DDB Enhanced:Added support to read Nested objects in attributesToProject Enhanced Scan and Enhanced query requests

Author: joviegas

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

@@ -0,0 +1,235 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License").
+ * You may not use this file except in compliance with the License.
+ * A copy of the License is located at
+ *
+ *  http://aws.amazon.com/apache2.0
+ *
+ * or in the "license" file accompanying this file. This file is distributed
+ * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+ * express or implied. See the License for the specific language governing
+ * permissions and limitations under the License.
+ */
+
+package software.amazon.awssdk.enhanced.dynamodb;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+import software.amazon.awssdk.annotations.SdkPublicApi;
+import software.amazon.awssdk.utils.Validate;
+
+/**
+ * High-level representation of a DynamoDB 'NestedAttributeName' that can be used in various situations where the API requires
+ * or accepts an Nested Attribute Name.
+ * Simple Attribute Name can be represented by passing just the name of the attribute.
+ * Nested Attributes are represented by List of String where each index of list corresponds to Nesting level Names.
+ * <p> While using attributeToProject in {@link software.amazon.awssdk.enhanced.dynamodb.model.QueryEnhancedRequest}
+ * and {@link software.amazon.awssdk.enhanced.dynamodb.model.ScanEnhancedRequest} we need  way to represent Nested Attributes.
+ * The normal DOT(.) separator is not recognized as a Nesting level separator by DynamoDB request,
+ * thus we need to use NestedAttributeName
+ * which can be used to represent Nested attributes.
+ * <p> Example : NestedAttributeName.create("foo") corresponds to a NestedAttributeName with elements list
+ * with single element foo which represents Simple attribute name "foo" without nesting.
+ * <p>NestedAttributeName.create("foo", "bar") corresponds to a NestedAttributeName with elements list "foo", "bar"
+ * respresenting nested attribute name "foo.bar".
+ */
+@SdkPublicApi
+public final class NestedAttributeName {
+
+    private final List<String> elements;
+
+    private NestedAttributeName(List<String> nestedAttributeNames) {
+        Validate.validState(nestedAttributeNames != null, "nestedAttributeNames must not be null.");
+        Validate.notEmpty(nestedAttributeNames, "nestedAttributeNames must not be empty");
+        Validate.noNullElements(nestedAttributeNames, "nestedAttributeNames must not contain null values");
+        this.elements =  Collections.unmodifiableList(nestedAttributeNames);
+    }
+
+    /**
+     * Creates a NestedAttributeName with a single element, which is effectively just a simple attribute name without nesting.
+     * <p>
+     * <b>Example:</b>create("foo") will create NestedAttributeName corresponding to Attribute foo.
+     *
+     * @param element Attribute Name. Single String represents just a simple attribute name without nesting.
+     * @return NestedAttributeName with attribute name as specified element.
+     */
+    public static NestedAttributeName create(String element) {
+        return new Builder().addElement(element).build();
+    }
+
+    /**
+     * Creates a NestedAttributeName from a list of elements that compose the full path of the nested attribute.
+     * <p>
+     * <b>Example:</b>create("foo", "bar") will create NestedAttributeName which represents foo.bar nested attribute.
+     *
+     * @param elements Nested Attribute Names. Each of strings in varargs represent the nested attribute name
+     *                 at subsequent levels.
+     * @return NestedAttributeName with Nested attribute name set as specified in elements var args.
+     */
+    public static NestedAttributeName create(String... elements) {
+        return new Builder().elements(elements).build();
+    }
+
+    /**
+     * Creates a NestedAttributeName from a list of elements that compose the full path of the nested attribute.
+     * <p>
+     * <b>Example:</b>create(Arrays.asList("foo", "bar")) will create NestedAttributeName
+     * which represents foo.bar nested attribute.
+     *
+     * @param elements List of Nested Attribute Names. Each of strings in List represent the nested attribute name
+     *                 at subsequent levels.
+     * @return NestedAttributeName with Nested attribute name set as specified in elements Collections.
+     */
+    public static NestedAttributeName create(List<String> elements) {
+        return new Builder().elements(elements).build();
+    }
+
+    /**
+     * Create a builder that can be used to create a {@link NestedAttributeName}.
+     */
+    public static Builder builder() {
+        return new Builder();
+    }
+
+    /**
+     * Gets elements of NestedAttributeName in the form of List. Each element in the list corresponds
+     * to the subsequent Nested Attribute name.
+     *
+     * @return List of nested attributes, each entry in the list represent one level of nesting.
