Ravindra -
So you have documents that represent *lines*, but for each line document you
want to render the 3 lines (documents) before and after.
Hmmm - tricky!
Velocity itself isn’t going to help you here. You’ll need to do additional
searches to get the “context documents”.
Given that you’re using VrW, I’d suggest an Ajaxy solution. For each hit
being rendering, the browser (not server-side Velocity) would use `line_no` and
do a query, something like q=line_no:[<current line_no - 3> TO <current
line_no + 3>] and render those as desired.
If you attempt this server-side, whew - honestly I wouldn’t do that within Solr
myself - so I’m not sure what exactly to advise.
To your specific question - it is possible to add custom Velocity “tools” to
the mix. The test cases for this look like this:
https://github.com/apache/lucene-solr/blob/e2521b2a8baabdaf43b92192588f51e042d21e97/solr/contrib/velocity/src/test/org/apache/solr/velocity/VelocityResponseWriterTest.java#L122-L144
(specifically note the $mytool.star(…) usage in that test method)
The configuration to plug in a custom tool looks like this:
https://github.com/apache/lucene-solr/blob/e2521b2a8baabdaf43b92192588f51e042d21e97/solr/contrib/velocity/src/test-files/velocity/solr/collection1/conf/solrconfig.xml#L40-L54
Here’s how the tool itself is written, which comes out pretty lean and clean:
https://github.com/apache/lucene-solr/blob/e2521b2a8baabdaf43b92192588f51e042d21e97/solr/contrib/velocity/src/test/org/apache/solr/velocity/MockTool.java
Again, though - I wouldn’t advise using Velocity trickery to do Solr searches
internal to template rendering (even though you can).
Erik
> On Jan 24, 2018, at 9:50 AM, Ravindra Soni <ravisoni5...@gmail.com> wrote:
>
> Hi,
>
> *Quick context of the application first.*
>
> I am currently using Solr in standalone mode to index thousands of
> text-like documents (not exactly textual documents).
>
> A single document has a structure like following:
>
> - *id* - unique file id
> - *line_text* - textual data
> - *file_local_url* - file's directory location path
> - *line_no* - line number of the line_text
>
> *What I am trying to achieve?*
>
> After I search on the line_text field, as a result I should see the
> matching text snippets. A text snippet can be the lines from (line_no - 3)
> to (line_no + 3). Currently for search front-end I am using Solr's in-built
> Velocity response writer and its templates.
>
> *How I am thinking of doing this?*
>
> I am using the default Velocity templates which are shipped with Solr. In
> the template file hit.vm, following is the way it currently fetches,
> processes and displays the responses:
>
> #foreach( $fieldName in $doc.fieldNames )
>
> <tr>
> <th align="right" valign="top" style="field-name">
> $esc.html($fieldName):
> </th>
>
> <td align="left" valign="top">
> #field($fieldName)
> </td>
> </tr>#end
>
> Now to get the snippet text I would like to define an external function
> somewhere in a Java class something of this form:
>
> public String getSnippet(file_local_url, line_no)
>
> which will return the snippet in a string format.
>
> Now I want to consume this response in the velocity template. There I am
> thinking of something like this:
>
> ## get the snippet string by calling the external ava function
> #set($snippet = $someClass.getSnippet(#field("file_local_url"),
> #field("line_no)))
>
> ## print the snippet
> snippet
>
> (I am not sure if this is the correct syntax.)
>
> *Questions:*
>
> 1. What kind of file should contain someClass.getSnippet()? Java file?
> Class file? A jar?
> 2. Where should I keep this file? How will velocity know where to find
> this class?
> 3. Am I using the write syntax to call the method and use its results in
> above Velocity template?
>
> I am quite not getting the bigger picture yet (especially the question 2
> above).
>
> Please provide some direction. Thanks.
> Ravi.
>
> --
>
> What if the cure for cancer is trapped inside the mind of someone who
> can't afford an education? - anonymous
