Add advanced generators for facet sub-paths generation

Author: Luc Boutier

elasticsearch-annotations/src/main/java/org/elasticsearch/annotation/query/IPathGenerator.java

@@ -0,0 +1,21 @@
+package org.elasticsearch.annotation.query;
+
+/**
+ * Created by lucboutier on 17/03/2016.
+ */
+public interface IPathGenerator {
+    /**
+     * Generate paths to be used from the one set on the annotation.
+     * 
+     * @param annotationPaths The paths configured on the annotation.
+     * @return A String array to override the annotationPaths
+     */
+    String[] getPaths(String[] annotationPaths);
+
+    class DEFAULT implements IPathGenerator {
+        @Override
+        public String[] getPaths(String[] annotationPaths) {
+            return annotationPaths;
+        }
+    }
+}

elasticsearch-annotations/src/main/java/org/elasticsearch/annotation/query/TermsFacet.java

@@ -27,6 +27,13 @@
      */
     String[] paths() default "";
 
+    /**
+     * Optional paths generator to override the paths property of the annotation for complex use-case or reflection etc.
+     * 
+     * @return the path generator.
+     */
+    Class<? extends IPathGenerator> pathGenerator() default IPathGenerator.DEFAULT.class;
+
     /**
      * The number of terms to return
      * 

elasticsearch-mapping/src/main/java/org/elasticsearch/mapping/FieldsMappingBuilder.java

@@ -215,10 +215,22 @@ private void processFilterAnnotation(List<IFilterBuilderHelper> classFilters, St
         }
     }
 
-    private void processFacetAnnotation(List<IFacetBuilderHelper> classFacets, List<IFilterBuilderHelper> classFilters, String esFieldName, Indexable indexable) {
+    private void processFacetAnnotation(List<IFacetBuilderHelper> classFacets, List<IFilterBuilderHelper> classFilters, String esFieldName,
+            Indexable indexable) {
         TermsFacet termsFacet = indexable.getAnnotation(TermsFacet.class);
         if (termsFacet != null) {
             String[] paths = termsFacet.paths();
+            if (termsFacet.pathGenerator() != null) {
+                // create an instance of the generator
+                try {
+                    IPathGenerator generator = termsFacet.pathGenerator().newInstance();
+                    paths = generator.getPaths(paths);
+                } catch (InstantiationException e) {
+                    e.printStackTrace(); // TODO better exception handling
+                } catch (IllegalAccessException e) {
+                    e.printStackTrace(); // TODO better exception handling
+                }
+            }
             for (String path : paths) {
                 path = path.trim();
                 boolean isAnalyzed = isAnalyzed(indexable);