| 1 | /* |
| 2 | * Copyright 2006-2007 the original author or authors. |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | package org.springframework.batch.support.transaction; |
| 17 | |
| 18 | import java.io.IOException; |
| 19 | import java.io.Writer; |
| 20 | |
| 21 | import org.springframework.transaction.support.TransactionSynchronizationAdapter; |
| 22 | import org.springframework.transaction.support.TransactionSynchronizationManager; |
| 23 | |
| 24 | /** |
| 25 | * Wrapper for a {@link Writer} that delays actually writing to or closing the |
| 26 | * buffer if a transaction is active. If a transaction is detected on the call |
| 27 | * to {@link #write(String)} the parameter is buffered and passed on to the |
| 28 | * underlying writer only when the transaction is committed. |
| 29 | * |
| 30 | * @author Dave Syer |
| 31 | * |
| 32 | */ |
| 33 | public class TransactionAwareBufferedWriter extends Writer { |
| 34 | |
| 35 | private static final String BUFFER_KEY_PREFIX = TransactionAwareBufferedWriter.class.getName() + ".BUFFER_KEY"; |
| 36 | |
| 37 | private static final String CLOSE_KEY_PREFIX = TransactionAwareBufferedWriter.class.getName() + ".CLOSE_KEY"; |
| 38 | |
| 39 | private final String bufferKey; |
| 40 | |
| 41 | private final String closeKey; |
| 42 | |
| 43 | private Writer writer; |
| 44 | |
| 45 | private final Runnable closeCallback; |
| 46 | |
| 47 | /** |
| 48 | * Create a new instance with the underlying writer provided, and a callback |
| 49 | * to execute on close. The callback should clean up related resources like |
| 50 | * output streams or channels. |
| 51 | * |
| 52 | * @param writer actually writes to output |
| 53 | * @param closeCallback callback to execute on close |
| 54 | */ |
| 55 | public TransactionAwareBufferedWriter(Writer writer, Runnable closeCallback) { |
| 56 | super(); |
| 57 | this.writer = writer; |
| 58 | this.closeCallback = closeCallback; |
| 59 | this.bufferKey = BUFFER_KEY_PREFIX + "." + hashCode(); |
| 60 | this.closeKey = CLOSE_KEY_PREFIX + "." + hashCode(); |
| 61 | } |
| 62 | |
| 63 | /** |
| 64 | * @return |
| 65 | */ |
| 66 | private StringBuffer getCurrentBuffer() { |
| 67 | |
| 68 | if (!TransactionSynchronizationManager.hasResource(bufferKey)) { |
| 69 | |
| 70 | TransactionSynchronizationManager.bindResource(bufferKey, new StringBuffer()); |
| 71 | |
| 72 | TransactionSynchronizationManager.registerSynchronization(new TransactionSynchronizationAdapter() { |
| 73 | @Override |
| 74 | public void afterCompletion(int status) { |
| 75 | try { |
| 76 | if (status == STATUS_COMMITTED) { |
| 77 | complete(); |
| 78 | } |
| 79 | } |
| 80 | catch (IOException e) { |
| 81 | throw new FlushFailedException("Could not write to output buffer", e); |
| 82 | } |
| 83 | finally { |
| 84 | clear(); |
| 85 | } |
| 86 | } |
| 87 | |
| 88 | private void complete() throws IOException { |
| 89 | StringBuffer buffer = (StringBuffer) TransactionSynchronizationManager.getResource(bufferKey); |
| 90 | if (buffer != null) { |
| 91 | writer.write(buffer.toString()); |
| 92 | writer.flush(); |
| 93 | if (TransactionSynchronizationManager.hasResource(closeKey)) { |
| 94 | writer.close(); |
| 95 | closeCallback.run(); |
| 96 | } |
| 97 | } |
| 98 | } |
| 99 | |
| 100 | private void clear() { |
| 101 | if (TransactionSynchronizationManager.hasResource(bufferKey)) { |
| 102 | TransactionSynchronizationManager.unbindResource(bufferKey); |
| 103 | } |
| 104 | if (TransactionSynchronizationManager.hasResource(closeKey)) { |
| 105 | TransactionSynchronizationManager.unbindResource(closeKey); |
| 106 | } |
| 107 | } |
| 108 | |
| 109 | }); |
| 110 | |
| 111 | } |
| 112 | |
| 113 | return (StringBuffer) TransactionSynchronizationManager.getResource(bufferKey); |
| 114 | |
| 115 | } |
| 116 | |
| 117 | /** |
| 118 | * Convenience method for clients to determine if there is any unflushed |
| 119 | * data. |
| 120 | * |
| 121 | * @return the current size of unflushed buffered data |
| 122 | */ |
| 123 | public long getBufferSize() { |
| 124 | if (!transactionActive()) { |
| 125 | return 0L; |
| 126 | } |
| 127 | return getCurrentBuffer().length(); |
| 128 | } |
| 129 | |
| 130 | /** |
| 131 | * @return |
| 132 | */ |
| 133 | private boolean transactionActive() { |
| 134 | return TransactionSynchronizationManager.isActualTransactionActive(); |
| 135 | } |
| 136 | |
| 137 | /* |
| 138 | * (non-Javadoc) |
| 139 | * |
| 140 | * @see java.io.Writer#close() |
| 141 | */ |
| 142 | @Override |
| 143 | public void close() throws IOException { |
| 144 | if (transactionActive()) { |
| 145 | if (getCurrentBuffer().length() > 0) { |
| 146 | TransactionSynchronizationManager.bindResource(closeKey, Boolean.TRUE); |
| 147 | } |
| 148 | return; |
| 149 | } |
| 150 | writer.close(); |
| 151 | closeCallback.run(); |
| 152 | } |
| 153 | |
| 154 | /* |
| 155 | * (non-Javadoc) |
| 156 | * |
| 157 | * @see java.io.Writer#flush() |
| 158 | */ |
| 159 | @Override |
| 160 | public void flush() throws IOException { |
| 161 | if (!transactionActive()) { |
| 162 | writer.flush(); |
| 163 | } |
| 164 | } |
| 165 | |
| 166 | /* |
| 167 | * (non-Javadoc) |
| 168 | * |
| 169 | * @see java.io.Writer#write(char[], int, int) |
| 170 | */ |
| 171 | @Override |
| 172 | public void write(char[] cbuf, int off, int len) throws IOException { |
| 173 | |
| 174 | if (!transactionActive()) { |
| 175 | writer.write(cbuf, off, len); |
| 176 | return; |
| 177 | } |
| 178 | |
| 179 | StringBuffer buffer = getCurrentBuffer(); |
| 180 | buffer.append(cbuf, off, len); |
| 181 | |
| 182 | } |
| 183 | |
| 184 | } |