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短时间断开网络连接后无法恢复连接

entitymanager jpa tomcat hibernate java
  •  2
  • slartidan  · 技术社区  · 9 年前

    我想在我的tomcat Web应用程序中使用JPA。因此,我创造了自己的 Filter (在web.xml中提到)。

    过滤器有三种方法:

    • 这个 init 方法创建 EntityManagerFactory 并将其存储在实例字段中(在应用程序部署时执行)
    • 这个 doFilter 方法使用存储的EntityManagerFactory创建entityManager,启动事务并在处理请求后关闭事务(和entityManager)
    • 这个 destroy 方法关闭存储的EntityManagerFactory

    该机制工作良好,速度相当快,但 一旦数据库连接丢失,应用程序就无法恢复 .

    如何刷新EntityManagerFactory,以便它创建新的数据库连接?还是应该销毁并重新创建EntityManagerFactory?我是否必须运行数据库查询来检查连接是否有效?

    我当前的筛选器是这样实现的: 

    package entityManagerTest;

import java.io.IOException;

import javax.persistence.*;
import javax.servlet.*;
import javax.servlet.annotation.WebFilter;

@WebFilter(urlPatterns = { "/JpaServlet" })
public class JpaFilter implements Filter {

    private EntityManagerFactory entityManagerFactory;

    @Override
    public void init(FilterConfig config) throws ServletException {
        entityManagerFactory = Persistence.createEntityManagerFactory("test");
    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        EntityManager entityManager = entityManagerFactory .createEntityManager();
        try {
            EntityTransaction transaction = entityManager.getTransaction();
            transaction.begin();
            try {
                request.setAttribute("entityManager", entityManager);
                chain.doFilter(request, response);
            } finally {
                transaction.commit();
            }
        } finally {
            entityManager.close();
        }
    }

    @Override
    public void destroy() {
        entityManagerFactory.close();
    }
}

    servlet如下所示: 

    package entityManagerTest;

import java.io.*;
import javax.persistence.*;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.*;

@WebServlet(urlPatterns={"/JpaServlet"})
public class JpaServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        EntityManager entityManager = (EntityManager) req.getAttribute("entityManager");

        Query query = entityManager.createNativeQuery("SELECT 42");
        Object singleResult = query.getSingleResult();

        PrintWriter writer = resp.getWriter();
        writer.write("DB:"+singleResult);
        writer.close();
    }
}

    我的persistence.xml: 

    <?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0" 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_2_0.xsd">
    <persistence-unit name="test">
        <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
        <properties>
            <property name="javax.persistence.jdbc.driver" value="com.microsoft.sqlserver.jdbc.SQLServerDriver" />
            <property name="javax.persistence.jdbc.url" value="jdbc:sqlserver:..." />
            <property name="javax.persistence.jdbc.user" value="x" />
            <property name="javax.persistence.jdbc.password" value="y" />
        </properties>
    </persistence-unit>
</persistence>

    我尝试添加 验证查询 ,但未发现任何行为变化: 

    <property name="hibernate.connection.validationQuery" value="select 1"/>
<property name="connection.validationQuery" value="select 1"/>

    当连接丢失时,我会得到一个回滚异常(不是意外): 

    Aug 18, 2015 11:41:30 AM org.hibernate.engine.jdbc.spi.SqlExceptionHelper logExceptions
WARN: SQL Error: 0, SQLState: 08S01
Aug 18, 2015 11:41:30 AM org.hibernate.engine.jdbc.spi.SqlExceptionHelper logExceptions
ERROR: Software caused connection abort: recv failed
Aug 18, 2015 11:41:30 AM org.apache.catalina.core.StandardWrapperValve invoke
SCHWERWIEGEND: Servlet.service() for servlet [entityManagerTest.JpaServlet] in context with path [/EntityManagerTests] threw exception
org.hibernate.TransactionException: rollback failed
    at org.hibernate.engine.transaction.spi.AbstractTransactionImpl.rollback(AbstractTransactionImpl.java:217)
    at org.hibernate.jpa.internal.TransactionImpl.commit(TransactionImpl.java:73)
    at entityManagerTest.JpaFilter.doFilter(JpaFilter.java:29)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:610)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1091)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:668)
    at org.apache.coyote.http11.Http11NioProtocol$Http11ConnectionHandler.process(Http11NioProtocol.java:223)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1517)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1474)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:745)
Caused by: org.hibernate.TransactionException: unable to rollback against JDBC connection
    at org.hibernate.engine.transaction.internal.jdbc.JdbcTransaction.doRollback(JdbcTransaction.java:167)
    at org.hibernate.engine.transaction.spi.AbstractTransactionImpl.rollback(AbstractTransactionImpl.java:211)
    ... 21 more
Caused by: com.microsoft.sqlserver.jdbc.SQLServerException: Die Verbindung wurde geschlossen.
    at com.microsoft.sqlserver.jdbc.SQLServerException.makeFromDriverError(SQLServerException.java:190)
    at com.microsoft.sqlserver.jdbc.SQLServerConnection.checkClosed(SQLServerConnection.java:389)
    at com.microsoft.sqlserver.jdbc.SQLServerConnection.rollback(SQLServerConnection.java:1955)
    at org.hibernate.engine.transaction.internal.jdbc.JdbcTransaction.doRollback(JdbcTransaction.java:163)
    ... 22 more

