reason:

Two Tomcat servers are started at the same time, or the Tomcat server port is occupied.

Solution:

Shut down one of the Tomcat servers

Modify the port number in tomcat7

 <!--tomcat7 Plugin -->
 <plugin>
   <groupId>org.apache.tomcat.maven</groupId>
   <artifactId>tomcat7-maven-plugin</artifactId>
   <version>2.2</version>
   <configuration>
     <port>8888</port>
   </configuration>
 </plugin>