Example of manually bootstraping SpringBoot AutoConfiguration with conditions depending on existance of spring boot properties

ManualBootstrapMailSenderAutoConfiguration.groovy

    @Test
    void "can send email without errors"() {
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext()

        StandardEnvironment environment = new StandardEnvironment()
        InputStream ins = Resources.getResourceAsStream("/application.properties")
        Properties props = new Properties()
        props.load(ins as InputStream);
        Closeables.closeQuietly(ins);
        environment.propertySources.addFirst(new PropertiesPropertySource("application", props))
        context.setEnvironment(environment)
        context.register(MailSenderAutoConfiguration)
        context.refresh()
        context.start()
        println context.getBean(MailerTest).host
        JavaMailSender mailSender = context.getBean(JavaMailSender)

        SpringTemplateEngine templateEngine = new SpringTemplateEngine();
        templateEngine.addTemplateResolver(new ClassLoaderTemplateResolver(prefix: "templates/", templateMode: "HTML5", order: 1))

        Mailer mailer = new Mailer(mailSender, templateEngine)
        mailer.merchantCreated(new Merchant(merchantName: "Test Merchant Name", contactName: "Contact Name", emailAddress: "leonard.siu@trioloop.com"))
        println "Method returned"
        ForkJoinPool.commonPool().awaitQuiescence(30, TimeUnit.SECONDS)
    }