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Example: Put, Get, Update, and Delete an Item Using the AWS SDK for Java Low-Level API
The following Java code example illustrates CRUD operations on an item. The example creates an item, retrieves it, performs various updates, and finally deletes the item.
Note
This code example assumes that you have already loaded data into Amazon DynamoDB for your account by following the instructions in the Getting Started section. Alternatively, you can load the data programmatically using the instructions in the Creating Example Tables and Uploading Data Using the AWS SDK for Java Low-Level API topic.
For step-by-step instructions to run the following example, see Running Java Examples for Amazon DynamoDB.
import java.io.IOException;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
import com.amazonaws.AmazonServiceException;
import com.amazonaws.auth.AWSCredentials;
import com.amazonaws.auth.PropertiesCredentials;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDBClient;
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.ConditionalCheckFailedException;
import com.amazonaws.services.dynamodbv2.model.DeleteItemRequest;
import com.amazonaws.services.dynamodbv2.model.DeleteItemResult;
import com.amazonaws.services.dynamodbv2.model.ExpectedAttributeValue;
import com.amazonaws.services.dynamodbv2.model.GetItemRequest;
import com.amazonaws.services.dynamodbv2.model.GetItemResult;
import com.amazonaws.services.dynamodbv2.model.PutItemRequest;
import com.amazonaws.services.dynamodbv2.model.PutItemResult;
import com.amazonaws.services.dynamodbv2.model.ReturnValue;
import com.amazonaws.services.dynamodbv2.model.UpdateItemRequest;
import com.amazonaws.services.dynamodbv2.model.UpdateItemResult;
public class LowLevelItemCRUDExample {
static AmazonDynamoDBClient client;
static String tableName = "ProductCatalog";
public static void main(String[] args) throws IOException {
createClient();
createItems();
retrieveItem();
// Perform various updates.
updateMultipleAttributes();
updateAddNewAttribute();
updateExistingAttributeConditionally();
// Delete the item.
deleteItem();
}
private static void createClient() throws IOException {
AWSCredentials credentials = new PropertiesCredentials(
LowLevelItemCRUDExample.class.getResourceAsStream("AwsCredentials.properties"));
client = new AmazonDynamoDBClient(credentials);
}
private static void createItems() {
try {
Map<String, AttributeValue> item1 = new HashMap<String, AttributeValue>();
item1.put("Id", new AttributeValue().withN("120"));
item1.put("Title", new AttributeValue().withS("Book 120 Title"));
item1.put("ISBN", new AttributeValue().withS("120-1111111111"));
item1.put("Authors", new AttributeValue()
.withSS(Arrays.asList("Author12", "Author22")));
item1.put("Price", new AttributeValue().withN("20.00"));
item1.put("Category", new AttributeValue().withS("Book"));
item1.put("Dimensions", new AttributeValue().withS("8.5x11.0x.75"));
item1.put("InPublication", new AttributeValue().withN("0")); // false
PutItemRequest putItemRequest1 = new PutItemRequest()
.withTableName(tableName)
.withItem(item1);
PutItemResult result1 = client.putItem(putItemRequest1);
Map<String, AttributeValue> item2 = new HashMap<String, AttributeValue>();
item2.put("Id", new AttributeValue().withN("121"));
item2.put("Title", new AttributeValue().withS("Book 121 Title"));
item2.put("ISBN", new AttributeValue().withS("121-1111111111"));
item2.put("Price", new AttributeValue().withN("20.00"));
item2.put("ProductCategory", new AttributeValue().withS("Book"));
item2.put("Authors", new AttributeValue()
.withSS(Arrays.asList("Author21", "Author22")));
item1.put("Dimensions", new AttributeValue().withS("8.5x11.0x.75"));
item1.put("InPublication", new AttributeValue().withN("1"));
PutItemRequest putItemRequest2 = new PutItemRequest()
.withTableName(tableName)
.withItem(item2);
PutItemResult result2 = client.putItem(putItemRequest2);
} catch (AmazonServiceException ase) {
System.err.println("Create items failed.");
}
}
private static void retrieveItem() {
try {
HashMap<String, AttributeValue> key = new HashMap<String, AttributeValue>();
key.put("Id", new AttributeValue().withN("120"));
GetItemRequest getItemRequest = new GetItemRequest()
.withTableName(tableName)
.withKey(key)
.withAttributesToGet(Arrays.asList("Id", "ISBN", "Title", "Authors"));
GetItemResult result = client.getItem(getItemRequest);
// Check the response.
System.out.println("Printing item after retrieving it....");
printItem(result.getItem());
} catch (AmazonServiceException ase) {
System.err.println("Failed to retrieve item in " + tableName);
}
}
private static void updateAddNewAttribute() {
try {
Map<String, AttributeValueUpdate> updateItems =
new HashMap<String, AttributeValueUpdate>();
HashMap<String, AttributeValue> key = new HashMap<String, AttributeValue>();
key.put("Id", new AttributeValue().withN("121"));
updateItems.put("NewAttribute",
new AttributeValueUpdate()
.withValue(new AttributeValue().withS("Some Value")));
ReturnValue returnValues = ReturnValue.ALL_NEW;
UpdateItemRequest updateItemRequest = new UpdateItemRequest()
.withTableName(tableName)
.withKey(key)
.withAttributeUpdates(updateItems)
.withReturnValues(returnValues);
UpdateItemResult result = client.updateItem(updateItemRequest);
// Check the response.
