title: Could not open JPA EntityManager for transaction; nested exception is javax.persistence.PersistenceException
body: <p>when i run my code, i get this exception:</p>
  
  <pre><code>com.mysql.jdbc.exceptions.jdbc4.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 sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
      at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
      at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
      at java.lang.reflect.Constructor.newInstance(Constructor.java:422)
      at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
      at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1121)
      at com.mysql.jdbc.MysqlIO.&lt;init&gt;(MysqlIO.java:357)
      at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2482)
      at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2519)
      at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2304)
      at com.mysql.jdbc.ConnectionImpl.&lt;init&gt;(ConnectionImpl.java:834)
      at com.mysql.jdbc.JDBC4Connection.&lt;init&gt;(JDBC4Connection.java:47)
      at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
      at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
      at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
      at java.lang.reflect.Constructor.newInstance(Constructor.java:422)
      at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
      at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:416)
      at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:346)
      at java.sql.DriverManager.getConnection(DriverManager.java:664)
      at java.sql.DriverManager.getConnection(DriverManager.java:208)
      at org.springframework.jdbc.datasource.DriverManagerDataSource.getConnectionFromDriverManager(DriverManagerDataSource.java:153)
      at org.springframework.jdbc.datasource.DriverManagerDataSource.getConnectionFromDriver(DriverManagerDataSource.java:144)
      at org.springframework.jdbc.datasource.AbstractDriverBasedDataSource.getConnectionFromDriver(AbstractDriverBasedDataSource.java:155)
      at org.springframework.jdbc.datasource.AbstractDriverBasedDataSource.getConnection(AbstractDriverBasedDataSource.java:120)
      at org.hibernate.engine.jdbc.connections.internal.DatasourceConnectionProviderImpl.getConnection(DatasourceConnectionProviderImpl.java:139)
      at org.hibernate.tool.hbm2ddl.SuppliedConnectionProviderConnectionHelper.prepare(SuppliedConnectionProviderConnectionHelper.java:51)
      at org.hibernate.tool.hbm2ddl.DatabaseExporter.&lt;init&gt;(DatabaseExporter.java:52)
      at org.hibernate.tool.hbm2ddl.SchemaExport.execute(SchemaExport.java:367)
      at org.hibernate.tool.hbm2ddl.SchemaExport.create(SchemaExport.java:304)
      at org.hibernate.tool.hbm2ddl.SchemaExport.create(SchemaExport.java:293)
      at org.hibernate.internal.SessionFactoryImpl.&lt;init&gt;(SessionFactoryImpl.java:517)
      at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1857)
  The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
  Aug 25, 2015 8:23:45 PM com.sun.jersey.spi.container.ContainerResponse mapMappableContainerException
  SCHWERWIEGEND: The RuntimeException could not be mapped to a response, re-throwing to the HTTP container
  org.springframework.transaction.CannotCreateTransactionException: Could not open JPA EntityManager for transaction; nested exception is javax.persistence.PersistenceException: org.hibernate.exception.JDBCConnectionException: Could not open connection
      at org.springframework.orm.jpa.JpaTransactionManager.doBegin(JpaTransactionManager.java:431)
      at org.springframework.transaction.support.AbstractPlatformTransactionManager.getTransaction(AbstractPlatformTransactionManager.java:373)
      at org.springframework.transaction.interceptor.TransactionAspectSupport.createTransactionIfNecessary(TransactionAspectSupport.java:457)
      at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:276)
      at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96)
      at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
      at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:207)
      at com.sun.proxy.$Proxy76.create(Unknown Source)
  </code></pre>
  
  <p>I don't know where is the problem. But yesterday i worked fine.</p>
  
  <p>my database.properties:</p>
  
  <pre><code>jdbc.driverClassName=com.mysql.jdbc.Driver
  jdbc.url=jdbc:mysql://localhost:3306/streaming
  jdbc.username=root
  jdbc.password=password
  
  hibernate.dialect=org.hibernate.dialect.MySQLDialect
  hibernate.showsql=true
  hibernate.hbm2ddl.auto=create
  </code></pre>
  
  <p>It is possible for me to run mysql directly from command line. Where is the problem? Was is wrong. 
  I use spring 4 and hibernate with mysql as database language.</p>
  
  <p>Has someone any ideas?</p>
  
  <p>Thank.</p>