Amazon DynamoDB
开发人员指南 (API Version 2012-08-10)
AWS 服务或AWS文档中描述的功能,可能因地区/位置而异。点 击 Getting Started with Amazon AWS to see specific differences applicable to the China (Beijing) Region.

示例:使用 AWS SDK for Java 文档 API 的 CRUD 操作

以下代码示例介绍对项目的 CRUD 操作。该示例创建一个项目、对其进行检索、执行多种更新,最终删除项目。

注意

适用于 Java 的开发工具包 还提供一个对象持久化模型,可用来将客户端类映射到 DynamoDB 表。该方法可以减少您必须编写的代码数量。有关更多信息,请参阅 Java:DynamoDBMapper

注意

此代码示例假定您已按照 创建表并加载示例数据 部分的说明,为您的账户将数据加载到了 DynamoDB 中。

有关运行以下示例的分步说明,请参阅 Java 代码示例

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// Copyright 2012-2015 Amazon.com, Inc. or its affiliates. All Rights Reserved. // Licensed under the Apache License, Version 2.0. package com.amazonaws.codesamples.document; import java.io.IOException; import java.util.Arrays; import java.util.HashMap; import java.util.HashSet; import java.util.Map; import com.amazonaws.services.dynamodbv2.AmazonDynamoDB; import com.amazonaws.services.dynamodbv2.AmazonDynamoDBClientBuilder; import com.amazonaws.services.dynamodbv2.document.DeleteItemOutcome; import com.amazonaws.services.dynamodbv2.document.DynamoDB; import com.amazonaws.services.dynamodbv2.document.Item; import com.amazonaws.services.dynamodbv2.document.Table; import com.amazonaws.services.dynamodbv2.document.UpdateItemOutcome; import com.amazonaws.services.dynamodbv2.document.spec.DeleteItemSpec; import com.amazonaws.services.dynamodbv2.document.spec.UpdateItemSpec; import com.amazonaws.services.dynamodbv2.document.utils.NameMap; import com.amazonaws.services.dynamodbv2.document.utils.ValueMap; import com.amazonaws.services.dynamodbv2.model.ReturnValue; public class DocumentAPIItemCRUDExample { static AmazonDynamoDB client = AmazonDynamoDBClientBuilder.standard().build(); static DynamoDB dynamoDB = new DynamoDB(client); static String tableName = "ProductCatalog"; public static void main(String[] args) throws IOException { createItems(); retrieveItem(); // Perform various updates. updateMultipleAttributes(); updateAddNewAttribute(); updateExistingAttributeConditionally(); // Delete the item. deleteItem(); } private static void createItems() { Table table = dynamoDB.getTable(tableName); try { Item item = new Item().withPrimaryKey("Id", 120).withString("Title", "Book 120 Title") .withString("ISBN", "120-1111111111") .withStringSet("Authors", new HashSet<String>(Arrays.asList("Author12", "Author22"))) .withNumber("Price", 20).withString("Dimensions", "8.5x11.0x.75").withNumber("PageCount", 500) .withBoolean("InPublication", false).withString("ProductCategory", "Book"); table.putItem(item); item = new Item().withPrimaryKey("Id", 121).withString("Title", "Book 121 Title") .withString("ISBN", "121-1111111111") .withStringSet("Authors", new HashSet<String>(Arrays.asList("Author21", "Author 22"))) .withNumber("Price", 20).withString("Dimensions", "8.5x11.0x.75").withNumber("PageCount", 500) .withBoolean("InPublication", true).withString("ProductCategory", "Book"); table.putItem(item); } catch (Exception e) { System.err.println("Create items failed."); System.err.println(e.getMessage()); } } private static void retrieveItem() { Table table = dynamoDB.getTable(tableName); try { Item item = table.getItem("Id", 120, "Id, ISBN, Title, Authors", null); System.out.println("Printing item after retrieving it...."); System.out.println(item.toJSONPretty()); } catch (Exception e) { System.err.println("GetItem failed."); System.err.println(e.getMessage()); } } private static void updateAddNewAttribute() { Table table = dynamoDB.getTable(tableName); try { UpdateItemSpec updateItemSpec = new UpdateItemSpec().withPrimaryKey("Id", 121) .withUpdateExpression("set #na = :val1").withNameMap(new NameMap().with("#na", "NewAttribute")) .withValueMap(new ValueMap().withString(":val1", "Some value")).withReturnValues(ReturnValue.ALL_NEW); UpdateItemOutcome outcome = table.updateItem(updateItemSpec); // Check the response. System.out.println("Printing item after adding new attribute..."); System.out.println(outcome.getItem().toJSONPretty()); } catch (Exception e) { System.err.println("Failed to add new attribute in " + tableName); System.err.println(e.getMessage()); } } private static void updateMultipleAttributes() { Table table = dynamoDB.getTable(tableName); try { UpdateItemSpec updateItemSpec = new UpdateItemSpec().withPrimaryKey("Id", 120) .withUpdateExpression("add #a :val1 set #na=:val2") .withNameMap(new NameMap().with("#a", "Authors").with("#na", "NewAttribute")) .withValueMap( new ValueMap().withStringSet(":val1", "Author YY", "Author ZZ").withString(":val2", "someValue")) .withReturnValues(ReturnValue.ALL_NEW); UpdateItemOutcome outcome = table.updateItem(updateItemSpec); // Check the response. System.out.println("Printing item after multiple attribute update..."); System.out.println(outcome.getItem().toJSONPretty()); } catch (Exception e) { System.err.println("Failed to update multiple attributes in " + tableName); System.err.println(e.getMessage()); } } private static void updateExistingAttributeConditionally() { Table table = dynamoDB.getTable(tableName); try { // Specify the desired price (25.00) and also the condition (price = // 20.00) UpdateItemSpec updateItemSpec = new UpdateItemSpec().withPrimaryKey("Id", 120) .withReturnValues(ReturnValue.ALL_NEW).withUpdateExpression("set #p = :val1") .withConditionExpression("#p = :val2").withNameMap(new NameMap().with("#p", "Price")) .withValueMap(new ValueMap().withNumber(":val1", 25).withNumber(":val2", 20)); UpdateItemOutcome outcome = table.updateItem(updateItemSpec); // Check the response. System.out.println("Printing item after conditional update to new attribute..."); System.out.println(outcome.getItem().toJSONPretty()); } catch (Exception e) { System.err.println("Error updating item in " + tableName); System.err.println(e.getMessage()); } } private static void deleteItem() { Table table = dynamoDB.getTable(tableName); try { DeleteItemSpec deleteItemSpec = new DeleteItemSpec().withPrimaryKey("Id", 120) .withConditionExpression("#ip = :val").withNameMap(new NameMap().with("#ip", "InPublication")) .withValueMap(new ValueMap().withBoolean(":val", false)).withReturnValues(ReturnValue.ALL_OLD); DeleteItemOutcome outcome = table.deleteItem(deleteItemSpec); // Check the response. System.out.println("Printing item that was deleted..."); System.out.println(outcome.getItem().toJSONPretty()); } catch (Exception e) { System.err.println("Error deleting item in " + tableName); System.err.println(e.getMessage()); } } }