System.out.println("Printing item after adding new attribute...");
printItem(result.getAttributes());
} catch (AmazonServiceException ase) {
System.err.println("Failed to add new attribute in " + tableName);
}
}
private static void updateMultipleAttributes() {
try {
Map<String, AttributeValueUpdate> updateItems =
new HashMap<String, AttributeValueUpdate>();
HashMap<String, AttributeValue> key = new HashMap<String, AttributeValue>();
key.put("Id", new AttributeValue().withN("120"));
// Add two new authors to the list.
updateItems.put("Authors",
new AttributeValueUpdate()
.withAction(AttributeAction.ADD)
.withValue(new AttributeValue().withSS("Author YY", "Author ZZ")));
// Add a new attribute.
updateItems.put("NewAttribute",
new AttributeValueUpdate()
.withValue(new AttributeValue().withS("someValue")));
ReturnValue returnValues = ReturnValue.ALL_NEW;
UpdateItemRequest updateItemRequest = new UpdateItemRequest()
.withTableName(tableName)
.withKey(key)
.withAttributeUpdates(updateItems)
.withReturnValues(returnValues);
UpdateItemResult result = client.updateItem(updateItemRequest);
// Check the response.
System.out.println("Printing item after multiple attribute update...");
printItem(result.getAttributes());
} catch (AmazonServiceException ase) {
System.err.println("Failed to update multiple attributes in " + tableName);
}
}
private static void updateExistingAttributeConditionally() {
try {
Map<String, AttributeValueUpdate> updateItems = new HashMap<String, AttributeValueUpdate>();
Map<String, ExpectedAttributeValue> expectedValues = new HashMap<String, ExpectedAttributeValue>();
HashMap<String, AttributeValue> key = new HashMap<String, AttributeValue>();
key.put("Id", new AttributeValue().withN("120"));
// Specify the desired price - 25.00
updateItems.put("Price",
new AttributeValueUpdate()
.withAction(AttributeAction.PUT)
.withValue(new AttributeValue().withN("25.00")));
// This updates the price only if current price is 20.00.
expectedValues.put("Price",
new ExpectedAttributeValue()
.withValue(new AttributeValue().withN("20.00")));
ReturnValue returnValues = ReturnValue.ALL_NEW;
UpdateItemRequest updateItemRequest = new UpdateItemRequest()
.withTableName(tableName)
.withKey(key)
.withAttributeUpdates(updateItems)
.withExpected(expectedValues)
.withReturnValues(returnValues);
UpdateItemResult result = client.updateItem(updateItemRequest);
// Check the response.
System.out.println("Printing item after conditional update to new attribute...");
printItem(result.getAttributes());
} catch (ConditionalCheckFailedException cse) {
// Reload object and retry code.
System.err.println("Conditional check failed in " + tableName);
} catch (AmazonServiceException ase) {
System.err.println("Error updating item in " + tableName);
}
}
private static void deleteItem() {
try {
Map<String, ExpectedAttributeValue> expectedValues = new HashMap<String, ExpectedAttributeValue>();
HashMap<String, AttributeValue> key = new HashMap<String, AttributeValue>();
key.put("Id", new AttributeValue().withN("120"));
expectedValues.put("InPublication",
new ExpectedAttributeValue()
.withValue(new AttributeValue().withN("0"))); // Boolean stored as 0 or 1.
ReturnValue returnValues = ReturnValue.ALL_OLD;
DeleteItemRequest deleteItemRequest = new DeleteItemRequest()
.withTableName(tableName)
.withKey(key)
.withExpected(expectedValues)
.withReturnValues(returnValues);
DeleteItemResult result = client.deleteItem(deleteItemRequest);
// Check the response.
System.out.println("Printing item that was deleted...");
printItem(result.getAttributes());
} catch (AmazonServiceException ase) {
System.err.println("Failed to get item after deletion " + tableName);
}
}
private static void printItem(Map<String, AttributeValue> attributeList) {
for (Map.Entry<String, AttributeValue> item : attributeList.entrySet()) {
String attributeName = item.getKey();
AttributeValue value = item.getValue();
System.out.println(attributeName + " "
+ (value.getS() == null ? "" : "S=[" + value.getS() + "]")
+ (value.getN() == null ? "" : "N=[" + value.getN() + "]")
+ (value.getB() == null ? "" : "B=[" + value.getB() + "]")
+ (value.getSS() == null ? "" : "SS=[" + value.getSS() + "]")
+ (value.getNS() == null ? "" : "NS=[" + value.getNS() + "]")
+ (value.getBS() == null ? "" : "BS=[" + value.getBS() + "] \n"));
}
}
}
