findMap() with beanCache should use idPoperty if mapKey = null

ebean-core/src/main/java/io/ebeaninternal/server/core/OrmQueryRequest.java

@@ -570,7 +570,12 @@ public final class OrmQueryRequest<T> extends BeanRequest implements SpiOrmQuery
   }
 
   private ElPropertyValue mapProperty() {
-    ElPropertyValue property = beanDescriptor.elGetValue(query.getMapKey());
+    ElPropertyValue property;
+    if (query.getMapKey() == null) {
+      property = beanDescriptor.idProperty();
+    } else {
+      property = beanDescriptor.elGetValue(query.getMapKey());
+    }
     if (property == null) {
       throw new IllegalStateException("Unknown map key property " + query.getMapKey());
     }

ebean-test/src/test/java/org/tests/basic/TestLoadBeanCache.java

@@ -2,12 +2,18 @@ package org.tests.basic;
 
 import io.ebean.BaseTestCase;
 import io.ebean.DB;
+import io.ebean.test.LoggedSql;
+
 import org.junit.jupiter.api.Test;
 import org.tests.model.basic.Country;
+import org.tests.model.basic.Customer;
 import org.tests.model.basic.ResetBasicData;
 
+import java.util.List;
 import java.util.Map;
 
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 public class TestLoadBeanCache extends BaseTestCase {
@@ -31,4 +37,30 @@ public class TestLoadBeanCache extends BaseTestCase {
 
     assertTrue(loadedNz == nz);
   }
+  
+  @Test
+  public void testLoadWithFindMap() {
+
+    ResetBasicData.reset();
+    
+    List<Object> ids = DB.find(Customer.class).findIds();
+    assertEquals(ids.size(), 4);
+
+    DB.getDefault().pluginApi().cacheManager().clearAll();
+    
+    // hit database
+    LoggedSql.start();
+    DB.find(Customer.class).where().idIn(ids).findMap();
+    List<String> sql = LoggedSql.stop();
+    assertThat(sql).hasSize(1);
+    
+    // hit beanCache
+    LoggedSql.start();
+    DB.find(Customer.class).where().idIn(ids).findMap();
+    sql = LoggedSql.stop();
+    assertThat(sql).hasSize(0);
+
+  }
+  
+  
 }