HTTP clients - Amazon SDK for Java 2.x
Available clientsClient recommendationsSmart defaults
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HTTP clients

You can change the HTTP client to use for your service client as well as change the default configuration for HTTP clients with the Amazon SDK for Java 2.x. This section discusses HTTP clients and settings for the SDK.

HTTP clients available in the SDK for Java

Synchronous clients

Synchronous HTTP clients in the SDK for Java implement the SdkHttpClient interface. A synchronous service client, such as the S3Client or the DynamoDbClient, requires the use of a synchronous HTTP client. The Amazon SDK for Java offers three synchronous HTTP clients.

ApacheHttpClient (default)

ApacheHttpClient is the default HTTP client for synchronous service clients. For information about configuring the ApacheHttpClient, see Configure the Apache-based HTTP client.

AwsCrtHttpClient

AwsCrtHttpClient provides high throughput and non-blocking IO. It is built on the Amazon Common Runtime (CRT) Http Client. For information about configuring the AwsCrtHttpClient and using it with service clients, see Configure Amazon CRT-based HTTP clients.

UrlConnectionHttpClient

To minimize the number of jars and third-party libraries you application uses, you can use the UrlConnectionHttpClient. For information about configuring the UrlConnectionHttpClient, see Configure the URLConnection-based HTTP client.

Asynchronous clients

Asynchronous HTTP clients in the SDK for Java implement the SdkAsyncHttpClient interface. An asynchronous service client, such as the S3AsyncClient or the DynamoDbAsyncClient, requires the use of an asynchronous HTTP client. The Amazon SDK for Java offers two asynchronous HTTP clients.

NettyNioAsyncHttpClient (default)

NettyNioAsyncHttpClient is the default HTTP client used by asynchronous clients. For information about configuring the NettyNioAsyncHttpClient, see Configure the Netty-based HTTP client.

AwsCrtAsyncHttpClient

The AwsCrtAsyncHttpClient is based on the Amazon Common Runtime (CRT) HTTP Client. For information about configuring the AwsCrtAsyncHttpClient, see Configure Amazon CRT-based HTTP clients.

HTTP client recommendations

Several factors come into play when you choose an HTTP client implementation. Use the following information to help you decide.

Recommendation flowchart

The following flowchart provides general guidance to help you determine which HTTP client to use.

Flowchart of HTTP client recommendations.

HTTP client comparison

The following table provides detailed information for each HTTP client.

HTTP client Sync or async When to use Limitation/drawback
Apache-based HTTP client

(default sync HTTP client)

 Sync Use it if you prefer low latency over high throughput Slower startup time compared to other HTTP clients
URLConnection-based HTTP client Sync Use it if you have a hard requirement for limiting third-party dependencies Does not support the HTTP PATCH method, required by some APIS like Amazon APIGateway Update operations
Amazon CRT-based sync HTTP client1 Sync

• Use it if your application is running in Amazon Lambda

• Use it if you prefer high throughput over low latency

• Use it if you prefer sync SDK clients

 N/A
Netty-based HTTP client

(default async HTTP client)

 Async

• Use it if your application invokes APIs that require HTTP/2 support such as Kinesis API SubscribeToShard

 Slower startup time compared to other HTTP clients
Amazon CRT-based async HTTP client1 Async

• Use it if your application is running in Amazon Lambda

• Use it if you prefer high throughput over low latency

• Use it if you prefer async SDK clients

• Does not support service clients that require HTTP/2 support such as KinesisAsynClient and TranscribeStreamingAsyncClient

1Because of their added benefits, we recommend that you use the Amazon CRT-based HTTP clients if possible.

Smart configuration defaults

The Amazon SDK for Java 2.x (version 2.17.102 or later) offers a smart configuration defaults feature. This feature optimizes two HTTP client properties along with other properties that don't affect the HTTP client.

The smart configuration defaults set sensible values for the connectTimeoutInMillis and tlsNegotiationTimeoutInMillis properties based on a defaults mode value that you provide. You choose the defaults mode value based on your application's characteristics.

For more information about smart configuration defaults and how to choose the defaults mode value that is best suited for your applications, see the Amazon SDKs and Tools Reference Guide.

Following are four ways to set the defaults mode for your application.

Service client

Use the service client builder to configure the defaults mode directly on the service client. The following example sets the defaults mode to auto for the DynamoDbClient.

DynamoDbClient ddbClient = DynamoDbClient.builder()
                            .defaultsMode(DefaultsMode.AUTO)
                            .build();
System property

You can use the aws.defaultsMode system property to specify the defaults mode. If you set the system property in Java, you need to set the property before initializing any service client.

The following example shows you how to set the defaults mode to auto using a system property set in Java.

System.setProperty("aws.defaultsMode", "auto");

The following example demonstrates how you set the defaults mode to auto using a -D option of the java command.

java -Daws.defaultsMode=auto
Environment variable

Set a value for environment variable Amazon_DEFAULTS_MODE to select the defaults mode for your application.

The following information shows the command to run to set the value for the defaults mode to auto using an environment variable.

Operating system Command to set environment variables

Linux, macOS, or Unix

 export Amazon_DEFAULTS_MODE=auto

Windows

 set Amazon_DEFAULTS_MODE=auto
Amazon config file

You can add a defaults_mode configuration property to the shared Amazon config file as the following example shows.

[default]
defaults_mode = auto

If you set the defaults mode globally with the system property, environment variable, or Amazon config file, you can override the settings when you build an HTTP client.

When you build an HTTP client with the httpClientBuilder() method, settings apply only to the instance that you are building. An example of this is shown here. The Netty-based HTTP client in this example overrides any default mode values set globally for connectTimeoutInMillis and tlsNegotiationTimeoutInMillis.