適用於 Java 的 AWS SDK 1.x 已於 2025 年 12 月 31 日end-of-support。我們建議您遷移至 [AWS SDK for Java 2.x](https://docs.aws.amazon.com/sdk-for-java/latest/developer-guide/home.html)，以繼續接收新功能、可用性改善和安全性更新。
本文為英文版的機器翻譯版本，如內容有任何歧義或不一致之處，概以英文版為準。
# 在 中使用項目 DynamoDB
在 中 DynamoDB，項目是*屬性*的集合，每個屬性都有*名稱*和*值*。屬性值可以是純量、集合或文件類型。如需詳細資訊，請參閱《 Amazon DynamoDB 開發人員指南》中的[命名規則和資料類型](https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/HowItWorks.NamingRulesDataTypes.html)。
## 從資料表擷取 (取得) 項目
呼叫 AmazonDynamoDB 的 `getItem`方法，並傳遞具有資料表名稱的 [GetItemRequest](https://docs.aws.amazon.com/sdk-for-java/v1/reference/com/amazonaws/services/dynamodbv2/model/GetItemRequest.html) 物件，以及您想要的項目主索引鍵值。它會傳回 [GetItemResult](https://docs.aws.amazon.com/sdk-for-java/v1/reference/com/amazonaws/services/dynamodbv2/model/GetItemResult.html) 物件。
您可以使用所傳回 `GetItemResult` 物件的 `getItem()` 方法來擷取與項目關聯之索引鍵 (字串) 和值的[對應](https://docs.oracle.com/javase/8/docs/api/index.html?java/util/Map.html) ([AttributeValue](https://docs.aws.amazon.com/sdk-for-java/v1/reference/com/amazonaws/services/dynamodbv2/model/AttributeValue.html)) 組。
**匯入**
```
import com.amazonaws.AmazonServiceException;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDB;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDBClientBuilder;
import com.amazonaws.services.dynamodbv2.model.AttributeValue;
import com.amazonaws.services.dynamodbv2.model.GetItemRequest;
import java.util.HashMap;
import java.util.Map;
```
**Code**
```
HashMap key_to_get =
new HashMap();
key_to_get.put("DATABASE_NAME", new AttributeValue(name));
GetItemRequest request = null;
if (projection_expression != null) {
request = new GetItemRequest()
.withKey(key_to_get)
.withTableName(table_name)
.withProjectionExpression(projection_expression);
} else {
request = new GetItemRequest()
.withKey(key_to_get)
.withTableName(table_name);
}
final AmazonDynamoDB ddb = AmazonDynamoDBClientBuilder.defaultClient();
try {
Map returned_item =
ddb.getItem(request).getItem();
if (returned_item != null) {
Set keys = returned_item.keySet();
for (String key : keys) {
System.out.format("%s: %s\n",
key, returned_item.get(key).toString());
}
} else {
System.out.format("No item found with the key %s!\n", name);
}
} catch (AmazonServiceException e) {
System.err.println(e.getErrorMessage());
System.exit(1);
```
請參閱 GitHub 上的[完整範例](https://github.com/awsdocs/aws-doc-sdk-examples/blob/master/java/example_code/dynamodb/src/main/java/aws/example/dynamodb/GetItem.java)。
## 新增項目到資料表
建立代表項目屬性的索引鍵值組[對應](https://docs.oracle.com/javase/8/docs/api/index.html?java/util/Map.html)。這些項目必須包含資料表主索引鍵欄位的值。如果主索引鍵識別的項目已存在，其欄位會透過請求*更新*。
**注意**
如果您的帳戶和區域不存在指定的資料表，會擲出 [ResourceNotFoundException](https://docs.aws.amazon.com/sdk-for-java/v1/reference/com/amazonaws/services/dynamodbv2/model/ResourceNotFoundException.html)。
**匯入**
```
import com.amazonaws.AmazonServiceException;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDB;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDBClientBuilder;
import com.amazonaws.services.dynamodbv2.model.AttributeValue;
import com.amazonaws.services.dynamodbv2.model.ResourceNotFoundException;
import java.util.ArrayList;
```
**Code**
```
HashMap item_values =
new HashMap();
item_values.put("Name", new AttributeValue(name));
for (String[] field : extra_fields) {
item_values.put(field[0], new AttributeValue(field[1]));
}
final AmazonDynamoDB ddb = AmazonDynamoDBClientBuilder.defaultClient();
try {
ddb.putItem(table_name, item_values);
} catch (ResourceNotFoundException e) {
System.err.format("Error: The table \"%s\" can't be found.\n", table_name);
System.err.println("Be sure that it exists and that you've typed its name correctly!");
System.exit(1);
} catch (AmazonServiceException e) {
System.err.println(e.getMessage());
System.exit(1);
```
請參閱 GitHub 上的[完整範例](https://github.com/awsdocs/aws-doc-sdk-examples/blob/master/java/example_code/dynamodb/src/main/java/aws/example/dynamodb/PutItem.java)。
## 更新資料表中的現有項目
您可以使用 AmazonDynamoDB 的 `updateItem`方法，提供資料表名稱、主索引鍵值和要更新的欄位映射，來更新已存在於資料表中的項目屬性。
**注意**
如果您的帳戶和區域不存在指定的資料表，或者如果您傳遞的主索引鍵所識別的項目不存在，會擲出 [ResourceNotFoundException](https://docs.aws.amazon.com/sdk-for-java/v1/reference/com/amazonaws/services/dynamodbv2/model/ResourceNotFoundException.html)。
**匯入**
```
import com.amazonaws.AmazonServiceException;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDB;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDBClientBuilder;
import com.amazonaws.services.dynamodbv2.model.AttributeAction;
import com.amazonaws.services.dynamodbv2.model.AttributeValue;
import com.amazonaws.services.dynamodbv2.model.AttributeValueUpdate;
