Writing a servlet with eclipse

Yesterday's problem, solved today, in fact, is a stick to combine and believe that the knowledge of the previous study of the correctness of the process.
The class classes that are generated by the Dynamic Web program (Dynamics Web Project) servlet in eclipse are indeed in the build directory, but not shown under the Eclipse's Project explorer.

When debugging runs in Eclipse, the address Http://localhost:8080/LearnJSP/helloservlet can succeed.

Directories in Eclipse:
The port being prompted is occupied and the external Tomcat needs to be stopped in the terminal.
If you need to test in this computer, move the WebContent folder in workspace to the WebApps directory of the Tomcat installation directory. And move the Classes folder in the Build folder to the WebContent Web-inf directory.
Start Tomcat
Firefox input address Http://localhost:8080/WebContent/helloservlet test succeeded.