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Simple tail like assertion

/ Published in: Java
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A simple testing assertion which looks up for a line within a file until a pre defined time frame ends (loosely based upon http://www.informit.com/guides/content.aspx?g=java&seqNum=226).

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  1. public class TailAssertor {
  2.  
  3.     private static final long sec = 1000L;
  4.  
  5.     private static final Log log = LogService.getLog(TailAssertor.class.getName());
  6.  
  7.     private static long sampleInterval = 5000;
  8.  
  9.     public static void assertNewLinesWithTail(final File logfile, final String expectedLine, int durationInSec) {
  10.  
  11.         long filePointer = logfile.length();// The file pointer keeps track of where we are in the file
  12.         RandomAccessFile file = null;
  13.         try {
  14.             file = new RandomAccessFile(logfile, "r");
  15.             for (final Date startTime = new Date(); new Date().getTime() - startTime.getTime() < durationInSec * sec;) {
  16.                 long fileLength = logfile.length();
  17.                 if (fileLength < filePointer) {// file has been cleared
  18.                     file = new RandomAccessFile(logfile, "r");
  19.                     filePointer = 0;
  20.                 }
  21.                 if (fileLength > filePointer) {
  22.                     file.seek(filePointer);// There is new data to read
  23.                     for (String line = file.readLine(); line != null;) {
  24.                         if (line.contains(expectedLine)) {
  25.                             return;
  26.                         }
  27.                         line = file.readLine();
  28.                     }
  29.                     filePointer = file.getFilePointer();
  30.                 }
  31.                 Thread.sleep(sampleInterval);// Sleep for the specified interval
  32.             }
  33.         } catch (Exception e) {
  34.             log.error(e);
  35.         } finally {
  36.             closeFile(file);
  37.         }
  38.         throw new AssertionError("the requested line wasn't found within the required time frame!");
  39.     }
  40.  
  41.     private static void closeFile(RandomAccessFile file) {
  42.         if (file != null) {
  43.             try {
  44.                 file.close();
  45.             } catch (IOException e) {
  46.                 log.error(e);
  47.             }
  48.         }
  49.     }
  50. }

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