Refactor Search to be Generic

[nik-suri]

I want to perform some custom handling of my search result. For example, I run a search across three different indices which share some common fields. For example:

Search search = new Search.Builder(searchSourceBuilder.toString())
    .addIndex("index1")
    .addIndex("index2")
    .addIndex("index3")
    .build()

However, since these indices don't all have the exact same schema, reading this response isn't as simple as calling

List<Article> articles = result.getSourceAsObjectList(Article.class);

Instead, I would like to iterate over each json element. Then depending on the index which the json element is from, I would like to cast the json to the corresponding class.

Currently, the Search class is tied to the SearchResult class. Therefore, if I wanted to use my own CustomSearchResult, I would need to copy/paste the entire Search class, only to change SearchResult to CustomSearchResult in the three places where it appears.

A better way to do this would be to use a generic class - GenericSearch, which implements all of the code in Search except using a generic type for the SearchResult class. The signature could look like this:

public class GenericSearch extends AbstractAction<T extends JestResult> { ... }

We can maintain backwards compatibility by using public class Search extends GenericSearch<SearchResult> {}. More importantly, anyone can use their own result handlers in a maintainable way by using either public class CustomSearch extends GenericSearch<CustomSearchResult> {} or (inline):

GenericSearch search = new GenericSearch<CustomSearchResult>.Builder(searchSourceBuilder.toString())
    .addIndex("index1")
    .addIndex("index2")
    .addIndex("index3")
    .build()

Would love to hear feedback from the team on this.