java.sql.SQLException: Connections could not be acquired from the underlying database!

java.lang.RuntimeException: java.sql.SQLException: Connections could not be acquired from the underlying database!
  at com.zhanshen.dao.impl.AccountDaoImpl.findAll(AccountDaoImpl.java:28)
  at com.zhanshen.service.impl.AccountServiceImpl.findAll(AccountServiceImpl.java:23)
  at com.zhanshen.test.AccountServiceTest.testFindAll(AccountServiceTest.java:28)
  at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
  at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
  at java.lang.reflect.Method.invoke(Method.java:498)
  at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
  at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
  at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
  at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
  at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
  at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
  at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
  at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
  at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
  at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
  at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
  at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
  at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
  at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
  at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
  at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
  at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
  at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
  at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
Caused by: java.sql.SQLException: Connections could not be acquired from the underlying database!
  at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:106)
  at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:529)
  at com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource.getConnection(AbstractPoolBackedDataSource.java:128)
  at org.apache.commons.dbutils.AbstractQueryRunner.prepareConnection(AbstractQueryRunner.java:156)
  at org.apache.commons.dbutils.QueryRunner.query(QueryRunner.java:303)
  at com.zhanshen.dao.impl.AccountDaoImpl.findAll(AccountDaoImpl.java:26)
  ... 25 more
Caused by: com.mchange.v2.resourcepool.CannotAcquireResourceException: A ResourcePool could not acquire a resource from its primary factory or source.
  at com.mchange.v2.resourcepool.BasicResourcePool.awaitAvailable(BasicResourcePool.java:1319)
  at com.mchange.v2.resourcepool.BasicResourcePool.prelimCheckoutResource(BasicResourcePool.java:557)
  at com.mchange.v2.resourcepool.BasicResourcePool.checkoutResource(BasicResourcePool.java:477)
  at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:525)
  ... 29 more
  at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:97)
  at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:122)
  at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:836)
  at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:456)
  at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:246)
  at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:199)
  at com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:134)
  at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:182)
  at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:171)
  at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:137)
  at com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1014)
  at com.mchange.v2.resourcepool.BasicResourcePool.access$800(BasicResourcePool.java:32)
  at com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask.run(BasicResourcePool.java:1810)
  at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)
Process finished with exit code 255

"jdbc:mysql://localhost:3306/test?useSSL=false&characterEncoding=utf-8&serverTimezone=GMT"