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Andy Kiesler
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Add support for flattening prefixes to DynamoDB fields
This makes enables clients to avoid conflicts if flattened schemas happen to share a field name. The design maintains backwards compatibility with existing codebases by requiring that users opt-in to this behavior explicitly. While this increases the mental overhead there is a design to enable the auto-prefixing as the default behavior when creating the mapper. However, that is outside of the scope of this current implementation.
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‎.changes/next-release/feature-AmazonDynamoDB-3f6308a.json

Lines changed: 6 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,6 @@
1+
{
2+
"category": "Amazon DynamoDB",
3+
"contributor": "kiesler",
4+
"type": "feature",
5+
"description": "Support optional prefix for `@DynamoDbFlatten` fields"
6+
}

‎services-custom/dynamodb-enhanced/src/main/java/software/amazon/awssdk/enhanced/dynamodb/mapper/BeanTableSchema.java

Lines changed: 10 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -203,7 +203,8 @@ private static <T> StaticTableSchema<T> createStaticTableSchema(Class<T> beanCla
203203
if (dynamoDbFlatten != null) {
204204
builder.flatten(TableSchema.fromClass(propertyDescriptor.getReadMethod().getReturnType()),
205205
getterForProperty(propertyDescriptor, beanClass),
206-
setterForProperty(propertyDescriptor, beanClass));
206+
setterForProperty(propertyDescriptor, beanClass),
207+
getFlattenedPrefix(propertyDescriptor, dynamoDbFlatten));
207208
} else {
208209
AttributeConfiguration attributeConfiguration =
209210
resolveAttributeConfiguration(propertyDescriptor);
@@ -225,6 +226,14 @@ private static <T> StaticTableSchema<T> createStaticTableSchema(Class<T> beanCla
225226
return builder.build();
226227
}
227228

229+
private static String getFlattenedPrefix(PropertyDescriptor propertyDescriptor, DynamoDbFlatten dynamoDbFlatten) {
230+
boolean useAutoPrefix = DynamoDbFlatten.AUTO_PREFIX.equals(dynamoDbFlatten.prefix());
231+
if (!useAutoPrefix) {
232+
return dynamoDbFlatten.prefix();
233+
}
234+
return attributeNameForProperty(propertyDescriptor) + ".";
235+
}
236+
228237
private static AttributeConfiguration resolveAttributeConfiguration(PropertyDescriptor propertyDescriptor) {
229238
boolean shouldPreserveEmptyObject = getPropertyAnnotation(propertyDescriptor,
230239
DynamoDbPreserveEmptyObject.class) != null;

‎services-custom/dynamodb-enhanced/src/main/java/software/amazon/awssdk/enhanced/dynamodb/mapper/ImmutableTableSchema.java

Lines changed: 10 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -201,7 +201,8 @@ private static <T, B> StaticImmutableTableSchema<T, B> createStaticImmutableTab
201201
if (dynamoDbFlatten != null) {
202202
builder.flatten(TableSchema.fromClass(propertyDescriptor.getter().getReturnType()),
203203
getterForProperty(propertyDescriptor, immutableClass),
204-
setterForProperty(propertyDescriptor, builderClass));
204+
setterForProperty(propertyDescriptor, builderClass),
205+
getFlattenedPrefix(propertyDescriptor, dynamoDbFlatten));
205206
} else {
206207
AttributeConfiguration beanAttributeConfiguration = resolveAttributeConfiguration(propertyDescriptor);
207208
ImmutableAttribute.Builder<T, B, ?> attributeBuilder =
@@ -225,6 +226,14 @@ private static <T, B> StaticImmutableTableSchema<T, B> createStaticImmutableTab
225226
return builder.build();
226227
}
227228

