Web application startup configuration

StartUpConfig.java

package org.davidmendoza.demo.config;

import org.sitemesh.config.ConfigurableSiteMeshFilter;
import org.springframework.web.WebApplicationInitializer;
import org.springframework.web.context.ContextLoaderListener;
import org.springframework.web.context.support.AnnotationConfigWebApplicationContext;
import org.springframework.web.filter.CharacterEncodingFilter;
import org.springframework.web.servlet.DispatcherServlet;

import javax.servlet.*;
import java.util.EnumSet;
import java.util.Set;

public class StartUpConfig implements WebApplicationInitializer {

    @Override
    public void onStartup(ServletContext servletContext) throws ServletException {
        AnnotationConfigWebApplicationContext context = new AnnotationConfigWebApplicationContext();
        context.register(ComponentConfig.class, DataConfig.class, MailConfig.class, WebConfig.class);
        context.setDisplayName("DemoApp");

        FilterRegistration.Dynamic sitemeshFilter = servletContext.addFilter("sitemeshFilter", new ConfigurableSiteMeshFilter());
        sitemeshFilter.addMappingForUrlPatterns(EnumSet.allOf(DispatcherType.class), true, "/*");

        FilterRegistration.Dynamic characterEncodingFilter = servletContext.addFilter("characterEncodingFilter", new CharacterEncodingFilter());
        characterEncodingFilter.addMappingForUrlPatterns(EnumSet.allOf(DispatcherType.class), true, "/*");
        characterEncodingFilter.setInitParameter("encoding", "UTF-8");
        characterEncodingFilter.setInitParameter("forceEncoding", "true");

        servletContext.addListener(new ContextLoaderListener(context));
        //servletContext.setInitParameter("defaultHtmlEscape", "false");

        DispatcherServlet servlet = new DispatcherServlet();
        // no explicit configuration reference here: everything is configured in the root container for simplicity
        servlet.setContextConfigLocation("");

        ServletRegistration.Dynamic appServlet = servletContext.addServlet("appServlet", servlet);
        appServlet.setLoadOnStartup(1);
        appServlet.setAsyncSupported(true);

        Set<String> mappingConflicts = appServlet.addMapping("/");
        if (!mappingConflicts.isEmpty()) {
            throw new IllegalStateException("'appServlet' cannot be mapped to '/' under Tomcat versions <= 7.0.14");
        }
    }

}