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Message Filter

Pattern	Message filter neglects the uninterested messages based on criteria and publishes the filtered message to another channel.
How Ballerina helps	Ballerina enables filtering messages using basic control structures such as if and switch statements.

Message FilterMessage ChannelMessage Endpoint

import ballerina/http;

type Ticket record {|
    string id;
    string url;
    string subject;
    HIGH_PRIORITY|MEDUIM_PRIORITY|LOW_PRIORITY priority;
|};

const HIGH_PRIORITY = 1;
const MEDUIM_PRIORITY = 2;
const LOW_PRIORITY = 3;

final http:Client notificationChannel = check new ("http://api.notification.channel.com.balmock.io");

⋯


service /api/v1 on new http:Listener(8080) {

    resource function post ticket(Ticket ticket) returns error? {
        if ticket.priority == 1 {
            _ = check notificationChannel->/email/notify.post(ticket, targetType = http:Response);
        }
    }
}