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1   /**
2   The contents of this file are subject to the Mozilla Public License Version 1.1 
3   (the "License"); you may not use this file except in compliance with the License. 
4   You may obtain a copy of the License at http://www.mozilla.org/MPL/ 
5   Software distributed under the License is distributed on an "AS IS" basis, 
6   WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License for the 
7   specific language governing rights and limitations under the License. 
8   
9   The Original Code is "FileBasedGenerator.java".  Description: 
10  "Replacement for the legagy MessageIDGenerator class" 
11  
12  The Initial Developer of the Original Code is University Health Network. Copyright (C) 
13  2001.  All Rights Reserved. 
14  
15  Contributor(s): ______________________________________. 
16  
17  Alternatively, the contents of this file may be used under the terms of the 
18  GNU General Public License (the  "GPL"), in which case the provisions of the GPL are 
19  applicable instead of those above.  If you wish to allow use of your version of this 
20  file only under the terms of the GPL and not to allow others to use your version 
21  of this file under the MPL, indicate your decision by deleting  the provisions above 
22  and replace  them with the notice and other provisions required by the GPL License.  
23  If you do not delete the provisions above, a recipient may use your version of 
24  this file under either the MPL or the GPL. 
25   */
26  package ca.uhn.hl7v2.util.idgenerator;
27  
28  import java.io.BufferedReader;
29  import java.io.File;
30  import java.io.FileInputStream;
31  import java.io.FileOutputStream;
32  import java.io.IOException;
33  import java.io.InputStreamReader;
34  import java.io.PrintWriter;
35  import java.util.concurrent.locks.ReentrantLock;
36  
37  import org.slf4j.Logger;
38  import org.slf4j.LoggerFactory;
39  
40  import ca.uhn.hl7v2.util.Home;
41  
42  /**
43   * Replacement for {@link ca.uhn.hl7v2.util.MessageIDGenerator}. You should not use this class
44   * directly, however, but wrap it into a {@link DelegatingHiLoGenerator} generator. Its primary
45   * improvement over {@link ca.uhn.hl7v2.util.MessageIDGenerator} is that you can set path and file
46   * name.
47   * <p>
48   * Reading and writing to the file is thread-safe, however, you should not use the same file from
49   * different Java processes because no read/write locks are being checked.
50   */
51  public class FileBasedGenerator extends InMemoryIDGenerator {
52  
53  	private static final Logger LOG = LoggerFactory.getLogger(FileBasedGenerator.class.getName());
54  
55  	private String directory = Home.getHomeDirectory().getAbsolutePath();
56  	private String fileName = "id_file";
57  	private boolean neverFail = true;
58  	private boolean used = false;
59  	private boolean minimizeReads = false;
60  	private ReentrantLock lock = new ReentrantLock();
61  
62  	public FileBasedGenerator() {
63  		this(1);
64  	}
65  
66  	FileBasedGenerator(int increment) {
67  		super(increment);
68  	}
69  
70  	public String getID() throws IOException {
71  		try {
72  			lock.lock();
73  			
74  			// If ID is 0, read initial value from file if possible
75  			if (!minimizeReads || !used) {
76  				long readInitialValue = readInitialValue(getFilePath());
77  				if (readInitialValue >= 0) {
78  					set(readInitialValue);
79  				}
80  				used = true;
81  			}
82  			
83  			String id = super.getID();
84  			// The id held in the file is always <increment> larger so that
85  			// the ID is still unique after a restart.
86  			writeNextValue(Long.parseLong(id) + getIncrement());
87  			return id;
88  		} finally {
89  			lock.unlock();
90  		}
91  	}
92  
93  
94  	private void writeNextValue(long id) throws IOException {
95  		PrintWriter pw = null;
96  		try {
97  			pw = new PrintWriter(new FileOutputStream(getFilePath(), false));
98  			pw.println(Long.toString(id));
99  		} catch (IOException e) {
100 			if (neverFail) {
101 				LOG.warn("Could not write ID to file {}, going to use internal ID generator. {}",
102 						getFilePath(), e.getMessage());
103 				return;
104 			}
105 			throw e;
106 		} finally {
107 			if (pw != null)
108 				pw.close();
109 		}
110 	}
111 
112 	private long readInitialValue(String path) throws IOException {
113 		BufferedReader br = null;
114 		String id = null;
115 		try {
116 			br = new BufferedReader(new InputStreamReader(new FileInputStream(path)));
117 			id = br.readLine();
118 			return Long.parseLong(id);
119 		} catch (IOException e) {
120 			LOG.info("Could not read ID file {} ", path);
121 			if (!neverFail) {
122 				throw e;
123 			}
124 			return -1;
125 		} catch (NumberFormatException e) {
126 			LOG.info("ID {} read from file is not a number", id);
127 			return -1;
128 		} finally {
129 			if (br != null)
130 				try {
131 					br.close();
132 				} catch (IOException e) {
133 				}
134 		}
135 	}
136 
137 	private String getFilePath() {
138 		return new File(directory, fileName).getAbsolutePath();
139 	}
140 
141 	public void setDirectory(String directory) {
142 		try {
143 			lock.lock();
144 			this.directory = directory;
145 		} finally {
146 			lock.unlock();
147 		}
148 	}
149 
150 	public void setFileName(String fileName) {
151 		try {
152 			lock.lock();
153 			this.fileName = fileName;
154 		} finally {
155 			lock.unlock();
156 		}
157 	}
158 
159 	/**
160 	 * If set to <code>true</code> (default is <code>false</code>) the generator
161 	 * minimizes the number of disk reads by caching the last read value. This means
162 	 * one less disk read per X number of IDs generated, but also means that multiple
163 	 * instances of this generator may clobber each other's values.
164 	 */
165 	public void setMinimizeReads(boolean theMinimizeReads) {
166 		minimizeReads = theMinimizeReads;
167 	}
168 
169 	/**
170 	 * If set to <code>false</code> (default is <code>true</code>),
171 	 * retrieving a new ID may fail if the ID file in the home
172 	 * directory can not be written/read. If set to true, failures
173 	 * will be ignored, which means that IDs may be repeated after
174 	 * a JVM restart.
175 	 */
176 	public void setNeverFail(boolean neverFail) {
177 		this.neverFail = neverFail;
178 	}
179 
180 	public void reset() {
181 		try {
182 			lock.lock();
183 			super.reset();
184 			writeNextValue(0l);
185 		} catch (IOException e) {
186 			throw new IllegalStateException("Cannot initialize persistent ID generator", e);
187 		} finally {
188 			lock.unlock();
189 		}
190 	}
191 
192 }