title: com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure when trying to build spring boot docker image
body: <p>I am trying to build my docker image for my spring boot application but keep encountering this error:</p>
  <pre><code> :: Spring Boot ::        (v2.2.5.RELEASE)
  
  2020-05-31 02:18:39.820  INFO 63 --- [           main] c.g.Apollo.ApolloApplicationTests        : Starting ApolloApplicationTests on 4b284b60945e with PID 63 (started by root in /build)
  2020-05-31 02:18:39.838  INFO 63 --- [           main] c.g.Apollo.ApolloApplicationTests        : No active profile set, falling back to default profiles: default
  2020-05-31 02:18:42.208  INFO 63 --- [           main] .s.d.r.c.RepositoryConfigurationDelegate : Bootstrapping Spring Data JPA repositories in DEFAULT mode.
  2020-05-31 02:18:42.467  INFO 63 --- [           main] .s.d.r.c.RepositoryConfigurationDelegate : Finished Spring Data repository scanning in 216ms. Found 3 JPA repository interfaces.
  2020-05-31 02:18:44.902  INFO 63 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
  2020-05-31 02:18:46.575 ERROR 63 --- [           main] com.zaxxer.hikari.pool.HikariPool        : HikariPool-1 - Exception during pool initialization.
  
  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-8.0.20.jar:8.0.20]
          at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:64) ~[mysql-connector-java-8.0.20.jar:8.0.20]
          at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:836) ~[mysql-connector-java-8.0.20.jar:8.0.20]
          at com.mysql.cj.jdbc.ConnectionImpl.&lt;init&gt;(ConnectionImpl.java:456) ~[mysql-connector-java-8.0.20.jar:8.0.20]
          at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:246) ~[mysql-connector-java-8.0.20.jar:8.0.20]
          at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:197) ~[mysql-connector-java-8.0.20.jar:8.0.20]
          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]
          at com.zaxxer.hikari.pool.PoolBase.newPoolEntry(PoolBase.java:202) ~[HikariCP-3.4.2.jar:na]
          at com.zaxxer.hikari.pool.HikariPool.createPoolEntry(HikariPool.java:473) ~[HikariCP-3.4.2.jar:na]
          at com.zaxxer.hikari.pool.HikariPool.checkFailFast(HikariPool.java:554) ~[HikariCP-3.4.2.jar:na]
          at com.zaxxer.hikari.pool.HikariPool.&lt;init&gt;(HikariPool.java:115) ~[HikariCP-3.4.2.jar:na]
          at com.zaxxer.hikari.HikariDataSource.getConnection(HikariDataSource.java:112) ~[HikariCP-3.4.2.jar:na]
  </code></pre>
  <p>Terminal when successfully running in intellij:</p>
  <pre><code> :: Spring Boot ::        (v2.2.5.RELEASE)
  
