FIX: Cache exist query results

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

@@ -339,6 +339,13 @@ public final class PersistRequestBean<T> extends PersistRequest implements BeanP
     }
   }
 
+  private void onFailedUpdateUndoGeneratedProperties() {
+    for (BeanProperty prop : beanDescriptor.propertiesGenUpdate()) {
+      Object oldVal = intercept.getOrigValue(prop.getPropertyIndex());
+      prop.setValue(entityBean, oldVal);
+    }
+  }
+
   private void onInsertGeneratedProperties() {
     for (BeanProperty prop : beanDescriptor.propertiesGenInsert()) {
       Object value = prop.getGeneratedProperty().getInsertValue(prop, entityBean, now());
@@ -857,6 +864,7 @@ public final class PersistRequestBean<T> extends PersistRequest implements BeanP
   public final void checkRowCount(int rowCount) {
     if (rowCount != 1 && rowCount != Statement.SUCCESS_NO_INFO) {
       if (ConcurrencyMode.VERSION == concurrencyMode) {
+        onFailedUpdateUndoGeneratedProperties();
         throw new OptimisticLockException("Data has changed. updated row count " + rowCount, null, bean);
       } else if (rowCount == 0 && type == Type.UPDATE) {
         throw new EntityNotFoundException("No rows updated");

ebean-core/src/test/java/org/tests/basic/TestIUDVanilla.java

@@ -10,6 +10,9 @@ import org.tests.model.basic.UTMaster;
 import javax.persistence.OptimisticLockException;
 import java.sql.Timestamp;
 
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
 public class TestIUDVanilla extends BaseTestCase {
 
   @Test
@@ -79,4 +82,26 @@ public class TestIUDVanilla extends BaseTestCase {
     e0.setVersion(42);
     e0.update();
   }
+
+  @Test
+  public void testOptimisticLockException() {
+    UTMaster e0 = new UTMaster("optLock");
+    DB.save(e0);
+
+    e0 = DB.find(UTMaster.class).where().eq("name", "optLock").findOne();
+    UTMaster e1 = DB.find(UTMaster.class).where().eq("name", "optLock").findOne();
+
+    int oldVersion = e0.getVersion();
+    e0.setDescription("foo");
+    e0.save();
+    assertThat(e0.getVersion()).isGreaterThan(oldVersion);
+
+    e1.setDescription("bar");
+    oldVersion = e1.getVersion();
+    assertThatThrownBy(e1::save).isInstanceOf(OptimisticLockException.class);
+    // after optimisticLockExecption, a restore of version is expected
+    assertThat(e1.getVersion()).isEqualTo(oldVersion);
+    // and subsequent saves must fail
+    assertThatThrownBy(e1::save).isInstanceOf(OptimisticLockException.class);
+  }
 }