FEATURE: Disable overwriting generated properties at transaction level

ebean-api/src/main/java/io/ebean/Transaction.java

@@ -260,6 +260,12 @@ static Transaction current() {
    */
   void setUpdateAllLoadedProperties(boolean updateAllLoadedProperties);
 
+  /**
+   * If set to false (default is true) generated propertes are only set, if it is the version property or have a null value.
+   * This may be useful in backup & restore scenarios, if you want set WhenCreated/WhenModified.
+   */
+  void setOverwriteGeneratedProperties(boolean overwriteGeneratedProperties);
+
   /**
    * Set if the L2 cache should be skipped for "find by id" and "find by natural key" queries.
    * <p>

ebean-core/src/main/java/io/ebeaninternal/api/SpiTransaction.java

@@ -103,6 +103,11 @@ public interface SpiTransaction extends Transaction {
    */
   Boolean isUpdateAllLoadedProperties();
 
+  /**
+   * Returns true, if generated properties are overwritten (default) or are only set, if they are null.
+   */
+  boolean isOverwriteGeneratedProperties();
+
   /**
    * Return the batchSize specifically set for this transaction or 0.
    * <p>

ebean-core/src/main/java/io/ebeaninternal/api/SpiTransactionProxy.java

@@ -248,6 +248,16 @@ public void setUpdateAllLoadedProperties(boolean updateAllLoaded) {
     transaction.setUpdateAllLoadedProperties(updateAllLoaded);
   }
 
+  @Override
+  public void setOverwriteGeneratedProperties(boolean overwriteGeneratedProperties) {
+    transaction.setOverwriteGeneratedProperties(overwriteGeneratedProperties);
+  }
+
+  @Override
+  public boolean isOverwriteGeneratedProperties() {
+    return transaction.isOverwriteGeneratedProperties();
+  }
+
   @Override
   public Boolean isUpdateAllLoadedProperties() {
     return transaction.isUpdateAllLoadedProperties();

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

@@ -274,24 +274,30 @@ private void onUpdateGeneratedProperties() {
       } else {
         // @WhenModified set without invoking interception
         Object oldVal = prop.getValue(entityBean);
-        Object value = generatedProperty.getUpdateValue(prop, entityBean, now());
-        prop.setValueChanged(entityBean, value);
-        intercept.setOldValue(prop.propertyIndex(), oldVal);
+        if (transaction == null || transaction.isOverwriteGeneratedProperties() || oldVal == null) { // version handled above
+          Object value = generatedProperty.getUpdateValue(prop, entityBean, now());
+          prop.setValueChanged(entityBean, value);
+          intercept.setOldValue(prop.propertyIndex(), oldVal);
+        }
       }
     }
   }
 
   private void onFailedUpdateUndoGeneratedProperties() {
     for (BeanProperty prop : beanDescriptor.propertiesGenUpdate()) {
-      Object oldVal = intercept.origValue(prop.propertyIndex());
-      prop.setValue(entityBean, oldVal);
+      if (transaction == null || transaction.isOverwriteGeneratedProperties() || prop.isVersion()) {
+        Object oldVal = intercept.origValue(prop.propertyIndex());
+        prop.setValue(entityBean, oldVal);
+      }
     }
   }
 
   private void onInsertGeneratedProperties() {
     for (BeanProperty prop : beanDescriptor.propertiesGenInsert()) {
-      Object value = prop.generatedProperty().getInsertValue(prop, entityBean, now());
-      prop.setValueChanged(entityBean, value);
+      if (transaction == null || transaction.isOverwriteGeneratedProperties() || prop.isVersion() || prop.getValue(entityBean) == null) {
+        Object value = prop.generatedProperty().getInsertValue(prop, entityBean, now());
+        prop.setValueChanged(entityBean, value);
+      }
     }
   }
 

ebean-core/src/main/java/io/ebeaninternal/server/transaction/ImplicitReadOnlyTransaction.java

@@ -272,6 +272,15 @@ public void setReadOnly(boolean readOnly) {
   public void setUpdateAllLoadedProperties(boolean updateAllLoadedProperties) {
   }
 