  2020-05-31 01:04:39.322  INFO 19524 --- [  restartedMain] c.g.Apollo.ApolloApplication             : Starting ApolloApplication on asd-PC with PID 19524 (C:\Projects\Apollo\target\classes started by asd in C:\Projects\Apollo)
  2020-05-31 01:04:39.324  INFO 19524 --- [  restartedMain] c.g.Apollo.ApolloApplication             : No active profile set, falling back to default profiles: default
  2020-05-31 01:04:39.354  INFO 19524 --- [  restartedMain] o.s.b.devtools.restart.ChangeableUrls    : The Class-Path manifest attribute in C:\Users\asd\.m2\repository\org\glassfish\jaxb\jaxb-runtime\2.3.2\jaxb-runtime-2.3.2.jar referenced one or more files that do not exist: file:/C:/Users/asd/.m2/repository/org/glassfish/jaxb/jaxb-runtime/2.3.2/jakarta.xml.bind-api-2.3.2.jar,file:/C:/Users/asd/.m2/repository/org/glassfish/jaxb/jaxb-runtime/2.3.2/txw2-2.3.2.jar,file:/C:/Users/asd/.m2/repository/org/glassfish/jaxb/jaxb-runtime/2.3.2/istack-commons-runtime-3.0.8.jar,file:/C:/Users/asd/.m2/repository/org/glassfish/jaxb/jaxb-runtime/2.3.2/stax-ex-1.8.1.jar,file:/C:/Users/asd/.m2/repository/org/glassfish/jaxb/jaxb-runtime/2.3.2/FastInfoset-1.2.16.jar,file:/C:/Users/asd/.m2/repository/org/glassfish/jaxb/jaxb-runtime/2.3.2/jakarta.activation-api-1.2.1.jar
  2020-05-31 01:04:39.354  INFO 19524 --- [  restartedMain] .e.DevToolsPropertyDefaultsPostProcessor : Devtools property defaults active! Set 'spring.devtools.add-properties' to 'false' to disable
  2020-05-31 01:04:39.354  INFO 19524 --- [  restartedMain] .e.DevToolsPropertyDefaultsPostProcessor : For additional web related logging consider setting the 'logging.level.web' property to 'DEBUG'
  2020-05-31 01:04:39.785  INFO 19524 --- [  restartedMain] .s.d.r.c.RepositoryConfigurationDelegate : Bootstrapping Spring Data JPA repositories in DEFAULT mode.
  2020-05-31 01:04:39.846  INFO 19524 --- [  restartedMain] .s.d.r.c.RepositoryConfigurationDelegate : Finished Spring Data repository scanning in 54ms. Found 3 JPA repository interfaces.
  2020-05-31 01:04:40.214  INFO 19524 --- [  restartedMain] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)
  2020-05-31 01:04:40.220  INFO 19524 --- [  restartedMain] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
  2020-05-31 01:04:40.221  INFO 19524 --- [  restartedMain] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.31]
  2020-05-31 01:04:40.293  INFO 19524 --- [  restartedMain] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
  2020-05-31 01:04:40.293  INFO 19524 --- [  restartedMain] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 939 ms
  2020-05-31 01:04:40.365  INFO 19524 --- [  restartedMain] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
  2020-05-31 01:04:40.702  INFO 19524 --- [  restartedMain] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.
  2020-05-31 01:04:40.731  INFO 19524 --- [  restartedMain] o.hibernate.jpa.internal.util.LogHelper  : HHH000204: Processing PersistenceUnitInfo [name: default]
  2020-05-31 01:04:40.800  INFO 19524 --- [  restartedMain] org.hibernate.Version                    : HHH000412: Hibernate ORM core version 5.4.12.Final
  2020-05-31 01:04:40.919  INFO 19524 --- [  restartedMain] o.hibernate.annotations.common.Version   : HCANN000001: Hibernate Commons Annotations {5.1.0.Final}
  2020-05-31 01:04:41.006  INFO 19524 --- [  restartedMain] org.hibernate.dialect.Dialect            : HHH000400: Using dialect: org.hibernate.dialect.MySQL8Dialect
  2020-05-31 01:04:41.407  INFO 19524 --- [  restartedMain] o.h.e.t.j.p.i.JtaPlatformInitiator       : HHH000490: Using JtaPlatform implementation: [org.hibernate.engine.transaction.jta.platform.internal.NoJtaPlatform]
  2020-05-31 01:04:41.413  INFO 19524 --- [  restartedMain] j.LocalContainerEntityManagerFactoryBean : Initialized JPA EntityManagerFactory for persistence unit 'default'
  2020-05-31 01:04:41.650  WARN 19524 --- [  restartedMain] JpaBaseConfiguration$JpaWebConfiguration : spring.jpa.open-in-view is enabled by default. Therefore, database queries may be performed during view rendering. Explicitly configure spring.jpa.open-in-view to disable this warning
  2020-05-31 01:04:41.717  INFO 19524 --- [  restartedMain] o.s.s.concurrent.ThreadPoolTaskExecutor  : Initializing ExecutorService 'applicationTaskExecutor'
  2020-05-31 01:04:41.967  INFO 19524 --- [  restartedMain] o.s.b.d.a.OptionalLiveReloadServer       : LiveReload server is running on port 35729
  2020-05-31 01:04:41.995  INFO 19524 --- [  restartedMain] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
  2020-05-31 01:04:41.997  INFO 19524 --- [  restartedMain] c.g.Apollo.ApolloApplication             : Started ApolloApplication in 2.911 seconds (JVM running for 3.899)
  </code></pre>
  <p>My Dockerfile:</p>
  <pre><code>FROM maven:3.6.3-jdk-11-slim AS MAVEN_BUILD
  
  COPY pom.xml /build/
  COPY src /build/src/
  WORKDIR /build/
  RUN mvn package
  
  FROM openjdk:11-jre-alpine
  
  WORKDIR /app
  COPY --from=MAVEN_BUILD /build/target/*.war /app/app.war
  ENTRYPOINT [&quot;java&quot;, &quot;-jar&quot;, &quot;app.war&quot;]
  </code></pre>
  <p>My application.properties:</p>
  <pre><code>## GraphQL SPQR ##
  server.port=8080
  graphql.spqr.gui.enabled=true
  graphql.spqr.http.endpoint=/graphql
  graphql.spqr.ws.endpoint=/graphql
  
  ## Database Properties ##
  spring.datasource.url=jdbc:mysql://localhost:3306/innodb
  spring.datasource.username=root
  spring.datasource.password=1234
  </code></pre>
  <p>My application works when I build and run the project in Intellij but not when I try and build my docker image. I am using MySQL and have just been connecting on localhost on port 3306.</p>