AWS Lambda Starter & Consistency Models

spring-boot-starter-aws-lambda/src/main/java/amazon/aws/AWSLambdaConfigurerAdapter.java

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+package amazon.aws;
+
+import com.amazonaws.auth.*;
+import com.amazonaws.services.lambda.AWSLambdaClientBuilder;
+import com.amazonaws.services.lambda.invoke.LambdaInvokerFactory;
+import com.amazonaws.services.securitytoken.AWSSecurityTokenServiceClient;
+import com.amazonaws.services.securitytoken.model.Credentials;
+import com.amazonaws.services.securitytoken.model.GetSessionTokenRequest;
+import org.springframework.stereotype.Component;
+
+import java.util.Date;
+
+/**
+ * This class is a client for interacting with Amazon S3 bucket resources.
+ *
+ * @author kbastani
+ */
+@Component
+public class AWSLambdaConfigurerAdapter {
+
+    private String accessKeyId;
+    private String accessKeySecret;
+    private Credentials sessionCredentials;
+
+    /**
+     * Create a new instance of the {@link AWSLambdaConfigurerAdapter} with the bucket name and access credentials
+     *
+     * @param accessKeyId     is the access key id credential for the specified bucket name
+     * @param accessKeySecret is the access key secret for the specified bucket name
+     */
+    public AWSLambdaConfigurerAdapter(String accessKeyId,
+                                      String accessKeySecret) {
+        this.accessKeyId = accessKeyId;
+        this.accessKeySecret = accessKeySecret;
+    }
+
+    /**
+     * Gets an instance of a function interface
+     * @param type
+     * @param <T>
+     * @return
+     */
+    public <T> T getFunctionInstance(Class<T> type) {
+        return LambdaInvokerFactory.builder()
+                .lambdaClient(AWSLambdaClientBuilder.standard()
+                        .withCredentials(new AWSStaticCredentialsProvider(
+                                getBasicSessionCredentials()))
+                        .build())
+                .build(type);
+    }
+
+    /**
+     * Get the basic session credentials for the template's configured IAM authentication keys
+     *
+     * @return a {@link BasicSessionCredentials} instance with a valid authenticated session token
+     */
+    private BasicSessionCredentials getBasicSessionCredentials() {
+
+        // Create a new session token if the session is expired or not initialized
+        if (sessionCredentials == null || sessionCredentials.getExpiration().before(new Date()))
+            sessionCredentials = getSessionCredentials();
+
+        // Create basic session credentials using the generated session token
+        return new BasicSessionCredentials(sessionCredentials.getAccessKeyId(),
+                sessionCredentials.getSecretAccessKey(),
+                sessionCredentials.getSessionToken());
+    }
+
+    /**
+     * Creates a new session credential that is valid for 12 hours
+     *
+     * @return an authenticated {@link Credentials} for the new session token
+     */
+    private Credentials getSessionCredentials() {
+        // Create a new session with the user credentials for the service instance
+        AWSSecurityTokenServiceClient stsClient =
+                new AWSSecurityTokenServiceClient(new BasicAWSCredentials(accessKeyId, accessKeySecret));
+
+        // Start a new session for managing a service instance's bucket
+        GetSessionTokenRequest getSessionTokenRequest =
+                new GetSessionTokenRequest().withDurationSeconds(43200);
+
+        // Get the session token for the service instance's bucket
+        sessionCredentials = stsClient.getSessionToken(getSessionTokenRequest).getCredentials();
+
+        return sessionCredentials;
+    }
+}