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1
43 package net.jforum.util;
44
45 import java.io.File  ;
46 import java.util.HashMap ;
47 import java.util.Map ;
48 import java.util.Timer ;
49 import java.util.TimerTask ;
50
51 import org.apache.log4j.Logger;
52
53
59 public class FileMonitor
60 {
61 private static Logger logger = Logger.getLogger(FileMonitor.class);
62 private static final FileMonitor instance = new FileMonitor();
63 private Timer timer;
64 private Map timerEntries;
65
66 private FileMonitor() {
67 this.timerEntries = new HashMap ();
68 this.timer = new Timer (true);
69 }
70
71 public static FileMonitor getInstance() {
72 return instance;
73 }
74
75
82 public void addFileChangeListener(FileChangeListener listener,
83 String filename, long period) {
84 this.removeFileChangeListener(filename);
85
86 logger.info("Watching " + filename);
87
88 FileMonitorTask task = new FileMonitorTask(listener, filename);
89
90 this.timerEntries.put(filename, task);
91 this.timer.schedule(task, period, period);
92 }
93
94
100 public void removeFileChangeListener(String filename) {
101 FileMonitorTask task = (FileMonitorTask)this.timerEntries.remove(filename);
102
103 if (task != null) {
104 task.cancel();
105 }
106 }
107
108 private class FileMonitorTask extends TimerTask {
109 private FileChangeListener listener;
110 private String filename;
111 private File monitoredFile;
112 private long lastModified;
113
114 public FileMonitorTask(FileChangeListener listener, String filename) {
115 this.listener = listener;
116 this.filename = filename;
117
118 this.monitoredFile = new File (filename);
119 if (!this.monitoredFile.exists()) {
120 return;
121 }
122
123 this.lastModified = this.monitoredFile.lastModified();
124 }
125
126 public void run() {
127 long latestChange = this.monitoredFile.lastModified();
128 if (this.lastModified != latestChange) {
129 this.lastModified = latestChange;
130
131 this.listener.fileChanged(this.filename);
132 }
133 }
134 }
135 }
136 |
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