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Work 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:
-
A table name that is unique for your account and region.
-
A primary key for which every value must be unique; no two items in your table can have the same primary key value.
A primary key can be simple, consisting of a single partition (HASH) key, or composite, consisting of a partition and a sort (RANGE) key.
Each key value has an associated data type, enumerated by the ScalarAttributeType
class. The key value can be binary (B), numeric (N), or a string (S). For more information, see Naming Rules and Data Types in the Amazon DynamoDB Developer Guide. -
Provisioned throughput are values that define the number of reserved read/write capacity units for the table.
Note Amazon DynamoDB pricing
is based on the provisioned throughput values that you set on your tables, so reserve only as much capacity as you think you’ll need for your table. Provisioned throughput for a table can be modified at any time, so you can adjust capacity as your needs change.
Create a table
Use the DynamoDbClient’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.
If a table with the name you chose already exists, an
DynamoDbException
Imports
import software.amazon.awssdk.core.waiters.WaiterResponse; import software.amazon.awssdk.regions.Region; import software.amazon.awssdk.services.dynamodb.model.CreateTableRequest; import software.amazon.awssdk.services.dynamodb.model.AttributeDefinition; import software.amazon.awssdk.services.dynamodb.model.ScalarAttributeType; import software.amazon.awssdk.services.dynamodb.model.ScalarAttributeType; import software.amazon.awssdk.services.dynamodb.model.KeySchemaElement; import software.amazon.awssdk.services.dynamodb.model.ProvisionedThroughput; import software.amazon.awssdk.services.dynamodb.model.KeyType; import software.amazon.awssdk.services.dynamodb.model.CreateTableResponse; import software.amazon.awssdk.services.dynamodb.model.DescribeTableRequest; import software.amazon.awssdk.services.dynamodb.model.DescribeTableResponse; import software.amazon.awssdk.services.dynamodb.model.DynamoDbException; import software.amazon.awssdk.services.dynamodb.DynamoDbClient; import software.amazon.awssdk.services.dynamodb.waiters.DynamoDbWaiter;
Create a table with a simple primary key
This code creates a table with a simple primary key (“Name”).
Code
public static String createTable(DynamoDbClient ddb, String tableName, String key) { DynamoDbWaiter dbWaiter = ddb.waiter(); CreateTableRequest request = CreateTableRequest.builder() .attributeDefinitions(AttributeDefinition.builder() .attributeName(key) .attributeType(ScalarAttributeType.S) .build()) .keySchema(KeySchemaElement.builder() .attributeName(key) .keyType(KeyType.HASH) .build()) .provisionedThroughput(ProvisionedThroughput.builder() .readCapacityUnits(new Long(10)) .writeCapacityUnits(new Long(10)) .build()) .tableName(tableName) .build(); String newTable =""; try { CreateTableResponse response = ddb.createTable(request); DescribeTableRequest tableRequest = DescribeTableRequest.builder() .tableName(tableName) .build(); // Wait until the Amazon DynamoDB table is created WaiterResponse<DescribeTableResponse> waiterResponse = dbWaiter.waitUntilTableExists(tableRequest); waiterResponse.matched().response().ifPresent(System.out::println); newTable = response.tableDescription().tableName(); return newTable; } catch (DynamoDbException e) { System.err.println(e.getMessage()); System.exit(1); } return ""; }
See the complete example
Create a table with a composite primary key
Add another
AttributeDefinition
Imports
import software.amazon.awssdk.regions.Region; import software.amazon.awssdk.services.dynamodb.model.DynamoDbException; import software.amazon.awssdk.services.dynamodb.model.AttributeDefinition; import software.amazon.awssdk.services.dynamodb.model.CreateTableRequest; import software.amazon.awssdk.services.dynamodb.model.CreateTableResponse; import software.amazon.awssdk.services.dynamodb.model.KeySchemaElement; import software.amazon.awssdk.services.dynamodb.model.KeyType; import software.amazon.awssdk.services.dynamodb.model.ProvisionedThroughput; import software.amazon.awssdk.services.dynamodb.model.ScalarAttributeType; import software.amazon.awssdk.services.dynamodb.DynamoDbClient;
Code
public static String createTableComKey(DynamoDbClient ddb, String tableName) { CreateTableRequest request = CreateTableRequest.builder() .attributeDefinitions( AttributeDefinition.builder() .attributeName("Language") .attributeType(ScalarAttributeType.S) .build(), AttributeDefinition.builder() .attributeName("Greeting") .attributeType(ScalarAttributeType.S) .build()) .keySchema( KeySchemaElement.builder() .attributeName("Language") .keyType(KeyType.HASH) .build(), KeySchemaElement.builder() .attributeName("Greeting") .keyType(KeyType.RANGE) .build()) .provisionedThroughput( ProvisionedThroughput.builder() .readCapacityUnits(new Long(10)) .writeCapacityUnits(new Long(10)).build()) .tableName(tableName) .build(); String tableId = ""; try { CreateTableResponse result = ddb.createTable(request); tableId = result.tableDescription().tableId(); return tableId; } catch (DynamoDbException e) { System.err.println(e.getMessage()); System.exit(1); }
See the complete example
List tables
You can list the tables in a particular region by calling the DynamoDbClient’s
listTables
method.
