1、问题1：

com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure

The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.

at com.mysql.cj.jdbc.exceptions.SQLError.createCommunicationsException(SQLError.java:174) ~[mysql-connector-java-8.0.19.jar:8.0.19]

at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:64) ~[mysql-connector-java-8.0.19.jar:8.0.19]

at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:836) ~[mysql-connector-java-8.0.19.jar:8.0.19]

at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:456) ~[mysql-connector-java-8.0.19.jar:8.0.19]

at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:246) ~[mysql-connector-java-8.0.19.jar:8.0.19]

at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:197) ~[mysql-connector-java-8.0.19.jar:8.0.19]

at com.zaxxer.hikari.util.DriverDataSource.getConnection(DriverDataSource.java:138) ~[HikariCP-3.4.2.jar:na]

at com.zaxxer.hikari.pool.PoolBase.newConnection(PoolBase.java:354) ~[HikariCP-3.4.2.jar:na]

原因：

ip变了，之前192.168.0.103 ，现在192.168.0.105

解决:

更换ip为192.168.0.105

2、问题2：

Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.

2020-05-04 08:07:52.736 ERROR 4964 --- [           main] o.s.boot.SpringApplication               : Application run failed

org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'requestMappingHandlerAdapter' defined in class path resource [org/springframework/boot/autoconfigure/web/servlet/WebMvcAutoConfiguration$EnableWebMvcConfiguration.class]: Unsatisfied dependency expressed through method 'requestMappingHandlerAdapter' parameter 1; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'mvcConversionService' defined in class path resource [org/springframework/boot/autoconfigure/web/servlet/WebMvcAutoConfiguration$EnableWebMvcConfiguration.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.format.support.FormattingConversionService]: Factory method 'mvcConversionService' threw exception; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'productCategoryRepository': Invocation of init method failed; nested exception is java.lang.IllegalArgumentException: Not a managed type: class com.imooc.dataobject.ProductCategory

原因：

实体类没有注释@Entity

解决：