Web 应用程序 [] 似乎启动了一个名为 [Abandoned connection cleanup thread] com.mysql.jdbc.AbandonedConnectionCleanupThread 的线程 [英] The web application [] appears to have started a thread named [Abandoned connection cleanup thread] com.mysql.jdbc.AbandonedConnectionCleanupThread

问题描述

在我的 Web 开发过程中，我刚刚在 Eclipse IDE 中关闭了我的 Web 应用程序，大约一分钟后，我在 Eclipse 控制台中看到了一个警告.

In the middle of my web-development I just close my web-app in my eclipse IDE, about a minute, I just saw a WARNING in my eclipse console.

WARNING: The web application [/Spring.MVC] registered the JDBC driver [com.mysql.jdbc.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
Sep 06, 2014 8:31:55 PM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
WARNING: The web application [/Spring.MVC] appears to have started a thread named [Abandoned connection cleanup thread] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
 java.lang.Object.wait(Native Method)
 java.lang.ref.ReferenceQueue.remove(Unknown Source)
 com.mysql.jdbc.AbandonedConnectionCleanupThread.run(AbandonedConnectionCleanupThread.java:40)
Sep 06, 2014 8:32:00 PM org.apache.catalina.core.ApplicationContext log
INFO: No Spring WebApplicationInitializer types detected on classpath
SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
SLF4J: Defaulting to no-operation (NOP) logger implementation
SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details.
Sep 06, 2014 8:32:00 PM org.apache.catalina.core.ApplicationContext log
INFO: Initializing Spring root WebApplicationContext
Sep 06, 2014 8:32:03 PM org.hibernate.jpa.internal.util.LogHelper logPersistenceUnitInformation
INFO: HHH000204: Processing PersistenceUnitInfo [
    name: personPU
    ...]

到目前为止它没有造成任何内存泄漏，我检查了我的 VisualVM，一切都照常工作，但是当我搜索更多关于这件事的时候，我意识到这个警告是由 MySQL 驱动程序没有释放资源或没有被关闭引起的正确地(我不知道如何准确地表达)，我在 SO 相关问题上发表了这篇文章

It did not caused any memory leak so far, I checked my VisualVM, everything is working as usual, but as I search more about this thing I realize that this warning is caused by the MySQL driver not releasing resources or not being closed properly(I dont know how to say it exactly) and I ended up in this post at SO related issue

而且 OP 是对的别担心"的答案是不够的.这个警告让我很困扰，因为它可能会给我带来一些未来的持久性问题，这让我很担心，我尝试了 OP 编写的代码，但我遇到了什么库的问题> 我应该用它来使这段代码工作吗?这就是我到目前为止所得到的..

and the OP is right the answer of "don't worry about it" won't be sufficient. This warning bothers me because it may give me some future persistence problems and that worries me a lot, I tried the code the OP has written but I'm having a problem what Libraries should I use to make this code work. This is what I got sor far..

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 javax.servlet.annotation.WebListener;
import org.hibernate.annotations.common.util.impl.LoggerFactory;
import com.mysql.jdbc.AbandonedConnectionCleanupThread;
@WebListener
public class ContextFinalizer implements ServletContextListener {

private static final Logger LOGGER = LoggerFactory.getLogger(ContextFinalizer.class);

public void contextInitialized(ServletContextEvent sce) {
}

public void contextDestroyed(ServletContextEvent sce) {
    Enumeration<Driver> drivers = DriverManager.getDrivers();
    Driver d = null;
    while (drivers.hasMoreElements()) {
        try {
            d = drivers.nextElement();
            DriverManager.deregisterDriver(d);
            LOGGER.warn(String.format("Driver %s deregistered", d));
        }
        catch (SQLException ex) {
            LOGGER.warn(String.format("Error deregistering driver %s", d), ex);
        }
    }
    try {
        AbandonedConnectionCleanupThread.shutdown();
    }
    catch (InterruptedException e) {
        logger.warn("SEVERE problem cleaning up: " + e.getMessage());
        e.printStackTrace();
    }
  }
}

我只想知道我需要什么库，或者如果我使用正确的库来正确实现这一点，我什至不知道我应该使用什么 Logger，谢谢您的帮助，

I just want to know what Libraries do I need or If I'm using the right libraries to implement this properly, I do not even know what Logger should I use, thank you for any help,

推荐答案

参见 这个答案.似乎 MySQL 驱动程序应该在应用程序之间共享的 {$TOMCAT]/lib 中.检查您是否没有将它包含在每个应用程序中.至少它对我有用，我已经能够删除警告.

See this answer. It seems that MySQL driver should be in {$TOMCAT]/lib shared between applications. Check that you are not including it with each application. At least it worked for me and I have been able to remove the warning.

如果您使用 Maven，请将依赖项标记为已提供.

If you are using Maven mark the dependency as provided.

更新:
根本原因是 Tomcat 在对驱动程序进行垃圾回收方面存在问题，因为它注册在多个应用程序通用的单例中.关闭一个应用程序不允许 Tomcat 释放驱动程序.请参阅此答案.

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