fileStream.write(b); 105 outputStream.write(b); 106 } 107 108 /** 109 * Flushes this output stream and forces any buffered output bytes 110 * to be written out. 111 * The <code>flush</code> method of <code>TeeStream</code> flushes 112 * the specified output stream and the file output stream. 113 * 114 * @throws IOException if an I/O error occurs. 115 */ 116 @Override 117 public void flush() throws IOException { 118 outputStream.flush(); 119 fileStream.flush(); 120 } 121 122 /** 123 * Closes underlying streams and resources. 124 * The external output stream won't be closed. 125 * This method is the member of AutoCloseable interface and 126 * it will be invoked automatically after the try-with-resources block. 127 * 128 * @throws IOException If an I/O error occurs. 129 */ 130 @Override 131 public void close() throws IOException { 132 try (OutputStream file = fileStream) { 133 flush(); 134 } 135 } 136 } 137 } 138
