#1406 - ENH: Add SqlQuery.findSingleAttributeList() ... for returning lists of scalar values via SqlQuery

src/main/java/io/ebean/SqlQuery.java

@@ -93,13 +93,42 @@ public interface SqlQuery extends Serializable {
    *     .setParameter(1, 2)
    *     .findSingleAttribute(BigDecimal.class);
    *
-   *
    * }</pre>
    *
+   * <p>
+   * The attributeType can be any scalar type that Ebean supports (includes javax time types, Joda types etc).
+   * </p>
+   *
    * @param attributeType The type of the returned value
    */
   <T> T findSingleAttribute(Class<T> attributeType);
 
+  /**
+   * Execute the query returning a list of scalar attribute values.
+   *
+   * <pre>{@code
+   *
+   *   String sql =
+   *   " select (unit_price * order_qty) " +
+   *   " from o_order_detail " +
+   *   " where unit_price > ? " +
+   *   " order by (unit_price * order_qty) desc";
+   *
+   *   //
+   *   List<BigDecimal> lineAmounts = Ebean.createSqlQuery(sql)
+   *     .setParameter(1, 3)
+   *     .findSingleAttributeList(BigDecimal.class);
+   *
+   * }</pre>
+   *
+   * <p>
+   * The attributeType can be any scalar type that Ebean supports (includes javax time types, Joda types etc).
+   * </p>
+   *
+   * @param attributeType The type of the returned value
+   */
+  <T> List<T> findSingleAttributeList(Class<T> attributeType);
+
   /**
    * The same as bind for named parameters.
    */

src/main/java/io/ebeaninternal/api/SpiEbeanServer.java

@@ -239,6 +239,11 @@ public interface SpiEbeanServer extends EbeanServer, BeanLoader, BeanCollectionL
    */
   <T> T findSingleAttribute(SpiSqlQuery query, Class<T> cls);
 
+  /**
+   * SqlQuery find single attribute list.
+   */
+  <T> List<T> findSingleAttributeList(SpiSqlQuery query, Class<T> cls);
+
   /**
    * DTO findList query.
    */

src/main/java/io/ebeaninternal/server/core/DefaultServer.java

@@ -1586,6 +1586,18 @@ public final class DefaultServer implements SpiServer, SpiEbeanServer {
     }
   }
 
+  @Override
+  public <T> List<T> findSingleAttributeList(SpiSqlQuery query, Class<T> cls) {
+    RelationalQueryRequest request = new RelationalQueryRequest(this, relationalQueryEngine, query, null);
+    try {
+      request.initTransIfRequired();
+      return request.findSingleAttributeList(cls);
+
+    } finally {
+      request.endTransIfRequired();
+    }
+  }
+
   @Override
   public <T> T findSingleAttribute(SpiSqlQuery query, Class<T> cls) {
 

src/main/java/io/ebeaninternal/server/core/RelationalQueryEngine.java

@@ -35,6 +35,11 @@ public interface RelationalQueryEngine {
    */
   <T> T findSingleAttribute(RelationalQueryRequest request, Class<T> cls);
 
+  /**
+   * Find single attribute list.
+   */
+  <T> List<T> findSingleAttributeList(RelationalQueryRequest request, Class<T> cls);
+
   /**
    * Collect SQL query execution statistics.
    */

src/main/java/io/ebeaninternal/server/core/RelationalQueryRequest.java

@@ -53,6 +53,10 @@ public final class RelationalQueryRequest extends AbstractSqlQueryRequest {
     }
   }
 
+  public <T> List<T> findSingleAttributeList(Class<T> cls) {
+    return queryEngine.findSingleAttributeList(this, cls);
+  }
+
   public <T> T findSingleAttribute(Class<T> cls) {
     return queryEngine.findSingleAttribute(this, cls);
   }

src/main/java/io/ebeaninternal/server/query/DefaultRelationalQueryEngine.java

@@ -92,6 +92,33 @@ public class DefaultRelationalQueryEngine implements RelationalQueryEngine {
     }
   }
 
+  @SuppressWarnings("unchecked")
+  @Override
+  public <T> List<T> findSingleAttributeList(RelationalQueryRequest request, Class<T> cls) {
+    ScalarType<T> scalarType = (ScalarType<T>) binder.getScalarType(cls);
+    return findScalarList(request, scalarType);
+  }
+
+  private <T> List<T> findScalarList(RelationalQueryRequest request, ScalarType<T> scalarType) {
+    try {
+      request.executeSql(binder, SpiQuery.Type.ATTRIBUTE);
+      List<T> list = new ArrayList<>();
+      while (request.next()) {
+        request.incrementRows();
+        list.add(scalarType.read(binder.createDataReader(request.getResultSet())));
+      }
+
+      request.logSummary();
+      return list;
+
+    } catch (Exception e) {
+      throw new PersistenceException(Message.msg("fetch.error", e.getMessage(), request.getSql()), e);
+
+    } finally {
+      request.close();
+    }
+  }
+
   @SuppressWarnings("unchecked")
   @Override
   public <T> T findSingleAttribute(RelationalQueryRequest request, Class<T> cls) {

src/main/java/io/ebeaninternal/server/querydefn/DefaultRelationalQuery.java

@@ -64,6 +64,11 @@ public class DefaultRelationalQuery implements SpiSqlQuery {
     return server.findSingleAttribute(this, cls);
   }
 
+  @Override
+  public <T> List<T> findSingleAttributeList(Class<T> cls) {
+    return server.findSingleAttributeList(this, cls);
+  }
+
   @Override
   public SqlRow findOne() {
     return server.findOne(this, null);