229+
private static String getFlattenedPrefix(ImmutablePropertyDescriptor propertyDescriptor, DynamoDbFlatten dynamoDbFlatten) {
230+
boolean useAutoPrefix = DynamoDbFlatten.AUTO_PREFIX.equals(dynamoDbFlatten.prefix());
231+
if (!useAutoPrefix) {
232+
return dynamoDbFlatten.prefix();
233+
}
234+
return attributeNameForProperty(propertyDescriptor) + ".";
235+
}
236+
228237
private static List<AttributeConverterProvider> createConverterProvidersFromAnnotation(Class<?> immutableClass,
229238
DynamoDbImmutable dynamoDbImmutable) {
230239

‎services-custom/dynamodb-enhanced/src/main/java/software/amazon/awssdk/enhanced/dynamodb/mapper/annotations/DynamoDbFlatten.java

Lines changed: 48 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -25,14 +25,62 @@
2525
* This annotation is used to flatten all the attributes of a separate DynamoDb bean that is stored in the current bean
2626
* object and add them as top level attributes to the record that is read and written to the database. The target bean
2727
* to flatten must be specified as part of this annotation.
28+
* The flattening behavior can be controlled by the prefix value of the annotation.
29+
* The default behavior is that no prefix is applied (this is done for backwards compatability).
30+
* If a String value is supplied then that is prefixed to the attribute names.
31+
* If a value of {@code DynamoDbFlatten.AUTO_PREFIX} is supplied then the attribute name of the flattened bean appended
32+
* with a period ('.') is used as the prefix.
33+
*
34+
* Example, given the following classes:
35+
* <pre>{@code
36+
* @DynamoDbBean
37+
* public class Flattened {
38+
* String getValue();
39+
* }
40+
*
41+
* @DynamoDbBean
42+
* public class Record {
43+
* @DynamoDbFlatten
44+
* Flattened getNoPrefix(); // translates to attribute 'value'
45+
* @DynamoDbFlatten(prefix = "prefix-")
46+
* Flattened getExplicitPrefix(); // translates to attribute 'prefix-value'
47+
* @DynamoDbFlatten(prefix = DynamoDbFlatten.AUTO_PREFIX)
48+
* Flattened getInferredPrefix(); // translates to attribute 'inferredPrefix.value'
49+
* @DynamoDbAttribute("custom")
50+
* @DynamoDbFlatten(prefix = DynamoDbFlatten.AUTO_PREFIX)
51+
* Flattened getFlattened(); // translates to attribute 'custom.value'
52+
* }
53+
*}</pre>
54+
* They would be mapped as such:
55+
* <pre>{@code
56+
* {
57+
* "value": {"S": "..."},
58+
* "prefix-value": {"S": "..."},
59+
* "inferredPrefix.value": {"S": "..."},
60+
* "custom.value": {"S": "..."},
61+
* }
62+
* }</pre>
2863
*/
2964
@Target({ElementType.METHOD})
3065
@Retention(RetentionPolicy.RUNTIME)
3166
@SdkPublicApi
3267
public @interface DynamoDbFlatten {
68+
/**
69+
* Values used to denote that the mapper should append the current attribute name to flattened fields.
70+
*/
71+
String AUTO_PREFIX = "AUTO_PREFIX";
72+
3373
/**
3474
* @deprecated This is no longer used, the class type of the attribute will be used instead.
3575
*/
3676
@Deprecated
3777
Class<?> dynamoDbBeanClass() default Object.class;
78+
79+
/**
80+
* Optional prefix to append to the flattened bean attributes in the schema.
81+
* Specifying a value of {@code DynamoDbFlatten.AUTO_PREFIX} will use the annotated methods attribute name as the
82+
* prefix.
83+
* default: {@code ""} (No prefix)
84+
*/
85+
String prefix() default "";
3886
}

‎services-custom/dynamodb-enhanced/src/test/java/software/amazon/awssdk/enhanced/dynamodb/mapper/BeanTableSchemaTest.java

