Unraveling the Mystery: Sevlets with @WebServlet annotation in JAR files not accessible (Wildfly 26.1.3.Final)

Are you stuck in the abyss of Wildfly 26.1.3.Final, struggling to access your Sevlets with @WebServlet annotation packaged in JAR files? Fear not, dear developer, for we’re about to embark on a thrilling adventure to conquer this conundrum together!

The problem: Sevlets in JAR files, inaccessible and invisible

Imagine you’ve created a Sevlet, adorned it with the @WebServlet annotation, and packaged it neatly in a JAR file. You deploy the JAR file to your Wildfly 26.1.3.Final server, expecting it to spring to life and respond to requests with enthusiasm. Alas, your Sevlet remains inaccessible, shrouded in an impenetrable veil of mystery.

Why does this happen? The key lies in understanding how Wildfly handles Sevlets packaged in JAR files. By default, Wildfly doesn’t scan JAR files for Sevlets annotated with @WebServlet. Instead, it relies on a file named `jboss-web.xml` or `web.xml` to discover Sevlets. But fear not, for we have a solution to bypass this limitation!

Solution 1: Using a WAR file instead of a JAR file

The simplest approach is to package your Sevlet in a WAR file instead of a JAR file. Here’s why:

• WAR files are specifically designed for web applications, making them the natural choice for Sevlets.
• Wildfly, by default, scans WAR files for Sevlets annotated with @WebServlet.
• You can include a `web.xml` file in the WAR file’s WEB-INF directory to specify Sevlet mappings.

Here’s an example of a `web.xml` file:

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.1" xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
         http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd">

    <servlet>
        <servlet-name>MySevlet</servlet-name>
        <servlet-class>com.example.MySevlet</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>MySevlet</servlet-name>
        <url-pattern>/mysevlet</url-pattern>
    </servlet-mapping>

</web-app>

Solution 2: Using a custom `servelt-container` in `jboss-web.xml`

If you’re stuck with a JAR file, don’t worry! You can still use a custom `servlet-container` in `jboss-web.xml` to make your Sevlet accessible. Here’s how:

In your JAR file’s META-INF directory, create a file named `jboss-web.xml` with the following content:

<?xml version="1.0" encoding="UTF-8"?>
<jboss-web>
    <servlet-container>
        <servlet>
            <servlet-name>MySevlet</servlet-name>
            <servlet-class>com.example.MySevlet</servlet-class>
        </servlet>
    </servlet-container>
</jboss-web>

This configuration tells Wildfly to scan the JAR file for Sevlets and make them accessible.

Solution 3: Programmatic Sevlet registration

In some cases, you might not be able to use a WAR file or modify the `jboss-web.xml` file. Fear not! You can still register your Sevlet programmatically using the `ServletContext` API.

Create a `ServletContextListener` that registers your Sevlet programmatically:

public class SevletRegisterer implements ServletContextListener {

    @Override
    public void contextInitialized(ServletContextEvent event) {
        ServletContext servletContext = event.getServletContext();
        Sevlet mySevlet = new MySevlet();
        ServletRegistration.Dynamic registration = servletContext.addServlet("MySevlet", mySevlet);
        registration.addMapping("/mysevlet");
    }

    @Override
    public void contextDestroyed(ServletContextEvent event) {
        // Nothing to do here
    }
}

In your Sevlet class, add the `@WebListener` annotation to register the `ServletContextListener`:

@WebListener
public class SevletRegisterer implements ServletContextListener {
    // ...
}

Troubleshooting tips and tricks

Still stuck? Don’t panic! Here are some troubleshooting tips to help you overcome common obstacles:

Issue	Solution
Sevlet not accessible	Check that the Sevlet is properly annotated with `@WebServlet` and that the `url-pattern` is correct.
Wildfly not scanning JAR file	Verify that the JAR file is properly deployed to the Wildfly server and that the `jboss-web.xml` file is in the correct location (META-INF).
ServletContextListener not called	Ensure that the `ServletContextListener` is properly registered using the `@WebListener` annotation.

Conclusion

And there you have it, folks! With these solutions and troubleshooting tips, you should be able to access your Sevlets packaged in JAR files using Wildfly 26.1.3.Final. Remember to stay calm, patient, and curious when tackling complex issues.

As the great coding philosopher once said, “A Sevlet is like a ninja – it’s only invisible when you don’t know where to look.”

May the coding force be with you!

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