+     * Example, A Two level Attribute name foo.bar will be represented as  ["foo", "bar"]
+     */
+    public List<String> elements() {
+        return elements;
+    }
+
+    /**
+     * Returns a builder initialized with all existing values on the request object.
+     */
+    public Builder toBuilder() {
+        return builder().elements(elements);
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        NestedAttributeName that = (NestedAttributeName) o;
+
+        return elements != null
+                ? elements.equals(that.elements) : that.elements == null;
+    }
+
+    @Override
+    public int hashCode() {
+        return elements != null ? elements.hashCode() : 0;
+    }
+
+    /**
+     * A builder for {@link NestedAttributeName}.
+     */
+    public static class Builder {
+        private List<String> elements = null;
+
+        private Builder() {
+
+        }
+
+        /**
+         * Adds a single element of NestedAttributeName.
+         * Subsequent calls to this method can add attribute Names at subsequent nesting levels.
+         * <p>
+         * <b>Example:</b>builder().addElement("foo").addElement("bar")  will add elements in NestedAttributeName
+         * which represent a Nested Attribute Name foo.bar
+         *
+         * @param element Attribute Name.
+         * @return Returns a reference to this object so that method calls can be chained together.
+         */
+        public Builder addElement(String element) {
+            if (elements == null) {
+                elements = new ArrayList<>();
+            }
+            elements.add(element);
+            return this;
+        }
+
+        /**
+         * Adds a single element of NestedAttributeName.
+         * Subsequent calls to this method will append the new elements to the end of the existing chain of elements
+         * creating new levels of nesting.
+         * <p>
+         * <b>Example:</b>builder().addElements("foo","bar")  will add elements in NestedAttributeName
+         * which represent a Nested Attribute Name foo.bar
+         *
+         * @param elements Nested Attribute Names. Each of strings in varargs represent the nested attribute name
+         *                 at subsequent levels.
+         * @return Returns a reference to this object so that method calls can be chained together.
+         */
+        public Builder addElements(String... elements) {
+            if (this.elements == null) {
+                this.elements = new ArrayList<>();
+            }
+            this.elements.addAll(Arrays.asList(elements));
+            return this;
+        }
+
+        /**
+         * Adds a List of elements to NestedAttributeName.
+         * Subsequent calls to this method will append the new elements to the end of the existing chain of elements
+         * creating new levels of nesting.
+         * <p>
+         * <b>Example:</b>builder().addElements(Arrays.asList("foo","bar"))  will add elements in NestedAttributeName
+         * to represent a Nested Attribute Name foo.bar
+         *
+         * @param elements List of Strings where each string corresponds to subsequent nesting attribute name.
+         * @return Returns a reference to this object so that method calls can be chained together.
+         */
+        public Builder addElements(List<String> elements) {
+            if (this.elements == null) {
+                this.elements = new ArrayList<>();
+            }
+            this.elements.addAll(elements);
+            return this;
+        }
+
+        /**
+         * Set elements of NestedAttributeName with list of Strings. Will overwrite any existing elements stored by this builder.
+         * <p>
+         * <b>Example:</b>builder().elements("foo","bar") will set the elements in NestedAttributeName
+         * to represent a nested attribute name of 'foo.bar'
+         *
+         * @param elements a list of strings that correspond to the elements in a nested attribute name.
+         * @return Returns a reference to this object so that method calls can be chained together.
+         */
+        public Builder elements(String... elements) {
+            this.elements = new ArrayList<>(Arrays.asList(elements));
+            return this;
+        }
+
+        /**
+         * Sets the elements that compose a nested attribute name. Will overwrite any existing elements stored by this builder.
+         * <p>
+         * <b>Example:</b>builder().elements(Arrays.asList("foo","bar")) will add elements in NestedAttributeName
+         * which represent a Nested Attribute Name foo.bar
+         *
+         * @param elements a list of strings that correspond to the elements in a nested attribute name.
+         * @return Returns a reference to this object so that method calls can be chained together.
+         */
+        public Builder elements(List<String> elements) {
+            this.elements = new ArrayList<>(elements);
+            return this;
+        }
+
+
+        public NestedAttributeName build() {
+            return new NestedAttributeName(elements);
+        }
+    }
+}

