#JAVA FILEWATCHER WATCH FOR FILE TYPE UPDATE#
#JAVA FILEWATCHER WATCH FOR FILE TYPE CODE#
#JAVA FILEWATCHER WATCH FOR FILE TYPE WINDOWS#

I found this particularly irritating since they provided eight notification filters to make the FileSystemWatcher send the Changed event. My primary issue is that the FileSystemWatcher allows you to be notified that a file in a folder has changed, but not precisely what change was made. It was then, that the thought occurred to me that these FileSystemWatcher problems have never really be addressed (that I could find). A day or so ago, someone posted a question regarding a similar task, and I immediately suggested the same route I had taken. I became immediately aware of the shortcomings of the FileSystemWatcher class, and those shortcomings have always kind stuck to my brain.

#JAVA FILEWATCHER WATCH FOR FILE TYPE WINDOWS#

One of my first official tasks as a DotNet programmer was to write a Windows Service which monitored a folder on a server for new files, processed those files, and then transferred them to another server (via FTP). Import static .View Part 2 of this article series.

#JAVA FILEWATCHER WATCH FOR FILE TYPE CODE#

Let's go directly to the code below: import java.io.File The idea behind this API is actually the same as the observer pattern: register a Watcher for a specified directory, and Java notifies you that the Watcher says the file has changed when the file in the directory changes.

Later, under the call of colleagues, we found a new API added to JDK7: File Watch Service. Since the above scheme is defective, think about other solutions. The size and the last modification time are always changing during the whole file transfer process.

If FTP is built on Unix operating system, there is no such problem.

In the transfer process, the value of the last Modified Time () of the File class in Java will not change if it is viewed through the last Modified Time () of the java file class. In the process of transmission, the value of the file will not change if it is viewed by lengh() of File class in java.įor the last modification time property, only at the beginning of the file creation and after the file transfer ratio, will the change occur. If FTP is built on windows operating system, there will be the following problems:Īt the beginning of a file transfer, the size of the file has been determined. Because when large files are encountered, it is very likely that they will not be passed through in 2 seconds. What I said above is 2 seconds, which is my own hypothesis.

The time interval between the values of the two attributes, size and final modification time, is also uncertain.

If the interval of reading directory A is not set properly, the reading frequency will be too frequent if it is set small if set too large, it may lead to a large backlog of files.

This scheme is generally competent, but it hides the following two minor problems:

#JAVA FILEWATCHER WATCH FOR FILE TYPE UPDATE#

After confirming that the file has been uploaded, parse the file and update it to the database.If there is a change, then make sure again every two seconds. If these two values remain unchanged, then the file is uploaded and uploaded. For a new file, first record its size and the last modification time, and then, every two seconds, read its two attribute values again.Comparing the list of files read twice, the new file name corresponds to the new file uploaded by the other party.Open a thread to read all files in directory A periodically.We only have the right to 'read' directory A, that is, we can't delete, rename and move the files in directory A.įor this need, the solution I first came up with was:.We need to parse and update the uploaded files (files in the uploaded state can not be processed) to the database.Upload files to the specified directory (assuming directory A) to the server.Recently, a requirement has been addressed, probably as follows:

Java filewatcher watch for file type