title: Spring Boot - NoClassDefFoundError: javax/servlet/Filter && Unable to start ServletWebServerApplicationContext when trying to use Netty
body: <p>I'm trying to use Netty server. So I excluded Tomcat in the pom.ml file;</p>
  
  <pre><code>&lt;dependencies&gt;
      &lt;dependency&gt;
          &lt;groupId&gt;org.springframework.boot&lt;/groupId&gt;
          &lt;artifactId&gt;spring-boot-starter-webflux&lt;/artifactId&gt;
      &lt;/dependency&gt;
      &lt;dependency&gt;
          &lt;groupId&gt;org.springframework.boot&lt;/groupId&gt;
          &lt;artifactId&gt;spring-boot-starter-web&lt;/artifactId&gt;
          &lt;exclusions&gt;
              &lt;exclusion&gt;
                  &lt;groupId&gt;org.springframework.boot&lt;/groupId&gt;
                  &lt;artifactId&gt;spring-boot-starter-tomcat&lt;/artifactId&gt;
              &lt;/exclusion&gt;
          &lt;/exclusions&gt;
      &lt;/dependency&gt;
  
      &lt;dependency&gt;
          &lt;groupId&gt;org.springframework.boot&lt;/groupId&gt;
          &lt;artifactId&gt;spring-boot-starter-security&lt;/artifactId&gt;
      &lt;/dependency&gt;
      &lt;dependency&gt;
          &lt;groupId&gt;org.springframework.boot&lt;/groupId&gt;
          &lt;artifactId&gt;spring-boot-devtools&lt;/artifactId&gt;
          &lt;scope&gt;runtime&lt;/scope&gt;
      &lt;/dependency&gt;
  &lt;/dependencies&gt;
  </code></pre>
  
  <p>When I run the application, I'm getting the error <strong>Caused by: java.lang.NoClassDefFoundError: javax/servlet/Filter</strong></p>
  
  <p>Then I add the dependency</p>
  
  <pre><code>&lt;dependency&gt;
          &lt;groupId&gt;javax.servlet&lt;/groupId&gt;
          &lt;artifactId&gt;javax.servlet-api&lt;/artifactId&gt;
          &lt;scope&gt;compile&lt;/scope&gt;
  &lt;/dependency&gt;
  </code></pre>
  
  <p>Then again when I run the application, I'm getting the error
  <strong>org.springframework.context.ApplicationContextException: Unable to start ServletWebServerApplicationContext due to missing ServletWebServerFactory bean.</strong></p>
  
  <p>I've checked several questions and no luck yet. </p>
  
  <p>Any ideas?</p>
  
  <h2>Enviroment</h2>
  
  <ul>
  <li>Boot:    2.1.3.RELEASE</li>
  <li>Eclipse: 4.7</li>
  </ul>