spring boot中出现com.mysql.cj.jdbc.exceptions.CommunicationsException

具体报错如下：

com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failureThe 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]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.<init>(HikariPool.java:115) [HikariCP-3.4.2.jar:na]at com.zaxxer.hikari.HikariDataSource.getConnection(HikariDataSource.java:112) [HikariCP-3.4.2.jar:na]at cn.whpu.springboot.Springboot05DataApplicationTests.contextLoads(Springboot05DataApplicationTests.java:21) [test-classes/:na]at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_161]at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_161]at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_161]at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_161]at org.junit.platform.commons.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:675) [junit-platform-commons-1.5.2.jar:1.5.2]at org.junit.jupiter.engine.execution.MethodInvocation.proceed(MethodInvocation.java:60) [junit-jupiter-engine-5.5.2.jar:5.5.2]at org.junit.jupiter.engine.execution.InvocationInterceptorChain$ValidatingInvocation.proceed(InvocationInterceptorChain.java:125) [junit-jupiter-engine-5.5.2.jar:5.5.2]at org.junit.jupiter.engine.extension.TimeoutExtension.intercept(TimeoutExtension.java:132) [junit-jupiter-engine-5.5.2.jar:5.5.2]at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestableMethod(TimeoutExtension.java:124) [junit-jupiter-engine-5.5.2.jar:5.5.2]at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestMethod(TimeoutExtension.java:74) [junit-jupiter-engine-5.5.2.jar:5.5.2]at org.junit.jupiter.engine.execution.ExecutableInvoker$ReflectiveInterceptorCall.lambda$ofVoidMethod$0(ExecutableInvoker.java:115) ~[junit-jupiter-engine-5.5.2.jar:5.5.2]at org.junit.jupiter.engine.execution.ExecutableInvoker.lambda$invoke$0(ExecutableInvoker.java:105) ~[junit-jupiter-engine-5.5.2.jar:5.5.2]at org.junit.jupiter.engine.execution.InvocationInterceptorChain$InterceptedInvocation.proceed(InvocationInterceptorChain.java:104) ~[junit-jupiter-engine-5.5.2.jar:5.5.2]at org.junit.jupiter.engine.execution.InvocationInterceptorChain.proceed(InvocationInterceptorChain.java:62) ~[junit-jupiter-engine-5.5.2.jar:5.5.2]at org.junit.jupiter.engine.execution.InvocationInterceptorChain.chainAndInvoke(InvocationInterceptorChain.java:43) ~[junit-jupiter-engine-5.5.2.jar:5.5.2]at org.junit.jupiter.engine.execution.InvocationInterceptorChain.invoke(InvocationInterceptorChain.java:35) ~[junit-jupiter-engine-5.5.2.jar:5.5.2]at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:104) ~[junit-jupiter-engine-5.5.2.jar:5.5.2]at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:98) ~[junit-jupiter-engine-5.5.2.jar:5.5.2]at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$invokeTestMethod$6(TestMethodTestDescriptor.java:202) ~[junit-jupiter-engine-5.5.2.jar:5.5.2]at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73) ~[junit-platform-engine-1.5.2.jar:1.5.2]at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.invokeTestMethod(TestMethodTestDescriptor.java:198) ~[junit-jupiter-engine-5.5.2.jar:5.5.2]at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:135) ~[junit-jupiter-engine-5.5.2.jar:5.5.2]at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:69) ~[junit-jupiter-engine-5.5.2.jar:5.5.2]at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:135) ~[junit-platform-engine-1.5.2.jar:1.5.2]at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73) ~[junit-platform-engine-1.5.2.jar:1.5.2]at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:125) ~[junit-platform-engine-1.5.2.jar:1.5.2]at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:135) ~[junit-platform-engine-1.5.2.jar:1.5.2]at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:123) ~[junit-platform-engine-1.5.2.jar:1.5.2]at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73) ~[junit-platform-engine-1.5.2.jar:1.5.2]at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:122) ~[junit-platform-engine-1.5.2.jar:1.5.2]at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:80) ~[junit-platform-engine-1.5.2.jar:1.5.2]at java.util.ArrayList.forEach(ArrayList.java:1257) ~[na:1.8.0_161]at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38) ~[junit-platform-engine-1.5.2.jar:1.5.2]at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:139) ~[junit-platform-engine-1.5.2.jar:1.5.2]at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73) ~[junit-platform-engine-1.5.2.jar:1.5.2]at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:125) ~[junit-platform-engine-1.5.2.jar:1.5.2]at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:135) ~[junit-platform-engine-1.5.2.jar:1.5.2]at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:123) ~[junit-platform-engine-1.5.2.jar:1.5.2]at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73) ~[junit-platform-engine-1.5.2.jar:1.5.2]at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:122) ~[junit-platform-engine-1.5.2.jar:1.5.2]at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:80) ~[junit-platform-engine-1.5.2.jar:1.5.2]at java.util.ArrayList.forEach(ArrayList.java:1257) ~[na:1.8.0_161]at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38) ~[junit-platform-engine-1.5.2.jar:1.5.2]at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:139) ~[junit-platform-engine-1.5.2.jar:1.5.2]at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73) ~[junit-platform-engine-1.5.2.jar:1.5.2]at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:125) ~[junit-platform-engine-1.5.2.jar:1.5.2]at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:135) ~[junit-platform-engine-1.5.2.jar:1.5.2]at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:123) ~[junit-platform-engine-1.5.2.jar:1.5.2]at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73) ~[junit-platform-engine-1.5.2.jar:1.5.2]at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:122) ~[junit-platform-engine-1.5.2.jar:1.5.2]at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:80) ~[junit-platform-engine-1.5.2.jar:1.5.2]at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.submit(SameThreadHierarchicalTestExecutorService.java:32) ~[junit-platform-engine-1.5.2.jar:1.5.2]at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:57) ~[junit-platform-engine-1.5.2.jar:1.5.2]at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:51) ~[junit-platform-engine-1.5.2.jar:1.5.2]at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:229) ~[junit-platform-launcher-1.5.2.jar:1.5.2]at org.junit.platform.launcher.core.DefaultLauncher.lambda$execute$6(DefaultLauncher.java:197) ~[junit-platform-launcher-1.5.2.jar:1.5.2]at org.junit.platform.launcher.core.DefaultLauncher.withInterceptedStreams(DefaultLauncher.java:211) ~[junit-platform-launcher-1.5.2.jar:1.5.2]at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:191) ~[junit-platform-launcher-1.5.2.jar:1.5.2]at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:128) ~[junit-platform-launcher-1.5.2.jar:1.5.2]at com.intellij.junit5.JUnit5IdeaTestRunner.startRunnerWithArgs(JUnit5IdeaTestRunner.java:69) ~[junit5-rt.jar:na]at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47) ~[junit-rt.jar:na]at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242) ~[junit-rt.jar:na]at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70) ~[junit-rt.jar:na]
Caused by: com.mysql.cj.exceptions.CJCommunicationsException: Communications link failure

我在网上找了，一种说是将mysql回收空闲连接的时间变长，在my.ini中设置：

[mysqld]
wait_timeout=86400

或者是

将 bind-address = 127.0.0.1
为 bind-address = 0.0.0.0

但是我试了都不是。
后来我去检查我的p’roperties文件才知道，自己配置错了。
在此提醒 ：