Reputation: 1169

Accessing the same file

I have a situation where in I write to a text file programmatically using java and simultaneously I read from the same file using jQuery.

The problem I face is jQuery is unable to find the updated content whenever a content is written into the text file via java.

I have Googled a lot but the only results I find are for java and java processing and not for java and javascript (i.e A Client side and Server side)

I am not sure if this is even possible.

More about the question:

I write into the file the crawling results using java and I am trying to display the same using javascript (jQuery.post() method).

JAVA

A multi-threaded crawling program that crawls a website and does some functionality. I am trying to write some content into a text file using the same java program as and when the crawling happens. The content I write mostly are the details about which thread is getting invoked and what is the current link that is being crawled.

The reason I write this in the text file is I need to show the output in the UI so that people looking at the UI will understand what happens.

Writing happens perfectly as expected.

JAVASCRIPT (jQUERY)

This using the

jQuery.get or post ("sample.txt", function (result) {
                  $("#someID").html(result);
                  });

It reads from the text file normally but when java and javascript both are trying to access the file, It is the java that dominates leaving javascript behind thus jQuery is unable to fetch the updated content as and when it happens.

I guess this explanation is more than sufficient to make people understand what exactly my problem is !

On the whole, java and javascript try to access the same file at the same time. So there comes this issue.

Any help is appreciated.

Thanks in advance

Upvotes: 0

Answers (4)

Arunkumar Srisailapathi

Reputation: 1169

Thanks for all those who were trying to help me out. I have finally come up with a solution. I, instead of using jquery post to directly read from file, am using another jsp file that reads the file contents and prints using out.println on screen, and after which I am using jQuery post to get the content written by that jsp file. Hence the synchronization problem is avoided.

Here is more about my explanation:

Earlier I had

java program -> Text File <- javascript (jQuery post) // Resulted in synchronization problem where in javascript was not able to access the updated content.

Now

java program -> Text file <- JSP file <- javascript (jQuery post) // Avoided the synchronization problem as that file is accessed by the same server side language. After that jQuery reads the content printed by JSP page.

After many changes, finally came up with one good working solution.

Thanks all.

Upvotes: 0

Jason

Reputation: 1309

I have a question, is it must be done with Ajax? I think you are trying to figure out about

Ajax push and pull

This is not very easy to do and I wouldn't really recommend it. However, there is a better technology called websocket. So what you can do is, client can submit request to the server to write data into a file then server can send back updated content to the client. Moreover, this is much better than achieving the same objective through numerous amount of HTTP requests.

Additionally, if you want the crossbrowser compatibility, have a look at http://socket.io/

Upvotes: 0