Decouple the crawler service for use in other frameworks

[BenDol]

This is following a Spring implementation soon, though I don't know how you guys want the package breakdown for a Spring implementation since the crawler service assumes Guice.

Todo:

• Decouple existing service servlet and filter.
• Write Spring implementation for filter and service.
• Test the new Guice implementation.
• Update documentation with new configurations.

Questions:

• Should the gwtp-crawler-service be renamed to gwtp-crawler-appengine?

Package Changes:

gwtp-core

gwtp-crawler

Sample Configurations:

Crawl Filter

@Configuration
public class CrawlFilterModule extends AbstractCrawlFilterModule {

    @Bean
    @Override
    protected String serviceUrl() {
        return "http://crawlservice.appspot.com/";
    }

    @Bean
    @Override
    protected String crawlKey() {
        return "123456";
    }

    // Can also override optional Logger
}

Crawler Service

@Configuration
public class CrawlerModule extends AbstractCrawlerServiceModule {

    @Bean
    @Override
    protected String crawlKey() {
        return "123456";
    }

    // Can also override optional WebClient, CrawlCacheService, or Logger
}

In relation to issue #739

[olafleur]

Hi @BenDol : do you need some code review or help with that pull request?

[BenDol]

Its functional, just the guice implementation needs to be tested. This is t allow me to use Spring backend for the crawler service.

[Chris-V]

That's a breaking change. We should either use inheritance or duplicate it and support classes from both the new and old packages.

[BenDol]

Does it really matter if its a breaking change in this case? Since its a simple import change?

[BenDol]

What if I just added a @Deprecated and directed them to the new ServiceKey annotation? Rather than bloat the code with unnecessary legacy support.

[Chris-V]

The changes look good so far. Please make sure the Guice implementation still works fine (I didn't see anything that would break it, but still).

Also be careful about package changes, those are breaking changes and we should support both the old and new packages if we rename them.

---

gwtp-crawler-service be renamed to gwtp-crawler-appengine?

The name change makes sense, though we'll have to keep a deprecated gwtp-crawler-service that inherits gwtp-crawler-appengine at first.

[olafleur]

@BenDol what can we do to help you with that PR?

[BenDol]

It would be a great help if someone could test this with a Guice implementation. I don't use Guice and don't have the time at the moment to figure it out and test it.

Also I am currently resolving the mentioned breaking changes.