Lines changed: 49 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -37,6 +37,7 @@
3737
import java.util.Optional;
3838
import org.junit.Rule;
3939
import org.junit.Test;
40+
import org.junit.jupiter.api.Assertions;
4041
import org.junit.rules.ExpectedException;
4142
import org.junit.runner.RunWith;
4243
import org.mockito.junit.MockitoJUnitRunner;
@@ -54,6 +55,7 @@
5455
import software.amazon.awssdk.enhanced.dynamodb.mapper.testbeans.EnumBean;
5556
import software.amazon.awssdk.enhanced.dynamodb.mapper.testbeans.ExtendedBean;
5657
import software.amazon.awssdk.enhanced.dynamodb.mapper.testbeans.FlattenedBeanBean;
58+
import software.amazon.awssdk.enhanced.dynamodb.mapper.testbeans.FlattenedBeanImmutable;
5759
import software.amazon.awssdk.enhanced.dynamodb.mapper.testbeans.FlattenedImmutableBean;
5860
import software.amazon.awssdk.enhanced.dynamodb.mapper.testbeans.IgnoredAttributeBean;
5961
import software.amazon.awssdk.enhanced.dynamodb.mapper.testbeans.InvalidBean;
@@ -178,18 +180,57 @@ public void dynamoDbAttribute_remapsAttributeName() {
178180
@Test
179181
public void dynamoDbFlatten_correctlyFlattensBeanAttributes() {
180182
BeanTableSchema<FlattenedBeanBean> beanTableSchema = BeanTableSchema.create(FlattenedBeanBean.class);
183+
184+
assertThat(beanTableSchema.attributeNames(), containsInAnyOrder("id", "attribute1", "attribute2",
185+
"prefix-attribute2", "autoPrefixBean.attribute2", "custom.attribute2"));
186+
181187
AbstractBean abstractBean = new AbstractBean();
182188
abstractBean.setAttribute2("two");
183189
FlattenedBeanBean flattenedBeanBean = new FlattenedBeanBean();
184190
flattenedBeanBean.setId("id-value");
185191
flattenedBeanBean.setAttribute1("one");
186192
flattenedBeanBean.setAbstractBean(abstractBean);
193+
flattenedBeanBean.setExplicitPrefixBean(abstractBean);
194+
flattenedBeanBean.setAutoPrefixBean(abstractBean);
195+
flattenedBeanBean.setCustomPrefixBean(abstractBean);
187196

188197
Map<String, AttributeValue> itemMap = beanTableSchema.itemToMap(flattenedBeanBean, false);
189-
assertThat(itemMap.size(), is(3));
198+
assertThat(itemMap.size(), is(6));
190199
assertThat(itemMap, hasEntry("id", stringValue("id-value")));
191200
assertThat(itemMap, hasEntry("attribute1", stringValue("one")));
192201
assertThat(itemMap, hasEntry("attribute2", stringValue("two")));
202+
assertThat(itemMap, hasEntry("prefix-attribute2", stringValue("two")));
203+
assertThat(itemMap, hasEntry("autoPrefixBean.attribute2", stringValue("two")));
204+
assertThat(itemMap, hasEntry("custom.attribute2", stringValue("two")));
205+
}
206+
207+
@Test
208+
public void dynamoDbFlatten_correctlyGetFlattenedBeanAttributes() {
209+
BeanTableSchema<FlattenedBeanBean> tableSchema = BeanTableSchema.create(FlattenedBeanBean.class);
210+
211+
AbstractBean abstractBean = new AbstractBean();
212+
abstractBean.setAttribute2("two");
213+
AbstractBean explicitPrefixBean = new AbstractBean();
214+
explicitPrefixBean.setAttribute2("three");
215+
AbstractBean autoPrefixBean = new AbstractBean();
216+
autoPrefixBean.setAttribute2("four");
217+
AbstractBean customPrefixBean = new AbstractBean();
218+
customPrefixBean.setAttribute2("five");
219+
220+
FlattenedBeanBean bean = new FlattenedBeanBean();
221+
bean.setId("id-value");
222+
bean.setAttribute1("one");
223+
bean.setAbstractBean(abstractBean);
224+
bean.setExplicitPrefixBean(explicitPrefixBean);
225+
bean.setAutoPrefixBean(autoPrefixBean);
226+
bean.setCustomPrefixBean(customPrefixBean);
227+
228+
assertThat(tableSchema.attributeValue(bean, "id"), equalTo(stringValue("id-value")));
229+
assertThat(tableSchema.attributeValue(bean, "attribute1"), equalTo(stringValue("one")));
230+
assertThat(tableSchema.attributeValue(bean, "attribute2"), equalTo(stringValue("two")));
231+
assertThat(tableSchema.attributeValue(bean, "prefix-attribute2"), equalTo(stringValue("three")));
232+
assertThat(tableSchema.attributeValue(bean, "autoPrefixBean.attribute2"), equalTo(stringValue("four")));
233+
assertThat(tableSchema.attributeValue(bean, "custom.attribute2"), equalTo(stringValue("five")));
193234
}
194235

