software.amazon.awssdk.enhanced.dynamodb.mapper.annotations

Annotation Type DynamoDbPreserveEmptyObject

@Target(value=METHOD)
 @Retention(value=RUNTIME)
public @interface DynamoDbPreserveEmptyObject

Specifies that when calling TableSchema.mapToItem(Map), a separate DynamoDB object that is stored in the current object should be initialized as empty class if all fields in this class are null. Note that if this annotation is absent, the object will be null.

Example using DynamoDbPreserveEmptyObject:

 
 @DynamoDbBean
 public class NestedBean {
     private AbstractBean innerBean1;
     private AbstractBean innerBean2;

     @DynamoDbPreserveEmptyObject
     public AbstractBean getInnerBean1() {
         return innerBean1;
     }
     public void setInnerBean1(AbstractBean innerBean) {
         this.innerBean1 = innerBean;
     }

     public AbstractBean getInnerBean2() {
         return innerBean;
     }
     public void setInnerBean2(AbstractBean innerBean) {
         this.innerBean2 = innerBean;
     }
 }

 BeanTableSchema beanTableSchema = BeanTableSchema.create(NestedBean.class);
 AbstractBean innerBean1 = new AbstractBean();
 AbstractBean innerBean2 = new AbstractBean();

 NestedBean bean = new NestedBean();
 bean.setInnerBean1(innerBean1);
 bean.setInnerBean2(innerBean2);

 Map itemMap = beanTableSchema.itemToMap(bean, true);
 NestedBean nestedBean = beanTableSchema.mapToItem(itemMap);

 // innerBean1 w/ @DynamoDbPreserveEmptyObject is mapped to empty object
 assertThat(nestedBean.getInnerBean1(), is(innerBean1));

 // innerBean2 w/o @DynamoDbPreserveEmptyObject is mapped to null.
 assertThat(nestedBean.getInnerBean2(), isNull());