services-custom/dynamodb-enhanced/src/main/java/software/amazon/awssdk/enhanced/dynamodb/internal/ProjectionExpressionConvertor.java

@@ -0,0 +1,107 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License").
+ * You may not use this file except in compliance with the License.
+ * A copy of the License is located at
+ *
+ *  http://aws.amazon.com/apache2.0
+ *
+ * or in the "license" file accompanying this file. This file is distributed
+ * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+ * express or implied. See the License for the specific language governing
+ * permissions and limitations under the License.
+ */
+
+package software.amazon.awssdk.enhanced.dynamodb.internal;
+
+import static software.amazon.awssdk.enhanced.dynamodb.internal.EnhancedClientUtils.cleanAttributeName;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.function.UnaryOperator;
+import java.util.stream.Collectors;
+import software.amazon.awssdk.annotations.SdkInternalApi;
+import software.amazon.awssdk.enhanced.dynamodb.NestedAttributeName;
+
+/**
+ * Wrapper method to get Projection Expression Name map and Projection Expressions from NestedAttributeNames.
+ */
+@SdkInternalApi
+public class ProjectionExpressionConvertor {
+
+    private static final String AMZN_MAPPED = "#AMZN_MAPPED_";
+    private static final UnaryOperator<String> PROJECTION_EXPRESSION_KEY_MAPPER = k -> AMZN_MAPPED + cleanAttributeName(k);
+    private final List<NestedAttributeName> nestedAttributeNames;
+
+    private ProjectionExpressionConvertor(List<NestedAttributeName> nestedAttributeNames) {
+        this.nestedAttributeNames = nestedAttributeNames;
+    }
+
+    public static ProjectionExpressionConvertor create(List<NestedAttributeName> nestedAttributeNames) {
+        return new ProjectionExpressionConvertor(nestedAttributeNames);
+    }
+    
+    private static Optional<Map<String, String>> convertToExpressionNameMap(NestedAttributeName attributeName) {
+        List<String> nestedAttributeNames = attributeName.elements();
+        if (nestedAttributeNames != null) {
+            Map<String, String> resultNameMap = new LinkedHashMap<>();
+            nestedAttributeNames.stream().forEach(nestedAttribute ->
+                            resultNameMap.put(PROJECTION_EXPRESSION_KEY_MAPPER.apply(nestedAttribute), nestedAttribute));
+            return Optional.of(resultNameMap);
+        }
+        return Optional.empty();
+    }
+
+    private static Optional<String> convertToNameExpression(NestedAttributeName nestedAttributeName) {
+
+        String name = nestedAttributeName.elements().stream().findFirst().orElse(null);
+
+        List<String> nestedAttributes = null;
+        if (nestedAttributeName.elements().size() > 1) {
+            nestedAttributes = nestedAttributeName.elements().subList(1, nestedAttributeName.elements().size());
+        }
+        if (name != null) {
+            List<String> hashSeparatedNestedStringList =
+                    new ArrayList<>(Arrays.asList(PROJECTION_EXPRESSION_KEY_MAPPER.apply(name)));
+            if (nestedAttributes != null) {
+                nestedAttributes.stream().forEach(hashSeparatedNestedStringList::add);
+            }
+            return Optional.of(String.join(".".concat(AMZN_MAPPED), hashSeparatedNestedStringList));
+        }
+        return Optional.empty();
+    }
+
+    public List<NestedAttributeName> nestedAttributeNames() {
+        return nestedAttributeNames;
+    }
+
+    public Map<String, String> convertToExpressionMap() {
+        Map<String, String> attributeNameMap = new LinkedHashMap<>();
+        if (this.nestedAttributeNames() != null) {
+            this.nestedAttributeNames().stream().forEach(attribs -> convertToExpressionNameMap(attribs)
+                    .ifPresent(attributeNameMap::putAll));
+        }
+        return attributeNameMap;
+    }
+
+    public Optional<String> convertToProjectionExpression() {
+        if (nestedAttributeNames != null) {
+            List<String> expressionList = new ArrayList<>();
+            this.nestedAttributeNames().stream().filter(Objects::nonNull)
+                    .filter(item -> item.elements() != null && !item.elements().isEmpty())
+                    .forEach(attributeName -> convertToNameExpression(attributeName)
+                            .ifPresent(expressionList::add));
+            String joinedExpression = String.join(",", expressionList.stream()
+                    .distinct().collect(Collectors.toList()));
+            return Optional.ofNullable(joinedExpression.isEmpty() ? null : joinedExpression);
+        }
+        return Optional.empty();
+    }
+
+}