[英]Strange error using JPA on OpenShift
我已經擔心了幾天的錯誤-也是因為很難測試它是否仍然發生。
從OpenShift托管的Java EE應用程序中,我正在連接到MySQL盒式磁帶。 我正在使用JPA(休眠)來處理我的連接並用於ORM。
連接和應用程序本身運行良好-但是,在幾個小時后嘗試訪問數據庫時(我猜想OpenShift將servlet休眠后,它不再起作用)。
我收到以下異常(這只是摘錄,但在我看來,這是最重要的部分):
Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: No operations allowed after connection closed.
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:377)
at com.mysql.jdbc.Util.getInstance(Util.java:360)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:956)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:935)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:924)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:870)
當然,我知道異常對我有什么作用-我只是不知道為什么會拋出該異常...
我的數據庫訪問類如下所示:
public class JPAUtils implements ServletContextListener {
private static final Logger log = LoggerFactory.getLogger(JPAUtils.class);
private static EntityManagerFactory emf;
private static EntityManager em;
public static EntityManagerFactory getEntityManagerFactoryInstance() {
if (emf == null || !emf.isOpen()) {
String environment = "test";
if (System.getenv("OPENSHIFT_MYSQL_DB_URL") != null) {
environment = "production";
}
emf = Persistence.createEntityManagerFactory(environment);
}
return emf;
}
public static EntityManager getEntityManagerInstance() {
if (em == null || !em.isOpen()) {
em = getEntityManagerFactoryInstance().createEntityManager();
}
return em;
}
@Override
public void contextInitialized(ServletContextEvent servletContextEvent) {
log.debug("Context initialized!");
}
@Override
public void contextDestroyed(ServletContextEvent servletContextEvent) {
try {
log.debug("Closing JPA connection...");
em.close();
emf.close();
em = null;
emf = null;
log.debug("Closed JPA connection!");
}
catch (Exception e) {
log.error("Error occurred during closing of JPA connection!", e);
}
}
}
persistence.xml中:
<persistence xmlns="http://java.sun.com/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence
http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd"
version="1.0">
<persistence-unit name="test">
<provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
<properties>
<property name="hibernate.archive.autodetection" value="class, hbm" />
<property name="hibernate.show_sql" value="false" />
<property name="hibernate.format_sql" value="true" />
<property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver" />
<property name="hibernate.connection.url" value="jdbc:mysql://localhost/<db_name>?autoReconnect=true" />
<property name="hibernate.connection.username" value="***" />
<property name="hibernate.connection.password" value="***" />
<property name="hibernate.hbm2ddl.auto" value="update" />
<property name="hibernate.c3p0.min_size" value="5" />
<property name="hibernate.c3p0.max_size" value="10" />
<property name="hibernate.c3p0.timeout" value="300" />
<property name="hibernate.c3p0.max_statements" value="50" />
<property name="hibernate.c3p0.idle_test_period" value="300" />
<property name="hibernate.dialect" value="org.hibernate.dialect.MySQL5InnoDBDialect" />
</properties>
</persistence-unit>
<persistence-unit name="production">
<!-- If you are running in a production environment, add a managed
data source, this example data source is just for development and testing! -->
<!-- The datasource is deployed as WEB-INF/kitchensink-quickstart-ds.xml, you
can find it in the source at src/main/webapp/WEB-INF/kitchensink-quickstart-ds.xml -->
<non-jta-data-source>java:comp/env/jdbc/MySQLDS</non-jta-data-source>
<properties>
<!-- Properties for Hibernate -->
<property name="hibernate.hbm2ddl.auto" value="update" />
<property name="hibernate.show_sql" value="false" />
<!--<property name="hibernate.transaction.jta.platform" value="org.hibernate.service.jta.platform.internal.JBossAppServerJtaPlatform" />-->
</properties>
</persistence-unit>
</persistence>
我已經查看了許多示例和教程-但是我找不到問題。
提前致謝!
始終不要使用對EntityManager
實例的引用,在您的情況下,靜態變量em
在關閉連接后將保持停頓對象。
有關將EntityManager
范圍限制到當前事務的最佳實踐建議。
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