Spring Integration入站通道适配器中的覆盖方法

Question

I have a Spring Integration listener, where the ApplicationContext is something as follow:

final AbstractApplicationContext context = new ClassPathXmlApplicationContext(

        // Spring Integration common xml
                "classpath:contexts/bp-common.xml",

                // File Upload Listener
                "classpath:contexts/bp-integration-fileupload-context.xml");

In Spring integration listener, I wish to ask the listener to rescan the folder everytime. So I do as follow:

Map< String, FileReadingMessageSource > fileReadingSourceMap = new HashMap< String, FileReadingMessageSource >( );

        fileReadingSourceMap = context.getBeansOfType( FileReadingMessageSource.class );

        List< FileReadingMessageSource > fileReadingSourceList = new ArrayList< FileReadingMessageSource >(
                fileReadingSourceMap.values( ) );

        for ( FileReadingMessageSource frms : fileReadingSourceList ) {
            frms.setScanEachPoll( true );
        }

I set the value of scanEachPoll to true, so that everytime it will rescan the directory again. Its work, I saw it scan the directory everytime. By default its false.

Edit a variable in FileReadingMessageSource class is not a problem. But I am facing some problem for edit a method inside this class.

There will be a method as follow in this class:

private void scanInputDirectory() {
        List<File> filteredFiles = scanner.listFiles(directory);
        Set<File> freshFiles = new LinkedHashSet<File>(filteredFiles);
        if (!freshFiles.isEmpty()) {
            toBeReceived.addAll(freshFiles);
            if (logger.isDebugEnabled()) {
                logger.debug("Added to queue: " + freshFiles);
            }
        }
    }

Because of my modification, this listener will scan the directory everytime. Thus, toBeReceived.addAll(freshFiles); will keep adding some same file. I wish to do something to override this method, so that I can clean the toBeReceived Queue first before addAll() .

I believe FileReadingMessageSource class is come from bp-integration-fileupload-context.xml .

<int-file:inbound-channel-adapter id="hostFilesOut" channel="hostFileOutChannel"
        directory="${hostfile.dir.out}" prevent-duplicates="false"
        filename-regex="${hostfile.out.filename-regex}" >
        <int:poller id="poller" cron="${poller.cron:0,4,8,12,16,20,24,28,32,36,40,44,48,52,56 * * * * * }"
            max-messages-per-poll="1" />
    </int-file:inbound-channel-adapter>

Anything I can "inject" into this xml portion to override the original FileReadingMessageSource class?

Or Kindly advise the better way to do it.

Maybe my question is confusing, let me add some example here:

actually its something like this:

Original version:

scanEachPoll is false by default.

So, scanInputDirectory() method wont be call everytime. It will only call when the Queue is empty.

But now, I change the scanEachPoll to true. ( This one can change easily )

When scanEachPoll is true, then scanInputDirectory() method will be call everytime, so it will something like:

1st time scan, add to queue (1,2,3,4,5) poll(), become (2,3,4,5) 2nd time scan, add to queue will be (2,3,4,5) + (2,3,4,5) => become (2,2,3,3,4,4,5,5) poll(), become (2,3,3,4,4,5,5) 3rd time scan, add to queue will become original queue + (3,4,5) ==> become (2,3,3,4,4,5,5,3,4,5) and so on...

Answer 1

I manage to handle this problem by creating my own Scanner.

which is

<bean id="myDirectoryScanner" class="bp.main.myDirectoryScanner" ></bean>

My scanner only return the first item:

protected File[] listEligibleFiles(File directory)
            throws IllegalArgumentException {

        File[] rootFiles = directory.listFiles();
        List<File> files = new ArrayList<File>(rootFiles.length);
        if ( rootFiles != null ) {
            files.add(rootFiles[0]);
        }
        return files.toArray(new File[files.size()]);
    }