Think2 Blog: Example Apex class to send a message to a Slack channel or direct message (DM) using the Slack API

SendSlackToChannel.cls

// Example Apex class to send a message to a Slack channel using the Slack API
// Read the entire blog at: https://www.think2.ai/

// Note that there is not a lot of error handling in this code. In a production environment, you should add more error handling and logging.
// This code is for demonstration purposes only and should not be used in a production environment without proper testing and error handling.
// This code is designed to be used as an InvocableMethod in Salesforce, which allows it to be called from Flow or AgentForce.

public with sharing class SendSlackToChannel {
    private static final String SLACK_API_URL = 'https://slack.com/api/chat.postMessage';
    private static final String HARDCODED_BOT_TOKEN = 'xoxb-your-token-here';

    // Input class for the InvocableMethod
    public class Input {
        @InvocableVariable(
            label='Channel ID',
            description='Slack Channel ID (e.g. C01XXXXXXX)'
        )
        public String channelId;

        @InvocableVariable(label='Message Text', description='Text of the message to send to the Slack channel')
        public String messageText;
    }

    // Output class for the InvocableMethod
    public class Output {
        @InvocableVariable(label='Output Message', description='Result message from Slack API')
        public String message;

        public Output(String message) {
            this.message = message;
        }
    }

    @InvocableMethod(
        label='Send Slack Message to Channel',
        description='Sends a simple message to a Slack channel using the Slack API'
    )
    public static List<Output> postMessage(List<Input> requests) {
        List<Output> outputs = new List<Output>();

        for (Input request : requests) {
            // Prepare the payload
            String payload = '{"channel":"' + request.channelId + '", "text":"' + request.messageText + '"}';
            String token = getBotToken();

            String responseMessage = slackApiCallout(SLACK_API_URL, 'POST', token, payload);
            outputs.add(new Output(responseMessage));
        }

        return outputs;
    }

    private static String getBotToken() {
        // This is a hardcoded token for demonstration purposes. In a real-world scenario, you should use a more secure method to store and retrieve tokens.
        // For example, you could use Custom Metadata Types.
        return HARDCODED_BOT_TOKEN;
    }

    private static String slackApiCallout(String endpoint, String method, String token, String payload) {
        if (String.isBlank(token)) {
            return 'No token provided';
        }

        if (String.isBlank(endpoint)) {
            return 'No endpoint provided';
        }

        try {
            HttpRequest req = new HttpRequest();
            req.setEndpoint(endpoint);
            req.setMethod(method);
            req.setHeader('Content-Type', 'application/json');
            req.setHeader('Authorization', 'Bearer ' + token);
            if (!String.isBlank(payload)) {
                req.setBody(payload);
            }

            Http http = new Http();
            HttpResponse res = http.send(req);

            if (res.getStatusCode() == 200) {
                System.debug('Slack API callout successful: ' + res.getBody());
                return 'Slack API callout successful';
            } else {
                System.debug('Slack API callout failed: ' + res.getBody());
                return 'Slack API callout failed: ' + res.getBody();
            }
        } catch (Exception e) {
            System.debug('HTTP response error: ' + e.getMessage());
            return 'HTTP response error: ' + e.getMessage();
        }
    }
}