Client Management

/**
 * Abstract base class for all AWS service client builders
 * @param <Subclass> The concrete builder subclass
 * @param <TypeToBuild> The service client type to build
 */
public abstract class AwsClientBuilder<Subclass extends AwsClientBuilder<Subclass, TypeToBuild>, TypeToBuild> {
    /**
     * Creates a new builder instance with default configuration
     * @return New builder instance
     */
    public static AwsClientBuilder<?, ?> standard();
    
    /**
     * Sets the credentials provider for the client
     * @param credentialsProvider Credentials provider implementation
     * @return Builder instance for method chaining
     */
    public Subclass withCredentials(AWSCredentialsProvider credentialsProvider);
    
    /**
     * Sets the AWS region for the client
     * @param region AWS region enum value
     * @return Builder instance for method chaining
     */
    public Subclass withRegion(Regions region);
    
    /**
     * Sets the client configuration for HTTP settings
     * @param clientConfiguration Configuration container
     * @return Builder instance for method chaining
     */
    public Subclass withClientConfiguration(ClientConfiguration clientConfiguration);
    
    /**
     * Sets a custom endpoint configuration
     * @param endpointConfiguration Custom endpoint and signing region
     * @return Builder instance for method chaining
     */
    public Subclass withEndpointConfiguration(EndpointConfiguration endpointConfiguration);
    
    /**
     * Builds the immutable service client instance
     * @return Configured service client
     */
    public TypeToBuild build();
}

/**
 * Custom endpoint configuration for non-standard endpoints
 */
public static class EndpointConfiguration {
    public EndpointConfiguration(String serviceEndpoint, String signingRegion);
    public String getServiceEndpoint();
    public String getSigningRegion();
}

import com.amazonaws.services.s3.AmazonS3ClientBuilder;
import com.amazonaws.regions.Regions;
import com.amazonaws.auth.DefaultAWSCredentialsProviderChain;

// Standard client creation
AmazonS3 s3Client = AmazonS3ClientBuilder.standard()
    .withCredentials(new DefaultAWSCredentialsProviderChain())
    .withRegion(Regions.US_WEST_2)
    .build();

// Default client (uses default credential chain and region detection)
AmazonS3 defaultS3Client = AmazonS3ClientBuilder.defaultClient();

// Custom endpoint configuration
AmazonS3 customS3Client = AmazonS3ClientBuilder.standard()
    .withEndpointConfiguration(new EndpointConfiguration(
        "https://s3.custom-domain.com", 
        "us-west-2"
    ))
    .build();

/**
 * Configuration container for AWS service clients
 */
public class ClientConfiguration {
    /**
     * Creates a new client configuration with default settings
     */
    public ClientConfiguration();
    
    /**
     * Sets the connection timeout in milliseconds (default: 10000)
     * @param connectionTimeout Timeout for establishing connections
     */
    public void setConnectionTimeout(int connectionTimeout);
    public int getConnectionTimeout();
    
    /**
     * Sets the socket timeout in milliseconds (default: 50000)
     * @param socketTimeout Timeout for socket read operations
     */
    public void setSocketTimeout(int socketTimeout);
    public int getSocketTimeout();
    
    /**
     * Sets the maximum number of HTTP connections (default: 50)
     * @param maxConnections Maximum concurrent connections
     */
    public void setMaxConnections(int maxConnections);
    public int getMaxConnections();
    
    /**
     * Sets the retry policy for failed requests
     * @param retryPolicy Retry policy implementation
     */
    public void setRetryPolicy(RetryPolicy retryPolicy);
    public RetryPolicy getRetryPolicy();
    
    /**
     * Configures proxy server settings
     */
    public void setProxyHost(String proxyHost);
    public String getProxyHost();
    public void setProxyPort(int proxyPort);
    public int getProxyPort();
    public void setProxyUsername(String proxyUsername);
    public String getProxyUsername();
    public void setProxyPassword(String proxyPassword);
    public String getProxyPassword();
    
