[英]Could not open JPA EntityManager for transaction; nested exception is javax.persistence.PersistenceException
when i run my code, i get this exception:当我运行我的代码时,我得到了这个异常:
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.<init>(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.<init>(ConnectionImpl.java:834)
at com.mysql.jdbc.JDBC4Connection.<init>(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.<init>(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.<init>(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)
I don't know where is the problem.我不知道问题出在哪里。 But yesterday i worked fine.
但是昨天我工作得很好。
my database.properties:我的database.properties:
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
It is possible for me to run mysql directly from command line.我可以直接从命令行运行 mysql。 Where is the problem?
问题出在哪里? Was is wrong.
是错的。 I use spring 4 and hibernate with mysql as database language.
我使用 spring 4 并使用 mysql 作为数据库语言进行休眠。
Has someone any ideas?有人有什么想法吗?
Thank.感谢。
There is CommunicationsException: Communications link failure.出现 CommunicationsException:通信链路故障。
If you get a SQLException: Connection refused or Connection timed out or a MySQL specific如果您收到 SQLException: Connection denied 或 Connection timed out 或 MySQL 特定的
CommunicationsException: Communications link failure
then it means that the DB isn't reachable at all.那么这意味着数据库根本无法访问。 This can have one or more of the following causes:
这可能有以下一种或多种原因:
To solve the one or the other, follow the following advices:要解决其中一个问题,请遵循以下建议:
Source: More Details资料来源: 更多详情
DB is down.数据库已关闭。 You must start the DB server and check connectivity with either telnet or mysql command line client first.
您必须先启动 DB 服务器并检查与 telnet 或 mysql 命令行客户端的连接。
I was not unable to figure out the exact cause, but I realized that it was because of some thread pools since I was able to connect to the db using the terminal.我无法找出确切的原因,但我意识到这是因为一些线程池,因为我能够使用终端连接到数据库。 for checking the connectivity you can use the below command.
要检查连接,您可以使用以下命令。
psql -h hostname -U username -d database
so restarting the server worked for me.所以重新启动服务器对我有用。
I see that @Amit Tamrakar have good answer but I want to add:我看到@Amit Tamrakar 有很好的答案,但我想补充:
.h.engine.jdbc.spi.SqlExceptionHelper : HikariPool-1 - Connection is not available, request timed out after 30005ms.
Could not open JPA EntityManager for transaction; nested exception is org.hibernate.exception.JDBCConnectionException: Unable to acquire JDBC Connection
You can try to increase db connection pool in application config file, for example:您可以尝试在应用程序配置文件中增加 db 连接池,例如:
spring.datasource.hikari.maximum-pool-size=20
You can set size which you need.你可以设置你需要的大小。 This config in app by
default
is 8
.应用程序中的此配置
default
为8
。 And we need remember that each db have own free db connection size which we don't need exceed.我们需要记住,每个数据库都有自己的空闲数据库连接大小,我们不需要超过。 I mean if db have 5 free connection and you want to use 10 connections in your app then we will receive so exceptions.
我的意思是,如果 db 有 5 个免费连接并且您想在您的应用程序中使用 10 个连接,那么我们将收到这样的异常。
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