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Working with Tables in DynamoDB

Tables are the containers for all items in a DynamoDB database. Before you can add or remove data from DynamoDB, you must create a table.

For each table, you must define:

Provisioned throughput for a table can be modified at any time, so you can adjust capacity if your needs change.

Create a Table

Use the DynamoDB client's createTable method to create a new DynamoDB table. You need to construct table attributes and a table schema, both of which are used to identify the primary key of your table. You must also supply initial provisioned throughput values and a table name. Only define key table attributes when creating your DynamoDB table.

Imports

import com.amazonaws.AmazonServiceException;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDB;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDBClientBuilder;
import com.amazonaws.services.dynamodbv2.model.AttributeDefinition;
import com.amazonaws.services.dynamodbv2.model.CreateTableRequest;
import com.amazonaws.services.dynamodbv2.model.CreateTableResult;
import com.amazonaws.services.dynamodbv2.model.KeySchemaElement;
import com.amazonaws.services.dynamodbv2.model.KeyType;
import com.amazonaws.services.dynamodbv2.model.ProvisionedThroughput;
import com.amazonaws.services.dynamodbv2.model.ScalarAttributeType;

Create a Table with a Simple Primary Key

This code creates a table with a simple primary key ("Name").

Code

CreateTableRequest request = new CreateTableRequest()
    .withAttributeDefinitions(new AttributeDefinition(
             "Name", ScalarAttributeType.S))
    .withKeySchema(new KeySchemaElement("Name", KeyType.HASH))
    .withProvisionedThroughput(new ProvisionedThroughput(
             new Long(10), new Long(10)))
    .withTableName(table_name);

final AmazonDynamoDB ddb = AmazonDynamoDBClientBuilder.defaultClient();

try {
    CreateTableResult result = ddb.createTable(request);
    System.out.println(result.getTableDescription().getTableName());
} catch (AmazonServiceException e) {
    System.err.println(e.getErrorMessage());
    System.exit(1);
}

See the complete example on GitHub.

Create a Table with a Composite Primary Key

Add another AttributeDefinition and KeySchemaElement to CreateTableRequest.

Code

CreateTableRequest request = new CreateTableRequest()
    .withAttributeDefinitions(
          new AttributeDefinition("Language", ScalarAttributeType.S),
          new AttributeDefinition("Greeting", ScalarAttributeType.S))
    .withKeySchema(
          new KeySchemaElement("Language", KeyType.HASH),
          new KeySchemaElement("Greeting", KeyType.RANGE))
    .withProvisionedThroughput(
          new ProvisionedThroughput(new Long(10), new Long(10)))
    .withTableName(table_name);

See the complete example on GitHub.

List Tables

You can list the tables in a particular region by calling the DynamoDB client's listTables method.

Imports

import com.amazonaws.AmazonServiceException;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDB;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDBClientBuilder;
import com.amazonaws.services.dynamodbv2.model.ListTablesRequest;
import com.amazonaws.services.dynamodbv2.model.ListTablesResult;

Code

final AmazonDynamoDB ddb = AmazonDynamoDBClientBuilder.defaultClient();

ListTablesRequest request;

boolean more_tables = true;
String last_name = null;

while(more_tables) {
    try {
        if (last_name == null) {
        	request = new ListTablesRequest().withLimit(10);
        }
        else {
        	request = new ListTablesRequest()
        			.withLimit(10)
        			.withExclusiveStartTableName(last_name);
        }

        ListTablesResult table_list = ddb.listTables(request);
        List<String> table_names = table_list.getTableNames();

        if (table_names.size() > 0) {
            for (String cur_name : table_names) {
                System.out.format("* %s\n", cur_name);
            }
        } else {
            System.out.println("No tables found!");
            System.exit(0);
        }

        last_name = table_list.getLastEvaluatedTableName();
        if (last_name == null) {
            more_tables = false;
        }

By default, up to 100 tables are returned per call—​use getLastEvaluatedTableName on the returned ListTablesResult object to get the last table that was evaluated. You can use this value to start the listing after the last returned value of the previous listing.

See the complete example on GitHub.

Describe (Get Information about) a Table

Call the DynamoDB client's describeTable method.

Imports

import com.amazonaws.AmazonServiceException;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDB;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDBClientBuilder;
import com.amazonaws.services.dynamodbv2.model.AttributeDefinition;
import com.amazonaws.services.dynamodbv2.model.ProvisionedThroughputDescription;
import com.amazonaws.services.dynamodbv2.model.TableDescription;

Code

final AmazonDynamoDB ddb = AmazonDynamoDBClientBuilder.defaultClient();

try {
    TableDescription table_info =
       ddb.describeTable(table_name).getTable();

    if (table_info != null) {
        System.out.format("Table name  : %s\n",
              table_info.getTableName());
        System.out.format("Table ARN   : %s\n",
              table_info.getTableArn());
        System.out.format("Status      : %s\n",
              table_info.getTableStatus());
        System.out.format("Item count  : %d\n",
              table_info.getItemCount().longValue());
        System.out.format("Size (bytes): %d\n",
              table_info.getTableSizeBytes().longValue());

        ProvisionedThroughputDescription throughput_info =
           table_info.getProvisionedThroughput();
        System.out.println("Throughput");
        System.out.format("  Read Capacity : %d\n",
              throughput_info.getReadCapacityUnits().longValue());
        System.out.format("  Write Capacity: %d\n",
              throughput_info.getWriteCapacityUnits().longValue());

        List<AttributeDefinition> attributes =
           table_info.getAttributeDefinitions();
        System.out.println("Attributes");
        for (AttributeDefinition a : attributes) {
            System.out.format("  %s (%s)\n",
                  a.getAttributeName(), a.getAttributeType());
        }
    }
} catch (AmazonServiceException e) {
    System.err.println(e.getErrorMessage());
    System.exit(1);
}

See the complete example on GitHub.

Modify (Update) a Table

You can modify your table’s provisioned throughput values at any time by calling the DynamoDB client's updateTable method.

Imports

import com.amazonaws.services.dynamodbv2.AmazonDynamoDB;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDBClientBuilder;
import com.amazonaws.services.dynamodbv2.model.ProvisionedThroughput;
import com.amazonaws.AmazonServiceException;

Code

ProvisionedThroughput table_throughput = new ProvisionedThroughput(
      read_capacity, write_capacity);

final AmazonDynamoDB ddb = AmazonDynamoDBClientBuilder.defaultClient();

try {
    ddb.updateTable(table_name, table_throughput);
} catch (AmazonServiceException e) {
    System.err.println(e.getErrorMessage());
    System.exit(1);
}

See the complete example on GitHub.

Delete a Table

Call the DynamoDB client's deleteTable method and pass it the table’s name.

Imports

import com.amazonaws.AmazonServiceException;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDB;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDBClientBuilder;

Code

final AmazonDynamoDB ddb = AmazonDynamoDBClientBuilder.defaultClient();

try {
    ddb.deleteTable(table_name);
} catch (AmazonServiceException e) {
    System.err.println(e.getErrorMessage());
    System.exit(1);
}

See the complete example on GitHub.

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