    /**
     * Sets custom user agent string
     * @param userAgent Custom user agent identifier
     */
    public void setUserAgent(String userAgent);
    public String getUserAgent();
    
    /**
     * Configures SSL/TLS settings
     */
    public void setProtocol(Protocol protocol);
    public Protocol getProtocol();
}

/**
 * Protocol enumeration for HTTP/HTTPS
 */
public enum Protocol {
    HTTP, HTTPS
}

import com.amazonaws.ClientConfiguration;
import com.amazonaws.retry.RetryPolicy;

// Custom configuration
ClientConfiguration config = new ClientConfiguration();
config.setConnectionTimeout(15000);  // 15 seconds
config.setSocketTimeout(60000);      // 60 seconds
config.setMaxConnections(100);       // 100 concurrent connections
config.setRetryPolicy(RetryPolicy.DEFAULT_BACKOFF_STRATEGY);

// Proxy configuration
config.setProxyHost("proxy.company.com");
config.setProxyPort(8080);
config.setProxyUsername("user");
config.setProxyPassword("password");

// Use with client builder
AmazonS3 s3Client = AmazonS3ClientBuilder.standard()
    .withClientConfiguration(config)
    .build();

/**
 * Abstract base class for all AWS service clients
 */
public abstract class AmazonWebServiceClient {
    /**
     * Sets the AWS region for this client
     * @param region AWS region for service endpoints
     */
    public void setRegion(Region region);
    
    /**
     * Sets a custom service endpoint
     * @param endpoint Custom endpoint URL
     */
    public void setEndpoint(String endpoint);
    
    /**
     * Shuts down the client and releases resources
     * Call this method when done using the client
     */
    public void shutdown();
    
    /**
     * Gets the service name for this client
     * @return AWS service name
     */
    public abstract String getServiceName();
}

/**
 * Retry policy interface for controlling request retry behavior
 */
public interface RetryPolicy {
    /**
     * Determines if a request should be retried
     * @param originalRequest The original request
     * @param exception The exception that occurred
     * @param retriesAttempted Number of retries already attempted
     * @return true if the request should be retried
     */
    boolean shouldRetry(AmazonWebServiceRequest originalRequest, 
                       AmazonServiceException exception, 
                       int retriesAttempted);
    
    /**
     * Calculates the delay before the next retry attempt
     * @param originalRequest The original request
     * @param exception The exception that occurred
     * @param retriesAttempted Number of retries already attempted
     * @return Delay in milliseconds
     */
    long getDelayBeforeNextRetry(AmazonWebServiceRequest originalRequest,
                                AmazonServiceException exception,
                                int retriesAttempted);
    
    /** Default retry policy with exponential backoff */
    RetryPolicy DEFAULT = new DefaultRetryPolicy();
    
    /** No retry policy */
    RetryPolicy NO_RETRY = new NoRetryPolicy();
}

import com.amazonaws.retry.RetryPolicy;
import com.amazonaws.retry.PredefinedRetryPolicies;

// Use default retry policy
ClientConfiguration config = new ClientConfiguration();
config.setRetryPolicy(RetryPolicy.DEFAULT);

// Use custom retry policy with higher retry count
RetryPolicy customRetry = PredefinedRetryPolicies.getDefaultRetryPolicyWithCustomMaxRetries(5);
config.setRetryPolicy(customRetry);

// Disable retries
config.setRetryPolicy(RetryPolicy.NO_RETRY);

/**
 * AWS region representation
 */
public class Region {
    public static Region getRegion(Regions region);
    public String getName();
    public String getDomain();
}

/**
 * Request metrics collector interface
 */
public interface RequestMetricCollector {
    void collectMetrics(Request<?> request, Response<?> response);
}

/**
 * Progress listener for tracking request progress
 */
public interface ProgressListener {
    void progressChanged(ProgressEvent progressEvent);
}