Execute AWS CLI Commands from Java: A Step-by-Step Guide (2026)

Interacting with AWS services programmatically is a common requirement for developers working in cloud environments. While AWS SDKs provide a robust way to interact with AWS services, sometimes you might need to execute AWS CLI commands directly from your Java code to leverage specific CLI functionalities or scripts. This tutorial will guide you through executing AWS CLI commands from Java, focusing on retrieving the size of an S3 bucket, a common task for managing cloud storage costs and performance.

Key Takeaways

• Learn how to execute AWS CLI commands within Java applications.
• Understand the prerequisites needed for executing shell commands from Java.
• Retrieve and process AWS S3 bucket data using CLI commands from Java.
• Handle common errors and troubleshooting tips for seamless execution.

Executing AWS CLI commands from a Java application allows for greater flexibility and can be a simpler alternative when the AWS SDK does not cover specific functionalities. This tutorial will walk you through each step of setting up and executing the `aws s3api list-objects` command from Java, which will list objects in an S3 bucket and calculate their total size. This knowledge is particularly useful for managing and optimizing your AWS resources programmatically.

Prerequisites

• Java Development Kit (JDK) 11 or later installed on your machine.
• AWS CLI version 2 installed and configured with appropriate access permissions.
• Basic knowledge of Java programming and familiarity with AWS services, particularly S3.

Step 1: Install and Configure AWS CLI

Before executing CLI commands from Java, ensure that the AWS CLI is installed and configured properly on your machine. If you haven't installed it yet, you can download it from the official AWS CLI website. Once installed, configure it using:

aws configure

This command will prompt you to enter your AWS Access Key, Secret Key, region, and output format. These credentials must have permissions for S3 actions.

Step 2: Set Up Your Java Project

Create a new Java project using your preferred IDE (such as IntelliJ IDEA or Eclipse). Ensure your project is set up for JDK 11 or later. You can create a Maven or Gradle project if you prefer dependency management.

Step 3: Write Java Code to Execute AWS CLI Command

In your Java project, you'll create a Java class that executes the AWS CLI command to retrieve S3 bucket size. Below is a simple example of how you can achieve this:

import java.io.BufferedReader;
import java.io.InputStreamReader;

public class AwsCliExecutor {
    public static void main(String[] args) {
        String bucketName = "your-bucket-name";
        String command = "aws s3api list-objects --bucket " + bucketName + " --output json --query '[sum(Contents[].Size), length(Contents[])]'";

        try {
            Process process = Runtime.getRuntime().exec(command);
            BufferedReader reader = new BufferedReader(new InputStreamReader(process.getInputStream()));
            String line;
            while ((line = reader.readLine()) != null) {
                System.out.println(line);
            }
            int exitCode = process.waitFor();
            if (exitCode != 0) {
                System.err.println("Failed to execute command. Exit code: " + exitCode);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

This code snippet uses Java's `Runtime.getRuntime().exec()` method to execute the CLI command. It captures the output using a `BufferedReader`, which allows you to read and process the command's output efficiently.

Step 4: Handle Output and Parse Results

The output of the above AWS CLI command will be a JSON containing the total size of objects and the count of objects in the specified S3 bucket. You can use Java's JSON processing libraries like Gson or Jackson to parse and handle this JSON data.

import com.google.gson.JsonArray;
import com.google.gson.JsonParser;

// Inside your main method, after reading all lines from the process:
StringBuilder jsonOutput = new StringBuilder();
String line;
while ((line = reader.readLine()) != null) {
    jsonOutput.append(line);
}

JsonArray jsonArray = JsonParser.parseString(jsonOutput.toString()).getAsJsonArray();
long totalSize = jsonArray.get(0).getAsLong();
int objectCount = jsonArray.get(1).getAsInt();
System.out.println("Total Size: " + totalSize);
System.out.println("Object Count: " + objectCount);

Common Errors/Troubleshooting

Executing shell commands from Java can lead to several issues. Here are some common errors and their solutions:

• Command not found: Ensure that AWS CLI is installed and properly added to your system's PATH environment variable.
• Access Denied: Confirm that your AWS credentials have the necessary S3 permissions.
• IOException: Check if the command syntax is correct and that there are no typos in your command string.

By following these steps and handling potential errors, you can effectively execute AWS CLI commands from your Java application, allowing you to perform a wide range of AWS operations programmatically.

Frequently Asked Questions

Can I use this method for other AWS services?

Yes, you can execute any AWS CLI command from Java as long as it's supported by the AWS CLI.

What are the security implications?

Ensure your credentials have the minimum necessary permissions and are securely stored.

Is there an alternative to using Runtime.exec() in Java?

Yes, you can use ProcessBuilder for more complex command executions and better control over the process environment.

How do I handle large outputs?

Consider processing the output in chunks or using a streaming library to handle large volumes of data efficiently.