Olá gente, tudo bom? A aplicação estava funcionando normalmente até eu começar a seguir os passos para alterar o web.xml. Vou transcrever o código abaixo. Está aparecendo o erro 404 agora, mas antes de alterar o web.xml estava tudo ok. Grato pelas respostas.
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd" id="WebApp_ID" version="4.0">
<display-name>gerenciador</display-name>
<welcome-file-list>
<welcome-file>index.html</welcome-file>
</welcome-file-list>
<filter>
<filter-name>MF</filter-name>
<filter-class>br.com.alura.gerenciador.servlet.MonitoramentoFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>MF</filter-name>
<url-pattern>/entrada</url-pattern>
</filter-mapping>
<filter>
<filter-name>AF</filter-name>
<filter-class>br.com.alura.gerenciador.servlet.AutorizacaoFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>AF</filter-name>
<url-pattern>/entrada</url-pattern>
</filter-mapping>
</web-app>