本文主要是介绍框架技术--hibernate jpa异常（Exception Description: Unable to acquire a connection from driver [null], use），希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
使用hibernate JPA在本地部署调试都没有问题，但是打成war包，放到服务后，就会抛出异常。
[#|2013-12-11T12:28:23.947+0800|SEVERE|glassfish3.1.2|javax.enterprise.system.std.com.sun.enterprise.server.logging|_ThreadID=25;_ThreadName=Thread-2;|javax.persistence.PersistenceException: Exception [EclipseLink-4021] (Eclipse Persistence Services - 2.3.2.v20111125-r10461): org.eclipse.persistence.exceptions.DatabaseException
Exception Description: Unable to acquire a connection from driver [null], user [null] and URL [null]. Verify that you have set the expected driver class and URL.
Check your login, persistence.xml or sessions.xml resource.
The jdbc.driver property should be set to a class that is compatible with your database platformat org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.deploy(EntityManagerSetupImpl.java:517)at org.eclipse.persistence.internal.jpa.EntityManagerFactoryDelegate.getDatabaseSession(EntityManagerFactoryDelegate.java:188)at org.eclipse.persistence.internal.jpa.EntityManagerFactoryDelegate.createEntityManagerImpl(EntityManagerFactoryDelegate.java:277)at org.eclipse.persistence.internal.jpa.EntityManagerFactoryImpl.createEntityManagerImpl(EntityManagerFactoryImpl.java:294)at org.eclipse.persistence.internal.jpa.EntityManagerFactoryImpl.createEntityManager(EntityManagerFactoryImpl.java:272)at com.haierpip.dao.impl.AdvDaoImpl.getAdvInfo(AdvDaoImpl.java:132)at com.haierpip.util.AdvUtil.advStrategy(AdvUtil.java:68)at com.haierpip.servlet.LiveEpgServlet.doPost(LiveEpgServlet.java:131)at com.haierpip.servlet.LiveEpgServlet.doGet(LiveEpgServlet.java:63)at javax.servlet.http.HttpServlet.service(HttpServlet.java:668)at javax.servlet.http.HttpServlet.service(HttpServlet.java:770)at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1550)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:343)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:217)at com.haierpip.util.visitRecord.AccessFilter.doFilter(AccessFilter.java:23)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:256)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:217)at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:279)at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:655)at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:595)at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:161)at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:331)at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:231)at com.sun.enterprise.v3.services.impl.ContainerMapper$AdapterCallable.call(ContainerMapper.java:317)at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:195)at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:860)at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:757)at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:1056)at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:229)at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:137)at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:104)at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:90)at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:79)at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:54)at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:59)at com.sun.grizzly.ContextTask.run(ContextTask.java:71)at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:532)at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:513)at java.lang.Thread.run(Thread.java:662)
Caused by: Exception [EclipseLink-4021] (Eclipse Persistence Services - 2.3.2.v20111125-r10461): org.eclipse.persistence.exceptions.DatabaseException
Exception Description: Unable to acquire a connection from driver [null], user [null] and URL [null]. Verify that you have set the expected driver class and URL. Check your login, persistence.xml or sessions.xml resource. The jdbc.driver property should be set to a class that is compatible with your database platformat org.eclipse.persistence.exceptions.DatabaseException.unableToAcquireConnectionFromDriverException(DatabaseException.java:376)at org.eclipse.persistence.sessions.DefaultConnector.connect(DefaultConnector.java:91)at org.eclipse.persistence.sessions.DatasourceLogin.connectToDatasource(DatasourceLogin.java:162)at org.eclipse.persistence.internal.sessions.DatabaseSessionImpl.loginAndDetectDatasource(DatabaseSessionImpl.java:584)at org.eclipse.persistence.internal.jpa.EntityManagerFactoryProvider.login(EntityManagerFactoryProvider.java:206)at org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.deploy(EntityManagerSetupImpl.java:488)... 39 more
|#]经一番搜索，找到点有用的资料： http://www.coderanch.com/t/502791/ORM/databases/exception-JPA-application
修改persistence.xmll配置文件中连接数据库参数即可使用：
<property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost/experiments"/>
<property name="javax.persistence.jdbc.user" value="root"/>
<property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver"/>
<property name="javax.persistence.jdbc.password" value=""/>
<property name="eclipelink.ddl-generation" value="create-tables"/>
<property name="eclipelink.jdbc.connections.min" value="1"/>
<property name="eclipelink.jdbc.connections.max" value="2"/>
<property name="eclipelink.logging.level" value="FINEST"/>至于原因还需要查找。
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