    但在网络连接再次恢复后,代码仍然失败,出现异常( 即使现在可以恢复连接 ): 

    Aug 18, 2015 11:42:54 AM org.apache.catalina.core.StandardWrapperValve invoke
SCHWERWIEGEND: Servlet.service() for servlet [entityManagerTest.JpaServlet] in context with path [/EntityManagerTests] threw exception
javax.persistence.PersistenceException: org.hibernate.TransactionException: JDBC begin transaction failed: 
    at org.hibernate.jpa.spi.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1763)
    at org.hibernate.jpa.spi.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1677)
    at org.hibernate.jpa.spi.AbstractEntityManagerImpl.throwPersistenceException(AbstractEntityManagerImpl.java:1771)
    at org.hibernate.jpa.internal.TransactionImpl.begin(TransactionImpl.java:64)
    at entityManagerTest.JpaFilter.doFilter(JpaFilter.java:24)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:610)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1091)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:668)
    at org.apache.coyote.http11.Http11NioProtocol$Http11ConnectionHandler.process(Http11NioProtocol.java:223)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1517)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1474)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:745)
Caused by: org.hibernate.TransactionException: JDBC begin transaction failed: 
    at org.hibernate.engine.transaction.internal.jdbc.JdbcTransaction.doBegin(JdbcTransaction.java:76)
    at org.hibernate.engine.transaction.spi.AbstractTransactionImpl.begin(AbstractTransactionImpl.java:162)
    at org.hibernate.internal.SessionImpl.beginTransaction(SessionImpl.java:1471)
    at org.hibernate.jpa.internal.TransactionImpl.begin(TransactionImpl.java:61)
    ... 20 more
Caused by: com.microsoft.sqlserver.jdbc.SQLServerException: Die Verbindung wurde geschlossen.
    at com.microsoft.sqlserver.jdbc.SQLServerException.makeFromDriverError(SQLServerException.java:190)
    at com.microsoft.sqlserver.jdbc.SQLServerConnection.checkClosed(SQLServerConnection.java:389)
    at com.microsoft.sqlserver.jdbc.SQLServerConnection.getAutoCommit(SQLServerConnection.java:1910)
    at org.hibernate.engine.transaction.internal.jdbc.JdbcTransaction.doBegin(JdbcTransaction.java:68)
    ... 23 more
    1 回复  |  直到 9 年前
        1
  •  4
  •   slartidan    9 年前

    摘录自 the official hibernate documentation :

    然而,Hibernate自己的连接池算法 初级的它旨在帮助您入门 不 用于生产系统 ,甚至是性能 测试。[…]例如,您可能希望使用c3p0。

    必须指定连接池数据源。连接池通常在使用连接之前检查连接的有效性。下面是连接池的C3P0(连接池数据源)和Hibernate配置的示例。我希望这对你有用。 

    <?xml version="1.0" encoding="UTF-8"?>

<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_2_0.xsd"
    version="2.0">
    <persistence-unit name="test" transaction-type="RESOURCE_LOCAL">
        <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>

        <properties>
            <property name="hibernate.dialect" value="org.hibernate.dialect.SQLServerDialect" />
            <property name="hibernate.show_sql" value="true" />
            <property name="hibernate.format_sql" value="true" />
            <property name="hibernate.hbm2ddl.auto" value="update"/>

            <!-- I am not exactly sure that which one is correct -->
            <!-- javax.persistence.* or hibernate.connection.* properties -->
            <property name="hibernate.connection.driver_class" value="com.microsoft.sqlserver.jdbc.SQLServerDriver"/>
            <property name="hibernate.connection.url" value="jdbc:sqlserver:..."/>
            <property name="hibernate.connection.username" value="x"/>
            <property name="hibernate.connection.password" value="y"/>


            <!-- Connection Pooling settings -->
            <property name="hibernate.connection.provider_class" value="org.hibernate.service.jdbc.connections.internal.C3P0ConnectionProvider" />
            <property name="hibernate.c3p0.max_size" value="100" />
            <property name="hibernate.c3p0.min_size" value="0" />
            <property name="hibernate.c3p0.acquire_increment" value="1" />
            <property name="hibernate.c3p0.idle_test_period" value="300" />
            <property name="hibernate.c3p0.max_statements" value="0" />
            <property name="hibernate.c3p0.timeout" value="100" />
            <property name="hibernate.c3p0.preferredTestQuery">SELECT 1;</property>

        </properties>
    </persistence-unit>
</persistence>

    此外,还需要将hibernate-c3p0添加到类路径中。 

        <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-c3p0</artifactId>
        <version>${hibernate.version}</version>
    </dependency>
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