How to put write lock on file

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I have text file on server.
User can read it and write in it.
I want to put write lock on file when first user come and open it ,
If another user comes in between and open the file he should just read the file not allow to write in file.

Posted 28-Oct-14 23:17pm

hemant malpote

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TorstenH. · Answer 1 · 2014-10-28T23:44:00

Solution 1

simplest approach:

Use a custom object "FileWithLock" instead of "File". You can simply set a lock on that one and react.

Java

import java.io.File;

public class FileWithLock extends File
{
    private boolean locked = false;
    public FileWithLock(String pathName){
    	super(pathName);
    }

    public void setLocked(boolean locked){
        this.locked = locked;
    }

    public boolean bisLocked(){
        return locked;
    }
}

Posted 28-Oct-14 23:44pm

TorstenH.

Comments

hemant malpote 29-Oct-14 5:52am

For second user new instance of file object will be create. So it will not comes in use.
It should be file specific. Like specific file is locked or not.

hemant malpote 29-Oct-14 6:03am

I am trying with channel lock.
But the channel lock doesn't not allowing to read file as well.
I want only write lock not read .

TorstenH. 29-Oct-14 6:09am

you mean like this?
http://www.java2s.com/Code/Java/File-Input-Output/DemonstratesfilelockingandsimplefilereadandwriteoperationsusingjavaniochannelsFileChannel.htm

It's a matter of design, how you approach this task.

hemant malpote 29-Oct-14 6:28am

In this example they are reading file when there will be no lock . See the if condition 'if (lock != null)'

TorstenH. 29-Oct-14 6:10am

It's a matter of design.
How do you access the file object?
How about a Hashmap holding the status?

hemant malpote 29-Oct-14 6:20am

Torsten it is preferable to use channel lock.
Just need to come out of read lock.