mon*_*ona 316 java tomcat jdbc
我运行我的Web应用程序时收到此消息.它运行正常,但我在关机期间收到此消息.
严重:Web应用程序注册了JBDC驱动程序[oracle.jdbc.driver.OracleDriver],但在Web应用程序停止时无法注销它.为防止内存泄漏,JDBC驱动程序已被强制取消注册.
任何帮助赞赏.
Bal*_*usC 295
从版本6.0.24开始,Tomcat附带了内存泄漏检测功能,当webapp中的JDBC 4.0兼容驱动程序在webapp启动期间使用API/WEB-INF/lib自动注册时,它会导致这种警告消息,但是在webapp关闭期间没有自动注销.这条消息纯粹是非正式的,Tomcat已经相应地采取了内存泄漏防护措施.ServiceLoader
你能做什么？
忽略这些警告.Tomcat正在做好自己的工作.实际的错误是在别人的代码(有问题的JDBC驱动程序)中,而不是在你的代码中.很高兴Tomcat正确地完成了它的工作并等到JDBC驱动程序供应商修复它以便你可以升级驱动程序.另一方面,您不应该在webapp中删除JDBC驱动程序/WEB-INF/lib,而只能在服务器中删除/lib.如果你仍然将它保存在webapp中/WEB-INF/lib,那么你应该使用a手动注册和取消注册ServletContextListener.
降级到Tomcat 6.0.23或更早版本,这样您就不会被这些警告所困扰.但它会默默地不断泄露记忆.不知道毕竟这是否有用.这些内存泄漏是Tomcat hotdeployments中出现OutOfMemoryError问题的主要原因之一.
将JDBC驱动程序移动到Tomcat的/lib文件夹,并使用连接池数据源来管理驱动程序.请注意,Tomcat的内置DBCP在关闭时不会正确注销驱动程序.另请参阅错误DBCP-322,它作为WONTFIX关闭.您更愿意将DBCP替换为另一个连接池,该连接池比DBCP更好地完成其工作.例如HikariCP,BoneCP或Tomcat JDBC Pool.
ae6*_*6rt 160
在您的servlet上下文侦听器contextDestroyed()方法中,手动取消注册驱动程序:
// This manually deregisters JDBC driver, which prevents Tomcat 7 from complaining about memory leaks wrto this class
Enumeration<Driver> drivers = DriverManager.getDrivers();
while (drivers.hasMoreElements()) {
Driver driver = drivers.nextElement();
try {
DriverManager.deregisterDriver(driver);
LOG.log(Level.INFO, String.format("deregistering jdbc driver: %s", driver));
} catch (SQLException e) {
LOG.log(Level.SEVERE, String.format("Error deregistering driver %s", driver), e);
}
}
meg*_*lop 78
虽然Tomcat强制为您注销JDBC驱动程序,但是如果您移动到另一个不执行Tomcat执行的内存泄漏防护检查的servlet容器,清除上下文销毁时由webapp创建的所有资源仍然是一种很好的做法.
但是,一揽子驾驶员注销的方法是危险的. 该DriverManager.getDrivers()方法返回的一些驱动程序可能已由父类ClassLoader(即servlet容器的类加载器)加载而不是webapp上下文的ClassLoader(例如,它们可能位于容器的lib文件夹中,而不是webapp的文件夹中,因此在整个容器中共享).取消注册这些将影响可能正在使用它们的任何其他Web应用程序(甚至容器本身).
因此,在取消注册之前,应检查每个驱动程序的ClassLoader是否为webapp的ClassLoader.所以,在ContextListener的contextDestroyed()方法中:
public final void contextDestroyed(ServletContextEvent sce) {
// ... First close any background tasks which may be using the DB ...
// ... Then close any DB connection pools ...
// Now deregister JDBC drivers in this context's ClassLoader:
// Get the webapp's ClassLoader
ClassLoader cl = Thread.currentThread().getContextClassLoader();
// Loop through all drivers
Enumeration<Driver> drivers = DriverManager.getDrivers();
while (drivers.hasMoreElements()) {
Driver driver = drivers.nextElement();
if (driver.getClass().getClassLoader() == cl) {
// This driver was registered by the webapp's ClassLoader, so deregister it:
try {
log.info("Deregistering JDBC driver {}", driver);
DriverManager.deregisterDriver(driver);
} catch (SQLException ex) {
log.error("Error deregistering JDBC driver {}", driver, ex);
}
} else {
// driver was not registered by the webapp's ClassLoader and may be in use elsewhere
log.trace("Not deregistering JDBC driver {} as it does not belong to this webapp's ClassLoader", driver);
}
}
}
Spi*_*der 25
我看到这个问题出现了很多.是的,Tomcat 7会自动取消注册,但它真的可以控制你的代码和良好的编码实践吗？当然,您想知道您拥有所有正确的代码来关闭所有对象,关闭数据库连接池线程,并删除所有警告.我当然这样做.
我就是这样做的.
第1步:注册监听器
web.xml中
<listener>
<listener-class>com.mysite.MySpecialListener</listener-class>
</listener>
第2步:实现监听器
com.mysite.MySpecialListener.java
public class MySpecialListener implements ServletContextListener {
@Override
public void contextInitialized(ServletContextEvent sce) {
// On Application Startup, please…
// Usually I'll make a singleton in here, set up my pool, etc.
