本文属于机器翻译版本。若本译文内容与英语原文存在差异，则一律以英文原文为准。 # 处理 DynamoDB 中的表 表是 DynamoDB 数据库中所有项目的容器。您必须先创建表，然后才能在 DynamoDB 中添加或删除数据。 对于每个表，您必须定义： + 表*名称*，它对于您的账户和所在区域是唯一的。 + 一个*主键*，每个值对于它都必须是唯一的；表中的任意两个项目不能具有相同的主键值。 主键可以是*简单*主键（包含单个分区 (HASH) 键）或*复合*主键（包含一个分区和一个排序 (RANGE) 键）。 每个键值均有一个由 [https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/services/dynamodb/model/ScalarAttributeType.html](https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/services/dynamodb/model/ScalarAttributeType.html) 类枚举的关联*数据类型*。键值可以是二进制 (B)、数字 (N) 或字符串 (S)。有关更多信息，请参阅《Amazon DynamoDB 开发人员指南》中的[命名规则和数据类型](https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/HowItWorks.NamingRulesDataTypes.html)。 + *预置吞吐量* 是定义为表保留的读取/写入容量单位数的值。 **注意** [Amazon DynamoDB 定价](https://aws.amazon.com/dynamodb/pricing/)基于您为表设置的预置吞吐量值，因此您应只为表保留可能需要的容量。 表的预置吞吐量可随时修改，以便您能够在需要更改时调整容量。 ## 创建表 使用 `DynamoDbClient’s` `createTable` 方法来创建新的 DynamoDB 表。您需要构造表属性和表架构，二者用于标识表的主键。您还必须提供初始预置吞吐量值和表名。 **注意** 如果使用您所选名称的表已存在，则将引发 `[DynamoDbException](https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/services/dynamodb/model/DynamoDbException.html)`。 ### 创建具有简单主键的表 此代码创建一个表，该表只有一个属性，这个属性是表的简单主键。该示例为 [https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/services/dynamodb/model/CreateTableRequest.html](https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/services/dynamodb/model/CreateTableRequest.html) 使用 `[AttributeDefinition](https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/services/dynamodb/model/AttributeDefinition.html)` 和 `[KeySchemaElement](https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/services/dynamodb/model/KeySchemaElement.html)` 对象。 **导入**。 ``` 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; ``` **代码** ``` 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 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 ""; } ``` 请参阅 GitHub 上的[完整示例](https://github.com/awsdocs/aws-doc-sdk-examples/blob/0b1785e42949ebf959eaa0f0da4dc2a48f92ea25/javav2/example_code/dynamodb/src/main/java/com/example/dynamodb/CreateTable.java)。 ### 创建具有复合主键的表 以下示例创建带有两个属性的表。这两个属性均用于复合主键。 **导入**。 ``` 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; ``` **代码** ``` 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); } return ""; } ``` 请参阅 GitHub 上的[完整示例](https://github.com/awsdocs/aws-doc-sdk-examples/blob/0b1785e42949ebf959eaa0f0da4dc2a48f92ea25/javav2/example_code/dynamodb/src/main/java/com/example/dynamodb/CreateTableCompositeKey.java)。 ## 列出表 您可以通过调用 `DynamoDbClient’s` `listTables` 方法列出特定区域中的表。 **注意** 如果您的账户和区域没有使用该名称的表，则将引发 [https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/services/dynamodb/model/ResourceNotFoundException.html](https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/services/dynamodb/model/ResourceNotFoundException.html) 异常。 **导入**。 ``` 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; ``` **代码** ``` 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 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); } } System.out.println("\nDone!"); } ``` 默认情况下，每次调用将返回最多 100 个表 – 对返回的 [https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/services/dynamodb/model/ListTablesResponse.html](https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/services/dynamodb/model/ListTablesResponse.html) 对象使用 `lastEvaluatedTableName` 可获得评估的上一个表。可使用此值在上一列出的最后一个返回值后开始列出。 请参阅 GitHub 上的[完整示例](https://github.com/awsdocs/aws-doc-sdk-examples/blob/0b1785e42949ebf959eaa0f0da4dc2a48f92ea25/javav2/example_code/dynamodb/src/main/java/com/example/dynamodb/ListTables.java)。 ## 描述表（获取相关信息） 使用 `DynamoDbClient’s` `describeTable` 方法获取有关表的信息。 **注意** 如果您的账户和区域没有使用该名称的表，则将引发 [https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/services/dynamodb/model/ResourceNotFoundException.html](https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/services/dynamodb/model/ResourceNotFoundException.html) 异常。 **导入**。 ``` 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; ``` **代码** ``` 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 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); } System.out.println("\nDone!"); } ``` 请参阅 GitHub 上的[完整示例](https://github.com/awsdocs/aws-doc-sdk-examples/blob/0b1785e42949ebf959eaa0f0da4dc2a48f92ea25/javav2/example_code/dynamodb/src/main/java/com/example/dynamodb/DescribeTable.java)。 ## 修改（更新）表 您可以通过调用 `DynamoDbClient’s` `updateTable` 方法随时修改表的预置吞吐量值。 **注意** 如果您的账户和区域没有使用该名称的表，则将引发 [ResourceNotFoundException](https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/services/dynamodb/model/ResourceNotFoundException.html) 异常。 **导入**。 ``` 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; ``` **代码** ``` 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); } System.out.println("Done!"); } ``` 请参阅 GitHub 上的[完整示例](https://github.com/awsdocs/aws-doc-sdk-examples/blob/0b1785e42949ebf959eaa0f0da4dc2a48f92ea25/javav2/example_code/dynamodb/src/main/java/com/example/dynamodb/UpdateTable.java)。 ## 删除表 要删除表，请调用 `DynamoDbClient’s` `deleteTable` 方法并提供表名称。 **注意** 如果您的账户和区域没有使用该名称的表，则将引发 [ResourceNotFoundException](https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/services/dynamodb/model/ResourceNotFoundException.html) 异常。 **导入**。 ``` 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; ``` **代码** ``` 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); } System.out.println(tableName +" was successfully deleted!"); } ``` 请参阅 GitHub 上的[完整示例](https://github.com/awsdocs/aws-doc-sdk-examples/blob/0b1785e42949ebf959eaa0f0da4dc2a48f92ea25/javav2/example_code/dynamodb/src/main/java/com/example/dynamodb/DeleteTable.java)。 ## 更多信息 + 《Amazon DynamoDB 开发人员指南》中的[表处理准则](https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/GuidelinesForTables.html) + 《Amazon DynamoDB 开发人员指南》中的[处理 DynamoDB 中的表](https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/WorkingWithTables.html)