#1300 - NEW: FetchCountDistinct ... add example to javadoc + support chaining use via ExpressionList

src/main/java/io/ebean/ExpressionList.java

@@ -480,6 +480,36 @@ public interface ExpressionList<T> {
    */
   Query<T> setUseQueryCache(CacheMode useCache);
 
+  /**
+   * Extended version for setDistinct in conjunction with "findSingleAttributeList";
+   *
+   * <pre>{@code
+   *
+   *  List<CountedValue<Order.Status>> orderStatusCount =
+   *
+   *     Ebean.find(Order.class)
+   *      .select("status")
+   *      .where()
+   *      .gt("orderDate", LocalDate.now().minusMonths(3))
+   *
+   *      // fetch as single attribute with a COUNT
+   *      .setCountDistinct(CountDistinctOrder.COUNT_DESC_ATTR_ASC)
+   *      .findSingleAttributeList();
+   *
+   *     for (CountedValue<Order.Status> entry : orderStatusCount) {
+   *       System.out.println(" count:" + entry.getCount()+" orderStatus:" + entry.getValue() );
+   *     }
+   *
+   *   // produces
+   *
+   *   count:3 orderStatus:NEW
+   *   count:1 orderStatus:SHIPPED
+   *   count:1 orderStatus:COMPLETE
+   *
+   * }</pre>
+   */
+  Query<T> setCountDistinct(CountDistinctOrder orderBy);
+
   /**
    * Calls {@link #setUseQueryCache(CacheMode)} with <code>ON</code> or <code>OFF</code>.
    *

src/main/java/io/ebean/Query.java

@@ -1279,6 +1279,32 @@ public interface Query<T> {
 
   /**
    * Extended version for setDistinct in conjunction with "findSingleAttributeList";
+   *
+   * <pre>{@code
+   *
+   *  List<CountedValue<Order.Status>> orderStatusCount =
+   *
+   *     Ebean.find(Order.class)
+   *      .select("status")
+   *      .where()
+   *      .gt("orderDate", LocalDate.now().minusMonths(3))
+   *
+   *      // fetch as single attribute with a COUNT
+   *      .setCountDistinct(CountDistinctOrder.COUNT_DESC_ATTR_ASC)
+   *      .findSingleAttributeList();
+   *
+   *     for (CountedValue<Order.Status> entry : orderStatusCount) {
+   *       System.out.println(" count:" + entry.getCount()+" orderStatus:" + entry.getValue() );
+   *     }
+   *
+   *   // produces
+   *
+   *   count:3 orderStatus:NEW
+   *   count:1 orderStatus:SHIPPED
+   *   count:1 orderStatus:COMPLETE
+   *
+   * }</pre>
+   *
    */
   Query<T> setCountDistinct(CountDistinctOrder orderBy);
 

src/main/java/io/ebeaninternal/server/expression/DefaultExpressionList.java

@@ -1,6 +1,7 @@
 package io.ebeaninternal.server.expression;
 
 import io.ebean.CacheMode;
+import io.ebean.CountDistinctOrder;
 import io.ebean.Expression;
 import io.ebean.ExpressionFactory;
 import io.ebean.ExpressionList;
@@ -493,6 +494,10 @@ public class DefaultExpressionList<T> implements SpiExpressionList<T> {
     return query.setUseQueryCache(useCache);
   }
 
+  public Query<T> setCountDistinct(CountDistinctOrder orderBy) {
+    return query.setCountDistinct(orderBy);
+  }
+
   @Override
   public Query<T> setUseDocStore(boolean useDocsStore) {
     return query.setUseDocStore(useDocsStore);

src/main/java/io/ebeaninternal/server/expression/JunctionExpression.java

@@ -1,6 +1,7 @@
 package io.ebeaninternal.server.expression;
 
 import io.ebean.CacheMode;
+import io.ebean.CountDistinctOrder;
 import io.ebean.Expression;
 import io.ebean.ExpressionList;
 import io.ebean.FetchPath;
@@ -792,6 +793,11 @@ class JunctionExpression<T> implements SpiJunction<T>, SpiExpression, Expression
     return exprList.setDisableReadAuditing();
   }
 
+  @Override
+  public Query<T> setCountDistinct(CountDistinctOrder orderBy) {
+    return exprList.setCountDistinct(orderBy);
+  }
+
   @Override
   public ExpressionList<T> startsWith(String propertyName, String value) {
     return exprList.startsWith(propertyName, value);