FIX: do not override empty (json) collections with null

Original: https://github.com/ebean-orm/ebean/commit/5551c35ec2496a9d62ab0afcaecbed739f17aa7c
Signed-off-by: Jonas Pöhler (JPo) <jonas.poehler@foconis.de>

ebean-core/src/main/java/io/ebeaninternal/server/query/SqlBeanLoad.java

@@ -6,6 +6,9 @@ import io.ebeaninternal.api.SpiQuery.Mode;
 import io.ebeaninternal.server.deploy.BeanProperty;
 import io.ebeaninternal.server.deploy.DbReadContext;
 
+import java.util.Collection;
+import java.util.Map;
+
 /**
  * Controls the loading of property data into a bean.
  * <p>
@@ -70,12 +73,7 @@ public class SqlBeanLoad {
 
     try {
       Object dbVal = prop.read(ctx);
-      if (!refreshLoading) {
-        prop.setValue(bean, dbVal);
-      } else {
-        prop.setValueIntercept(bean, dbVal);
-      }
-
+      load(prop, dbVal);
       return dbVal;
 
     } catch (Exception e) {
@@ -89,6 +87,14 @@ public class SqlBeanLoad {
    * Load the given value into the property.
    */
   public void load(BeanProperty target, Object dbVal) {
+    if (dbVal == null) {
+      Object current = target.getValue(bean);
+      if ((current instanceof Collection && ((Collection<?>) current).isEmpty())
+        || current instanceof Map && ((Map<?, ?>) current).isEmpty()) {
+        dbVal = current; // do not modify
+      }
+    }
+
     if (!refreshLoading) {
       target.setValue(bean, dbVal);
     } else {

ebean-core/src/test/java/org/tests/json/TestDbJson_List.java

@@ -221,4 +221,18 @@ public class TestDbJson_List extends BaseTestCase {
 
     DB.delete(bean);
   }
+
+  @Test
+  public void testNullToEmpty() {
+    EBasicJsonList bean = new EBasicJsonList();
+    bean.setFlags(null);
+    bean.setTags(null);
+    bean.setBeanMap(null);
+    DB.save(bean);
+
+    bean = DB.find(EBasicJsonList.class)
+      .setId(bean.getId()).findOne();
+
+    assertThat(bean.getFlags()).isEmpty();
+  }
 }