195236
@Test
@@ -248,12 +289,18 @@ public void dynamoDbFlatten_correctlyFlattensImmutableAttributes() {
248289
flattenedImmutableBean.setId("id-value");
249290
flattenedImmutableBean.setAttribute1("one");
250291
flattenedImmutableBean.setAbstractImmutable(abstractImmutable);
292+
flattenedImmutableBean.setExplicitPrefixImmutable(abstractImmutable);
293+
flattenedImmutableBean.setAutoPrefixImmutable(abstractImmutable);
294+
flattenedImmutableBean.setCustomPrefixImmutable(abstractImmutable);
251295

252296
Map<String, AttributeValue> itemMap = beanTableSchema.itemToMap(flattenedImmutableBean, false);
253-
assertThat(itemMap.size(), is(3));
297+
assertThat(itemMap.size(), is(6));
254298
assertThat(itemMap, hasEntry("id", stringValue("id-value")));
255299
assertThat(itemMap, hasEntry("attribute1", stringValue("one")));
256300
assertThat(itemMap, hasEntry("attribute2", stringValue("two")));
301+
assertThat(itemMap, hasEntry("prefix-attribute2", stringValue("two")));
302+
assertThat(itemMap, hasEntry("autoPrefixImmutable.attribute2", stringValue("two")));
303+
assertThat(itemMap, hasEntry("custom.attribute2", stringValue("two")));
257304
}
258305

259306
@Test

‎services-custom/dynamodb-enhanced/src/test/java/software/amazon/awssdk/enhanced/dynamodb/mapper/ImmutableTableSchemaTest.java

Lines changed: 56 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -17,6 +17,9 @@
1717

1818
import static java.util.Collections.singletonMap;
1919
import static org.hamcrest.MatcherAssert.assertThat;
20+
import static org.hamcrest.Matchers.contains;
21+
import static org.hamcrest.Matchers.containsInAnyOrder;
22+
import static org.hamcrest.Matchers.equalTo;
2023
import static org.hamcrest.Matchers.hasEntry;
2124
import static org.hamcrest.Matchers.is;
2225
import static software.amazon.awssdk.enhanced.dynamodb.internal.AttributeValues.nullAttributeValue;
@@ -25,6 +28,8 @@
2528
import java.util.Arrays;
2629
import java.util.HashMap;
2730
import java.util.Map;
31+
import java.util.stream.Collectors;
32+
import org.junit.jupiter.api.Assertions;
2833
import org.junit.jupiter.api.Test;
2934
import software.amazon.awssdk.enhanced.dynamodb.mapper.testbeans.AbstractBean;
3035
import software.amazon.awssdk.enhanced.dynamodb.mapper.testbeans.AbstractImmutable;
@@ -213,37 +218,86 @@ public void documentImmutable_map_correctlyMapsImmutableAttributes() {
213218
public void dynamoDbFlatten_correctlyFlattensBeanAttributes() {
214219
ImmutableTableSchema<FlattenedBeanImmutable> tableSchema =
215220
ImmutableTableSchema.create(FlattenedBeanImmutable.class);
221+
222+
assertThat(tableSchema.attributeNames(), containsInAnyOrder("id", "attribute1", "attribute2",
223+
"prefix-attribute2", "autoPrefixBean.attribute2", "custom.attribute2"));
224+
216225
AbstractBean abstractBean = new AbstractBean();
217226
abstractBean.setAttribute2("two");
218227
FlattenedBeanImmutable flattenedBeanImmutable =
219228
new FlattenedBeanImmutable.Builder().setId("id-value")
220229
.setAttribute1("one")
221230
.setAbstractBean(abstractBean)
231+
.setExplicitPrefixBean(abstractBean)
232+
.setAutoPrefixBean(abstractBean)
233+
.setCustomPrefixBean(abstractBean)
222234
.build();
223235