import com.amazonaws.services.dynamodbv2.model.ResourceNotFoundException;
import java.util.ArrayList;
```
**Code**
```
HashMap item_key =
new HashMap();
item_key.put("Name", new AttributeValue(name));
HashMap updated_values =
new HashMap();
for (String[] field : extra_fields) {
updated_values.put(field[0], new AttributeValueUpdate(
new AttributeValue(field[1]), AttributeAction.PUT));
}
final AmazonDynamoDB ddb = AmazonDynamoDBClientBuilder.defaultClient();
try {
ddb.updateItem(table_name, item_key, updated_values);
} catch (ResourceNotFoundException e) {
System.err.println(e.getMessage());
System.exit(1);
} catch (AmazonServiceException e) {
System.err.println(e.getMessage());
System.exit(1);
```
請參閱 GitHub 上的[完整範例](https://github.com/awsdocs/aws-doc-sdk-examples/blob/master/java/example_code/dynamodb/src/main/java/aws/example/dynamodb/UpdateItem.java)。
## 使用 DynamoDBMapper 類別
[適用於 Java 的 AWS SDK](https://aws.amazon.com/sdk-for-java/) 提供 [DynamoDBMapper](https://docs.aws.amazon.com/sdk-for-java/v1/reference/com/amazonaws/services/dynamodbv2/datamodeling/DynamoDBMapper.html) 類別，可讓您將用戶端類別映射至 Amazon DynamoDB 資料表。若要使用 [DynamoDBMapper](https://docs.aws.amazon.com/sdk-for-java/v1/reference/com/amazonaws/services/dynamodbv2/datamodeling/DynamoDBMapper.html) 類別，您可以使用註釋 （如下列程式碼範例所示），定義 DynamoDB 資料表中項目與程式碼中對應物件執行個體之間的關係。[DynamoDBMapper](https://docs.aws.amazon.com/sdk-for-java/v1/reference/com/amazonaws/services/dynamodbv2/datamodeling/DynamoDBMapper.html) 類別可讓您存取資料表；執行各種建立、讀取、更新和刪除 (CRUD) 操作；以及執行查詢。
**注意**
[DynamoDBMapper](https://docs.aws.amazon.com/sdk-for-java/v1/reference/com/amazonaws/services/dynamodbv2/datamodeling/DynamoDBMapper.html) 類別不允許您建立、更新或刪除資料表。
**匯入**
```
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.DynamoDBTable;
import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBRangeKey;
import com.amazonaws.services.dynamodbv2.model.AmazonDynamoDBException;
```
**Code**
下列 Java 程式碼範例示範如何使用 [DynamoDBMapper](https://docs.aws.amazon.com/sdk-for-java/v1/reference/com/amazonaws/services/dynamodbv2/datamodeling/DynamoDBMapper.html) 類別將內容新增至 *Music* 資料表。將內容新增至資料表後，請注意，會使用*分割區*和*排序*索引鍵載入項目。然後，*獎勵*項目會更新。如需建立*音樂*資料表的資訊，請參閱《 Amazon DynamoDB 開發人員指南》中的[建立資料表](https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/getting-started-step-1.html)。
```
AmazonDynamoDB client = AmazonDynamoDBClientBuilder.standard().build();
MusicItems items = new MusicItems();
try{
// Add new content to the Music table
items.setArtist(artist);
items.setSongTitle(songTitle);
items.setAlbumTitle(albumTitle);
items.setAwards(Integer.parseInt(awards)); //convert to an int
// Save the item
DynamoDBMapper mapper = new DynamoDBMapper(client);
mapper.save(items);
// Load an item based on the Partition Key and Sort Key
// Both values need to be passed to the mapper.load method
String artistName = artist;
String songQueryTitle = songTitle;
// Retrieve the item
MusicItems itemRetrieved = mapper.load(MusicItems.class, artistName, songQueryTitle);
System.out.println("Item retrieved:");
System.out.println(itemRetrieved);
// Modify the Award value
itemRetrieved.setAwards(2);
mapper.save(itemRetrieved);
System.out.println("Item updated:");
System.out.println(itemRetrieved);
System.out.print("Done");
} catch (AmazonDynamoDBException e) {
e.getStackTrace();
}
}
@DynamoDBTable(tableName="Music")
public static class MusicItems {
//Set up Data Members that correspond to columns in the Music table
private String artist;
private String songTitle;
private String albumTitle;
private int awards;
@DynamoDBHashKey(attributeName="Artist")
public String getArtist() {
return this.artist;
}
public void setArtist(String artist) {
this.artist = artist;
}
@DynamoDBRangeKey(attributeName="SongTitle")
public String getSongTitle() {
return this.songTitle;
}
public void setSongTitle(String title) {
this.songTitle = title;
}
@DynamoDBAttribute(attributeName="AlbumTitle")
public String getAlbumTitle() {
return this.albumTitle;
}
public void setAlbumTitle(String title) {
this.albumTitle = title;
}
@DynamoDBAttribute(attributeName="Awards")
public int getAwards() {
return this.awards;
}
public void setAwards(int awards) {
this.awards = awards;
}
}
```
請參閱 GitHub 上的[完整範例](https://github.com/awsdocs/aws-doc-sdk-examples/blob/master/java/example_code/dynamodb/src/main/java/aws/example/dynamodb/UseDynamoMapping.java)。
## 詳細資訊
+ 《 Amazon DynamoDB 開發人員指南》中的[使用項目的指導方針](https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/GuidelinesForItems.html)
+ 《 Amazon DynamoDB 開發人員指南》中的[使用 中的項目 DynamoDB](https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/WorkingWithItems.html)