Fix for issue 2211

foundation/org.eclipse.persistence.core/src/main/java/org/eclipse/persistence/internal/jpa/jpql/JPQLFunctionsAbstractBuilder.java

@@ -63,13 +63,26 @@ public void visit(IdExpression expression) {
         //Get id attribute name
         ClassDescriptor descriptor = this.queryContext.getDeclaration(variableName).getDescriptor();
         List<DatabaseField> primaryKeyFields = descriptor.getPrimaryKeyFields();
-        String idAttributeName = getIdAttributeNameByField(descriptor.getMappings(), primaryKeyFields.get(0));
-        StateFieldPathExpression stateFieldPathExpression = new StateFieldPathExpression(expression.getParent(), variableText + "." + idAttributeName);
-        expression.setStateFieldPathExpression(stateFieldPathExpression);
+        if (!isEmbeddable(descriptor.getMappings())) {
+            for (DatabaseField primaryKeyField : primaryKeyFields) {
+                String idAttributeName = getIdAttributeNameByField(descriptor.getMappings(), primaryKeyField);
+                StateFieldPathExpression stateFieldPathExpression = new StateFieldPathExpression(
+                        expression.getParent(), variableText + "." + idAttributeName);
+                expression.setStateFieldPathExpression(stateFieldPathExpression);
+                // Continue with created StateFieldPathExpression
+                // It handle by ObjectBuilder booth @Id/primary key types (simple/composite)
+                expression.getStateFieldPathExpression().accept(this);
+            }
+        } else {
+            String idAttributeName = getIdAttributeNameByField(descriptor.getMappings(), primaryKeyFields.get(0));
+            StateFieldPathExpression stateFieldPathExpression = new StateFieldPathExpression(
+                    expression.getParent(), variableText + "." + idAttributeName);
+            expression.setStateFieldPathExpression(stateFieldPathExpression);
+            // Continue with created StateFieldPathExpression
+            // It handle by ObjectBuilder booth @Id/primary key types (simple/composite)
+            expression.getStateFieldPathExpression().accept(this);
 
-        //Continue with created StateFieldPathExpression
-        //It handle by ObjectBuilder booth @Id/primary key types (simple/composite)
-        expression.getStateFieldPathExpression().accept(this);
+        }
     }
 
     /**
@@ -96,10 +109,24 @@ public void visit(VersionExpression expression) {
 
     private String getIdAttributeNameByField(List<DatabaseMapping> databaseMappings, DatabaseField field) {
         for (DatabaseMapping mapping : databaseMappings) {
-            if (field.equals(mapping.getField()) || mapping.isPrimaryKeyMapping()) {
+            if (mapping.getFields().size() > 1 && (field.equals(mapping.getField()) || mapping.isPrimaryKeyMapping())) {
                 return mapping.getAttributeName();
+            } else {
+                if ((field.equals(mapping.getField()) && mapping.isPrimaryKeyMapping())) {
+                    return mapping.getAttributeName();
+                }
             }
         }
         return null;
     }
+
+    private boolean isEmbeddable(List<DatabaseMapping> databaseMappings) {
+
+        for (DatabaseMapping databaseMapping : databaseMappings) {
+            if (databaseMapping.isPrimaryKeyMapping() && databaseMapping.getFields().size() > 1) {
+                return true;
+            }
+        }
+        return false;
+    }
 }

foundation/org.eclipse.persistence.core/src/main/java/org/eclipse/persistence/internal/jpa/jpql/ReportItemBuilder.java

@@ -41,6 +41,7 @@
 import org.eclipse.persistence.jpa.jpql.parser.EntryExpression;
 import org.eclipse.persistence.jpa.jpql.parser.ExtractExpression;
 import org.eclipse.persistence.jpa.jpql.parser.FunctionExpression;
+import org.eclipse.persistence.jpa.jpql.parser.IdExpression;
 import org.eclipse.persistence.jpa.jpql.parser.IdentificationVariable;
 import org.eclipse.persistence.jpa.jpql.parser.IndexExpression;
 import org.eclipse.persistence.jpa.jpql.parser.Join;
@@ -630,7 +631,7 @@ private void visitAbstractSelectClause(AbstractSelectClause expression) {
         multipleSelects = false;
         expression.getSelectExpression().accept(this);
 
-        if (multipleSelects) {
+        if (multipleSelects || (expression.getSelectExpression()  instanceof IdExpression)) {
             query.returnWithoutReportQueryResult();
         }
         else {

jpa/eclipselink.jpa.testapps/jpa.test.jpql/src/test/java/org/eclipse/persistence/testing/tests/jpa/jpql/advanced/compositepk/JUnitJPQLComplexAggregateTest.java

@@ -24,6 +24,7 @@
 import org.eclipse.persistence.testing.models.jpa.advanced.compositepk.CompositePKTableCreator;
 import org.eclipse.persistence.testing.models.jpa.advanced.compositepk.Cubicle;
 import org.eclipse.persistence.testing.models.jpa.advanced.compositepk.Scientist;
+import org.eclipse.persistence.testing.models.jpa.advanced.compositepk.ScientistPK;
 import org.junit.Assert;
 
 import java.util.Arrays;
@@ -60,7 +61,7 @@ public static Test suite() {
         suite.addTest(new JUnitJPQLComplexAggregateTest("testSetup"));
 
         suite.addTest(new JUnitJPQLComplexAggregateTest("complexCountOnJoinedCompositePK"));
-
+        suite.addTest(new JUnitJPQLComplexAggregateTest("testCompositePrimaryKey"));
         return suite;
     }
 
@@ -121,4 +122,53 @@ public void complexCountOnJoinedCompositePK() {
         }
     }
 
+    public void testCompositePrimaryKey() {
+    EntityManager em = createEntityManager();
+    try {
+        // Start the transaction
+        beginTransaction(em);
+
+        // Create and set up the Scientist and Cubicle entities
+        Scientist scientist = new Scientist();
+        scientist.setFirstName("John");
+        scientist.setLastName("Doe");
+
+        Cubicle cubicle = new Cubicle();
+        cubicle.setCode("G");
+        cubicle.setScientist(scientist);
+
+        scientist.setCubicle(cubicle);
+
+        // Persist the entities
+        em.persist(cubicle);
+        em.persist(scientist);
+        em.flush();
+
+        // Execute the query to retrieve the primary keys
+        List<ScientistPK> keys = em.createQuery(
+            "SELECT ID(THIS) FROM Scientist WHERE firstName = :firstName ORDER BY idNumber", 
+            ScientistPK.class
+        )
+        .setParameter("firstName", "John")
+        .getResultList();
+
+        // Ensure the result size is greater than 0
+        assertTrue("The result size should be greater than 0", !keys.isEmpty());
+
+    } catch (Exception e) {
+        // If there's an exception, rollback the transaction
+        rollbackTransaction(em);
+        throw e;
+    } finally {
+        // Ensure the transaction is rolled back if not committed
+        if (em.getTransaction().isActive()) {
+            rollbackTransaction(em);
+        }
+        // Close the entity manager
+        em.close();
+    }
+}
+
+
+
 }