224236
Map<String, AttributeValue> itemMap = tableSchema.itemToMap(flattenedBeanImmutable, false);
225-
assertThat(itemMap.size(), is(3));
237+
assertThat(itemMap.size(), is(6));
226238
assertThat(itemMap, hasEntry("id", stringValue("id-value")));
227239
assertThat(itemMap, hasEntry("attribute1", stringValue("one")));
228240
assertThat(itemMap, hasEntry("attribute2", stringValue("two")));
241+
assertThat(itemMap, hasEntry("prefix-attribute2", stringValue("two")));
242+
assertThat(itemMap, hasEntry("autoPrefixBean.attribute2", stringValue("two")));
243+
assertThat(itemMap, hasEntry("custom.attribute2", stringValue("two")));
229244
}
230245

231246
@Test
232247
public void dynamoDbFlatten_correctlyFlattensImmutableAttributes() {
233248
ImmutableTableSchema<FlattenedImmutableImmutable> tableSchema =
234249
ImmutableTableSchema.create(FlattenedImmutableImmutable.class);
250+
251+
assertThat(tableSchema.attributeNames(), containsInAnyOrder("id", "attribute1", "attribute2",
252+
"prefix-attribute2", "autoPrefixImmutable.attribute2", "custom.attribute2"));
253+
235254
AbstractImmutable abstractImmutable = AbstractImmutable.builder().attribute2("two").build();
236255
FlattenedImmutableImmutable FlattenedImmutableImmutable =
237256
new FlattenedImmutableImmutable.Builder().setId("id-value")
238257
.setAttribute1("one")
239258
.setAbstractImmutable(abstractImmutable)
259+
.setExplicitPrefixImmutable(abstractImmutable)
260+
.setAutoPrefixImmutable(abstractImmutable)
261+
.setCustomPrefixImmutable(abstractImmutable)
240262
.build();
241263

