ClassNotFoundException: org.glassfish.jersey.servlet.ServletContainer
<p>I downloaded Eclipse Luna and Tomcat 8.0.24 some months ago but I started using it. I've been creating a web app without Maven. I downloaded manually Jersey 2.23, Jersey media moxy 2.23, java-son 1.0 , jdbc mysql 5.x and sql2o 1.5.4. I'm starting to learn Angular and I successfully created one page without any issue.</p>

<p>I remember have added my jars manually in the Build Path of my project and I was forced to add them in the Deployment Assemblies also. Fine.</p>

<p>Since 2 weeks I didn't shutdown my laptop, just in sleep mode. But yesterday I did shutdown. Since then I suffered to make it work again. I use postman chrome to test my restful services and I received after the shutting down the 404 error.</p>

<p>I realized that I started to see the exception in the console: </p>

<blockquote>
  <p>java.lang.ClassNotFoundException: org.glassfish.jersey.servlet.ServletContainer</p>
</blockquote>

<p>I deleted my folders of tomcat and eclipse to start again from scratch desperately. However, I got the same issue. The last thing that I remember I was playing with, were these modified options.</p>

<ol>
<li>Double click in server from servers tab</li>
<li>Change from Use workspace metadata to Use Tomcat installation</li>
<li>Properties in Server</li>
<li>Switch Location from metadata to localhost.server</li>
</ol>

<p>It was thanks to these questions that I solved my issue:</p>

<ul>
<li><a href="https://stackoverflow.com/questions/22022114/org-glassfish-jersey-servlet-servletcontainer-classnotfoundexception">org.glassfish.jersey.servlet.ServletContainer ClassNotFoundException</a></li>
<li><a href="https://stackoverflow.com/questions/26444790/java-lang-classnotfoundexception-org-glassfish-jersey-servlet-servletcontainer">java.lang.ClassNotFoundException: org.glassfish.jersey.servlet.ServletContainer</a></li>
</ul>

<p>Now, after "reinstalling" eclipse and tomcat, when I add the jars in the library tab, they are now added in deployment assemblies automatically. (Surprised)</p>

<p>According to the previous attached questions, I added all the jars in WEB-INF/lib from my workspace as also in the tomcat/wtpwebapps/myproject/WEB-INF/lib. If I don't do this, I won't be able to make it work. Postman finally gives me the desired output. </p>

<p>Nevertheless, I realized when I copy the jars manually through windows explorer, the console in Eclipse displays the tomcat restarting again. BUT I still see the exception: <strong>java.lang.ClassNotFoundException: org.glassfish.jersey.servlet.ServletContainer</strong>. At least I can run my project in the browser or in postman without any issue. Very strange.</p>

<p>I want to add a new User Library in Windows > Preferences > Java > Build Path > User Libraries, but my list is EMPTY!!! So...  </p>

<p>Finally, my questions:</p>

<ul>
<li>What's going on with Eclipse? </li>
<li>Why am I not able to see my user libraries previously added? 
<a href="https://i.stack.imgur.com/dQXk3.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/dQXk3.png" alt="enter image description here"></a></li>
<li>Why do I still see the exception of glassfish.jersey in the console if I added the jars in the web-inf folder which makes it work apparently. </li>
<li>Why do I need to add the jars in web-inf, if when I see all the jars included in the Tomcat library all my jars are there because I forgot to mention that I added a folder called External in lib of my Tomcat folder.</li>
</ul>

<p><a href="https://i.stack.imgur.com/cR3w8.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/cR3w8.png" alt="enter image description here"></a></p>

<p><a href="https://i.stack.imgur.com/1zXOK.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/1zXOK.png" alt="enter image description here"></a></p>

<p>For all these changes, I restarted Eclipse</p>