How to define and in servlet 3.0's web.xml-less?

Question

I have existing web-app which I want to convert into web.xml-less of servlet\'s 3.0. I\'ve managed to make it working, however there are 2 tags in web.xml which I still don\

Answer 1

In Spring Boot or general Spring MVC app for following scenario:

Static files can be served from locations registered with a custom ResourceHandlerRegistry. We have a static resource index.html and it can accessed at localhost:8080/index.html. We want to just redirect localhost:8080/ request to localhost:8080/index.html, following code will can be used.

package in.geekmj.config;

import org.springframework.context.annotation.Configuration;

import org.springframework.web.servlet.config.annotation.EnableWebMvc;

import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;

import org.springframework.web.servlet.config.annotation.ViewControllerRegistry;

import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;

@Configuration
@EnableWebMvc
public class WebConfiguration extends WebMvcConfigurerAdapter {

private static final String[] CLASSPATH_RESOURCE_LOCATIONS = { "classpath:/META-INF/resources/",
        "classpath:/resources/", "classpath:/static/", "classpath:/public/" };

@Override
public void addResourceHandlers(ResourceHandlerRegistry registry) {
    registry.addResourceHandler("/**").addResourceLocations(CLASSPATH_RESOURCE_LOCATIONS);
}

@Override
public void addViewControllers(ViewControllerRegistry registry) {
    registry.addRedirectViewController("/", "/index.html");
}
}

Now accessing localhost:8080/ will redirect to localhost:8080/index.html

Answer 2

For analog welcome-page-list put this in

@EnableWebMvc
@Configuration
@ComponentScan("com.springapp.mvc")
public class MvcConfig extends WebMvcConfigurerAdapter {
...
    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {
        registry.addResourceHandler("/*.html").addResourceLocations("/WEB-INF/pages/");
    }

    @Override
    public void addViewControllers(ViewControllerRegistry registry) {
        registry.addViewController("/").setViewName("forward:/index.html");
    }
...
}

Answer 3

In Servlets 3.0 you don't need a web.xml for many cases, however, sometimes it's required or just useful. Your case is just one of them - there is no special annotations to define welcome-file list or error-pages.

Another thing is - would you really like to have them hardcoded? There are some valid use-cases for annotation / programmatic based configuration and for declarative configuration in XML. Moving to Servlets 3.0 doesn't necessarily means getting rid of web.xml at all cost.

I would find the entries you posted a better example of configuration in XML. Firstly - they can be changed from deployment to deployment and secondly - they affect whole application and not any particular Servlet.