#1331 - ENH: Support Aggregation formula with findSingleAttribute() ... max, min, avg, count and count(distinct ..)

src/main/java/io/ebeaninternal/server/deploy/DynamicPropertyAggregationFormula.java

@@ -0,0 +1,52 @@
+package io.ebeaninternal.server.deploy;
+
+import io.ebeaninternal.server.query.SqlBeanLoad;
+import io.ebeaninternal.server.type.ScalarType;
+
+import javax.persistence.PersistenceException;
+
+/**
+ * Dynamic property based on aggregation (max, min, avg, count).
+ */
+class DynamicPropertyAggregationFormula extends DynamicPropertyBase {
+
+  private final String parsedAggregation;
+
+  private final BeanProperty asTarget;
+
+  DynamicPropertyAggregationFormula(String name, ScalarType<?> scalarType, String parsedAggregation, BeanProperty asTarget) {
+    super(name, name, null, scalarType);
+    this.parsedAggregation = parsedAggregation;
+    this.asTarget = asTarget;
+  }
+
+  @Override
+  public String toString() {
+    return "DynamicPropertyFormula[" + parsedAggregation + "]";
+  }
+
+  @Override
+  public boolean isAggregation() {
+    return true;
+  }
+
+  @Override
+  public void load(SqlBeanLoad sqlBeanLoad) {
+
+    try {
+      Object value = scalarType.read(sqlBeanLoad.ctx().getDataReader());
+      if (asTarget != null) {
+        sqlBeanLoad.load(asTarget, value);
+      }
+
+    } catch (Exception e) {
+      throw new PersistenceException("Error loading on " + fullName, e);
+    }
+  }
+
+  @Override
+  public void appendSelect(DbSqlContext ctx, boolean subQuery) {
+    ctx.appendParseSelect(parsedAggregation);
+  }
+
+}