DynamoDBMapper.CRUDExample1.md

Example: CRUD operations

The following Java code example declares a CatalogItem class that has Id, Title, ISBN, and Authors properties. It uses the annotations to map these properties to the ProductCatalog table in DynamoDB. The example then uses the DynamoDBMapper to save a book object, retrieve it, update it, and then delete the book item.

Note
This code example assumes that you have already loaded data into DynamoDB for your account by following the instructions in the Creating tables and loading data for code examples in DynamoDB section.
For step-by-step instructions to run the following example, see Java code examples.

/**
 * Copyright 2010-2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 *
 * This file is 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/
 *
 * 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 com.amazonaws.codesamples.datamodeling;

import java.io.IOException;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;

import com.amazonaws.services.dynamodbv2.AmazonDynamoDB;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDBClientBuilder;
import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBAttribute;
import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBHashKey;
import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMapper;
import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMapperConfig;
import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBTable;

public class DynamoDBMapperCRUDExample {

    static AmazonDynamoDB client = AmazonDynamoDBClientBuilder.standard().build();

    public static void main(String[] args) throws IOException {
        testCRUDOperations();
        System.out.println("Example complete!");
    }

    @DynamoDBTable(tableName = "ProductCatalog")
    public static class CatalogItem {
        private Integer id;
        private String title;
        private String ISBN;
        private Set<String> bookAuthors;

        // Partition key
        @DynamoDBHashKey(attributeName = "Id")
        public Integer getId() {
            return id;
        }

        public void setId(Integer id) {
            this.id = id;
        }

        @DynamoDBAttribute(attributeName = "Title")
        public String getTitle() {
            return title;
        }

        public void setTitle(String title) {
            this.title = title;
        }

        @DynamoDBAttribute(attributeName = "ISBN")
        public String getISBN() {
            return ISBN;
        }

        public void setISBN(String ISBN) {
            this.ISBN = ISBN;
        }

        @DynamoDBAttribute(attributeName = "Authors")
        public Set<String> getBookAuthors() {
            return bookAuthors;
        }

        public void setBookAuthors(Set<String> bookAuthors) {
            this.bookAuthors = bookAuthors;
        }

        @Override
        public String toString() {
            return "Book [ISBN=" + ISBN + ", bookAuthors=" + bookAuthors + ", id=" + id + ", title=" + title + "]";
        }
    }

    private static void testCRUDOperations() {

        CatalogItem item = new CatalogItem();
        item.setId(601);
        item.setTitle("Book 601");
        item.setISBN("611-1111111111");
        item.setBookAuthors(new HashSet<String>(Arrays.asList("Author1", "Author2")));

        // Save the item (book).
        DynamoDBMapper mapper = new DynamoDBMapper(client);
        mapper.save(item);

        // Retrieve the item.
        CatalogItem itemRetrieved = mapper.load(CatalogItem.class, 601);
        System.out.println("Item retrieved:");
        System.out.println(itemRetrieved);

        // Update the item.
        itemRetrieved.setISBN("622-2222222222");
        itemRetrieved.setBookAuthors(new HashSet<String>(Arrays.asList("Author1", "Author3")));
        mapper.save(itemRetrieved);
        System.out.println("Item updated:");
        System.out.println(itemRetrieved);

        // Retrieve the updated item.
        DynamoDBMapperConfig config = DynamoDBMapperConfig.builder()
            .withConsistentReads(DynamoDBMapperConfig.ConsistentReads.CONSISTENT)
        .build();
        CatalogItem updatedItem = mapper.load(CatalogItem.class, 601, config);
        System.out.println("Retrieved the previously updated item:");
        System.out.println(updatedItem);

        // Delete the item.
        mapper.delete(updatedItem);

        // Try to retrieve deleted item.
        CatalogItem deletedItem = mapper.load(CatalogItem.class, updatedItem.getId(), config);
        if (deletedItem == null) {
            System.out.println("Done - Sample item is deleted.");
        }
    }
}