242264
Map<String, AttributeValue> itemMap = tableSchema.itemToMap(FlattenedImmutableImmutable, false);
243-
assertThat(itemMap.size(), is(3));
265+
assertThat(itemMap.size(), is(6));
244266
assertThat(itemMap, hasEntry("id", stringValue("id-value")));
245267
assertThat(itemMap, hasEntry("attribute1", stringValue("one")));
246268
assertThat(itemMap, hasEntry("attribute2", stringValue("two")));
269+
assertThat(itemMap, hasEntry("prefix-attribute2", stringValue("two")));
270+
assertThat(itemMap, hasEntry("autoPrefixImmutable.attribute2", stringValue("two")));
271+
assertThat(itemMap, hasEntry("custom.attribute2", stringValue("two")));
272+
}
273+
274+
@Test
275+
public void dynamoDbFlatten_correctlyGetFlattenedBeanAttributes() {
276+
ImmutableTableSchema<FlattenedBeanImmutable> tableSchema =
277+
ImmutableTableSchema.create(FlattenedBeanImmutable.class);
278+
279+
AbstractBean abstractBean = new AbstractBean();
280+
abstractBean.setAttribute2("two");
281+
AbstractBean explicitPrefixBean = new AbstractBean();
282+
explicitPrefixBean.setAttribute2("three");
283+
AbstractBean autoPrefixBean = new AbstractBean();
284+
autoPrefixBean.setAttribute2("four");
285+
AbstractBean customPrefixBean = new AbstractBean();
286+
customPrefixBean.setAttribute2("five");
287+
FlattenedBeanImmutable bean = new FlattenedBeanImmutable.Builder().setId("id-value")
288+
.setAttribute1("one")
289+
.setAbstractBean(abstractBean)
290+
.setExplicitPrefixBean(explicitPrefixBean)
291+
.setAutoPrefixBean(autoPrefixBean)
292+
.setCustomPrefixBean(customPrefixBean)
293+
.build();
294+
295+
assertThat(tableSchema.attributeValue(bean, "id"), equalTo(stringValue("id-value")));
296+
assertThat(tableSchema.attributeValue(bean, "attribute1"), equalTo(stringValue("one")));
297+
assertThat(tableSchema.attributeValue(bean, "attribute2"), equalTo(stringValue("two")));
298+
assertThat(tableSchema.attributeValue(bean, "prefix-attribute2"), equalTo(stringValue("three")));
299+
assertThat(tableSchema.attributeValue(bean, "autoPrefixBean.attribute2"), equalTo(stringValue("four")));
300+
assertThat(tableSchema.attributeValue(bean, "custom.attribute2"), equalTo(stringValue("five")));
247301
}
248302

249303
@Test

‎services-custom/dynamodb-enhanced/src/test/java/software/amazon/awssdk/enhanced/dynamodb/mapper/testbeans/FlattenedBeanBean.java

Lines changed: 29 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -15,6 +15,7 @@
1515

1616
package software.amazon.awssdk.enhanced.dynamodb.mapper.testbeans;
1717

18+
import software.amazon.awssdk.enhanced.dynamodb.mapper.annotations.DynamoDbAttribute;
1819
import software.amazon.awssdk.enhanced.dynamodb.mapper.annotations.DynamoDbBean;
1920
import software.amazon.awssdk.enhanced.dynamodb.mapper.annotations.DynamoDbFlatten;
2021
import software.amazon.awssdk.enhanced.dynamodb.mapper.annotations.DynamoDbPartitionKey;
@@ -24,6 +25,9 @@ public class FlattenedBeanBean {
2425
private String id;
2526
private String attribute1;
2627
private AbstractBean abstractBean;
28+
private AbstractBean explicitPrefixBean;
29+
private AbstractBean autoPrefixBean;
30+
private AbstractBean customPrefixBean;
2731

2832
@DynamoDbPartitionKey
2933
public String getId() {
@@ -47,4 +51,29 @@ public AbstractBean getAbstractBean() {
4751
public void setAbstractBean(AbstractBean abstractBean) {
4852
this.abstractBean = abstractBean;
4953
}
54+
55+
@DynamoDbFlatten(prefix = "prefix-")
56+
public AbstractBean getExplicitPrefixBean() {
57+
return explicitPrefixBean;
58+
}
59+
public void setExplicitPrefixBean(AbstractBean explicitPrefixBean) {
60+
this.explicitPrefixBean = explicitPrefixBean;
61+
}
62+
63+
@DynamoDbFlatten(prefix = DynamoDbFlatten.AUTO_PREFIX)
64+
public AbstractBean getAutoPrefixBean() {
65+
return autoPrefixBean;
66+
}
67+
public void setAutoPrefixBean(AbstractBean autoPrefixBean) {
68+
this.autoPrefixBean = autoPrefixBean;
69+
}
70+
71+
@DynamoDbAttribute("custom")
72+
@DynamoDbFlatten(prefix = DynamoDbFlatten.AUTO_PREFIX)
73+
public AbstractBean getCustomPrefixBean() {
74+
return customPrefixBean;
75+
}
76+
public void setCustomPrefixBean(AbstractBean customPrefixBean) {
77+
this.customPrefixBean = customPrefixBean;
78+
}
5079
}

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