If the named table doesn’t exist for your account and region, a
ResourceNotFoundException
Imports
import software.amazon.awssdk.regions.Region; import software.amazon.awssdk.services.dynamodb.model.DynamoDbException; import software.amazon.awssdk.services.dynamodb.model.ListTablesResponse; import software.amazon.awssdk.services.dynamodb.model.ListTablesRequest; import software.amazon.awssdk.services.dynamodb.DynamoDbClient; import java.util.List;
Code
public static void listAllTables(DynamoDbClient ddb){ boolean moreTables = true; String lastName = null; while(moreTables) { try { ListTablesResponse response = null; if (lastName == null) { ListTablesRequest request = ListTablesRequest.builder().build(); response = ddb.listTables(request); } else { ListTablesRequest request = ListTablesRequest.builder() .exclusiveStartTableName(lastName).build(); response = ddb.listTables(request); } List<String> tableNames = response.tableNames(); if (tableNames.size() > 0) { for (String curName : tableNames) { System.out.format("* %s\n", curName); } } else { System.out.println("No tables found!"); System.exit(0); } lastName = response.lastEvaluatedTableName(); if (lastName == null) { moreTables = false; } } catch (DynamoDbException e) { System.err.println(e.getMessage()); System.exit(1); } }
By default, up to 100 tables are returned per call—use
lastEvaluatedTableName
on the returned
ListTablesResponse
See the complete example
Describe (get information about) a table
Call the DynamoDbClient’s describeTable
method.
If the named table doesn’t exist for your account and region, a
ResourceNotFoundException
Imports
import software.amazon.awssdk.regions.Region; import software.amazon.awssdk.services.dynamodb.model.DynamoDbException; import software.amazon.awssdk.services.dynamodb.DynamoDbClient; import software.amazon.awssdk.services.dynamodb.model.AttributeDefinition; import software.amazon.awssdk.services.dynamodb.model.DescribeTableRequest; import software.amazon.awssdk.services.dynamodb.model.ProvisionedThroughputDescription; import software.amazon.awssdk.services.dynamodb.model.TableDescription; import java.util.List;
Code
public static void describeDymamoDBTable(DynamoDbClient ddb,String tableName ) { DescribeTableRequest request = DescribeTableRequest.builder() .tableName(tableName) .build(); try { TableDescription tableInfo = ddb.describeTable(request).table(); if (tableInfo != null) { System.out.format("Table name : %s\n", tableInfo.tableName()); System.out.format("Table ARN : %s\n", tableInfo.tableArn()); System.out.format("Status : %s\n", tableInfo.tableStatus()); System.out.format("Item count : %d\n", tableInfo.itemCount().longValue()); System.out.format("Size (bytes): %d\n", tableInfo.tableSizeBytes().longValue()); ProvisionedThroughputDescription throughputInfo = tableInfo.provisionedThroughput(); System.out.println("Throughput"); System.out.format(" Read Capacity : %d\n", throughputInfo.readCapacityUnits().longValue()); System.out.format(" Write Capacity: %d\n", throughputInfo.writeCapacityUnits().longValue()); List<AttributeDefinition> attributes = tableInfo.attributeDefinitions(); System.out.println("Attributes"); for (AttributeDefinition a : attributes) { System.out.format(" %s (%s)\n", a.attributeName(), a.attributeType()); } } } catch (DynamoDbException e) { System.err.println(e.getMessage()); System.exit(1); }
See the complete example
Modify (update) a table
You can modify your table’s provisioned throughput values at any time by calling the
DynamoDbClient’s updateTable
method.
If the named table doesn’t exist for your account and region, a
ResourceNotFoundException
Imports
import software.amazon.awssdk.regions.Region; import software.amazon.awssdk.services.dynamodb.model.ProvisionedThroughput; import software.amazon.awssdk.services.dynamodb.DynamoDbClient; import software.amazon.awssdk.services.dynamodb.model.UpdateTableRequest; import software.amazon.awssdk.services.dynamodb.model.DynamoDbException;
Code
public static void updateDynamoDBTable(DynamoDbClient ddb, String tableName, Long readCapacity, Long writeCapacity) { System.out.format( "Updating %s with new provisioned throughput values\n", tableName); System.out.format("Read capacity : %d\n", readCapacity); System.out.format("Write capacity : %d\n", writeCapacity); ProvisionedThroughput tableThroughput = ProvisionedThroughput.builder() .readCapacityUnits(readCapacity) .writeCapacityUnits(writeCapacity) .build(); UpdateTableRequest request = UpdateTableRequest.builder() .provisionedThroughput(tableThroughput) .tableName(tableName) .build(); try { ddb.updateTable(request); } catch (DynamoDbException e) { System.err.println(e.getMessage()); System.exit(1); }
See the complete example
Delete a table
Call the DynamoDbClient’s
deleteTable
method and pass it the table’s name.
If the named table doesn’t exist for your account and region, a
ResourceNotFoundException
Imports
import software.amazon.awssdk.regions.Region; import software.amazon.awssdk.services.dynamodb.model.DynamoDbException; import software.amazon.awssdk.services.dynamodb.DynamoDbClient; import software.amazon.awssdk.services.dynamodb.model.DeleteTableRequest;
Code
public static void deleteDynamoDBTable(DynamoDbClient ddb, String tableName) { DeleteTableRequest request = DeleteTableRequest.builder() .tableName(tableName) .build(); try { ddb.deleteTable(request); } catch (DynamoDbException e) { System.err.println(e.getMessage()); System.exit(1); }
See the complete example
More information
-
Guidelines for Working with Tables in the Amazon DynamoDB Developer Guide
-
Working with Tables in DynamoDB in the Amazon DynamoDB Developer Guide