为什么在将 ftp java dsl 配置引入 spring 集成核心时过滤器行为发生了变化

Question

At Spring Integration 4 I had code like this using the spring integration java dsl project:

      FtpInboundChannelAdapterSpec ftpAdapterSpec = Ftp.inboundAdapter(ftpSessionFactory)
                .preserveTimestamp(true)
                .remoteDirectory(remoteFolder)
                .filter(new FtpPersistentAcceptOnceFileListFilter(metaDataStore, "ftp-inbound-" + id + ":"))
                .regexFilter(".*")                
                .localDirectory(Paths.get(System.getProperty("java.io.tmpdir"), "ftp-inbound", localPath).toFile()).autoCreateLocalDirectory(true)
                .deleteRemoteFiles(false);

Notice how it includes a regex filter and a FtpPersistentAcceptOnceFilterListFilter. This worked great.

The code for filter (the original java dsl project) which regexFilter wraps is:

public S filter(FileListFilter<F> filter) {
    if (this.filter == null) {
        if (filter instanceof CompositeFileListFilter) {
            this.filter = (CompositeFileListFilter<F>) filter;
        }
        else {
            this.filter = new CompositeFileListFilter<F>();
            this.filter.addFilter(filter);
        }
        this.synchronizer.setFilter(this.filter);
    }
    else {
        this.filter.addFilter(filter);
    }
    return _this();
}

So as you can see it builds up a composite filter from the passed in filter (and stacks as you pass in more).

But then when java dsl was brought in to core integration the filter method changed to :

public S filter(FileListFilter<F> filter) {
    this.synchronizer.setFilter(filter);
    return _this();
}

That's fine by itself but then methods like regexFilter became :

    @Override
    public FtpInboundChannelAdapterSpec regexFilter(String regex) {
        return filter(composeFilters(new FtpRegexPatternFileListFilter(regex)));
    }

    @SuppressWarnings("unchecked")
    private CompositeFileListFilter<FTPFile> composeFilters(FileListFilter<FTPFile> fileListFilter) {
        CompositeFileListFilter<FTPFile> compositeFileListFilter = new CompositeFileListFilter<>();
        compositeFileListFilter.addFilters(fileListFilter,
                new FtpPersistentAcceptOnceFileListFilter(new SimpleMetadataStore(), "ftpMessageSource"));
        return compositeFileListFilter;
    }

So now the code that I had no does do what I desired as the FtpPersistentAcceptOnceFileListFilter which takes my persistent metadatastore is now replaced by a FtpPersistentAcceptOnceFileListFilter which takes a SimpleMetaDataStore.

So now although the code compiles fine when it runs it receives duplicates.

So the question is why was it changed and is there a good reason why it was changed? Because as it stands because of the non obvious side effect of the regexFilter method it becomes fairly unusable.

Answer 1

It has been changed the way that filter(FileListFilter<F> filter) has a precedence over all other filtering options the way like it is with the XML configuration for consistency. The reason of such a behavior just because we don't know the order you would like to compose those filters. So, to ensure the proper order you need to build a CompositeFileListFilter , including a required FtpRegexPatternFileListFilter , by yourself and and inject it into this fitler() option.

The regexFilter() and patternFilter() are still here for convenience to configure simple common use-cases, when you have only this filter and nothing more.