+  @Override
+  public void setOverwriteGeneratedProperties(boolean overwriteGeneratedProperties) {
+  }
+
+  @Override
+  public boolean isOverwriteGeneratedProperties() {
+    return true;
+  }
+
   @Override
   public Boolean isUpdateAllLoadedProperties() {
     return null;

ebean-core/src/main/java/io/ebeaninternal/server/transaction/JdbcTransaction.java

@@ -53,6 +53,7 @@ class JdbcTransaction implements SpiTransaction, TxnProfileEventCodes {
   private boolean queryOnly = true;
   private boolean localReadOnly;
   private Boolean updateAllLoadedProperties;
+  private boolean overwriteGeneratedProperties = true;
   private boolean oldBatchMode;
   private boolean batchMode;
   private boolean batchOnCascadeMode;
@@ -448,6 +449,16 @@ public final Boolean isUpdateAllLoadedProperties() {
     return updateAllLoadedProperties;
   }
 
+  @Override
+  public void setOverwriteGeneratedProperties(boolean overwriteGeneratedProperties) {
+    this.overwriteGeneratedProperties = overwriteGeneratedProperties;
+  }
+
+  @Override
+  public boolean isOverwriteGeneratedProperties() {
+    return overwriteGeneratedProperties;
+  }
+
   @Override
   public final void setBatchMode(boolean batchMode) {
     this.batchMode = batchMode;

ebean-core/src/main/java/io/ebeaninternal/server/transaction/NoTransaction.java

@@ -230,6 +230,15 @@ public void setPersistCascade(boolean persistCascade) {
   public void setUpdateAllLoadedProperties(boolean updateAllLoadedProperties) {
   }
 
+  @Override
+  public void setOverwriteGeneratedProperties(boolean overwriteGeneratedProperties) {
+  }
+
+  @Override
+  public boolean isOverwriteGeneratedProperties() {
+    return true;
+  }
+
   @Override
   public void setSkipCache(boolean skipCache) {
   }

ebean-test/src/test/java/org/tests/generated/TestGeneratedProperties.java

@@ -1,10 +1,13 @@
 package org.tests.generated;
 
-import io.ebean.xtest.BaseTestCase;
 import io.ebean.DB;
+import io.ebean.Transaction;
+import io.ebean.xtest.BaseTestCase;
 import org.junit.jupiter.api.Test;
 import org.tests.model.EGenProps;
 
+import java.time.Instant;
+
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
 
@@ -47,4 +50,42 @@ public void test_insert() {
 
     DB.delete(bean);
   }
+
+  @Test
+  public void test_update_no_overwrite() {
+    EGenProps bean = new EGenProps();
+    bean.setName("updating");
+    DB.save(bean);
+
+    bean = DB.find(EGenProps.class, bean.getId());
+    bean.setInstantCreated(Instant.parse("2022-01-01T00:00:00Z"));
+    bean.setInstantUpdated(Instant.parse("2022-01-02T00:00:00Z"));
+    try (Transaction txn = DB.beginTransaction()) {
+      txn.setOverwriteGeneratedProperties(false);
+      DB.save(bean);
+      txn.commit();
+    }
+
+    bean = DB.find(EGenProps.class, bean.getId());
+    assertThat(bean.getInstantCreated()).isEqualTo(Instant.parse("2022-01-01T00:00:00Z"));
+    assertThat(bean.getInstantUpdated()).isEqualTo(Instant.parse("2022-01-02T00:00:00Z"));
+  }
+
+  @Test
+  public void test_insert_no_overwrite() {
+    EGenProps bean = new EGenProps();
+    try (Transaction txn = DB.beginTransaction()) {
+      txn.setOverwriteGeneratedProperties(false);
+      bean.setName("inserting");
+      bean.setInstantCreated(Instant.parse("2022-01-01T00:00:00Z"));
+      bean.setInstantUpdated(Instant.parse("2022-01-02T00:00:00Z"));
+      DB.save(bean);
+      txn.commit();
+    }
+
+
+    bean = DB.find(EGenProps.class, bean.getId());
+    assertThat(bean.getInstantCreated()).isEqualTo(Instant.parse("2022-01-01T00:00:00Z"));
+    assertThat(bean.getInstantUpdated()).isEqualTo(Instant.parse("2022-01-02T00:00:00Z"));
+  }
 }