#125 - ENH: Add support for query returning a List of single Attribute type

src/test/java/com/avaje/ebeaninternal/api/TDSpiEbeanServer.java

@@ -520,6 +520,11 @@ public class TDSpiEbeanServer implements SpiEbeanServer {
     return null;
   }
 
+  @Override
+  public <A> List<A> findSingleAttributeList(Query<?> query, Transaction transaction) {
+    return null;
+  }
+
   @Override
   public <T> T findUnique(Query<T> query, Transaction transaction) {
     return null;

src/test/java/com/avaje/tests/query/other/TestQuerySingleAttribute.java

@@ -0,0 +1,128 @@
+package com.avaje.tests.query.other;
+
+import com.avaje.ebean.BaseTestCase;
+import com.avaje.ebean.Ebean;
+import com.avaje.ebean.Query;
+import com.avaje.tests.model.basic.Customer;
+import com.avaje.tests.model.basic.ResetBasicData;
+import org.junit.Test;
+
+import java.sql.Date;
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class TestQuerySingleAttribute extends BaseTestCase {
+
+
+  @Test
+  public void exampleUsage() {
+
+    ResetBasicData.reset();
+
+    List<String> names =
+        Ebean.find(Customer.class)
+          .setDistinct(true)
+          .select("name")
+          .where().eq("status", Customer.Status.NEW)
+          .orderBy().asc("name")
+          .setMaxRows(100)
+          .findSingleAttributeList();
+
+    assertThat(names).isNotNull();
+  }
+
+  @Test
+  public void exampleUsage_otherType() {
+
+    ResetBasicData.reset();
+
+    List<Date> dates =
+        Ebean.find(Customer.class)
+            .setDistinct(true)
+            .select("anniversary")
+            .where().isNotNull("anniversary")
+            .orderBy().asc("anniversary")
+            .findSingleAttributeList();
+
+    assertThat(dates).isNotNull();
+  }
+
+  @Test
+  public void withOrderBy() {
+
+    Query<Customer> query =
+        Ebean.find(Customer.class)
+            .setDistinct(true)
+            .select("name")
+            .where().eq("status", Customer.Status.NEW)
+            .orderBy().asc("name")
+            .setMaxRows(100);
+
+    query.findSingleAttributeList();
+    assertThat(query.getGeneratedSql()).contains("select distinct t0.name c0 from o_customer t0 where t0.status = ?  order by t0.name ");
+  }
+
+  @Test
+  public void basic() {
+
+    ResetBasicData.reset();
+
+    Query<Customer> query = Ebean.find(Customer.class).select("name");
+
+    List<String> names = query.findSingleAttributeList();//String.class);
+
+    assertThat(query.getGeneratedSql()).contains("select t0.name c0 from o_customer t0");
+    assertThat(names).isNotNull();
+  }
+
+  @Test
+  public void distinctAndWhere() {
+
+    ResetBasicData.reset();
+
+    Query<Customer> query = Ebean.find(Customer.class)
+        .setDistinct(true)
+        .select("name")
+        .where().eq("status", Customer.Status.NEW)
+        .query();
+
+    List<String> names = query.findSingleAttributeList();
+
+    assertThat(query.getGeneratedSql()).contains("select distinct t0.name c0 from o_customer t0 where t0.status = ? ");
+    assertThat(names).isNotNull();
+  }
+
+  @Test
+  public void distinctWhereWithJoin() {
+
+    ResetBasicData.reset();
+
+    Query<Customer> query = Ebean.find(Customer.class)
+        .setDistinct(true)
+        .select("name")
+        .where().eq("status", Customer.Status.NEW)
+        .istartsWith("billingAddress.city", "auck")
+        .query();
+
+    List<String> names = query.findSingleAttributeList();
+
+    assertThat(query.getGeneratedSql()).contains("select distinct t0.name c0 from o_customer t0 left outer join o_address t1 on t1.id = t0.billing_address_id  where t0.status = ?  and lower(t1.city) like ?");
+    assertThat(names).isNotNull();
+  }
+
+
+  @Test
+  public void queryPlan_expect_differentPlans() {
+
+    ResetBasicData.reset();
+
+    Query<Customer> query = Ebean.find(Customer.class).select("name");
+    query.findSingleAttributeList();
+    assertThat(query.getGeneratedSql()).contains("select t0.name c0 from o_customer t0");
+
+    Query<Customer> query2 = Ebean.find(Customer.class).select("name");
+    query2.findList();
+    assertThat(query2.getGeneratedSql()).contains("select t0.id c0, t0.name c1 from o_customer t0");
+  }
+}