}
@Override
public void contextDestroyed(ServletContextEvent sce) {
// On Application Shutdown, please…
// 1. Go fetch that DataSource
Context initContext = new InitialContext();
Context envContext = (Context)initContext.lookup("java:/comp/env");
DataSource datasource = (DataSource)envContext.lookup("jdbc/database");
// 2. Deregister Driver
try {
java.sql.Driver mySqlDriver = DriverManager.getDriver("jdbc:mysql://localhost:3306/");
DriverManager.deregisterDriver(mySqlDriver);
} catch (SQLException ex) {
logger.info("Could not deregister driver:".concat(ex.getMessage()));
}
// 3. For added safety, remove the reference to dataSource for GC to enjoy.
dataSource = null;
}
}
请随时评论和/或添加...
小智 14
这纯粹是mysql驱动程序或tomcats webapp-classloader中的驱动程序注册/注销问题.将mysql驱动程序复制到tomcats lib文件夹(因此它由jvm直接加载,而不是由tomcat加载),并且消息将消失.这使得mysql jdbc驱动程序仅在JVM关闭时被卸载,然后没有人关心内存泄漏.
如果您从Maven构建的war获取此消息,请更改要提供的JDBC驱动程序的范围,并将其副本放在lib目录中.像这样:
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.18</version>
<!-- put a copy in /usr/share/tomcat7/lib -->
<scope>provided</scope>
</dependency>
这是我为解决问题而编写的一个监听器:如果驱动程序已经注册并且相应地执行操作,它会自动检测
重要说明:它仅用于在WEB-INF/lib中部署驱动程序jar时使用,而不是像许多人建议的那样在Tomcat/lib中部署,这样每个应用程序都可以处理自己的驱动程序并在未受影响的Tomcat上运行.这就是恕我直言的方式.
只需在web.xml之前配置监听器,然后再享受.
在web.xml顶部附近添加:
<listener>
<listener-class>utils.db.OjdbcDriverRegistrationListener</listener-class>
</listener>
另存为utils/db/OjdbcDriverRegistrationListener.java:
package utils.db;
import java.sql.Driver;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Enumeration;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import oracle.jdbc.OracleDriver;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Registers and unregisters the Oracle JDBC driver.
*
* Use only when the ojdbc jar is deployed inside the webapp (not as an
* appserver lib)
*/
public class OjdbcDriverRegistrationListener implements ServletContextListener {
private static final Logger LOG = LoggerFactory
.getLogger(OjdbcDriverRegistrationListener.class);
private Driver driver = null;
/**
* Registers the Oracle JDBC driver
*/
@Override
public void contextInitialized(ServletContextEvent servletContextEvent) {
this.driver = new OracleDriver(); // load and instantiate the class
boolean skipRegistration = false;
Enumeration<Driver> drivers = DriverManager.getDrivers();
while (drivers.hasMoreElements()) {
Driver driver = drivers.nextElement();
if (driver instanceof OracleDriver) {
OracleDriver alreadyRegistered = (OracleDriver) driver;
if (alreadyRegistered.getClass() == this.driver.getClass()) {
// same class in the VM already registered itself
skipRegistration = true;
this.driver = alreadyRegistered;
break;
}
}
}
try {
if (!skipRegistration) {
DriverManager.registerDriver(driver);
} else {
LOG.debug("driver was registered automatically");
}
LOG.info(String.format("registered jdbc driver: %s v%d.%d", driver,
driver.getMajorVersion(), driver.getMinorVersion()));
} catch (SQLException e) {
LOG.error(
"Error registering oracle driver: " +
"database connectivity might be unavailable!",
e);
throw new RuntimeException(e);
}
}
/**
* Deregisters JDBC driver
*
* Prevents Tomcat 7 from complaining about memory leaks.
*/
@Override
public void contextDestroyed(ServletContextEvent servletContextEvent) {
if (this.driver != null) {
try {
DriverManager.deregisterDriver(driver);
LOG.info(String.format("deregistering jdbc driver: %s", driver));
} catch (SQLException e) {
LOG.warn(
String.format("Error deregistering driver %s", driver),
e);
}
this.driver = null;
} else {
LOG.warn("No driver to deregister");
}
}
}
我将在Spring论坛上添加这些内容.如果将JDBC驱动程序jar移动到tomcat lib文件夹,而不是使用webapp将其部署,则警告似乎消失了.我可以确认这对我有用
小智 6
我发现实现一个简单的destroy()方法来取消注册任何JDBC驱动程序都可以很好地工作.
/**
* Destroys the servlet cleanly by unloading JDBC drivers.
*
* @see javax.servlet.GenericServlet#destroy()
*/
public void destroy() {
String prefix = getClass().getSimpleName() +" destroy() ";
ServletContext ctx = getServletContext();
try {
Enumeration<Driver> drivers = DriverManager.getDrivers();
while(drivers.hasMoreElements()) {
DriverManager.deregisterDriver(drivers.nextElement());
}
} catch(Exception e) {
ctx.log(prefix + "Exception caught while deregistering JDBC drivers", e);
}
ctx.log(prefix + "complete");
}
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