Thanks. Is there a way to overcome the exhausting if-else if- else if
structure, some magical way to support new crawlers in the system without
"register" them in that factory?
On Monday, March 16, 2015 at 3:57:56 PM UTC+2, Laszlo Ferenczi wrote:
>
> Hi,
>
> There are many ways to solve this problem, one easy enough to understand:
>
> @Inject
> Provider<CrawlerOne> crawlerOneProvider;
>
> @Inject
> Provider<CrawlerTwo> crawlerTwo;
>
>
> public Crawler getCrawler(String url) {
> if (url...) {
> return crawlerOneProvider.get();
> }
> else {
> return crawlerTwoProvider.get();
> }
> }
>
>
> As an alternative you can inject the injector itself and get the instance
> from it.
>
> Also a slightly more advanced, but much more elgant way is to use
> AssistedInject (it's exectly for this use case) See the guice docs for more
> info.
>
> PS: no need to make everything static, the whole point of the DI framework
> that you don't need static anchors in your code.
>
> --
> L
>
> --
> L
>
> On Sun, Mar 15, 2015 at 4:37 PM, Barak Yaish <[email protected]
> <javascript:>> wrote:
>
>> Hi,
>>
>> Doing my first steps with Guice, I thought the fastest way to understand
>> it would migrate parts of existing application to Guice style. The
>> application is kind of web crawler, and I have factory creating crawlers
>> based on the input url:
>>
>> public static Crawler getCrawler( String url )
>> {
>> try
>> {
>> if( url.contains( "www.site1.com" ) )
>> return new Site1( AppConfig.getInstance() );
>> else if( url.contains( "www.site2.com" ) )
>> return new Site2( AppConfig.getInstance() );
>> }
>> catch ( Exception e )
>> {
>> logger.error( "failure", e );
>> }
>>
>> return null;
>> }
>>
>>
>> Is the Guice version is only take the crawler instances from the injector
>> and injecting the AppConfig?
>>
>> public static Crawler getCrawler( String url )
>> {
>> try
>> {
>> if( url.contains( "www.site1.com" ) )
>> return GuiceInjector.getInstance( Site1.class );
>> else if( url.contains( "www.site2.com" ) )
>> return GuiceInjector.getInstance( Site2.class );
>> }
>> catch ( Exception e )
>> {
>> logger.error( "failure", e );
>> }
>>
>> return null;
>> }
>>
>> Is there a better and/or more elegant way?
>>
>> Thanks!
>>
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>
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