Your code defines a producer method in the EmailServiceProvider class that dynamically creates and provides an implementation of EmailService based on the configuration (email.driver). The choice of the email client to be used (e.g., SqsEmailServiceImpl or LocalSmtpEmailServiceImpl) is determined by the email.driver value.

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How to Use This in Your Application

The produced EmailService can be injected wherever it's needed within your application. Here's a breakdown of the steps:

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1. Set the Configuration for email.driver

The configuration value email.driver must be available to the application. Depending on the environment or framework, you can set this in various ways:

• microprofile-config.properties file:

  email.driver=sqs

• Environment Variable:

  export email.driver=sqs

• System Property:

  -Demail.driver=sqs

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2. Inject the EmailService Where Needed

In classes that require EmailService, inject it using CDI (@Inject):

package com.gappify.messaging;

import javax.inject.Inject;

public class EmailManager {

    @Inject
    private EmailService emailService;

    public void sendEmail(String recipient, String subject, String body) {
        emailService.send(recipient, subject, body);
    }
}

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3. Ensure EmailService and Its Implementations are Defined

For this to work:

• The EmailService interface must be implemented by SqsEmailServiceImpl and LocalSmtpEmailServiceImpl.
• Both implementations must be valid CDI beans (annotated with @ApplicationScoped, @Dependent, etc.).

Example:

package com.gappify.messaging.service;

import javax.enterprise.context.ApplicationScoped;

@ApplicationScoped
public class SqsEmailServiceImpl implements EmailService {
    @Override
    public void send(String recipient, String subject, String body) {
        // Logic for sending email via SQS
    }
}

package com.gappify.messaging.service;

import javax.enterprise.context.ApplicationScoped;

@ApplicationScoped
public class LocalSmtpEmailServiceImpl implements EmailService {
    @Override
    public void send(String recipient, String subject, String body) {
        // Logic for sending email via Local SMTP
    }
}

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4. Run the Application

When the application runs:

• The EmailServiceProvider producer is invoked.
• The producer reads the value of email.driver from the configuration.
• The corresponding implementation (SqsEmailServiceImpl or LocalSmtpEmailServiceImpl) is instantiated and injected wherever EmailService is used.

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Debugging and Validation

• Ensure the email.driver configuration value is correctly set and accessible.
• Confirm the implementations (SqsEmailServiceImpl, LocalSmtpEmailServiceImpl) are correctly annotated and discoverable by CDI.
• Use a logging or debugging mechanism to verify which implementation is being selected.

This structure ensures flexibility, as you can easily switch email drivers by changing the configuration without modifying the application code.