CODEWITHSUNDEEP
servletsmappingprogrammatic-config
Marta Ginosian
Marta Ginosian

Reputation: 117

Map servlet programmatically instead of using web.xml or annotations

How can I implement this mapping programmatically without web.xml or annotations? The mission is not to use any framework like spring or something else.

<servlet>
    <servlet-name>hello</servlet-name>
    <servlet-class>test.HelloServlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>hello</servlet-name>
    <url-pattern>/hello</url-pattern>
</servlet-mapping>

Upvotes: 8

Views: 5178

Answers (3)

BalusC
BalusC

Reputation: 1108972

Since Servlet 3.0 you can use ServletContext#addServlet() for this.

servletContext.addServlet("hello", test.HelloServlet.class);

Depending on what you're developing, there are two hooks where you can run this code.

  1. If you're developing a publicly reusable modular web fragment JAR file such as existing frameworks like JSF and Spring MVC, then use a ServletContainerInitializer.

    public class YourFrameworkInitializer implements ServletContainerInitializer {

    @Override
    public void onStartup(Set<Class<?>> c, ServletContext servletContext) throws ServletException {
        servletContext.addServlet("hello", test.HelloServlet.class);
    }

}

  2. Or, if you're using it as an internally integrated part of your WAR application, then use a ServletContextListener.

    @WebListener
public class YourFrameworkInitializer implements ServletContextListener {

    @Override
    public void contextInitialized(ServletContextEvent event) {
        event.getServletContext().addServlet("hello", test.HelloServlet.class);
    }

    // ...
}

You only need to make sure that your web.xml is compatible with Servlet 3.0 or newer (and thus not Servlet 2.5 or older), otherwise the servletcontainer will run in fallback modus complying the declared version and you will lose all Servlet 3.0 features.

<?xml version="1.0" encoding="UTF-8"?>
<web-app 
    xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
    version="3.0"
>
    <!-- Config here -->
</web-app>

See also:

Upvotes: 9

anacron
anacron

Reputation: 6721

You can use annotations to achieve this using code. 

import java.io.IOException;

import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet("/hello")
public class HelloServlet extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)
        throws IOException {
        response.getWriter().println("Hello");
    }
}

You can read about annotations here, here and here

Upvotes: 6

Jekin Kalariya
Jekin Kalariya

Reputation: 3507

If you are using tomcat 7 or above you can done this by annotation 

@WebServlet("/hello")

Upvotes: 1

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