Java 服务器 (Tomcat 7) 的 404 错误

Question

    HTTP Status 404 -

type Status report

message

description The requested resource is not available.

Apache Tomcat/7.0.68 (Ubuntu)

我尝试使用手动启动服务器

sudo service tomcat7 start

我得到了这个

Job for tomcat7.service failed because the control process exited with error code. 
See "systemctl status tomcat7.service" and "journalctl -xe" for details.

systemctl status tomcat7.service 已尝试systemctl status tomcat7.service

  ● 
    tomcat7.service - LSB: Start Tomcat.
           Loaded: loaded (/etc/init.d/tomcat7; bad; vendor preset: enabled)
           Active: failed (Result: exit-code) since Wed 2017-03-08 03:02:07 MST; 1min 50
             Docs: man:systemd-sysv-generator(8)
          Process: 15031 ExecStart=/etc/init.d/tomcat7 start (code=exited, status=1/FAIL

 Starting LSB: Start Tomcat....
  * Starting Tomcat servlet engine tomca
tomcat7[15031]:    ...fail!
 tomcat7.service: Control process exited, co
 Failed to start LSB: Start Tomcat..
 tomcat7.service: Unit entered failed state.
tomcat7.service: Failed with result 'exit-c

我正在尝试创建一个简单的 java servlet。

Web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
  <display-name>CloudComputing</display-name>

  <servlet>
  <servlet-name>ReqResp</servlet-name>
  <servlet-class>cc.Cloudpi</servlet-class>
  </servlet>

 <servlet-mapping>
 <servlet-name>ReqResp</servlet-name>
 <url-pattern>/Cloudpi</url-pattern>

 </servlet-mapping>

  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
</web-app>

请帮助（新手警报！）